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Tegazzini, Diana. "Design, synthesis and activity evaluation of antioxidant peptides." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603073.
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Reactive Oxygen Species (ROS) produced during normal aerobic metabolism, if not promptly removed by the detoxification mechanisms of the cells, can easily react with cell components, especially lipids, producing secondary cytotoxic molecules called reactive carbonyl species (RCSs). RCSs exhibit significant chemical reactivity and can cause protein modification and dysfunction. One of the most important ReSs is 4-hydroxinonenal (HNE), an unsaturated aldehyde that has been strongly linked to Alzheimer'S disease (AD). A new series of dipeptide histidyl hydrazide analogues of carnosine was prepared, with the aim of producing molecules with enhanced HNE scavenging activity. These compounds were demonstrated to scavenge HNE and to protect SH-SY5Y cells from HNE-induced tOxlcity and were superior in action to carnosine. The synthesis of an analogue of the best compound of the series containing caffeic acid, resulted in the generation of a new molecule exhibiting complete retention of HNE-scavenging activity and also possessing free Radical Scavenging Activity (RSA). Mitochondria are the major sites of high levels of oxidative stress and the targeting of a reactive carbonyl scavenger directly to these organelles would result in extinguishing the primary source of RCS, thus arresting any consequent cellular damage. In the present work, the possibility of specifying the cellular localization of histidyl hydrazide was investigated using previously described mitochondria penetrating peptides (MPPs) and new examples of such sequences I modified to be more resistant to protease degradation. The ligation of histidyl hydrazide to a previously reported MPP was successful in targeting the former to the mitochondria of HeLa cells. Finally. a particular chemical ligation approach was investigated for the development of a system of linking a common peptide vector and a variety of cargo molecules of choice through facile in situ coupling, without requiring the de novo synthesis of a new chemical conjugate in each instance.
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Matias, Guilhermina do Carmo Andrade Negrinho. "Síntese e avaliação da atividade biológica de bisfosfonatos derivados do indazole." Master's thesis, Universidade de Évora, 2012. http://hdl.handle.net/10174/15991.
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Os bisfosfonatos são uma classe importante de fármacos com largo espetro de aplicações no tratamento de doenças do metabolismo mineral do osso. Recentemente, tem sido estudada as suas atividades antitumoral e contra diversos microrganismos.
Neste trabalho, efetuou-se a síntese de bisfosfonatos derivados do indazole. Os bisfosfonatos utilizados neste trabalho foram sujeitos a estudos de avaliação de atividade antioxidante, toxicidade e atividade biológica.
A atividade antioxidante foi determinada por dois métodos: o método do DPPH (1,1-difenil-2-picril-hidrazil) e o método do β-caroteno/ácido linoleico. Os BPs apresentaram atividade antioxidante preferencialmente pelo segundo método.
Na avaliação da toxicidade, utilizou-se a Artemia salina, com determinação do valor de CL50. Os BPs estudados apresentaram uma toxicidade superior ao BP comercial estudado.
Foi ainda avaliada a atividade antimicrobiana pelo método de difusão em meio sólido e a determinação da concentração mínima inibitória. Nestes ensaios, os BPs mostraram-se mais ativos para as bactérias patogénicas gram negativas, especialmente para Enterobactereaceae; ABSTRACT: Bisphosphonates (BPs) are an important class of drugs with broad spectrum of applications in the treatment of diseases of bone mineral metabolism. Recently, it has been studied their antitumoral activity and against microorganisms. Here, we report the synthesis of bisphosphonates derived from indazole. These bisphosphonates were evaluated towards their antioxidant activity, toxicity and biologic activity.
The antioxidant activity of BPs was evaluated using two different methods: the DPPH (1,1-diphenyl-2-picril-hidrazyl) and the β-carotene/linoleic acid methods. The BPs showed higher antioxidant activity using the second method.
The evaluation of their toxicity was done using Artemia salina since it is a good environmental bioindicator. The BPs showed higher toxicity than a commercial BP used as standard.
The evaluation of the antimicrobial activity was done by the diffusion method on solid medium and the determination of minimum inhibitory concentration (CMI). In these tests, BPs showed more active towards gram negative pathogenic bacteria, especially for Enterobactereaceae.
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Santos, Nádia Alexandra Esteves. "Synthesis and evaluation of new pyrazoles, glycosylpyrazoles and rutheniumpyrazoles for antioxidant and antitumoral activity." Master's thesis, Universidade de Aveiro, 2017. http://hdl.handle.net/10773/22521.
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Mestrado em Biotecnologia - Biotecnologia Molecular<br>O cancro é a segunda maior razão de morte em Portugal, a seguir às doenças cardiovasculares. A quimioterapia continua a ser o tratamento mais utilizado e eficaz, no entanto o intervalo onde a dose é eficiente e ao mesmo tempo segura ainda é muito pequeno, podendo ser tóxico para o organismo do paciente. Dessa forma, a procura de novos agentes antitumorais eficientes e seguros tem sido crucial, tendo os pirazóis e os complexos de ruténio (II) um papel muito importante. Vários compostos contendo o anel de pirazol nas suas estruturas já demonstraram grande poder antitumoral ao inibirem enzimas cinases, tais como as aurosa cinases e as cinases dependentes de ciclina, ao induzirem a apoptose e até agindo como agentes citotóxicos contra linhas celulares tumorais. Os complexos de ruténio, por sua vez, contribuem para uma ação antitumoral mais seletiva, por terem propriedades redox ou pela incorporação de ligandos lábeis que criam locais de ligação a biomoléculas.
Neste trabalho pretende-se sintetizar novos derivados de pirazol, proceder à sua glicosilação e ligação com um complexo de ruténio. Serão feitos estudos de citotoxicidade dos compostos sintetizados, para estudar o seu efeito antitumoral, e ainda testes para avaliar a sua atividade antioxidante, uma vez que a formação de espécies reativas de oxigénio, inflamação crónica e o desenvolvimento de cancro, estão muitas vezes associados. Com base nestes estudos estabelecer-se-ão importantes relações estrutura-atividade biológica que ajudarão a perceber quais os requisitos estruturais mais importantes para a atividade destes compostos.<br>Cancer is the second main cause of death in Portugal, after cardiovascular diseases. Chemotherapy is still the most used and effective treatment, however the window in which the dose is still safe and efficient is small and consequently it can be toxic to patient’s body. For that reason, the design and discovery of non-traditional antitumoral agents that are both efficient and safe is a key research issue, where pyrazoles and ruthenium (II) complexes have an important role. Several pyrazole-derived compounds have already demonstrated great antitumoral activity by inhibiting kinase enzymes such as aurora kinases and cyclin-dependent kinases, by inducing apoptosis and also by being cytotoxic to several cancer cell lines. Ruthenium complexes contribute to the antitumoral action by having redox properties and by being able to incorporate labile ligands that create, in vivo, active bonding sites for biomolecules.
The present work aims the synthesis of new pyrazole derivatives, following by their glycosylation and incorporation into ruthenium(II) complexes. Cytotoxicity studies will be carried out to evaluate their antitumoral effect. In addition, antioxidant activities will be studied since reactive oxygen species, chronic inflammation and cancer development are often connected. Finally, important structure-activity relationships will be established, based on the results of the biological tests, highlighting the key structural requirements needed for the activity of these compounds.
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Baugaard, Carlo. "The synthesis and electrochemical studies of chalcones and flavanones: an investigation of their antioxidant activity." Thesis, University of Western Cape, 2013. http://hdl.handle.net/11394/3312.
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>Magister Scientiae - MSc<br>Flavonoids, one of the biggest classes of secondary metabolites, are found abundantly in
nature in a broad range of fruits, vegetables and beverages such as tea, coffee, beer, wine and fruit drinks. Flavonoids have been reported to exert multiple biological functions as well as tremendous pharmacological activity, including anticancer activity, protection, antioxidant activity, cardiovascular protection, antibacterial, antifungal and antiviral activity. The antioxidant activity of flavones is reported to be associated with those bearing hydroxyl functions. In the present study, several reaction steps have been carried out to synthesize three sub classes of flavonoids namely; chalcones, dihydrochalcones and flavanones with various substituents attached. The first step involved protection of hydroxyl groups of acetophenone and benaldehyde as starting materials. Thereafter the Clasien Schmidt condensation reaction, under basic conditions, was performed to afford chalcone intermediates. Treatment of these chalcones with sodium acetate, under reflux, afforded flavanones as a single product in high yields. Thereafter all protecting groups where removed to yield the final products. All products and intermediates where purified by column chromatography and were characterized by Nuclear Magnetic Resonance Spectroscopy (NMR) (1H NMR and 13C NMR). An electrochemical analysis on all flavonoid compounds was performed by Cyclic
Voltammetry (CV) and Square Wave Voltammetry (SWV) to give information on the
accessible redox couples identified by their oxidation potentials. Oxidation potentials,
which gave valuable information about reducing ability and hence the antioxidant activity, where used to compare all compounds. The antioxidant activity was observed to increase with the addition of hydroxyl groups on the B-ring. Compounds with a combination of hydroxyl groups on the A-ring and methoxy groups on the B-ring showed increased antioxidant activity when compared to those with only hydroxyl groups on the base structure. 2, 5, 4’-trihydroxy dihydrochalcone showed moderate antioxidant ability. However the 2, 5, 4’-trihydroxychalcone, containing the α, β unsaturated double bond, proved to have the greatest antioxidant ability.
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Al, Bittar Sheiraz. "3-Deoxyanthocyanins : Chemical synthesis, structural transformations, affinity for metal ions and serum albumin, antioxidant activity." Thesis, Avignon, 2016. http://www.theses.fr/2016AVIG0264.
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Ce travail porte sur la synthèse chimique d’analogues simples d’anthocyanes, une classe majeure de pigments naturels solubles dans l’eau. Onze ions flavylium substitués par des groupements hydroxyl,méthoxyl et beta-D-glucopyranosyloxyl en positions 4’, 5 et 7 ont été préparés en utilisant des procédures simples. De plus, les deux principales 3-désoxyanthocyanidines du sorgho rouge, l’apigéninidine (APN) et la lutéolinidine (LTN), ont été synthétisées en une seule étape. Les propriétés physico-chimiques ainsi que l’activité antioxydante ont été étudiées pour le chlorure de 3’,4’,7-trihydroxyflavylium (P1), son 7-O-beta-D-glucoside (P2) et le chlorure de 3’,4’,5,7-tétrahydroxyflavylium (LTN). Grâce à leur noyau catéchol, ces pigments complexent rapidement FeIII, AlIII and CuI et ne se lient que faiblement à FeII tout en stimulant son autoxydation en FeIII. Suite à la complexation de CuII, les pigments subissent une oxydation. Les aglycones P1 et LTN sont des ligands modérés de l’albumine de sérum humain (HSA) et leurs chalcones ont montré une plus grande affinité pour la HSA que leurs formes colorées. Leur capacité antioxydante a été démontrée par le test de réduction du radical stable DPPH et par l’inhibition de la peroxydation lipidique induite par le fer héminique, un modèle de stress oxydant postprandial dans l’estomac. Les aglycones P1 et LTN (particulièrement, dans leur forme incolore chalcone) sont plus efficaces que le glucoside P2<br>This work deals with the chemical synthesis of simple analogs of anthocyanins, the main class of watersolublenatural pigments. Eleven flavylium ions with hydroxyl, methoxyl and beta-D-glucopyranosyloxylsubstituents at positions 4’, 5 and 7 have been prepared by straightforward chemical procedures.Moreover, the two main 3-deoxyanthocyanidins of red sorghum, apigeninidin (APN) and luteolinidin(LTN), have been synthesized in a one-step protocol. The physicochemical properties and antioxidantactivity are investigated for 3’,4’,7-trihydroxyflavylium chloride (P1), its 7-O-beta-D-glucoside (P2) and3’,4’,5,7-tetrahydroxyflavylium chloride (LTN). Owing to their catechol B-ring, they rapidly bind FeIII,AlIII and CuI, more weakly interact with FeII while promoting its autoxidation to FeIII. Following CuIIbinding, the pigments undergo oxidation. Aglycones P1 and LTN are moderate ligands of human serumalbumin (HSA) with chalcones having a higher affinity for HSA than the corresponding colored forms.The antioxidant activity of P1, P2 and LTN is investigated via two tests: reduction of the stable DPPHradical and inhibition of heme-induced lipid peroxidation (a model of postprandial oxidative stress inthe stomach). Aglycones P1 and LTN (especially in their colorless chalcone form) are more potent thanglucoside P2
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SERRA, ELENA. "Design, Synthesis, Characterization and Investigation of Structure-Activity Relationships on Antioxidants and/or UV Filtering Properties of New Potential Sunscreen Molecules." Doctoral thesis, Università degli studi di Ferrara, 2020. http://hdl.handle.net/11392/2487895.
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Il mio lavoro di dottorato nasce da una collaborazione tra l’Universita’ di Ferrara e il centro ricerche Aptuit, (presso Verona) avendo come tutor rispettivamente il Prof. Stefano Manfredini e il Dr. Daniele Andreotti.
I raggi UV (ultravioletto) sono responsabili della maggior parte degli effetti cutanei causati dal sole quali invecchiamento precoce, tumore della pelle, melanoma,etc. Esistone diversi strumenti per proteggersi durante l’esposizione dagli effetti dannosi di tali raggi UVA e UVB, come ad esempio l’utilizzo di cappelli, indumenti di fibre naturali, occhiali da sole, ma anche strumenti di tipo chimico come appunto l’utilizzo di filtri solari. I raggi UVB sono più energetici rispetto a quelli UVA e sono responsabili di eritemi solari e scottature. I raggi UVA hanno una maggiore lunghezza d’onda e riescono a penetrare nella pelle piu’ in profondità causando la produzione dei radicali liberi responsabili di alterazioni cellulari, sviluppo di tumori della pelle, fotoinvecchiamento, etc. Da una recente ricerca bibliografica si evince che negli ultimi anni si e’ diffuso l’approccio di incorporare nelle formulazioni solari o di includere nella dieta l’utilizzo di antiossidanti, che abbiano un effetto fotoprotettivo della cute prevenendo i danni causati dai radicali liberi (ROS, Reactin Oxygen Species), di cui i raggi UVA sono appunto la fonte. L’obiettivo del mio lavoro di ricerca e’ stato quello di sintetizzare molecule con una un’attivita dualistica, in cui la proprieta’ filtrante ad ampio spettro nei confronti dei raggi UVA-B fosse associata ad una capacita’ antiossidante. Il punto di partenza e’ stato il PBSA (acido 2-fenil-1H-benzimidazolo-5-solfonico), un filtro solare commerciale efficace contro i raggi UVB, che però non offre una protezione dai raggi UVA ed è completamente privo di attività antiossidante. Modificando isostericamente la sua struttura sono state ottenute tre differenti classi di derivati (benzo-tiazolo, imidazo-pirimidine e purine).In particolar modo la serie chimica delle purine ha richiesto un approccio sintetico completamente differente dalle altre due classi. Tutti i composti sintetizzati sono stati valutati per l’attivita’ antiossidante utilizzando come saggi il DPPH e il FRAP e per l’attivita’ filtrante ad ampio spettro utilizzando delle tecniche spettrofotometriche.
Il composto N0256-27-1, appartenente alla classe delle purine, ha mostrato un interessante profilo dal punto di vista del SPF (Fattore di Protezione Solare) e della capacita’ antiossidante.
Nella seconda parte del mio lavoro di dottorato mi sono occupata di introdurre ad un filtro commerciale ad ampio spettro, Tinosorb S, capacita’ antiossidante
Il composto N0256-39-1, appartente a questa classe di derivati. ha mostrato il miglior profilo raggiunto durante il lavoro di dottorato e verra’ caratterizzato ulteriormente per un ulteriore sviluppo.<br>This PhD thesis was elaborated under the joint supervision of Prof. Stefano Manfredini University of Ferrara, Dip. di Scienze della Vita e Biotecnologie, and Dr. Daniele Andreotti VP, Head of Medicinal Chemistry II at Aptuit, an Evotec company based in Verona, Italy.
The spectrum of ultraviolet (UV) radiation is the major component of solar radiation, and it is associated with a multitude of effects on the skin (skin cancer and many other skin diseases such as tumors and premature photo-aging). In order to provide protection from the deleterious effects of solar radiation, especially the UV component (UV A/B), various measures have been adopted since time immemorial. Besides the use of physical protective measures, such as protective clothing and shields, various medicinal preparations which provide a barrier between the sun and the skin have been in use in the form of sunscreens. Of late, a new trend has emerged wherein an antioxidant preparation is employed to supplement the body’s antioxidant defence system in order to cope with the oxidative damage induced by solar radiation. The main goals of a sunscreen are to protect against UVB radiation and long-wavelength UVA radiation, to act as a reactive oxygen species (ROS) scavenger, and consequently to prevent damage to cells and DNA. So, with this purpose in mind the aim of my project is to design and synthesize compounds with dual capabilities, that filter broadly against UV A/B radiation and display antioxidant activity. The first approach explored was to use the commercial sunscreen PBSA (2-phenyl-1H-benzimidazole-5-sulfonic acid) as starting point. PBSA provides good protection against UVB rays but lacks filtering capacity for UVA radiation and it is devoid of antioxidant activity.
Accordingly, 3 classes of derivatives, benzothiazoles, imidazopyrimidines and purines, were obtained via isosteric modification of PBSA. This last series of purine derivates required a completely different synthetic approach, which will be described in detail. Synthesized compounds were evaluated for their UV-filter and antioxidant activity. The best compound identified from the purine series was N0256-27-1, which features a high SPF and good antioxidant activity.
In the second part of my thesis I will introduce the second starting point, Tinosorb S (bis-ethylhexyloxyphenol methoxyphenyl triazine) a photo-stable broad-spectrum UV filter. Again, my interest was in developing new derivatives to get a dual acting compound: broad filter UV A/B and antioxidant. To achieve this aim I proposed different chemical modifications of Tinosorb S, based on the scientific literature. The photoprotective capacity was determined using a spectrophotometric transmittance technique, whereas 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and Ferric Reducing Antioxidant Power (FRAP) assays were performed to determine antioxidant activity. Among the Tinosorb S derivatives, compound N0256-39-1 was found to offer the desired multifunctional profile to be considered as a potential candidate for development as a sunscreen component.
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Mari, Giacomo. "Synthesis of various and interesting heterocycles included berberino derivatives." Doctoral thesis, Urbino, 2018. http://hdl.handle.net/11576/2656415.
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Jinno, Shuji. "Studies on Synthesis and Structure-Activity Relationship of Phenolic Antioxidants of Yeasts." Kyoto University, 1999. http://hdl.handle.net/2433/181405.
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Tarushi, Alketa, Chrisoula Kakoulidou, Catherine P. Raptopoulou, et al. "Zinc complexes of diflunisal: Synthesis, characterization, structure, antioxidant activity, and in vitro and in silico study of the interaction with DNA and albumins." ELSEVIER SCIENCE INC, 2017. http://hdl.handle.net/10150/623572.
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From the reaction of ZnCl2 with the non-steroidal anti-inflammatory drug diflunisal (Hdifl), complex [Zn(difl-O)(2)(MeOH)(4)], 1 was formed, while in the presence of a N,N'-donor heterocyclic ligand 2,2'-bipyridylamine (bipyam), 2,2'-bipyridine (bipy), 1,10-phenanthroline (phen) and 2,2'-dipyridylketone oxime (Hpko), the complexes [Zn(difl-O,O')(2)(bipyam)], 2, [Zn(difl-O,O')(2)(bipy)], 3, [Zn(difl-O,O')(2)(phen)], 4 and [Zn(difl-O)2(Hpko)(2)], 5 were isolated, respectively. The complexes were characterized by physicochemical and spectroscopic techniques and the crystal structures of complexes 2, 3 and 5 were determined by X-ray crystallography. The ability of the complexes to scavenge 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) and hydroxyl radicals and to inhibit soybean lipoxygenase was studied and the complexes were more active than free Hdifl. The interaction of the complexes with serum albumins was monitored by fluorescence emission spectroscopy and the corresponding binding constants were calculated. UV-vis spectroscopy, viscosity measurements and fluorescence emission spectroscopy for the competitive studies of the complexes with ethidium bromide were employed to investigate the interaction of the complexes with calf-thymus DNA and revealed intercalation as the most possible DNA-binding mode. Computational techniques were used to identify possible binding sites of albumins and DNA, and determine the druggability of human and bovine serum albumins with the five novel complexes. The majority of the complexes are stronger binders than the free Hdifl. This is the first study incorporating experimental and computational results to explore the binding activity of metal-NSAID complexes with DNA and serum albumins, suggesting their application as potential metallodrugs.
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Santos, Bruna Celeida Silva. "Síntese e modelagem molecular de análogos do metil chavicol e seus potenciais farmacológicos." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/6070.
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Previous issue date: 2017-02-24<br>Metil chavicol é um fenilpropanoide encontrado em óleos essenciais e suas atividades antimicrobiana, anti-inflamatória, anestésica local e inseticida têm sido destacadas. O objetivo deste estudo foi sintetizar e avaliar o perfil de interação molecular do metil chavicol e análogos, assim como investigar as atividades antioxidante, antilipidêmica e anti-inflamatória tópica usando métodos in vivo, in vitro e in silico. A síntese dos análogos foi realizada por reações clássicas da química orgânica. A atividade antioxidante foi determinada pelos métodos DPPH e peroxidação lipídica, enquanto o efeito antilipidêmico foi testado contra a enzima lipase pancreática. O efeito anti-inflamatório tópico foi avaliado pelo método de edema de orelha usando óleo de Cróton, fenol e histamine como agentes irritantes. Análises histopatológicas e ensaios de mieloperoxidase (MPO), N-acetil-β-D-glicosaminidase (NAG), óxido nitrico, fator necrose tumoral (TNF-α), interleucina 6 (IL-6) e ciclooxigenase in vitro foram realizados. Os ligantes foram gerados pelo Programa Marvin Sketch e refinado por método PM7 presente no Programa MOPAC2012. As enzimas foram obtidas do Protein Data Bank sob os códigos 1EQG e 5IKT (COX-1 e -2), 1R35 (iNOS) e 1LPA (lipase pancreática). O reconhecimento molecular foi definido usando o programa Discovery Studio v 4.5 2016. 2-[(4-metoxifenil)metil] oxirano (2), 3-(4-metoxifenil)propan-1,2-diol (8), 2-metoxi-3-(4 metoxifenil)propan-1-ol (10), 1-metoxi-3-(4 metoxifenil)propan-2-ol (17) e 3-(4-metoxifenil)propanal (18) foram os análogos sintetizados. Metil chavicol reduziu significativamente (p < 0,001) a espessura e a massa do edema de orelha induzido por óleo de Cróton, fenol e histamina. Houve uma redução significativa de mieloperoxidase, N-acetil-β-D-glicosaminidase, óxido nítrico, fator necrose tumoral (TNF-α) e interleucina 6 (IL-6). Metil chavicol foi incapaz de inibir COX-1 e -2 em estudo in vitro e o docking molecular mostrou ausência de interação, incluindo os análogos 2, 8, 17 e 18. Além disso, os estudos in vitro e de docking molecular revelaram que o metil chavicol e seus análogos inibiram a enzima lipase pancreática. Os resultados obtidos sugerem que o metil chavicol e seus análogos são promissores agentes terapêuticos que podem ser utilizados em doenças associadas a processos inflamatórios, oxidativos e metabólicos.<br>Methyl chavicol is a phenylpropanoid found in essential oils and its antimicrobial, anti-inflammatory, local anesthetic and insecticide activities have been highlighted. The objective of this study was to synthesize and evaluate the molecular interaction profile of the methyl chavicol and analogues, as well as to investigate the antioxidant, antilipidemic and topical anti-inflammatory activities using in vivo, in vitro and in silico methods. Synthesis of the analogues was performed by classical reactions of organic chemistry. Antioxidant activity was determined by DPPH and lipid peroxidation methods, while the antilipidemic effect was essayed against to pancreatic lipase. Anti-inflammatory activity was evaluated using Croton oil-, phenol-, and histamine-induced ear edema models in mice. Histopathological analyzes and the myeloperoxidase (MPO), N-acetyl-β-D-glucosaminidase (NAG), nitric oxide, tumor necrosis tumor (TNF-α), interleukin 6 (IL-6) and cyclooxygenase assays were determined. The bindings were generated by the Marvin Sketch Program and refined by PM7 method present in the MOPAC2012 Program. Enzymes were obtained from protein database under 1EQG and 5IKT (COX-1 and -2), 1R35 (iNOS) and 1LPA (pancreatic lipase) codes. Molecular recognition was determined using the program Discovery Studio v 4.5 2016. 2 - [(4-methoxyphenyl) methyl] oxirane (2), 3-(4-methoxyphenyl) propane-1,2-diol (8), 2- Methoxy-3-(4-methoxyphenyl) propan-1-ol), 1-methoxy-3-(4-methoxyphenyl) propan-2-ol (17) and 3-(4-methoxyphenyl) propanal (18) were the synthesized analogues. Methyl chavicol significantly decreased the thickness and mass of ear edema induced by irritants (p < 0.001). A significant reduction on myeloperoxidase, N-acetyl-β-D-glucosaminidase, nitric oxide, tumor necrosis tumor (TNF-α) and interleukin 6 (IL-6) was revealed (p < 0.05, p < 0.01 or p < 0.001). Methyl chavicol was unable to inhibit COX-1 and-2 in in vitro test and the molecular docking showed no interaction, including the analogues 2, 8, 17 and 18. In addition, molecular docking showed an inhibitory effect of the methyl chavicol and its analogues on the pancreatic lipase. The results indicate that methyl chavicol and its analogues are promising therapeutic agents that can be used in diseases associated with inflammatory, oxidative and metabolic processes.
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Brizzolari, A. "BIOLOGICAL ACTIVITY OF SOME NATURAL AND SYNTHETIC N6-SUBSTITUTED ADENOSINE DERIVATIVES (CYTOKININ RIBOSIDES)." Doctoral thesis, Università degli Studi di Milano, 2015. http://hdl.handle.net/2434/337370.
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In this Ph.D project, some natural N6 – substituted adenosine derivatives, cytokinin ribosides (CKRs) have been investigated with the aim to draw a profile of their biological activity. CKRs belong to a class of plant hormones playing various roles in many aspects of plant development. We chose the most representative among natural cytokinin ribosides, namely N6 – isopentenyl adenosine (iPAdo), kinetin riboside (KR), N6-benzyl adenosine (BA) and its hydroxylated derivative, ρ- topolin riboside (p-TR).
In the first part of the thesis, the platelet anti aggregation activity CKRs has been evaluated in vitro as inhibitors of platelet aggregation. The activity has been interpreted by in silico docking experiments as due to interaction of CKRs with P2Y12 receptor. ρ -Topolin riboside showed the best platelet anti aggregation activity and in silico interaction with P2Y12 receptor, followed by N6 – benzyladenosine.
Some synthetic N6 – substituted adenosine derivatives have been synthesized and investigated as antagonists toward the human adenosine receptors A1, A2A, A2B, A3. p-TR again was the best antagonist of A2A and A2B adenosine receptors, both involved in the platelet aggregation mechanism. Synthetic N6 – substituted adenosine derivatives were antagonists of A3 adenosine receptor much stronger than natural CKRs.
In a structure-activity study, the cytotoxic activity of natural CKRs and the synthetic analogues of p-TR were evaluated on 661W and Neuro2A cell lines trough Trypan blue and Tunel assays. Synthetic N6 – substituted adenosine derivatives showed a cytotoxic activity stronger than p-TR itself, that, in turn, exhibited the best apoptotic property.
Many biological activities shown by the CKRs examined in this thesis could be related to an effect of these compounds on the cellular oxidative stress. Thus, as a part of the PhD project, the antioxidant profile of natural and synthetic CKRs has been investigated using the most common antioxidant tests in vitro. The heterogeneity of the results suggests in some instance a possible structure – activity relationship. However, since not all the compounds are active in every antioxidant assay, further characterization of the antioxidant profile of CKRs seems desirable, including suitable cellular assays.
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Arts, Mariken J. T. J. "Assessing antioxidant activity." [Maastricht : Maastricht : Universiteit Maastricht] ; University Library, Universiteit Maastricht [host], 2007. http://arno.unimaas.nl/show.cgi?fid=8676.
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O'Reilly, James Daniel. "Antioxidant activity of dietary flavonoids." Thesis, King's College London (University of London), 1999. https://kclpure.kcl.ac.uk/portal/en/theses/antioxidant-activity-of-dietary-flavonoids(10c771a4-169d-405b-a1cd-354e86ebd109).html.
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James, Leanne. "Manganese complexes with biomimetic antioxidant activity." Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/7073.
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Several seven-coordinate manganese complexes have been synthesised, characterised and tested for both superoxide dismutase and catalase activity. Macrocyclic ring contractions have led to a series of new seven coordinate mononuclear manganese(II) macrocycles that have potential for their use as working superoxide dismutase mimics. Numerous polynuclear seven coordinate manganese(II) macrocycles have been synthesised via Schiff base condensation. Subsequent reduction of the imine bonds has led to a variety of reduced amine analogues with varying axial ligands. The geometry has been compared about the manganese centres where possible. From the results of each complex tested for superoxide dismutase activity, the µ-chloro bridged tetranuclear complex [Mn2(C24H29N6O2)(Cl)2]2(ClO4)2 has proved to be the most efficient mimic with a calculated KMcCF value of 7.7 x 106 [M-1 s-1]. A method for measuring catalase activity has been developed, and the most efficient catalase active compound was found to be [Mn5(C24H29N6O2)2(OAc)2(ClO4)2](ClO4)2 with one molecule of complex breaking down approximately 59000 molecules of hydrogen peroxide after one minute. Catalase testing showed that a reduction of the imine bonds produced an increase in activity overall for the complexes of H2L1 (C24H29N6O2), but a decrease was observed for the reduced tripodal complexes. An increase in the number of manganese centres resulted in a rise in catalase activity. Many of the complexes tested for catalase activity showed an induction period prior to the activity being observed. This may suggest that the complexes undergo a change in structure, or that there is a rearrangement occurring before catalase activity may be observed. The results that are presented indicate that the axial ligands have an effect on the rate of catalase activity and the observed induction period. Of the molecules that were tested for both superoxide dismutase and catalase activity, the pentanuclear complex [Mn5(C24H29N6O2)2(OAc)2(ClO4)2](ClO4)2 showed high activity for both analyses. This may be due to the extra manganese centre within the complex and the axial ligands that are present when compared with other tetranuclear complexes. The complex [Mn5(HL1)(OAc)2(ClO4)2](ClO4)2 may prove to be a good candidate for a working superoxide dismutase mimic. Ring contracted complexes show high rates of superoxide dismutase activity but possess limited catalase activity. Attempts have been made to produce a direct method of measuring superoxide dismutase activity using a stop-flow technique to complement the results using the indirect NBT (Nitro blue Tetrazoleum) method. This was carried out by analysing low concentration solutions of both complex and superoxide on a millisecond timescale. Progress has been made for this method with preliminary results being obtained.
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Williamson, E. "The antioxidant activity of #DELTA#'5-avenasterol." Thesis, University of Reading, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233864.
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Branco, Diana Patrícia Rodrigues. "Metallothionein functions: metal chelation and antioxidant activity." Master's thesis, Universidade de Aveiro, 2011. http://hdl.handle.net/10773/7317.
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Mestrado em Biologia Aplicada - Biologia Molecular Celular<br>It is generally accepted that the principal roles of metallothioneins (MTs) lie in the detoxification of toxic metals and regulation of the metabolism of essential trace metals. However, there is increasing evidence that it can act as a free radical scavenger. Although the great number of studies on the antioxidant activity of MTs, the effective physiological role of this protein is still unclear. In order to understand the role of MTs in the protection against metal contamination and oxidative stress, the bivalve Cerastoderma edule was used to evaluate the response of MTs in both situations. Cadmium, a widely reported MT inducer, was used to simulate metal contamination whereas H2O2, an oxidizing compound, was used to simulate oxidative stress. In the first approach, cockles were exposed to a range of Cd and H2O2 concentrations and MTs and TBARS were quantified. Results showed that both treatments induced MT synthesis, confirming the involvement of MTs in metal contamination and oxidative stress. Indeed, the use of MTs as biomarkers for metal pollution was questioned due to the similar synthesis of MT in the two highest concentration used. At last, one concentration of Cd (10 μM) and of H2O2 (20 μM) were selected and cockles were exposed again. TBARS concentration and the intracellular amount of H2O2 were determined. Metal-MT complexes in the two conditions and control were isolated by size exclusion chromatography, and the binding of Zn and Cd to MTs and other cytosolic proteins was evaluated. Furthermore, MTs were quantified and their content in each treatment and control was compared to the amount of Zn associated to them. Results showed that the >H2O2 treatment induced high levels of oxidative stress, demonstrated by the high lipid peroxidation and intracellular concentration of H2O2. Data also indicated that Cd was mainly associated with MTs pool in the Cd treatment, confirming that the protective role of MTs in metal contamination in this bivalve species was due to the binding of MTs to Cd ions. Additionally, the percentage of Zn bound to MTs decreased in the H2O2 treatment, indicating Zn release in oxidative stress. Also, MTs molecules were not as metalated as in the control, confirming Zn release from MTs in oxidative stress and indicating that MTs were needed for demands other than Zn distribution. Further studies on the redox status of MTs are needed to determine the redox status of MTs in the oxidative stress, and understand if, in this bivalve, MTs are acting as ROS scavengers.<br>Os papéis geralmente associados às metalotioninas (MTs) resumem-se á desintoxicação de metais tóxicos e à regulação do metabolismo dos metais essenciais. No entanto, existem evidências cada vez mais acentuadas de que as MTs atuam na proteção contra o stresse oxidativo. Apesar do grande número de estudos que se focam na actividade antioxidante das MTs, o papel fisiológico efetivo destas proteínas não foi ainda clarificado. A fim de compreender o papel das MTs no stress oxidativo e na proteção contra o efeito dos metais, o bivalve Cerastoderma edule foi selecionado neste estudo para avaliar a resposta das MTs em ambas as situações. O cádmio, um forte indutor das MTs foi usado para causar contaminação metálica enquanto o H2O2, sendo um composto oxidante, foi usado para provocar stresse oxidativo. Numa primeira abordagem, os berbigões foram expostos a uma gama de concentrações de Cd e H2O2 e as MTs e os TBARS foram quantificados. Os resultados mostraram que apenas o H2O2 provocou peroxidação lipídica no berbigão e que ambos os tratamentos induziram a síntese de MTs, confirmando o envolvimento destas na contaminação metálica e no stresse oxidativo. De facto, a utilização das MTs como biomarcadores de poluição metálica foi neste estudo questionada devido á síntese de quantidades semelhantes de MTs nas duas concentrações mais elevadas de Cd e H2O2. Numa segunda abordagem, os berbigões foram novamente expostos a uma concentração selecionada para cada tratamento (10 μM de Cd e 20 μM de H2O2). A concentração dos TBARS e a quantidade intracelular de H2O2 foram determinados. Os complexos metal-MT em ambas as condições e no controlo foram isolados por cromatografia de exclusão molecular e a ligação entre os iões de Zn e Cd e as MTs e outras proteínas citosólicas foi avaliada. Para além disso, As MTs foram quantificadas em cada tratamento e no controlo, sendo o seu conteúdo comparado com a quantidade de Zn ligado. Os dados indicaram que o tratamento com H2O2 induziu elevados níveis de stresse oxidativo, demonstrado pela elevada peroxidação lipídica e pela grande concentração intracelular de H2O2. Relativamente aos resultados da cromatografia, os iões de Cd estavam principalmente ligados às MTs no tratamento com Cd, confirmando o efeito protector das MTs na contaminação metálica nesta espécie de bivalve. Adicionalmente, a percentagem de Zn ligado às MTs diminuiu no tratamento com H2O2, indicando que o stresse oxidativo impõe a libertação de Zn por parte das MTs. Em jeito de confirmação, as MTs estavam menos metaladas no tratamento com H2O2 do que no controlo. Seriam necessários estudos complementares para perceber se neste bivalve as MTs actuam como eliminadoras de ROS.
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Keceli, Turkan. "Antioxidant and antimicrobial activity of olive oil phenolics." Thesis, University of Reading, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.325073.
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Quartley, Benjamin J. P. "The antioxidant activity of green tea in vivo." Thesis, University of Surrey, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308646.
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Mohamed, Amal. "Antioxidant activity of flaxseed proteins and their hydrolysates." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=119689.
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Certain components of flaxseed are known to exhibit antioxidant activity. The objective of this research was to study the antioxidant activity of flaxseed proteins and protein hydrolysates. Proteins and their hydrolysates were prepared from defatted, non-defatted, and demucilaged flaxseed with and without dialysis, and the antioxidant activities were examined by DPPH scavenging assay, reducing power assay, and metal ion chelating assay. The degree of hydrolysis (DH) of the proteins using bacterial protease was higher than using trypsin. Using bacterial protease, higher DH was observed for demucilaged and defatted flaxseed protein/dialysis (DDFPD, 30% DH), defatted flaxseed protein/dialysis (DFPD, 28% DH), and non-defatted flaxseed proteins/dialysis with 14% DH, compared to flaxseed protein/non-dialysis which were DDFPND 28% DH, DFPND 25% DH, and NDFPND with 12% DH. Proteins from dialysis treatment as well as their hydrolysates showed positive effect on antioxidant activity. DDFPD hydrolysates using bacterial protease showed higher DPPH radical scavenging activity (73.23%) and reducing power activity (0.15) at the concentration of 2.5 mg/ml as well as Fe2+ chelating ability (75%) at of concentration 1 mg/ml. SDS-PAGE and native-PAGE results of non-hydrolyzed samples showed no change in electrophoretic behavior as a result of the treatments; a major band corresponding to MW 48 KDa and three minor bands with MW of 16, 23, and 34 KDa. SDS-PAGE of DDFPNDH and NDFPNDH hydrolysates obtained using trypsin showed one resistant band.<br>Certaines composantes des graines de lin sont reconnues pour avoir des effets antioxydants. L'objectif du projet de recherche ci-présent est d'étudier les effets antioxydants des protéines des graines de lin et de leurs hydrolysâtes. Les protéines et leurs hydrolysâtes ont été préparé à partir de graines de lin dégraissées ou natures et démucilaginées, avec et sans dialyse. Leurs effets antioxydants ont été examinés avec le test de scannage DPPH, le test du pouvoir de réduction, et le test des ions métalliques chélates. Le degré d'hydrolyse (DH) des protéines était plus élevé avec l'utilisation d'une protéase bactériale qu'avec l'utilisation de trypsine. En utilisant la protéase bactériale, un DH plus élevé a été observé avec les graines démucilaginées et dégraissées avec dialyse/protéine (DDFPD, 30% DH), les graines dégraissées avec dialyse/protéine (DFPD, 28% DH), et les graines nature avec dialyse/protéines (14% DH), comparé aux graines protéine/sans dialyse qui ont eu comme résultat DDFPND 28%, DFPND 25% DH, et NDFPND avec 12% DH. Les protéines et leurs hydrolysâtes du traitement avec dialyse ont montré qu'il y avait bel et bien un effet antioxydant. Les hydrolysâtes, du test DDFPD et de l'utilisation du protéase bactériale, ont montré un niveau d'activité de radicaux libres plus élevé (DPPH 73.23%) ainsi qu'un pouvoir de réduction de (0.15) à une concentration de 2.5 mg/ml, de même qu'une habilité au Fe2+ de 75% à la concentration de 1mg/ml. Les résultats de SDS-PAGE et PAGE-original des échantillons non hydrolysés montrent qu'il n'y a aucun changement dans le comportement électrophorétique résultant du traitement: une bande majeure qui correspond au MW 48 KDa et trois bandes mineures avec un MW de 16, 23, et 34 KDa. Dans les échantillons d'hydrolysâtes SDS-PAGE du DDFPNDH et les hydrolysâtes du NDFPNDH obtenus en utilisant la trypsine ont montré une bande résistante.
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Johnson, Michelle E., W. Andrew Clark, S. E. Dahlman, W. D. Elrod, and C. M. Stanage. "Betalain in Beets Enhance Antioxidant Activity in Hummus." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/etsu-works/2515.
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Liu, Zheng-Xian. "Antioxidant activity of Mn-salophen complex and its effects on antioxidant enzymes in Escherichia coli." Diss., Virginia Tech, 1994. http://hdl.handle.net/10919/40046.
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Mn-salophen complex with superoxide-scavenging activity was prepared from manganese(III) acetate dihydrate and salophen in ethanol. Visible absorption spectrum of the red-brown solution exhibited a broad absorption band at 430 - 450 nm with two shoulders between 500 and 600 nm which were absent with either salophen or manganic acetate alone. Titration of salophen with manganese(III) was consistent with a 1:1 Mn to salophen stoichiometry of the complex based on changes in the absorbance at 500 nm or of superoxide scavenging activity. The SOD-like activity of the complex in the xanthine-xanthine oxidase/cytochrome <i>c</i> assay was 1450 units/mg salophen. The SOD activity of the complex was suppressed 50% in the presence of EDTA (1 mM), but was not altered in the presence of bovine serum albumin (1 mg/ml) or crude protein extract of <i>E. coli</i> QC779 <i>sodA sodB</i> (1 mg/ml). <i>E. coli</i> QC779 <i>sodA sodB</i> grew scantily after an 8 hour lag phase in aerobic M63 glucose minimal medium.<br>Ph. D.
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Niero, Giovanni. "Development of analytical methods for phenotypic characterization of antioxidant compounds and antioxidant activity of milk." Doctoral thesis, Università degli studi di Padova, 2017. http://hdl.handle.net/11577/3427152.
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Free radicals are unstable and reactive molecules, with one ore more unpaired electrons in the outer orbit and adverse effects on plant, animal, and human cells. In particular free radicals are responsible of lipids peroxidation, proteins oxidative damages, and DNA cleavage, resulting in increased risk of mutation. Antioxidants represent an important defence against these injuries. Vegetable derived foods are known as important sources of dietary antioxidants such as phenols, anthocyanin, tocopherols, tocotrienols, carotenoids, retinol precursors, and ascorbate.
With this background, the aims of this Ph.D. project were: i) to develop and validate analytical methods for quantification of tocopherols, thiols, and total antioxidant activity (TAA) of milk; ii) to describe the phenotypic variation of thiols in milk of dairy and dual-purpose cow breeds; iii) to describe the phenotypic variation of TAA in milk of cow, buffalo, goat, and sheep; iv) to evaluate the feasibility of mid infrared spectroscopy to predict TAA of cow milk; v) to evaluate the effect of skimming and heat treatments on milk tocopherols and TAA.
In the 1st Chapter, a simplified saponification protocol, followed by cheap HPLC method based on methanol elution and sensible fluorescence detection was developed and validated for the quantification of α-tocopherol and γ-tocopherol, in different types of commercial fluid milk. Chromatograms showed two analytical peaks, corresponding to α-T and γ-T. The method was able to detect the adverse effects of skimming and UHT treatment on α-T and γ-T concentrations. The proposed method could be usefully adopted in future for large scale studies, aiming to investigate phenotypic variation of tocopherols in milk.
The 2nd Chapter represent a first contribution to the characterization of low molecular weight thiols in milk of different cattle breeds. Thiols were extracted from the soluble fraction of milk, and following a derivatization protocol they were separated by reverse phase HPLC and detected fluorimetrically. Six thiol species were detected and two of them, glutathione (GSH) and cysteine-glycine (Cys-Gly), were identified and quantified. The average concentration of Cys-Gly in milk was greater than that of GSH, and milk from dual-purpose breeds was richer in thiols than milk from dairy cows.
The 3rd Chapter deals with the development and the validation of a robust and fast spectrophotometric method for the determination of TAA of different types of milk. The method was linear, and highly repeatable and reproducible. Preservative added on raw milk had negligible effects on TAA measurement. The greatest TAA was measured on skimmed pasteurised milk, followed by skimmed UHT milk, raw milk, whole pasteurised milk, and whole UHT milk.
The 4th Chapter is the first contribution to the phenotypic characterization of TAA of bovine milk. This phenotype exhibited an exploitable variability, similar to that of other quality traits. Favourable phenotypic correlations of TAA with fat, protein, and casein percentages were observed, as well as with somatic cell score. Total antioxidant activity of milk increased across lactation. Mid-infrared prediction models developed to predict milk TAA were not enough accurate for analytical purposes.
The 5th Chapter deals with the phenotypic characterization of TAA of buffalo, goat, and sheep milk. Sheep milk showed the greatest TAA. This is probably due to its relatively high content in fat, protein, and casein percentages, that are known as compounds contributing to milk antioxidant capacity. Accordingly, buffalo and goat milk had lower TAA as well as lower fat, protein and casein percentages. Milk TAA was unfavourably correlated with milk yield, but the relationship was significant only for buffalo, whereas protein and casein percentages were positively correlated with TAA of goat milk.<br>I radicali liberi sono molecole reattive e instabili, con uno o più elettroni spaiati nell'orbitale esterno, con possibili effetti negative a livello di cellule vegetali e animali. In particolare, i radicali liberi sono responsabili della perossidazione dei lipidi, dell'ossidazione delle proteine e del danneggiamento del DNS, che causa un aumento del rischio di mutazioni. Gli antiossidanti rappresentano un'importante difesa contro questi danni. Gli alimenti di origine vegetale sono noti come risorse primarie di antiossidanti, come i fenoli, gli antociani, i tocoferoli, i carotenoidi, i precursori del retinolo e l'ascorbato.
In questo contesto, gli scopi della presente tesi di dottorato sono: i) lo sviluppo e la validazione di metodi analitici per la quantificazione dei tocoferoli, dei tioli e della capacità antiossidante totale nel latte; ii) la descrizione della variazione fenotipica dei tioli in vacche da latte e a duplice attitudine; iii) la descrizione della variabilità della capacità antiossidante totale (TAA) nel latte di vacca, di bufala, pecora e capra; iv) la valutazione della capacità del medio infrarosso nella predizione della TAA del latte vaccino; v) la valutazione dell'effetto della scrematura e del trattamento al calore sulla concentrazione in tocoferoli e sulla TAA.
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Singh, Prabhjot. "Antioxidant activity of food proteins and food protein hydrolysates." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=104895.
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The objective of this research was to study the antioxidant activity of soybean protein hydrolysates (SPH) and chickpea protein hydrolysates (CPH) at different concentrations, and to measure the antioxidant activity of fractions collected from the RP-HPLC analysis of SPH and CPH. Protein hydrolysates were prepared by the proteolytic enzyme trypsin. The hydrolysates obtained were subjected to DPPH (1, 1-diphenyl-2 picrylhydrazyl) radical scavenging assay. The SPH and CPH at concentration of 2.5-10 mg/ml showed antioxidant activity of 16.5-32 % and 3.4-26.8 %. SPH and CPH were fractionated by using RP-HPLC on C18 column. The antioxidant activity of four SPH and CPH fractions (F I, F II, F III, and F IV) was measured by using DPPH radical scavenging assay. For SPH, antioxidant activity of F III (47.7 %) was higher than other fractions at protein concentration of 1 mg/mL and for CPH; F II showed maximum antioxidant activity 27.9 % at protein concentration 1 mg/mL. The results from the SDS-PAGE confirmed the hydrolysis of protein samples. The second part of the study was to measure the impact of high pressure processing (HPP) on the degree of hydrolysis and antioxidant activity of proteins. High pressure processing (HPP) of isolated soybean protein (ISP) and isolated chickpea protein (ICP) was done at 400 MPa and 600 MPa for 5 min and 10 min. The degree of hydrolysis of isolated soybean protein and isolated chickpea protein treated with high pressure processing and with trypsin hydrolysis showed continuous increase from 12.4 to 24.9 % for SPH and 13.6 to 26.2 % for CPH. The DPPH radical scavenging assay showed a more than two fold increase in antioxidant activity of SPH and CPH: 67 % as compared to the 32 % of SPH without HPP and 56.6 % as compared to the 26.8 % of CPH without HPP at concentration 10 mg/mL. These results show that HPP increased the degree of hydrolysis and antioxidant activity of protein hydrolysates.<br>Le but principal de cette recherche constituait l'analyse du potentiel antioxydant, à diverses concentrations, d'hydrolysats de protéine de soya (HPS) et d'hydrolysats de protéine de pois chiche (HPP). Les hydrolysats de protéine ont été isolés à l'aide de l'enzyme protéolytique trypsine. Les HPS et HPP démontraient respectivement un potentiel antioxydant de 16.5 à 32% et 3.4 à 26.8 % lorsque présents à des concentrations de 2.5 à 10 mg/mL. L'utilisation d'une colonne C18 a permis de séparer, par CLHP-PI, les HPS et HPP en quatre fractions (F I, F II, F III, et F IV) qui furent dosées avec du DPPH (1,1-diphényl-2-picrylhydrazyle) afin de comparer leur pouvoir de scavenging sur les radicaux. Pour les HPS, le potentiel antioxydant de F III (47.7 %) était supérieur à celui des autres échantillons alors que pour les HPP, 27.9 % (F II) était le seuil maximal. Dans les deux cas, les hydrolysats étaient concentrés à 1mg/mL. L'hydrolyse des échantillons de protéine a été confirmée par SDS-page. La deuxième partie de l'étude visait à mesurer l'impact de la pascalisation sur le degré d'hydrolyse et le potentiel antioxydant des protéines. Des isolats de protéine de soya (IPS) et de protéine de pois chiche (IPP) ont été traités à haute pression (400 MPa et 600 MPa) pendant 5 et 10 min. Le degré d'hydrolyse des IPS et IPP soumis à la pascalisation et à la trypsin ont démontré une augmentation constante allant de 12.4 à 24.9 % pour les isolats de protéine de soya et de 13.6 à 26.2 % pour les isolats de protéine de pois chiche. L'analyse au DPPH du pouvoir d'épuration des radicaux a montré que le potentiel antioxydant des hydrolysats a plus que doublé, passant de 32 à 67 % pour les HPS et de 26.8 à 56.6 % pour les HPP, lorsqu'ils étaient traités par hautes pressions. Cela démontre que la pascalisation améliore le degré d'hydrolyse et le potentiel antioxydant des hydrolysats de protéines.
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Juan-Badaturuge, Malindra. "Antioxidant activity and phytochemical evaluations of selected medicinal plants." Thesis, University of Greenwich, 2010. http://gala.gre.ac.uk/8098/.
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The methanolic crude extract of aerial parts of the plant Scrophularia nodosa was shown to have potent DPPH radical scavenging activity (IC50 = 48.75 ± 7.00 μg/ml). Activity-guided fractionation resulted in the isolation of three principal antioxidant compounds; acteoside, angoroside C and angoroside A. Acteoside (yield = 1.21%, IC50 = 15.2 μM) appeared to be the most abundant and most antioxidant-active. The potent antioxidant activity is in support of the traditional use of the plant for wound healing and anti-inflammatory conditions. The methanolic extract of aerial parts of Tanacetum vulgare has potent DPPH radical scavenging activity (IC50 = 37.00 ± 1.20 μg/ml). Activity-guided fractionation on the methanolic extract of T. vulgare resulted in the isolation of 3,5-di-caffeoylquinic acid (3,5-DCQA), axillarin and luteolin. 3,5-DCQA appeared to be the most abundant and most antioxidant-active compound (yield = 7.28%, IC50 = 9.7 μM). The potent antioxidant activity is in support of the traditional use of the herb for fever, rheumatic conditions and anti-inflammatory conditions. The methanolic crude extract of Cassia auriculata and its fractions were shown to have potent scavenging activity on DPPH, hydroxyl and hydroperoxide radicals, moderate superoxide radical scavenging activity and potent ion(III) reducing power. The activity-directed studies resulted in the isolation of kaempferol-3-0-β-D-rutinoside, kaempferol, luteolin, quercetin and unknown antioxidant inactive compound. The previously reported pharmacological aspects of the above flavonoids and flavonoid glycosides (anti-carcinogenic, anti-inflammatory, hyperglycaemic, antidiabetic) along with the shown antioxidant behaviour explain the traditional medicinal values of the plant. Cassia alata L crude extract and its fractions showed potent radical scavenging activity against formation of lipid peroxide radicals. The activity directed isolations resulted in the isolation of kaempferol along with p-hydroxybenzoic acid. These may contribute towards the traditional medicinal values of the plant as an antidiabetic, anti-microbial and for skin diseases.
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Tsang, Catherine. "Antioxidant activity, protective effects and absorption of polyphenolic compounds." Thesis, University of Glasgow, 2004. http://theses.gla.ac.uk/1560/.
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The objectives of the studies presented in this thesis were to identify and quantify the major phenolic components of red wine and to assess the contribution of individual compounds to the total antioxidant activity. Red wines were analysed for their phenolic content and antioxidant activity using a range of complementary techniques including HPLC-tandem mass spectrometry, preparative HPLC and HPLC with an on-line antioxidant detection system. HPLC-MS2 revealed the presence of a number of flavoids and phenolic compounds of which 19 were identified, with gallic acid, the flavin-3-ols and anthocyanins being the most abundant. Preparative HPLC was used in an effort to isolate the antioxidant components in red wine and 60 aliquots were collected. Each wine fraction was analysed for total phenolics, catechins and anthocyanins, while antioxidant activity was determined by electron spin resonance spectroscopy (ESR). The preparative HPLC step did into completely separate the compounds in red wine, nonetheless increasing antioxidant activity was highly and significantly associated with total phenolics (r = 0.816, P < 0.001) and total catechins (r = 0.188, p = 0.151). HPLC with an on-line antioxidant detection system was subsequently used to separate and identify red wine phenolics. The findings from this study indicate that gallic acid, (+)-catechin, (-)-epicatechin, and procyanidin dimersB1 and B2 were the major in vitro antioxidants identified in red wine. Collectively, the flavin-3-ols contributed > 50% of the total antioxidant capacity of each wine, while gallic acid contributed between 24-44%. The flavonols and anthocyanins were minor antioxidant components in red wines. By combining HPLC, MS2 and on-line assessment of antioxidant activity, the major phenolic compounds present in red wine were identified, together with their direct contribution to the total antioxidant activity.
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Kasase, Chitundu. "Antihypertensive and antioxidant activity of peptides derived from fish." Thesis, University of Surrey, 2009. http://epubs.surrey.ac.uk/844585/.
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Peptides derived from food proteins after enzymatic treatment and/or processing, are known to be bioactive in both biological and food systems; for this reason fish muscle peptides were investigated for their antihypertensive and antioxidant activity. Atlantic mackerel muscle proteins were hydrolysed with pepsin and pancreatine and the resultant hydrolysate was sequentially fractionated on 2 kDa membrane ultrafilters and further by gel filtration, ion exchange and high performance liquid chromatography and the resultant peptide fraction contained the amino acids histidine, proline, tyrosine, methionine, leucine, tryptophan and lysine. For ACE inhibitory activity, the peptide fraction (MFPH-V-JPA) had an inhibitory concentration (IC50) of 0.15 mg/ml and showed competitive inhibition for ACE with an inhibition constant (Ki) of 0.32 mg/ml. In terms of antioxidant activity, the HPLC isolated peptide fraction (LC1-Z) contained the amino acids serine, histidine, tyrosine, phenylalanine, tryptophan and lysine. It inhibited the formation of both peroxides and malonaldehyde in a linoleic acid model emulsion in a dose dependent manner with lipid oxidation inhibitory concentration (IC50) of 1.80 mg/ml. At concentration of 8 mg/ml, the inhibition of linoleic acid oxidation was more than that of 0.01 % butylated hydroxytoluene (BHT) and trolox (p < 0.001). The mechanism of antioxidant activity of the peptide (LC1-Z) was by carbon centered radical scavenging (5.34 %), hydroxyly radical scavenging (IC50 value of 1.60 mg/ml), metal chelating (5.72 %) and reducing ability. In caco-2 cells, 1 mg/ml of the peptide (LC1-Z) was not toxic to the cells seeded at 2 x 104 cells/well. Proxidant tBHP (2.5 mM) reduced cell viability significantly (79.3 %) but this increased to 94.7 % in the presence of the peptide or trolox. The peptide (1 mg/ml) also reduced TBARS formation (33.18 mug/ml) in cells compared to cells treated with tBHP alone (38.18 mug/ml). The activity of caspases-3 and -7, was higher in caco-2 cells treated with tBHP only (157.5 +/- 7.99 %) compared with those treated with the peptide (25.7 + 3.92 %). Morphological modification of the caco-2 cells treated with tBHP was evident as the cells appeared detached from the flask surface compared to those treated with the peptide (LC1-Z) which were healthy and attached to the flask surface. In Ea.hy 926 cells, reactive oxygen species were reduced by 26 % and 39 % in the lucigenin-chemiluminscence and flourescence methods respectively in cells treated with the peptide. In a caco-2 cell monolayer, transepithelial transport of the peptide was observed in both directions with a basolateral to apical apparent permeability of 0.95 +/- 0.12 cm-1 and apical to basolateral flux of 0.74 + 0.20 cm-1. HPLC chromatograms of the buffer solution taken from the apical and basolateral side showed the presence of the peptide in both sides i.e. 11.5% for apical to basolateral flux and 12.2 % for basolateral to apical. These results demonstrate that peptides with antihypertensive and antioxidant activity can be derived from Atlantic mackerel muscle proteins, with potential for neutraceutical applications.
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Rosales, Soto Maria U. "Phenolics, anthocyanins and antioxidant activity in red raspberry muffins." Pullman, Wash. : Washington State University, 2008. http://www.dissertations.wsu.edu/Thesis/Fall2008/M_Rosales_082708.pdf.
Full textAbstract:
Thesis (M.S. in food science)--Washington State University, December 2008.<br>Title from PDF title page (viewed on Dec. 31, 2008). "School of Food Science and Human Nutrition." Includes bibliographical references.
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Wattamwar, Paritosh P. "SYNTHESIS AND CHARACTERIZATION OF POLYMERIC ANTIOXIDANT DELIVERY SYSTEMS." UKnowledge, 2011. http://uknowledge.uky.edu/cme_etds/2.
Full textAbstract:
Even though the role of oxidative stress in a variety of disease states is known, strategies to alleviate this oxidative stress by antioxidants have not been able to achieve clinical success. Particularly, treatment of oxidative stress by small molecule antioxidants has not received due attention because of the challenges associated with its delivery. Antioxidant polymers, where small molecule antioxidants are incorporated into the polymer backbone, are an emerging class of materials that can address some of these challenges.
In this work, biodegradable polymers incorporating phenolic antioxidants in the polymer backbone were synthesized. Antioxidant polymers were then characterized for their in vitro degradation, antioxidant release and their effect on oxidative stress levels (redox state) in the cells. Trolox, a water-soluble analogue of vitamin E, was polymerized to synthesize poly(trolox ester) with 100% antioxidant content which undergoes biodegradation to release trolox. Nanoparticles of poly(trolox ester) were able to suppress oxidative stress injury induced by metal nanoparticles in an in vitro cell injury model.
In another study, we polymerized polyphenolic antioxidants (e.g. curcumin, quercetin) using a modified non-free-radical polymerization poly(β-amino ester) chemistry. This synthesis scheme can be extended to all polyphenolic antioxidants and allows tuning of polymer degradation rate by choosing appropriate co-monomers from a large library of monomers available for β-amino ester chemistry. Poly(antioxidant β-amino esters) (PABAE) were synthesized and characterized for their degradation, cytotoxicity and antioxidant activity. PABAE degradation products suppressed oxidative stress levels in the cells confirming antioxidant activity of degradation products.
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Mothapo, Mmaphefo Patricia. "Comparative evaluation of three fundamentally different analytical methods antioxidant activity determination with reference to bush tea (anthrixia phylicoides." Thesis, University of Limpopo, 2016. http://hdl.handle.net/10386/1517.
Full textAbstract:
Thesis (M.Sc. (Chemistry)) -- University of Limpopo, 2016<br>In this study, antioxidant activity methodologies were evaluated in terms of analytical performances. The total antioxidant activity from Athrixia phylicoides leaves (Bush tea) determined using 2,2-diphenyl-1-picrylhydrazyl radical scavenging (DPPH•) method, cupric ion reducing power (CUPRAC) method and cyclic voltammetry (CV). Folin-Ciocalteu method was used to quantify total phenolic content (TPC) in Athrixia phylicoides leaves. The influence of chemical and physical parameters on the total phenolic content and antioxidant activity determination were investigated. Results from direct sample and crude sample were compared. Antioxidant activity and phenolic content from Athrixia phylicoides leaves were compared with those from commercialised green tea, black tea and rooibos tea using two chosen antioxidant capacity method with acceptable characteristics.
Results from the evaluation of the methods demonstrated excellent recoveries (99 to 103%) consistently, good linearity within the calibration concentration range (R2 = 0.997) and repeatable low coefficient of variation < 5% were indicative of good precision except for CV method. The average total antioxidant activity of various extracts of Athrixia phylicoides leaves ranged from 0.039 to 0.122 mg/mL (EC50), 0.031 to 0.233 mg/mL (EC50) and 339 to 429 mV (anodic potential) for DPPH method, CUPRAC method and CV method, respectively. The total antioxidant activity values for each Athrixia phylicoides samples determined by CUPRAC method were higher than the values produced by DPPH and CV methods.
The highest antioxidant activities in the DPPH and CUPRAC methods were found in water extracts (direct sample). However, concentrated samples for DPPH method and CV gave a different trend with the methanol extract (crude sample) displaying the highest antioxidant capacity. Increasing the infusion time only increased total antioxidant activity determined by CUPRAC method, whilst DPPH and CV methods had the highest antioxidant activity in the lowest infusion time (3 min). Even though the results are inconclusive with regard to the effect of solid to solvent ratio effect on the total antioxidant activity, 1:150 ratio and 1:100 ratio extracts for both CUPRAC and DPPH methods and for CV gave the highest antioxidant capacities, respectively.
The total antioxidant activities in pure antioxidant standards and in the teas were ranked in the following order by both CUPRAC and DPPH methods: Quercetin > catechin > Trolox and Chinese green tea > Joko black tea > Athrixia phylicoides leaves > Laager rooibos tea, respectively. Comparative study showed the necessity of employing more than one method, as each method for the same sample yielded different results. CUPRAC and DPPH methods displayed higher sensitivity and repeatability as compared to the CV method with poor precision.
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Betancor, Fernández Alejandro José. "Biological properties of micronutrients: antioxidant capacity and structure activity relationships." [S.l.] : [s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=970026293.
Full text
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ZHONG-YOU, LAI, and 賴忠佑. "Synthesis and antioxidant activity of Ugonin T derivatives." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/y5krx6.
Full textAbstract:
碩士<br>中國文化大學<br>化學系應用化學碩士班<br>107<br>Several flavonoids were found from Helminthostachys zeylanica. Ugonin T (1) was isolated and characterized as a minor component from the rhizomes of Helminthostachys zeylanica. Ugonin T possesses a flavone skeleton containing a dihydrofuran ring. Ugonin T was found to show anti-inflammatory activity. Until now, the total synthesis of ugonin T has not been reported yet. In this thesis, an efficient synthetic method for the total synthesis of ugonin T and analogues was established.
The key intermediate 1-(6-hydroxy-4-methoxy-2,3,3-trimethyl-2,3-dihydrobenzofuran-5-yl)ethanone 13 was prepared from 2’,4’,6’-trihydroxyacetophenone in seven steps. Reaction of 13 with methyl 3,4-bis((tert-butyldimethylsilyl)oxy)benzoate 16 gave analogue 22, followed by demethylation to yield ugonin T. Using the similar manner, analogues 23, 24, 27, and 28 were obtained. The antioxidative activity of synthesized compounds using DPPH method was evaluated. Compounds 1, 22, and 27 showed similar DPPH radical scavenging activity as those of luteolin and -tocopherol (a positive control). However, analogues 23, 24, and 28 showed no activity. The results indicated with the dihydroxyl group of B ring in 1, 22, 27, and luteolin is important for good antioxidative activity.
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MCGRATH, ALAINA J. "Synthesis, Redox Chemistry and Antioxidant Activity of Sulfenic Acids." Thesis, 2010. http://hdl.handle.net/1974/6222.
Full textAbstract:
Sulfenic acids figure prominently in biological and natural products chemistry as important intermediates. For example, cysteine derived sulfenic acids are key intermediates in cell signaling and play both catalytic and structural roles in enzymes. Due to the ubiquitous nature of protein sulfenic acids in cells, methods have been developed to detect and quantitate them. Although they can be detected, the mechanisms by which they form and react remain unclear.
In addition, sulfenic acids are important enzymatic intermediates in Allium chemistry. Garlic, a member of the Allium genus, is known to have powerful antioxidant activity and this has recently been attributed to allyl sulfenic acid. Allicin, the thisolufinate that gives garlic its characteristic odor and flavor, decomposes to yield allyl sulfenic acid, which is believed to trap chain-carrying peroxyl radicals by readily donating a hydrogen atom, thus inhibiting autoxidations of hydrocarbons.
Despite their important biological roles, little is known of the physicochemical properties of sulfenic acids. This is primarily due to their instability in air and high reactivity as both electrophiles and nucleophiles, giving them the tendency to self-condense and form thiosulfinates. Few persistent sulfenic acids, stabilized by alkyl steric protecting groups surrounding the sulfenic acid functional group, have been reported in the literature. Herein we report our synthetic efforts toward two such sulfenic acids, 9-triptycene sulfenic acid, and trans-9-decalinsulfenic acid, which were expected to be appropriate models for cysteine-derived and allyl sulfenic acids. Using 9-triptycene sulfenic acid, we were able to provide insight into the thermodynamics (O-H BDE) and kinetics (kinh) of the reactions of sulfenic acids with peroxyl radicals, which provide a clear connection between the antioxidant activity in garlic and sulfenic acids. We also preliminarily characterized the electrochemical behaviour of this compound, as well as determined its pKa.<br>Thesis (Master, Chemistry) -- Queen's University, 2010-12-03 17:33:02.142
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Mao, Qinyong. "The synthesis and antioxidant capacities of a range of resveratrol and related phenolic glucosides." Thesis, 2015. http://hdl.handle.net/2440/97992.
Full textAbstract:
The resveratrol analogues have attracted great attension by scientists as these compounds exhibit numerous bioactive properties due to their outstanding antioxidant capacity. However, the role of the antioxidant activity of these molecules is still not quite clear. This thesis details the development and biological evaluation of a library of resveratrol analogues in order to provide a better understanding of their pharmaceutical value. This thesis begins with an overview of an important hydroxylated stilbene (resveratrol) and its analogues present in natural plants, food and beverage. Consequently, these studies are summarised and aided in the selection of a new library of substrates to be synthesised herein and biologically evaluated. Chapter two details the successful synthesis of resveratrol glycosides from resveratrol. Pleasingly, all chemical transformations carried out herein were performed in excellent yields. In-vitro anti-oxidant studies on these substrates revealed glycosylation of resveratrol leads to a decreased antioxidant capacity. In addition, these studies suggested the para hydroxyl group on resveratrol has a higher reactivity than the meta hydroxyl group. Chapter three details the synthesis of a hydroxylated resveratrol (piceatannol) and many of its glycosides. Almost all of the targeted compounds were prepared by applying a modified strategy designed for resveratrol glycosides in high efficiency. The anti-oxidant assays suggested that piceatannol is a more powerful antioxidant than resveratrol. The assays also revealed that the antioxidant activity of piceatannol glycosides is quite dependent on the glycosylation position. Chapter four then details the preparation of several common resveratrol dimers. The individual products were obtained via a one step oxidation of resveratrol followed by acetylation of the products, separation, and base hydrolysis. In addition, successful isomerisation of some of the trans-dimers into their cis forms was achieved in this study. With a simple protocol now in place to synthesise such resveratrol dimers, it paves the way for future work on the synthesis of glucosylated dimers of resveratrol. Such compounds would be expected to have a diverse range of antioxidant properties and other related bioactivities and are worthy of further exploration. Finally, Chapter five contains the associated experimental procedures and characterisation data for all synthesised resveratrol and piceatannol analogues along with a range of oligomers.<br>Thesis (Ph.D.) -- University of Adelaide, School of Agriculture, Food and Wine, 2015
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Chen, Yan-Ru, and 陳燕茹. "Synthesis and Evaluation of [6]-Paradol and Zingerol Derivatives on Antioxidant Activity." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/k8d528.
Full textAbstract:
碩士<br>弘光科技大學<br>化妝品科技研究所<br>104<br>In this study, we synthesized five [6]-paradol derivatives from 4-hydroxybenzoic acid, β-resorcylic acid, gentisic acid, 3-methoxysalicylic acid and vanillic acid, respectively. We also prepared three zingerol derivatives from β-resorcylic acid, gentisic acid and vanillic acid, respectively. This study aimed to evaluate their antioxidant activities in different systems including of DPPH, ABTS free radical scavenging, ferric reducing power and FRAP assay in order to determine the different reactivities of [6]-paradol and zingerol derivatives. [6]-Paradol and zingerol shows great antioxidant activities and the IC50 values of DPPH assays are 95.91 and 130.94 μM, respectively. Their IC50 values of ABTS assays are 216.81 and 346.49 μM, respectively. Vitamin C is used as a reference standard in DPPH assay and the IC50 value is 88.75 μM. In ABTS assay, trolox is used to provide a reference standard and the IC50 value is 410.53 μM. Among the synthetic [6]-paradol derivatives, the [6]-paradol derivative from gentisic acid (68) shows the best DPPH and ABTS free radical scavenging activity and the IC50 values are 50.28 and 150.48 μM, respectively. Similarly, the zingerol derivative from gentisic acid (75) also shows the best DPPH and ABTS free radical scavenging activity and the IC50 values are 77.39 and 204.72 μM, respectively. Both of them have better Fe3+ reducing ability than [6]-paradol and zingerol. Therefore, the [6]-paradol and zingerol derivative not only increases the antioxidant capacity in free radical scavenging, but also improves the activity of Fe3+ reducing ability. It is predicted that the [6]-paradol and zingerol derivatives have the potential to use as antioxidants in the skin care products.
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Lin, Chi-Wei, and 林季緯. "Synthesis and Evaluation of Novel Zingerol Derivatives on Tyrosinase Inhibition and Antioxidant Activity." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/49s4vb.
Full textAbstract:
碩士<br>弘光科技大學<br>化妝品科技研究所<br>103<br>In this study, we synthesized four zingerol derivatives from hydroxybenzoic acids and evaluated their tyrosinase inhibition and antioxidant activities in order to determine the bioactivity of zingerol and the four derivatives.
Zingerol shows no significant inhibitory effect on mushroom tyrosinase in 10 mM concentration. IC50 value of tyrosinase inhibition of β-arbutin used as a control group is 5.48 mM. Zingerol has great antioxidant activities and the IC50 values of ABTS and DPPH are 102.84 and 73.13 μM, respectively. Vitamin C is used as a control group and the IC50 values are 195.57 and 89.78 μM, respectively.
Among the synthetic zingerol derivatives, the zingerol derivative from β-resorcylic acid performs the best inhibitory effect on tyrosinase and the IC50 value is 4.41 mM. It is a non-competitive inhibitior. Further, the synthetic zingerol derivative from gentisic acid demonstrates the best antioxidant activity and the IC50 values are 70.97 and 47.95 μM, respectively. It means that zingerol derivatives from hydroxybenzoic acids not only improve the activity of zingerol in FRAP assay but also increase the antioxidant capacity in free radical scavenging. It is predicted that the zingerol derivatives have the potential to use as tyrosinase inhibitors and antioxidants in the skin care products.
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Bhuyan, Bhaskar Jyoti. "Design And Synthesis Of Novel Angiotensin Converting Enzyme (ACE) Inhibitors Having Antioxidant Activity." Thesis, 2010. https://etd.iisc.ac.in/handle/2005/1339.
Full textAbstract:
Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (AngII). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to its inactive form. Therefore, inhibition of ACE is one of the treatments of hypertension. A number of ACE inhibitory antihypertensive drugs are known. ‘Oxidative stress’ is another disease state caused by an imbalance in the production of oxidants and antioxidants in the body. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension.
Generally, selenium compounds exhibit better antioxidant behavior than their sulfur analogues. Therefore, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as antihypertensive drug. Similar to captopril, the selenium analogues of captopril exhibited excellent ACE inhibition property. It was observed that these compounds are very good scavengers of peroxynitrite (PN), a strong oxidizing as well as nitrating agent found in vivo. The orientation of the chiral centers in these compounds was found to be very important for their ACE inhibition behavior.
A number of selenocysteine- and cysteine-containing dipeptides and tripeptides were synthesized as inhibitors of ACE. It was observed that the ACE inhibition properties of these compounds depend on various factors such as orientation of the amino functionality, substitution at the C-terminal of the inhibitor, ring size of the proline moiety or the availability of the terminal acid group in carboxylate form etc. A structure-function correlation was drawn for the ACE inhibition properties of the peptide-based selenium-or sulfur-containing compounds. These studies reveal that the antioxidant properties do not depend on the side-chain functional groups, but they depend on the availability of selenium or sulfur centers. Selenium-based compounds were found to be better antioxidants than those containing sulfur moieties. In conclusion, the present study reveals that the replacement of sulfur atom in captopril and its analogues by selenium enhances the antioxidant activity.
The reaction products of lactoperoxidase (LPO)-catalyzed iodination of Ang II were separated and characterized. It was observed that LPO-catalyzed iodination of Ang II takes place preferentially at the tyrosine residue. LPO-catalyzed iodination of Ang II is inhibited by commonly used antithyroid drugs such as MMI, MTU, PTU and also by antihypertensive drug captopril. It was also observed that the monoiodo Ang I is a better substrate for ACE compared to the natural substrate Ang I. The site of nitration of Ang II by PN was also determined by MS-MS analyses. This study reveals that the nitration takes place at the tyrosine residue.
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Bhuyan, Bhaskar Jyoti. "Design And Synthesis Of Novel Angiotensin Converting Enzyme (ACE) Inhibitors Having Antioxidant Activity." Thesis, 2010. http://etd.iisc.ernet.in/handle/2005/1339.
Full textAbstract:
Angiotensin converting enzyme (ACE) catalyzes the conversion of angiotensin I (Ang I) to angiotensin II (AngII). ACE also cleaves the terminal dipeptide of vasodilating hormone bradykinin (a nonapeptide) to its inactive form. Therefore, inhibition of ACE is one of the treatments of hypertension. A number of ACE inhibitory antihypertensive drugs are known. ‘Oxidative stress’ is another disease state caused by an imbalance in the production of oxidants and antioxidants in the body. A number of studies suggest that hypertension and oxidative stress are interdependent. Therefore, ACE inhibitors having antioxidant property are considered beneficial for the treatment of hypertension.
Generally, selenium compounds exhibit better antioxidant behavior than their sulfur analogues. Therefore, we have synthesized a number of selenium analogues of captopril, an ACE inhibitor used as antihypertensive drug. Similar to captopril, the selenium analogues of captopril exhibited excellent ACE inhibition property. It was observed that these compounds are very good scavengers of peroxynitrite (PN), a strong oxidizing as well as nitrating agent found in vivo. The orientation of the chiral centers in these compounds was found to be very important for their ACE inhibition behavior.
A number of selenocysteine- and cysteine-containing dipeptides and tripeptides were synthesized as inhibitors of ACE. It was observed that the ACE inhibition properties of these compounds depend on various factors such as orientation of the amino functionality, substitution at the C-terminal of the inhibitor, ring size of the proline moiety or the availability of the terminal acid group in carboxylate form etc. A structure-function correlation was drawn for the ACE inhibition properties of the peptide-based selenium-or sulfur-containing compounds. These studies reveal that the antioxidant properties do not depend on the side-chain functional groups, but they depend on the availability of selenium or sulfur centers. Selenium-based compounds were found to be better antioxidants than those containing sulfur moieties. In conclusion, the present study reveals that the replacement of sulfur atom in captopril and its analogues by selenium enhances the antioxidant activity.
The reaction products of lactoperoxidase (LPO)-catalyzed iodination of Ang II were separated and characterized. It was observed that LPO-catalyzed iodination of Ang II takes place preferentially at the tyrosine residue. LPO-catalyzed iodination of Ang II is inhibited by commonly used antithyroid drugs such as MMI, MTU, PTU and also by antihypertensive drug captopril. It was also observed that the monoiodo Ang I is a better substrate for ACE compared to the natural substrate Ang I. The site of nitration of Ang II by PN was also determined by MS-MS analyses. This study reveals that the nitration takes place at the tyrosine residue.
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CHAN, YI-HSUAN, and 詹依璇. "Study on Antioxidant Activity of Synthetic Chlorogenic Acid Derivatives." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/p87vj6.
Full textAbstract:
碩士<br>弘光科技大學<br>化妝品應用研究所<br>107<br>The objectives of the present study were to chlorogenic acid derivatives
((E)-2-amino-3-((3-((3-(3,4-dihydroxyphenyl)acryloyl)oxy)-1,4,5-trihydroxycyclo
hexanecarbonyl) thio) propanoic acid, CGAC) were synthesized by the esterification reaction of chlorogenic acid and cysteine. Characterization of CGAC was performed by FTIR, 1H and 13C NMR spectroscopic methods analysis. Antioxidant activity of the CGAC was evaluated using DPPH, ABTS▪+, total
phenolic content, β-carotene-linoleic acid assay. The whitening effects of CGAC
by the activity of chelating ability Cu2+ power, and inhibitory activity of
mushroom tyrosinase were studied. The results indicated: In the DPPH radical
scavenging, the IC50 value of CGAC is 44.092 μM. In the ABTS▪+ reaction, the
IC50 values of CGAC is 174.140 μM lower than positive controls (the IC50 values
of ascorbic acid is 183.223 μM). the results of total phenolic content test, the CGAC total phenolic content 0.554 (μg of GAE/μg of substance) is less than
chlorogenic acid content 0.636 (μg of GAE/μg of substance). In the Chelating
ability Cu2+ power reaction, the CGAC showed stronger antioxidant activity than
chlorogenic acid the effect is 2.44 factor of chlorogenic acid. The CGAC had
favorable activity than chlorogenic acid in the β-carotene-linoleic acid assay.
Therefore, the CGAC has been successfully synthesized and identified, and has
better antioxidant activity. In the inhibition of mushroom tyrosinase test,
chlorogenic acid and CGAC to be confirmed.
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Lin, Kun-ying, and 林昆瑩. "Studies on Synthesis of Hydroxy Subsituted of N-Benzoyltyramine Derivatives as Inhibitory Activity of Antioxidant and Tyrosinase." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/28a93n.
Full textAbstract:
碩士<br>嘉南藥理科技大學<br>化妝品科技研究所<br>97<br>This research utilized the method of organic synthesis to put different amounts and positions of hydroxy-substituted tyramine or hydroxy- substituted dopamine into benzoic acid so as to produce a series of hydroxy-substituted N-benzoyltyramine derivatives (Compounds 1~20). Through the following tests, I. The ability of antioxidant—to scavenge DPPH free radical and ABTS free radical, II. The activity test of inhibit tyrosinase, III. The activity test of absorb UV in UV-Vis spectrometer. Compared with controlled groups, such as trolox, vitamine C, arbutin, and octyl salicylate, and this research studies those compounds’ applied value of cosmetics.
The results of the experiment to scavenging DPPH free radical shows that hydroxy-substituted N-benzoyltyramine derivatives has the ability in antioxidant, the SC50 of which ranges from 10.36±0.41μg/ml to 32.59±4.54 μg/ml. More specifically, compound 17 has the most outstanding effect in antioxidant (SC50 = 10.36±0.41μg/ml), compared with controlled group, trolox (SC50 = 13.36±0.42 μg/ml). In sums, that all derivatives ability to scavenge DPPH free radical which is related to the amount of substitution of hydroxy groups and their positions. The more hydroxy groups substituted at the benzene ring, the scavenging of DPPH free radical is more stronger, otherwise, the substitution of two hydroxy groups are at the ortho-position or para-position of carboxylic acid benzene ring, the ability of antioxidant is apparently more stronger.
The results in the experiments of the ability of antioxidant—to scavenge ABTS free radical—shows that all hydroxy substituted N-benzoyltyramine derivatives have good antioxidant activity, the SC50 of which ranges from 2.56±0.12μg/ml to 6.08±0.37 μg/ml. Almost each derivatives are stronger than controlled group, trolox (SC50 =5.27±0.79 μg/ml), except mono-hydroxy substituted derivative (Compound 13, IC50 =6.08±0.37 μg/ml).
The result of inhibiting tyrosinase shows that compound 17(IC50=0.11±0.01 mg/ml) have the ability to inhibit tyrosinase. It’s activity is better than arbutin (IC50=0.96±0.07 mg/ml), and similar with vitamin C.
According to the result of absorbing UV shows that all derivatives have the absorbing ultraviolet. The λmax absorbed is between 258~275 nm, and Abs is between 0.208~1.160. Remarkably, the ability to Abs of compounds 1, 2, 3, 4, 7, 8, 10, 11, 14, 16 and 17 is better than controlled group, octyl salicylate (Abs=0.152). Moreover, Compounds 5, 6, 15, 16 are proven to be able to absorb UVA. In sums, that hydroxy-substituted N-benzoyltyramine derivatives have the ability of absorbing ultraviolet.
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Lo, Chen-Wei, and 羅振維. "Studies on Synthesis of Hydroxy Substituted of N-Benzoylserotonin Derivatives as Inhibitory Activity of Antioxidant and Tyrosinase." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/57j96v.
Full textAbstract:
碩士<br>嘉南藥理科技大學<br>化妝品科技研究所<br>97<br>This research utilized the method of organic synthesis, researching different amounts and positions of hydroxy-substituted benzoic acid and serotonin into amide reaction, so as to produce a series of polyhydroxy substituted N-benzoylserotonin derivatives (compound 1-10). Accordingly, this study conducts the following four tests. I. The activity of antioxidant and the experiment of ability to scavenge DPPH free radical, II. The ability of overall antioxidant—the activity of TEAC, III. The activity test of inhibit Tyrosinase, and IV. The study of absorbing UV / VIS Spectrophotometers. This study use trolox, arbutin, and octyl salicylate as the control groups, and to test the ability of anti-oxidation, the activity of inhibit Tyrosinase, and the ability of absorbing UV. This research ultimately intends to investigate the applied value of those compounds into cosmetics.
The results of the ability of anti-oxidation scavenging DPPH free radical shows that polyhydroxy substituted N-benzoylserotonin derivatives (compound 1-10) have the generally better ability of anti-oxidation than control group (trolox), in which the IC50 of compound 1-10 ranges 8.75 to 18.02 μg/ml and the IC50 of trolox is 13.04 μg/ml. The abilities of anti-oxidation of compound 1, 4, 5, 7, and 10 are all better than the control group, trolox. Among all, compound 10 has the best ability of anti-oxidation (IC50 is 8.75 μg/ml). This study also discovers that the ability of scavenging DPPH free radical is strongly related to the number and the position of hydroxyl. The more the number of hydroxyl substitution in phenyl ring, the better the ability of scavenging DPPH free radical. That is, trihydroxy is better than dihydroxy, and dihydroxy is better than monohydroxy. Moreover, when the polyhydroxy exists in phenyl ring and it is ortho-position or para-position, the ability of scavenging DPPH free radical is better too.
In the study of testing the overall ability of anti-oxidation, polyhydroxy substituted N-benzoylserotonin derivatives (compound 1-10) still have the better overall ability of anti-oxidation than control group, trolox. The IC50 values of compound 1-10 range 2.49 to 3.92, while the IC50 value of trolox is 5.23 μg/ml. Compound 10 is still the best derivative which has the best overall ability of anti-oxidation; IC50 value is 2.49 μg/ml.
In the activity study of inhibit Tyrosinase, compound 5 and compound 10 show better ability than control group, arbutin, in which the IC50 value of arbutin is 1.19 mg/ml. Between the two compounds, compound 5 shows the best whitening effect (IC50 value is 0.18 mg/ml).
In the study of UV absorbing test, polyhydroxy substituted N-benzoylserotonin derivatives (compound 1-10) shows better ability to absorb UV and shows wider range of absorbing UVB than control group, octyl salicylate. With respect to octyl salicylate, octyl salicylate can abosorb the highest wavelength up to 306 nm under UVB (wavelength ranges 280 nm ~320 nm), and the ε is 4.03 × 103 ㎝-1M-1. However, the ε of polyhydroxy substituted N-benzoylserotonin derivatives (compound 1-10) under 306 nm range 4.14 × 103 ~ 11.45 × 103㎝-1M-1. It is reasonable that the compounds in this study can not only absorb the individual wavelength amoung the wavelenght of UVB, but also absorb wider range of wavelength. Amoung 10 compounds (polyhydroxy substituted N-benzoylserotonin derivatives), compound 4 shows the highest number of ε. The ε of compound 4 is high up to 11.43 × 103㎝-1M-1, which is the 2.84 times of the ε of control group, octyl salicylate. Moreover, compound 4 can absorb all the wavelength if UVB (280 nm - 320 nm), so compound 4 can provide the best protection from UVB. Additionally, this study also discovers that the compound 5 not only can absorb UVB, but also can absorb UVA.
Keywords: N-Benzoylserotonin, amide reaction, synthesis, Antioxidant, free radical, anti-aging, whitening, Tyrosine, Tyrosinase, UV
41
Tseng, Wei-Yi, and 曾維毅. "Studies on Synthesis of Hydroxy Subsituted of N-Cinnamoyltyramine Derivatives as Inhibitory Activity of Antioxidant and Tyrosinase." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/51837851753789707963.
Full textAbstract:
碩士<br>嘉南藥理科技大學<br>化妝品科技研究所<br>96<br>This research utilized the method of organic synthesis to put different amounts and positions of Hydroxy-substituted Tyramine and Hydroxy-substituted Dopamine into Cinnamic acid or Caffeic acid so as to produce a series of Hydroxy-substituted N-Cinnamoyltyramine Derivatives (Compounds 1~16). Through the following tests, this research studies those compounds’ applied value of cosmetics. I. The activity of antioxidant and the experiment of ability to scavenge DPPH free radical, II. The ability of total antioxidant—the activity of TEAC, III. The activity test of inhibit Tyrosinase, IV. The ability to absorb UV in UV-Vis spectrometer.
The result of scavenging DPPH free radical by the Hydroxy-substituted N-Cinnamoyltyramine Derivatives shows that the ability to scavenge DPPH free radical is related to the position of substitution of hydroxy group. The more hydroxy groups substituted at the carboxylic acid benzene ring, the stronger the ability to scavenge DPPH free radical. Moreover, Bi-Hydroxy substitution at the carboxylic acid benzene ring has the better ability to scavenge DPPH free radical than Mono-Hydroxy substitude derivatives or Methoxy substituted derivatives does. For example, Caffeic acid has Bi-Hydroxy substitution and orth-substitution, so that it has stronger ability to scavenge DPPH free radical. On the other hand, the carboxylic acid benzene ring which has only mono-hydroxy substituted is not significantly good at scavenging the DPPH free radical, no matter its position. On the contrary, at amino benzene ring, bi-Hydroxy substituted Dopamine have better ability to scavenge DPPH free radical than Hydroxy substituted, and the mono-Hydroxy substituted derivatives at carboxylic acid benzene ring, which is related to Tyramine, is not significantly able to scavenge the free radical. In sum, in the experiment of the ability to scavenge DPPH free radical, Dopamine derivatives are better than Tyramine derivatives, the fact of which is related to the amount of Hydroxy substitution at amino benzene ring. Moreover, the derivative (Compound 9) synthesized by caffeic acid and Dopamine is the best at scavenging DPPH free radical (IC50 =8.08±1.09 μg/ml), and the derivative synthesized by caffeic acid and Tyramine is second to it (Compound 1; IC50 =10.52±0.82 μg/ml).
The results in the experiments of the ability of total antioxidant—the activity of TEAC—shows that, Hydroxy substituted N-Cinnamoyltyramine Derivatives all have good antioxidant activity. Almost each derivatives are stronger than controlled group, Trolox (IC50 =5.41±0.22 μg/ml), except Methoxy substituted derivatives (Compound 15, IC50 =10.18±0.43 μg/ml). We can infer the reason from the amount of Hydroxy substitution. When there is bi-Hydroxy substituted Benzamides derivatives at carboxylic acid benzene ring, the ability of antioxidant are normally stronger than mono substitution, but not significant. However, this study found that Methoxy substituted Tyamine derivatives (Compound 7) is pretty good at scavenging free radical.
The result of applying Hydroxy substituted N-Cinnamoyltyramine Derivatives to inhibit tyrosinase and whitening shows that all the derivative have a activity to inhibit tyrosinase, and meta-Coumaric acid, Isoferulic acid, and 4-Methoxycinnamic acid’s Benzamides derivatives (compound 3, 6, 7, 11) have significant effects. Both Dopamine and Tyramine substitution at Amino benzene ring have stronger tyrosinase inhibition than Vitamin C (IC50=133.71±15.80). Further, meta-Coumaric acid and Isoferulic acid’s Tyramine derivatives (Compounds 3, 6) have strong inhibition than kojic acid (IC50=91.35±12.59).
Hydroxy substituted N-Cinnamoyltyramine Derivatives are proven to be able to absorb UVB and UVC in UV-Vis spectrometer, especially when the derivatives are C=C structured. On the other hand, Tyramine derivatives have better ability to absorb UVB and UVC, compared with Dopamine, the fact of which results from the amount of hydroxy groups substituted at the carboxylic acid benzene ring, and the ability is better when Bi-substituted derivatives at the carboxylic acid benzene ring than Mono-substituted derivatives. Moreover, when there is Methoxy-substitution at R3 in carboxylic acid benzene ring, such as compound 7 and 15 (ε= 93.67 andε= 83.50 L/mole*cm, respectively), it is better at absorbing UVB and UVC. The result can be supported by the controlled group, Parsol MNX (ε= 103.01 L/mole*cm), which has similar structure— Methoxy-substitution at R3 in carboxylic acid benzene ring.
42
Zhuang, Ting-xun, and 莊庭珣. "Studies on Synthesis of Hydroxy Substituted of N-Cinnamoylserotonin Compounds as Inhibitory Activity of Antioxidant and Tyrosinase." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/76315860712577844861.
Full textAbstract:
碩士<br>嘉南藥理科技大學<br>化妝品科技研究所<br>96<br>This research utilized the method of organic synthesis to put Hydroxy Substituted of N-Cinnamoyl Derivatives and Serotonin together, undergoing Benzamides reaction, so as to acquire a series of Hydroxy-substituted of N-Cinnamoylserotonin compounds (compound 1~8). Accordingly, this research would discuss the compounds’ ability of antioxidant, their ability of inhibiting tyrosinase, and their ability of absorbing UV, compared with controlled groups, such as Vitamin C, Vitamin E, kojic acid, and PMCX. Through the following tests, this research studies those compounds’ applied value of cosmetics.
The result of the experiment to scavenge DPPH free radical shows that all derivatives has the ability in antioxidant, the IC50 of which ranges from 1.17μg/ml to 17.87μg/ml. More specifically, compound 7 has the most outstanding effect in antioxidant (IC50 = 11.17μg/ml), compared with controlled group, trolox (IC50 = 11.76μg/ml).
The results in the experiments of testing the ability of total antioxidant—the activity of TEAC—shows that compound 1~8 are significant in the ability of total antioxidant, the IC50 of which ranges from3.00μg/ml to 4.42μg/ml, compared to controlled group, trolox (IC50 = 5.33μg/ml).
The result of inhibiting tyrosinase shows that all the derivatives have the ability to inhibit tyrosinase—IC50 of which ranges from 82.12μg/ml to 180.82μg/ml—except compounds 1, 4, and 6, which the IC50 are greater than 348μg/ml. Remarkably, the ability to inhibit tyrosinase of compound 5(IC50 = 86.95μg/ml) is better than kojic acid(IC50 = 86.95μg/ml); compound 3(IC50 = 95.82±13.30μg/ml) is better than Vitamin C; and compound 2 (IC50 = 114.08±21.57μg/ml) has nearly the same ability to inhibit tyrosinase with controlled group, vitamin C.
The result of absorbing UV shows that all derivatives have the ability of absorbing ultraviolet. The λmax absorbed is between 260 and 400nm, and Abs is between 0.116 and 0.486. Although some of the derivatives of this study do not perform, as expected, better than controlled group Parsol MCX (Abs=0.620), we must admit that those derivatives of this study have the ability, to some extend, of absorbing UV.
43
Bhabak, Krishna Pada. "Synthetic Antioxidants : Structure-Activity Correlation Studies Of Glutathione Peroxidase Mimics And Peroxynitrite Scavengers." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/996.
Full textAbstract:
Reactive oxygen species (ROS) such as superoxide radical anion (O2•¯), hydroxylradical (OH•), hydrogen peroxide (H2O2) and peroxynitrite (ONOO-) that are produced during the metabolism of oxygen under oxidative stress in aerobic organisms destroy several key biomolecules and lead to a number of disease states. Mammalian systems possess several effective defense mechanisms including antioxidant enzymes to detoxify these ROS. The selenocysteine-containing Glutathione peroxidase (GPx) is particularly an efficient enzyme in the detoxification of H2O2 and other hydroperoxides by using glutathione (GSH) as cofactor. The chemistry at the active siteof GPx has been extensively investigated with the help of synthetic selenium compounds. Although the anti-inflammatory compound ebselen(2-phenyl-1,2-benzoisoselenazol-3(2H)-one) is undergoing phase III clinical trial as antioxidant, the chemistry of ebselen is still not understood.
The present study on a number of ebselen derivatives with various N-substitutions reveals that the substitution at the N atom is important for the antioxidant activity. This study also suggests that the nature for thiol cofactor has a dramatic effect on the GPx activity of ebselen derivatives. It has been shown that ebselen exhibits very poor catalytic activity in the presence of aromatic thiols mainly due to strong Se….O nonbonded interactions that lead to extensive thiol exchange reactions in the selenenyl sulfide intermediate. To prevent the se….O interactions, a series of tertiary amide-based diselenides have been synthesized along with their secondary amide counterparts.
Detailed structure-activity correlation studies reveal that the GPx-like activity of the sec-amide-based compounds can be significantly enhanced by the substitution at the free-NH group of sec-amide functionality. The N,N-dialkylbenzylamine-based diselenides exhibit their catalytic activities via the generation of selenols which was confirmed by the reaction with anti-arthritic gold(I) compounds. Interestingly, the replacement of the hydrogen atom at the 6th position of the benzene ring of N,N-dialkylbenzylamine-based diselenides by a methoxy group prevents the thiol exchange reactions mainly be weakening the Se…N interactions and thus enhances the GPx activity. On the other hand, the catalytic activity of the tert-amine-based diselenides can also be increased by replacing the tert-amino groups with the corresponding sec-amine moieties. It has been observed that the basic amino group in the amine-based diselenides deprotonates the selenol and also the thiol cofactor, which is crucial for the higher catalytic activities of the amine-based compounds.
Peroxynitrite (PN, ONOO), a strong nitrating agent, is known to inactivate a number of proteins, enzymes and other biomolecules by nitration of tyrosine residues. In this study, we have shown that the commonly used antithyroid drugs and their analogues inhibit protein tyrosine nitration. This study reveals that antithyroid agents having PN scavenging activity may be beneficial of hyperthyroidism as these compounds may protect the thyroid gland from nitrative or nitrosative stress.
44
Bhabak, Krishna Pada. "Synthetic Antioxidants : Structure-Activity Correlation Studies Of Glutathione Peroxidase Mimics And Peroxynitrite Scavengers." Thesis, 2009. http://hdl.handle.net/2005/996.
Full textAbstract:
Reactive oxygen species (ROS) such as superoxide radical anion (O2•¯), hydroxylradical (OH•), hydrogen peroxide (H2O2) and peroxynitrite (ONOO-) that are produced during the metabolism of oxygen under oxidative stress in aerobic organisms destroy several key biomolecules and lead to a number of disease states. Mammalian systems possess several effective defense mechanisms including antioxidant enzymes to detoxify these ROS. The selenocysteine-containing Glutathione peroxidase (GPx) is particularly an efficient enzyme in the detoxification of H2O2 and other hydroperoxides by using glutathione (GSH) as cofactor. The chemistry at the active siteof GPx has been extensively investigated with the help of synthetic selenium compounds. Although the anti-inflammatory compound ebselen(2-phenyl-1,2-benzoisoselenazol-3(2H)-one) is undergoing phase III clinical trial as antioxidant, the chemistry of ebselen is still not understood.
The present study on a number of ebselen derivatives with various N-substitutions reveals that the substitution at the N atom is important for the antioxidant activity. This study also suggests that the nature for thiol cofactor has a dramatic effect on the GPx activity of ebselen derivatives. It has been shown that ebselen exhibits very poor catalytic activity in the presence of aromatic thiols mainly due to strong Se….O nonbonded interactions that lead to extensive thiol exchange reactions in the selenenyl sulfide intermediate. To prevent the se….O interactions, a series of tertiary amide-based diselenides have been synthesized along with their secondary amide counterparts.
Detailed structure-activity correlation studies reveal that the GPx-like activity of the sec-amide-based compounds can be significantly enhanced by the substitution at the free-NH group of sec-amide functionality. The N,N-dialkylbenzylamine-based diselenides exhibit their catalytic activities via the generation of selenols which was confirmed by the reaction with anti-arthritic gold(I) compounds. Interestingly, the replacement of the hydrogen atom at the 6th position of the benzene ring of N,N-dialkylbenzylamine-based diselenides by a methoxy group prevents the thiol exchange reactions mainly be weakening the Se…N interactions and thus enhances the GPx activity. On the other hand, the catalytic activity of the tert-amine-based diselenides can also be increased by replacing the tert-amino groups with the corresponding sec-amine moieties. It has been observed that the basic amino group in the amine-based diselenides deprotonates the selenol and also the thiol cofactor, which is crucial for the higher catalytic activities of the amine-based compounds.
Peroxynitrite (PN, ONOO), a strong nitrating agent, is known to inactivate a number of proteins, enzymes and other biomolecules by nitration of tyrosine residues. In this study, we have shown that the commonly used antithyroid drugs and their analogues inhibit protein tyrosine nitration. This study reveals that antithyroid agents having PN scavenging activity may be beneficial of hyperthyroidism as these compounds may protect the thyroid gland from nitrative or nitrosative stress.
45
BORTOLAMI, MARTINA. "Design, synthesis and in vitro evaluation of new cholinesterase inhibitors with metal-chelating and antioxidant properties as multitarget compounds for Alzheimer’s disease." Doctoral thesis, 2019. http://hdl.handle.net/11573/1354090.
Full textAbstract:
Alzheimer’s disease (AD) is a multifactorial neurodegenerative syndrome, as many factors are involved in its pathogenesis, including: cholinergic system alterations; hyperproduction and aggregation of β-amyloid (Aβ) neurotoxic peptide; increased oxidative stress; dyshomeostasis of some bio-metals, which promote aggregation of the Aβ peptide and catalyze the formation of reactive oxygen species (ROS). Based on these considerations, series of pyrimidine, pyridine and deferiprone derivatives have been designed, synthesized and evaluated in vitro with the hypothesis that they can restore the cholinergic tone, contrast the toxicity and deposition of the β-amyloid peptide, attenuate the dyshomeostasis of the metals mainly involved in the pathology and reduce the oxidative stress, in order to obtain multitarget molecules for Alzheimer’s therapy. Specifically, the compounds were designed as potential cholinesterases inhibitors able to interact with both the active catalytic site (CAS) and the peripheral anionic site (PAS) of the enzyme, inserting two small aromatic groups separated by an aliphatic linker. Metal ions chelating groups and, in some cases, antioxidant moieties were incorporated into these compounds, in order to obtain molecules potentially able to chelate bio-metals colocalized in Aβ plaques and involved in the generation of radical species and to reduce the oxidative stress. Totally, 74 new compounds were synthesized, which were tested by enzymatic inhibition studies towards EeAChE and eqBChE by Ellman’s method. Among the tested compounds the most potent inhibitor of EeAChE showed a mixed-type inhibition mechanism with a Ki = 0.312 ± 0.108 uM, while the most potent inhibitor of eqBChE showed a mixed-type inhibition mechanism with a Ki = 0.099 ± 0.071 uM. For the most potent cholinesterases inhibitors, the ability to chelate iron, copper and zinc ions was assessed through UV-vis spectrophotometry. The tested compounds showed chelating capacities towards metal ions mainly involved in the pathogenesis of AD (all towards Fe3+, many towards Cu2+ and some towards Zn2+). On the most potent cholinesterases inhibitors among phenolic derivatives, the antioxidant activity assay was carried out according to DPPH spectrophotometric method. Biological studies for the evaluation of the anti-aggregating activity towards Aβ42 and Tau and of the cytotoxicity are still ongoing and the relative results will be useful to identify the best compounds among those synthesized and to deepen the assessments regarding the optimal structural characteristics in order to obtain multitarget compounds for AD.
46
Tomé, Sara Mirassol. "Synthesis of flavonoid-type compounds and sugar-substituted phenolics of pharmacological importance." Doctoral thesis, 2021. http://hdl.handle.net/10773/31390.
Full textAbstract:
Flavonoids are a large class of secondary metabolites widespread in the Plant
Kingdom. These natural organic compounds possess a prominent interest as
therapeutic agents. Among the vast range of biological properties of both natural
and synthetic derivatives are their antioxidant and anti-inflammatory activities.
Among the naturally occurring oxygen containing heterocyclic compounds,
flavones (2-arylchromones) assume pronounced importance due to both their
spread and diverse abundance as well as their well-known wide range of
pharmacological properties. Halogenated derivatives of this privileged structure
already proved to display enhanced biological activities and are also valuable
frameworks as intermediates in the synthesis of more elaborated compounds,
namely through metal cross-coupling reactions. Although several methods have
already been developed towards the synthesis of haloflavones, there is still much
room for improvement regarding the regioselectivity control of the halogenation
process. The chemistry of this scarce group of natural compounds remains,
therefore, an interesting challenge to organic chemists.
Part of the work described in this thesis was focused on the synthesis of
flavonoid-type compounds. Regarding the synthesis of flavones, synthetic
pathways towards different substituted patterns of methoxy-, hydroxy- and
chloroflavones were studied. The newly synthesised compounds were evaluated
for their antioxidant, anti-inflammatory and antidiabetic properties and several of
them exhibited remarkable activities including a great potential towards the
treatment of type 2 diabetes mellitus. The structure–activity relationship study
(SAR) of the prepared compounds was performed. Moreover, it were achieved
the stereoselective synthesis of the novel (E,E)-aminoaurone-type compounds,
as well as the preparation of different new analogues of
iodophenyloxybenzaldeydes and iodoxanthones.
Natural occurring phenolic compounds are frequently attached to carbohydrate
moieties. The recognized prominent interest on C-glycosyl-substituted phenolic
compounds in medicinal chemistry lies on the combination of the distinguishing
hydrolytic stability of their C-glycosidic bond and the high hydrophilic character
of the carbohydrate unit together with the well-known biological activities of
phenolic compounds. Accordingly, the development of general approaches for
the synthesis of C-glycosyl phenolic compounds is of great importance. In this thesis the study on the synthesis of C–C sugar-substituted phenolics is
also described. The used synthetic strategy was based on the Heck cross coupling of vinylfuranose or vinylpyranose sugar scaffolds with different
halophenolic frameworks. This straightforward wide in scope methodology lead
to different types of phenolic-sugar hybrid molecules: phenoxybenzaldehyde–,
xanthone–, chromone–, (E)-2-styrylchromone–, and (E,E)-aminoaurone-type–
sugar hybrids.
The unequivocal structural elucidation of all synthesised compounds was
performed by 1D and 2D nuclear magnetic resonance experiments and
supported by mass spectrometry and by either elemental analysis or high
resolution mass spectrometry.<br>Os flavonoides são uma ampla família de metabolitos secundários ubíquos no
Reino Vegetal. Estes compostos orgânicos de ocorrência natural têm sido alvo
de grande interesse de estudo devido ao seu reconhecido potencial
farmacológico. Entre as suas múltiplas propriedades biológicas destacam-se as
atividades antioxidante e anti-inflamatória tanto de derivados naturais como de
derivados sintéticos.
No universo dos compostos heterocíclicos de oxigénio, as flavonas (2-
arilcromonas) assumem especial importância devido à sua abundância,
diversidade e amplo leque de propriedades farmacológicas às quais estão
associadas. Alguns derivados halogenados desta estrutura molecular tão
privilegiada provaram possuir atividades biológicas aprimoradas, sendo ainda
valiosos intermediários na síntese de outros compostos orgânicos,
nomeadamente mediante reações de acoplamento cruzado. Apesar de
existirem vários métodos de síntese de haloflavonas, muito permanece ainda
por desvendar relativamente ao controlo da regiosseletividade na halogenação.
Parte do trabalho descrito nesta tese centrou-se na síntese de compostos do
tipo flavonoide. Foram desenvolvidas novas rotas de síntese para a obtenção
de novas flavonas com diferentes padrões de substituição: flavonas
metoxiladas, hidroxiladas e cloradas em várias posições do seu esqueleto
carbonado. Foi efetuada a avaliação biológica destes compostos assim como o
estudo da relação estrutura–atividade (SAR), tendo alguns derivados exibido
atividades antioxidante e anti-inflamatória muito satisfatórias e comprovado
potencial no tratamento da diabetes mellitus tipo 2. Foram ainda estudadas a
síntese estereoesseletiva de novos derivados do tipo (E,E)-aminoaurona e a
preparação de novos análogos de iodofeniloxibenzaldeídos e iodoxantonas.
Na natureza os compostos fenólicos encontram-se frequentemente associados
a unidades de hidratos de carbono. No âmbito da química medicinal, o
reconhecido e crescente interesse nos compostos fenólicos C-glicosilados
advém da combinação de várias caraterísticas vantajosas a estes inerentes: a
distinta estabilidade hidrolítica da ligação C-glicosídica, o elevado caráter
hidrofílico proporcionado pelas unidades de açúcar e ainda tudo isto associado
à reconhecida importância biológica dos compostos fenólicos. Nesta dissertação é também descrito o estudo efetuado no âmbito da síntese
de novos compostos fenólicos substituídos por unidades de açúcar mediante
ligações C–C. Para tal, foram preparados derivados vinilados de açúcar (do tipo
furanose e piranose) e também derivados halofenólicos do tipo
fenoxibenzaldeído, xantona, cromona, (E)-2-estirilcromona e (E,E)-
aminoaurona. Tendo como estratégia-chave a reação de acoplamento cruzado
de Heck, foi possível a síntese de vários novos derivados fenólicos contendo
unidades de açúcar.
A elucidação estrutural inequívoca de todos os compostos sintetizados foi
efetuada através da espetroscopia de ressonância magnética nuclear 1D e 2D
e sustentada pela análise de espetrometria de massa, análise elementar ou
espetrometria de massa de alta resolução.<br>Programa Doutoral em Química
47
Correia, Catarina Marçal. "(E)-2-styrylchromones: synthesis and evaluation of the inhibitory effects on the oxidative burst produced by human monocytes." Master's thesis, 2021. http://hdl.handle.net/10773/33584.
Full textAbstract:
Several studies have attributed the onset and progression of several diseases,
including degenerative and cardiovascular diseases, cell aging and cancer, to
the production of free radicals and inflammatory processes. Consequently, a
large number of investigations have been carried out in order to find new, safer
and potent antioxidant and anti-inflammatory drugs, and to elucidate their
corresponding mechanisms of action. The evaluation of antioxidant vs
antiradicalar and anti-inflammatory activity of phenolic compounds, either of
natural or synthetic origin, is nowadays an important area of research in the
field of medicinal chemistry.
This work presents a brief introduction about oxidative stress and the origin of
reactive oxygen and nitrogen species, and about inflammation and the cells
involved in this process, specifically monocytes. The relationship between the
inflammatory process and the oxidative burst produced by human monocytes is
addressed.
Polyphenols, secondary metabolites of several plants, are recognized as an
important source of flavonoids, including 2-styrylchromones, which have
demonstrated important biological activities. Thus, several examples of (E)-2-
styrylchromones of natural and synthetic origin and the biological activities
associated with them are presented herein, with emphasis on antioxidant and
anti-inflammatory activities. The major goal of this work relies on the design
and synthesis of a library of nine (E)-2-styrylchromones and their inhibitory
effects on the oxidative burst produced by human monocytes and the
establishment of structure-activity relationship studies (SARS). At last, the most
used methods for the synthesis of (E)-2-styrylchromones containing relevant
substituent groups to their antioxidant and anti-inflammatory activity, namely
hydroxyl and halogen groups, as well as the procedures for the in chemico and
in vitro biological assays, are described.<br>O aparecimento e progressão de várias doenças, incluindo doenças
neurodegenerativas, cardiovasculares, envelhecimento celular e cancro, têm
sido associados à produção de radicais livres assim como a processos
inflamatórios, de acordo com vários estudos realizados. Por conseguinte, têm
sido realizadas diversas investigações com a finalidade de encontrar novos
fármacos com potencial antioxidante e anti-inflamatório, mais eficazes e
seguros, e de compreender os seus mecanismos de ação. Atualmente, a
avaliação da atividade antioxidante e/ou antirradicalar e anti-inflamatória de
compostos polifenólicos, classe de compostos onde se incluem as 2-
estirilcromonas, quer de origem natural quer sintéticos, é uma área de estudo
de grande interesse.
Neste trabalho apresenta-se uma breve introdução sobre o stress oxidativo e a
origem das espécies reativas de oxigénio e nitrogénio e sobre a inflamação e
as células intervenientes neste processo, mais especificamente, acerca dos
monócitos. Aborda-se a relação entre o processo inflamatório e o burst
oxidativo produzido por monócitos humanos.
Os polifenóis, metabolitos secundários de várias plantas, são reconhecidos
como uma fonte importante de flavonóides, incluindo 2-estirilcromonas, que
têm demonstrado importantes atividades biológicas. Seguidamente são
apresentados vários exemplos de (E)-2-estirilcromonas de origem natural e
sintética e as atividades biológicas que lhes estão associadas, destacando-se
as atividades antioxidantes e anti-inflamatórias. O grande foco deste trabalho
reside no desenho e síntese de um painel de nove (E)-2-estirilcromonas e o
seu efeito inibitório no burst oxidativo produzido por monócitos humanos e
ainda o estudo da relação estrutura-atividade (SARS). Por fim, são descritos
os métodos mais utilizados para a síntese de (E)-2-estirilcromonas contendo
grupos substituintes relevantes para a sua atividade antioxidante e antiinflamatória,
nomeadamente grupos hidroxilo e halogéneos, assim como os
métodos utilizados nos ensaios in chemico e in vitro.<br>Mestrado em Bioquímica
48
Domingues, Maria Augusta da Graça. "Synthesis, characterization and anti-oxidant activity of thio-imidate N-oxides TIO sugars." Master's thesis, 2011. http://hdl.handle.net/10400.6/3907.
Full textAbstract:
The thioimidate N-oxide function is a rare and original function. The objective of this work is
the synthesis of heterocyclic rings linked to the sugar moiety by a C-C bond and the
characterization of obtained compounds. Regio and stereoselective branched-chain
construction starting from D-ribose which led to the synthesis of thio-imidate N-oxide sugar
derivates.
The synthesis of compounds was made by several reactions, starting from D-ribose. The
protection of D-ribose by isopropylidene group allows us to obtain the 2,3-O-isopropylidene-β-
D-ribofuranose (1). The reduction and oxidative cleavage of the 2,3-O-isopropylidene-β-Dribofuranose
allows to obtain the 2,3-O-isopropylideno-L-erithrose (2), the ring opening with
hydroxylamine hydrochloride lead to aldoxime 3. Protection of 3 with tert-butyldimethylsilyl
group lead to compounds 4 and 5. The introduction of the thiohydroximate function was
made with ethanethiol and triethyhamine. The thiohydroximate cyclized to generate
efficiently the thio-imidate N-oxide by Mitsunobu reaction.
The protection of D-ribose by methyl group and isopropylidene group lead to compound 9.
The ionic deoxygenation of the hydroxyl group in the compoud 9 allows obtaining the deosyiodenesugar
10. The deosyiodine-sugar after reductive elimination leads to aldehyde 11.
Compound 11 undergoes reduction to generate 12 which lead to compound 13.
The obtained compounds were isolated and purified by column chromatography. The
characterization of compounds was made by NMR analysis (1H NMR, and 13C NMR), infrared
spectrum and by mass spectroscopy. The anti-oxidant activities were also evaluated for some
obtained compounds by DPPH method.
Determination of antioxidant activity of some compounds was made by the method of DPPH
radical (2,2-diphenyl-1-picrylhydrazyl) based on the ability of this radical has to react with
hydrogen donor for knowledge of their antioxidant activity, using as a reference commercially
product known as Trolox.
Compounds 3, 10 and 13 show the antioxidant activities of 60%, 56% and 68% respectively.
The remaining compounds just demonstrate residual antioxidant activity.<br>A função N-óxido de tio-imidato é uma função rara e original. O objectivo deste trabalho foi a
síntese, caracterização e determinação da actividade antioxidante de um composto derivado
da D-ribose, o N-óxido de tio-imidato, assim como de todos os compostos sintetizados.
A síntese do N-óxido de tioimidato 8, foi efectuada por duas sequências diferentes de
reacções a partir da D-ribose. A primeira sequência de reacções iniciou-se com a protecção
dos grupos hidroxilo das posições 2 e 3 da D-ribose utilizando o grupo isopropilideno como
grupo protector. A redução, seguida de clivagem oxidativa permite obter a 2,3-Oisopropilideno-L-eritrose (2) com 58% de rendimento, que após tratamento com cloreto de
hidroxilamina originou a aldoxima 3 com 73% de rendimento. A protecção do grupo hidroxilo
da posição 4 com o grupo ter-butildimetilsililico foi efectuada por reacção da aldoxima 3 com
cloreto de ter-butildimetilsililo, tendo-se obtido o éter sililico 4 com 19% de rendimento e o
éter sililico 5 com 63% de rendimento. A introdução da função tio-hidroximato foi efectuada
por reacção do composto 4 ou por reacção do composto 5 com etanotiol e tri-etilamina,
originando o composto 6 com 63% e 18% de rendimento respectivamente. O grupo hidroxilo da
posição 4 foi desprotegido por reacção com difluortrifenilsilicato de tetrabutilamónio (TBAT)
dando origem ao composto 7, com 40% de rendimento. A ciclização foi efectuada por reacção
de Mitsunobu, obtendo-se o N-óxido de tioimidato (8) com 50% de rendimento na forma de
um sólido cristalino branco.
Iniciou-se a segunda sequência reaccional com a protecção dos grupos hidroxilo 1, 2 e 3 da Dribose, com metanol e acetona respectivamente, em meio ácido. A substituição nucleófilica
do grupo hidroxilo desprotegido (posição 4) foi realizada com trifenilfosfina, iodo e imidazol,
originando o desoxi-iodo açúcar 10 com 71% de rendimento. Seguidamente efectuou-se a
abertura do anel de açúcar com butil lítio a -78ºC, obtendo-se aldeído 11, que foi utilizado,
sem ser isolado, para a reacção de obtenção do álcool 12, tendo este sido obtido com 70% de
rendimento. Este composto foi protegido com cloreto de terbutildimetilsililo, originando o
composto 13, com 70% de rendimento na forma de um líquido incolor.
Os compostos obtidos foram isolados e purificados por cromatografia em coluna. A análise da
sua estrutura foi efectuada por espectroscopia de Infravermelho, de Ressonância Magnética
Nuclear (RMN) de protão (
1H RMN) e de carbono treze (13C RMN). Assim como por
espectrometria de massa. Foram também determinados os pontos de fusão (dos compostos
sólidos) e os poderes rotatórios específicos dos compostos isolados.
Foi realizada a determinação da actividade antioxidante para os compostos 3, 5, 6, 7, 8, 10 e
11 utilizando o método do radical DPPH (2,2-difenil-1-picril-hidrazilo), baseado na capacidade que este radical tem em reagir com doadores de hidrogénio para conhecimento da sua
actividade antioxidante, utilizando como referência o antioxidante sintético comercialmente
conhecido como Trolox.
Dos compostos analisados a aldoxima 3, o desoxi-iodo-açúcar 10 e o éter sililico 13
apresentam actividade antioxidante. O composto 13 tem uma actividade antioxidante de 68%,
seguido da aldoxima 3 com uma actividade antioxidante de 60% e por último o desoxi-iodoaçúcar 10 com uma actividade de 56%. Os restantes compostos analisados apresentam
actividade antioxidante residual.
O dexosi-iodo-açúcar 10 apresenta uma concentração eficiente de 8084µg/mL para uma
concentração inicial de 16500µg/mL e uma concentração eficiente de 8586µg/mL para uma
concentração inicial de 12530µg/mL, o que demonstra ser um potencial antioxidante.
Foi possivel obter o N-óxido de tio-imidato pela primeira sequência de reacções, o seu ponto
de fusão é 139-143 ºC, o seu poder rotatório é de 143 a sua actividade antioxidante é de 34%.
49
Li, Liao. "Chemical Forays of Fungal Metabolites." Phd thesis, 2018. http://hdl.handle.net/1885/148782.
Full textAbstract:
This thesis contains six chapters and the research presented within focuses on three parts. The first part (chapter one to three) was the isolation of antibacterial and antioxidant mushroom metabolites, and the synthesis towards analogues of discovered natural products. The following part (chapter four) was to assess antioxidant activities of synthetic compounds and investigate their SAR (structure-activity relationship), by use of a developed DPPH assay. The last part (chapter five to six) was the discovery of an abiotic halogenation reaction among a class of fungal metabolites, azaphilones. A series of their synthetic analogues were applied as model compounds to understand the mechanism of the discovered unusual and facile non-enzymatic nucleophilic halogenation reaction.
Chapter one is a review of antioxidants in mushrooms. The components with antioxidant activities discovered from mushrooms were summarised by their chemical structures and representative samples were listed. In addition, the potential mechanisms of those antioxidants were described in this chapter.
In chapter two, extracts of 20 mushrooms from PNG (Papua New Guinea) were screened against both Gram-positive and Gram-negative bacteria, six of them were chosen as chemical survey candidates for their strong antibacterial activities. Extracts of 37 PNG mushrooms were screened for their antioxidant using a modified DPPH assay, 14 of them were chosen as chemical survey candidates based on their antioxidant capacities. In chemical examination guided by bioactivity, five natural products including two novel furan fatty acids (2.1-2.2) and three known compounds, i.e. grifolin (2.3), grifolic acid (2.4) and grifolic acid methyl ether (2.5), were isolated from four selected mushroom samples.
Chapter three described the synthetic efforts towards analogues of three isolated antioxidant fungal metabolites (2.3-2.5). Inspired by 15 synthetic targets, a short and versatile general synthetic route was established to deliver 40 compounds possessing structures related to the natural products. Based on these structures, a compound library was established for antioxidant assessment in the following SAR research. The synthetic work resulted in the preparation of 33 novel structures.
In chapter four, various antioxidant assays and their working mechanisms were reviewed, as well as their corresponding advantages and drawbacks. A developed DPPH assay was optimised to offer an accurate and reproducible antioxidant evaluation for SAR research in the achieved compound library. The results indicated that a structure with an aromatic ring to be allylated with a carbon chain in addition to the presence of phenols, is required to show an antioxidant activity, and the increased length of a carbon chain (more prenyl units) enhances the antioxidant activity.
Chapter five focused on naturally occurring organohalogen compounds with biotic origins. The representative halogenated natural products with a variety of bioactivities were categorised following a chemical structural classification as well as a bioactive classification, to showcase both their structural diversity and bioactive variety. The biosynthetic mechanisms of halogenated natural products were reviewed in this chapter.
Chapter six detailed the investigation of a novel halogenation reaction that was discovered to be occurring with some azaphilone fungal metabolites, for example the conversion of (+)-deschlorosclerotiorin (6.2) into (+)-sclerotiorin (6.1). Various non-halogenated model compounds with an azaphilone core structure were created to shed light on the authenticity of numerous halogenated azaphilones reported as natural products. The ensuing synthetic work resulted in an efficient general procedure producing the required targets. The following investigation of the halogenation revealed a novel, facile, non-enzymatic nucleophilic reaction and its proposed mechanism is discussed. The synthetic efforts resulted in the creation of 22 novel structures.
50
"Antioxidant activity of cyclolinopeptides." Thesis, 2013. http://hdl.handle.net/10388/ETD-2013-06-984.
Full textAbstract:
Cyclolinopeptides (CLs) are hydrophobic cyclic peptides found in flaxseed. They show immunosuppressive activity, but the biological function of these compounds is largely unknown. This thesis presents the results of studies that were conducted to determine whether CLs could act as antioxidants. In the first study, flaxseed oil was passed over a silica adsorbent column to remove polar compounds. The polar compounds were then eluted from the silica absorbant using a series of increasingly polar solvents. Individual polar fractions were then added back to the silica-treated flaxseed oil and the oxidative stability index of these samples was determined at 100 °C. A polar fraction containing mainly CLA, β/γ- and δ-tocopherol increased the induction time of silica-treated flaxseed oil from 2.3 ± 0.28 h to 3.2 ± 0.41 h. A positive effect of the polar fraction containing a mixture of CLA and CLD-CLG on the oxidative stability of oil was also observed. The antioxidant mechanism of CLs was investigated in several model systems using electron spin resonance spectroscopy. The concentration of radicals in a DMPO (5,5-dimethyl-1-pyrroline-N-oxide) radical-CLs reaction mixture was monitored. All CLs exhibited dose dependent scavenging activities. CLA–CLC reactions with DMPO-OH at a concentration of 5 mM resulted in a 24–30% decrease in electron paramagnetic resonance (EPR) signal intensity. The reaction of CLs and the stable radical 2,2-diphenyl-1-picrylhydrazyl (DPPH•) revealed a more complex interaction than simple radical scavenging. Peptides (CLG and CLG") that contained both tryptophan and methionine showed stronger radical scavenging activity than did CLs containing methionine or methionine sulfoxide but not tryptophan (CLB and CLC). Irradiation of the reaction mixture of DPPH• and peptide with UV light also affected the radical scavenging behaviour. Scavenging activities of DPPH• by CLB, CLC and CLA were enhanced by light, whereas scavenging of DPPH• by the tryptophan containing peptides CLG and CLG″ was not affected. High-performance liquid chromatography with mass spectrometry (HPLC-MS) analysis of the reaction mixtures after a radical scavenging reaction was used to determine the impact of radical scavenging on the peptides. These reactions revealed new masses that were identified and characterized. It was established that DPPH• reacted with the methionine of CLB and with tryptophan in CLG and CLG, by formation of a new covalently-bonded species. Covalent linkages between these amino acids (alone or in peptides) and DPPH• have not been reported previously.