Добірка наукової літератури з теми "Antioxidant synergies"

The incidences of diabetes are on the constant rise, and thus need an alternative dietary approach to improve glucose metabolism in type II diabetes patients. Fruits and vegetables have long been known for their beneficial fiber, phenolics and antioxidants, and by incorporating these dietary components into our everyday diet have proven beneficial in controlling the glucose metabolism. In this study, Prime-Jan and Kiowa blackberry cultivars were evaluated for their anti-diabetic properties using a variety of in vitro assays. Overall, the Kiowa blackberry reigned supreme over the Prime-Jan blackberry in the majority of functionality assays, more specifically alpha-amylase, alpha-glucosidase, total soluble phenolics and DPPH free radical scavenging activity. In an attempt to incorporate anti-hypertensive properties into this study, we chose to integrate the Bartlett pear, known as the most widely consumed pear in the United States and recognized for its moderate ACE inhibition. Our results indicated a combination of 70% pear to 30% blackberry as the most beneficial ratio for exhibiting high alpha-amylase (96.5%) and alpha-glucosidase inhibition (95.6%). Additionally, the 70/30 combination exhibited high DPPH free radical scavenging activity (80.7%), total soluble phenolics (1.9 mg/g FW), while also maintaining moderately high ACE inhibition (25.2%). Therefore, there is vast potential for a combination of 70% pear to 30% blackberry to serve as a beneficial alternative in the diet of patients suffering from type 2 diabetes.

For well over 20 years the Oxygen Radical Absorbance Capacity (ORAC) assay has been an important research tool in identifying antioxidant candidates in food and serum samples. The ORAC value is derived from a series of fluorescence intensity measurements taken over a period of time, usually a few hours. The kinetics of this reaction is controlled by the sustained release of peroxyl radicals at 37°C by an azo compound (AAPH). The peroxyl radicals attack the fluorescent probe causing a gradual decrease in fluorescence intensity. Ultimately, the test yields fluorescence decay curves over time, with the presence of any antioxidants in a sample having a protective effect, delaying probe decay and resulting in a greater area under the decay curve. This forms the basis of the ORAC measurement. Concerns have been raised about the applicability of this assay, chemical interferences influencing the data, and the use of ORAC values to attribute health benefits of foods. In an effort to curb misrepresentation of health benefits from ORAC data, the USDA retracted its ORAC database in 2012 and published a statement by Dr Ronald Prior, a founding researcher for the ORAC assay. The explanatory statement by Dr Prior identified the misapplication of ORAC values and misleading perceived health benefits as major reasons for withdrawal of the database. Despite this, ORAC remains a popular assay, and the method is widely used as a product development and marketing tool. Some researchers have reported that ORAC values can be influenced by factors such as choice of solvent, chemical constituents in matrices, and pH conditions. However, little has been published on antioxidant synergies in food systems and their contribution to the ORAC value. Given the predisposition of the assay to interferences, a better understanding of antioxidant synergies is necessary to understand the contributing factors to measurement in real foods, and also to determine how these values may be manipulated. With the USDA caution in mind, this research was carried out to systematically investigate the factors influencing the ORAC measurement and its interpretation. Firstly, an alternative mode of reporting antioxidant activity to consumers on product labeling was proposed. Calculations needed to convert ORAC units from μM Trolox equivalents (μM T.E/kg or μM T.E/L) to mass units (g T.E/kg or g T.E/L) of Trolox equivalents per kg or per L of foodstuff are provided. We propose that mass units are less misleading to consumers, by not reporting very large and impressive-looking values when a simple conversion reveals most of them to be much more modest when viewed as a mass of vitamin E equivalent. For example, the antioxidant activity of blueberries when measured by the ORAC assay was equivalent to over 71,000 μM of Trolox equivalents. When converted, the blueberries can be said to have the same antioxidant activity as 17.9g of vitamin E per kg of fruit (17.9g T.E/kg). This new mode of reporting was successfully applied to a range of commodities including fruit, confection and beverages. Influencing factors, including environmental conditions, role of additives and nanoparticles and interactions between classes of chemical constituents were all investigated. Environmental conditions, specifically rainfall, were found to influence the levels of antioxidant compounds/bioactives in Australian wines. Six chemical constituents were identified as warranting further investigation; namely 6-methylcoumarin, protocatechuic acid, vanillic acid, p-coumaric acid, rutin and chlorogenic acid. Significant differences were also observed between the antioxidant capacity of wines by in vitro ORAC and ex vivo CAA-RBC assays, where wines with similar ORAC values had vastly different bioavailability and activity in the cellular system. Amino acids and CuNPs additives were found to greatly influence the antioxidant measurements of “superfoods”. Results indicated strong enhancements and synergies related to the properties of the amino acids and complexes formed with Cu(I) and essentially matrix independent.. The order of antioxidant enhancement in bilberry, coffee berry, and apple concentrates was Tryptophan > Tyrosine > Methionine ≥ Histidine ≥ 4-Hydroxyproline. This order was also consistent with the order of calculated bond dissociation energies (BDEs), reflecting the inherent antioxidant potentials of the amino acids studied. Density Functional Theory (DFT) was used to support a proposed “substrate zone” and “antioxidant zone” postulate for amino acids and related additives and this concept assists in demonstrating potential mechanisms involved in achieving such extraordinary enhancements and synergies. Histidine was used as a model system for DFT calculations, and allowable species had homolytic BDEs ranging from high (deactivated) to very low (activated), in the case of species (b) the BDE was at a level well below that of vitamin E, making it an excellent and potentially potent antioxidant. DFT calculations revealed that the histidine-Cu(I) complex had a comparable BDE to that of Trolox, again demonstrating how interactions between chemical constituents can influence, and in this case enhance antioxidant activity measurements. Synergies and antagonisms were also reported for eight classes of chemical constituents typically found in navel oranges. These mixtures were prepared based on the levels reported in nutritional data tables, and analyzed by ORAC and CAA-RBC assays. A correlation analysis revealed that the ORAC and CAA-RBC data did not correlate overall, however distinct clustering and several interesting outliers were noted. Cluster (a) had low ORAC and low CAA-RBC values, involving combinations of preservatives, sugars and CuNPs. Cluster (b) had low to moderate responses in both assays, and was made up primarily of vitamins in combination with CuNPs, preservatives, sugars and flavonoids. Cluster (c) was dominated by phenolics and their interactions with a number of groups, which gave high antioxidant activity in both ORAC and CAA-RBC assays, and amino acids are the main contributors in cluster (d). Organic acids featured in both outliers, firstly with a high antioxidant activity in both assays when combined with polyphenolics, and secondly as having an auto-oxidation effect in the CAA-RBC assay but a high ORAC value when analysed individually. Antioxidant activities of individual mixtures and combinations of classes of compounds showed antagonism/suppression of antioxidant activity between sugars and vitamins, and between polyphenolics and flavonoids in the ORAC assay. However, these same solutions resulted in antioxidant synergy in the CAA-RBC assay. In fact, the auto-oxidation effect of organic acids was reversed and synergies were noted in interaction with polyphenolics. A number of synergisms ex vivo involved polyphenolics in combination with other constituents such as vitamins, the amino acid Tryptophan, preservatives and CuNPs. These findings support the postulate that interactions at the “substrate zone” are influencing factors of antioxidant capacity at the molecular level. Computational chemistry was used to postulate mechanisms for antioxidant synergy, activation and deactivation of phenolic O-H groups, using quercetin and (-)-epicatechin-3-gallate as examples. It was concluded that factors including rainfall, amino acid and CuNPs addition, and interactions between common classes of food constituents influenced antioxidant activity in food systems. Computational chemical calculations were used to postulate mechanisms for antioxidant enhancement and synergy, a major influencing factor in antioxidant measurements. This research describes the potential for unlocking new and powerful antioxidant synergies in food systems, nutrition and health and the medical/pharmaceutical fields.

Dissertação de mestrado em Genética Molecular
Propolis is a complex mixture composed by resinous and balsamic material, produced by bees from branches, flowers, pollen, buds and exudates of trees and mixed with bees’ salivary secretions. Bees use propolis in the defense against invaders, protecting the hive from infections resulting from putrefaction. The chemical composition of propolis varies geographically, with the available flora, the climate, the harvesting time and the bee species. Different groups of compounds can be found in propolis extracts, such as flavonoids, phenolic acids and their esters. These compounds have been associated with different biological activities such as antimicrobial; antitumor; antioxidant and free radical scavenger; antigenotoxic and genotoxic; and antimutagenic. The aim of this work relates to the investigation on Portuguese propolis, particularly with regard to its chemical characterization and the evaluation of biological activities of this product in order to assess the possibility of its use/ exploitation in medical applications, cosmeticeutics and nutraceutics. The propolis samples selected for this study were collected in an apiary from Gerês, over four consecutive years and were used to prepare ethanol extracts (EE) which were tested in different assays, using the simple eukaryote S. cerevisiae as biological model. The comet assay was performed to analyze the genotoxicity/ antigenotoxicity and the results suggest that the EE prepared with propolis from Gerês harvested in 2012 (G12.EE) do not display significant genotoxic effect. On the other hand, propolis from Gerês does not protect cells against DNA damages caused by H2O2 either, a behavior displayed by any of the tested extracts (G11.EE, G12.EE, G13.EE e G14.EE). However, cells co- and pre-incubated with G.EE and 10 mM H2O2 displayed higher viability than cells incubated only with H2O2, suggesting that G.EEs protect yeast cells against oxidative stress. The same antioxidant activity was demonstrated by flow cytometry – a lower fluorescence of the intracellular fluorochrome dichlorofluorescein diacetate (H2DCFDA) was detected in cells co- and pre-incubated with G.EE and 5 mM H2O2 as compared with cells incubated only with H2O2 - and corroborated by several other assays in vitro that show the free radical scavenging activity of G.EEs. Antimicrobial activity was evaluated by the agar dilution method and the results suggest that G.EEs have antimicrobial activity, especially against Gram-positive spore forming bacteria. A synergistic effect of G.EEs when mixed with gentamicin was also demonstrated in the present work. The analysis of cells treated with G.EEs in the presence of the fluorochrome rhodamine 123 showed that propolis from Gerês has an influence on the inner mitochondrial membrane potential, decreasing the emitted fluorescence. All the studied propolis samples exhibited a very similar behavior in the different evaluated bioactivities, which in generally is contrary to the variability attributed to this natural product when harvested in different years, even from a single location. For this more constant bioactivities profile possibly contributes the type of standardized production of propolis used by the beekeeper in charge, unlike what makes the great majority of other beekeepers, particularly the Portuguese. A preliminary chemical analysis of G11.EE and G12.EE reveals no significant differences in terms of phenolics profiles, compounds to which the bioactivities of propolis are attributed, thus justifying the more constant behavior evidenced by the four studied extracts.
Própolis é uma mistura complexa formada por material resinoso e balsâmico, produzida pelas abelhas a partir de ramos, flores, pólen, brotos e exsudados de árvores, a qual é misturada com secreções salivares das abelhas. As abelhas utilizam o própolis na defesa contra invasores, protegendo a colmeia de infeções resultantes da putrefação. A composição química do própolis pode variar geograficamente, com a flora disponível, o clima, com a altura da colheita e a espécie de abelha. Diferentes grupos de compostos têm sido identificados em própolis, tais como flavonóides, ácidos fenólicos e os seus ésteres. Estes compostos têm sido associados com diversas atividades biológicas, nomeadamente: antimicrobiana; anti tumoral; antioxidante e quelante de radicais livres; anti-genotóxica e genotóxica; e antimutagénica. O objetivo deste trabalho prende-se com o estudo de amostras de própolis português, particularmente no que diz respeito à sua caracterização química e à avaliação das suas bioatividades, visando a possibilidade da sua utilização/ exploração em aplicações médicas, cosmecêuticas e nutracêuticas. O própolis selecionado para este estudo foi colhido num apiário no Gerês (G), em quatro anos consecutivos, e foi utilizado para preparar extratos etanólicos (EE), que por sua vez foram testados em diferentes ensaios, usando o eucariota simples Saccharomyces cerevisiae como modelo biológico. O ensaio cometa foi realizado para analisar a genotoxicidade/ antigenotoxicidade e os resultados evidenciam que o EE preparado com própolis do Gerês recolhido em 2012 (G12.EE) não apresenta efeito genotóxico significativo. Por outro lado, o própolis do Gerês também não protege as células contra os danos de DNA causados por peróxido de hidrogénio (H2O2), um comportamento exibido por qualquer um dos extratos testados (G11.EE, G12.EE, G13.EE e G14.EE. Contudo, células co- ou pré-incubadas com G.EEs e H2O2 10 mM exibiram maior viabilidade do que células incubadas apenas com H2O2, sugerindo que o propolis protege as células de levedura contra o stresse oxidativo. Esta atividade antioxidante foi também demonstrada por citometria de fluxo - a oxidação do fluorocromo intracelular diacetato de diclorofluoresceina (H2DCFDA) foi menor em células co- ou pré-incubadas com G.EEs e H2O2 do que em células incubadas apenas com H2O2 - e corroborada por outros ensaios in vitro que demonstraram um efeito quelante de radicais livres por parte dos G.EEs. Foi ainda constatado que os G.EEs, embora revelem baixa citotoxicidade para as células eucariotas testadas, têm atividade antimicrobiana particularmente expressiva contra bactérias Gram-positivas produtoras de esporos, tendo sido igualmente observado um efeito sinérgico com o antibiótico gentamicina. A análise de células tratadas com os vários G.EEs, na presença do fluorocromo rodamina 123, mostrou que o própolis do Gerês exerce influência sobre o potencial da membrana mitocondrial interna. Todas as amostras de própolis estudadas exibiram um comportamento muito semelhante nas diversas bioatividades avaliadas, o que de um modo geral contraria a variabilidade atribuída a este produto natural quando colhido em diferentes anos, mesmo que proveniente de um só local. Para este perfil de bioatividades mais constante contribui possivelmente o tipo de produção padronizada de própolis usada pelo apicultor responsável, ao contrário do que faz a grande maioria de outros apicultores, particularmente os portugueses. Uma análise química preliminar de G11.EE e G12.EE, releva não haver diferenças significativas em termos do seu perfil em compostos fenólicos, aos quais se atribuem as bioatividades de propolis, justificando assim o comportamento mais constante evidenciado pelos quatro extratos estudados.

Phospholipids can regenerate oxidized tocopherols and help delay lipid oxidation. The impact of emulsifier type, tocopherol homologue and phospholipid head group on tocopherol-phospholipid interaction was investigated in this study. Three µmol tocopherol/kg emulsion and 15.0µmol/kg emulsion of PE or PS were dissolved in oil and emulsions were prepared. Tween 20 or bovine serum albumin(BSA) was used as emulsifier and the continuous phase contained 10mM imidazole/acetate buffer at pH 7. Lipid hydroperoxides and hexanal were measured as lipid oxidation products and the lag phase was determined. With Tween 20 as the emulsifier, α and δ-tocopherol had a hexanal lag phase of 2 and 4 days respectively. PE and PS both extended the lag phase to 7 and 10 days respectively in presence of δ-tocopherol. Whereas, PS extended the lag phase to 6 days and PE could not exhibit any synergism with α-tocopherol. With BSA as the emulsifier, α and δ-tocopherol had a lag phase of 4 days. PE and PS extended the lag phase to 11 days and 10 days respectively in presence of δ-tocopherol and to 7 and 8 days respectively in presence of α-tocopherol. PE and PS both exhibited synergism with mixed tocopherol and the extent of synergism was in less than δ-tocopherol but more than α-tocopherol. Phospholipids could potentially be used with tocopherols to improve the oxidative stability of emulsions. PE was more effective with BSA whereas PS was equally effective with both emulsifiers.

Type II diabetes mellitus (T2DM) is a chronic disease that has a worldwide prevalence which is expected to rise dramatically over the course of the next thirty years. The disease has reached pandemic stages of development in many cultures, most notably in developing countries, followed somewhat closely by developed countries with access to an overabundance of refined carbohydrates and fat (refined oils). T2DM is a condition that can be prevented or managed, but not cured; therefore a method of stymieing the development of this disease is paramount to halting its progressively increasing morbidity. In this study, bartlett pear and kiowa blackberry were investigated in relation to their ability to modify and improve both glucose metabolism and hypertension management with in vitro assay models. Effectiveness and bioactive functionality was evaluated by various in vitro assays to study the properties of: 100% bartlett pear juice, 100% kiowa blackberry juice and a ratio of 70:30 pear: blackberry juice found to have increased phenolic properties due to synergy in previous studies. These assays aimed at determining: alpha-amylase and alpha-glucosidase inhibition, angiotensin converting enzyme inhibition, total soluble phenolic content and antioxidant capabilities. These juices were also fermented with Lactobacillus helveticus and Bifidobacterium longum, common yogurt culture strains, to investigate if fermentation would improve the bioactive functionality of pear: blackberry synergies. A secondary goal of the experiment was to investigate if these fruit juices could prevent the growth of Helicobacter pylori, which is a common bacterium found in the stomach which can lead to cancer.