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1
BREZILLON, CHRISTOPHE. "Metabolismes endogene et bacterien des catechines composes polyphenoliques majeurs du vin rouge. Etude in vitro et in vivo chez le rat a flore humaine." Paris, Institut national d'agronomie de Paris Grignon, 2001. http://www.theses.fr/2001INAP0015.
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La catechine et l'epicatechine sont des microconstituants polyphenoliques accredites d'une action preventive vis-a-vis des maladies cardio-vasculaires et de certains cancers. Notre objectif etait d'identifier, en comparant le rat sans germe (rsg) et le rat heteroxenique a flore humaine (rfh), des metabolites endogenes et bacteriens susceptibles d'activites biologiques. Des methodes chromatographiques (clhp) et spectrometriques (sm et rmn) conduisent a caracteriser les metabolites. Des etudes in vitro servent a identifier des bacteries responsables. En associant des bilans digestifs et metaboliques, chez le rsg, nous montrons que la catechine ingeree est largement absorbee et metabolisee au niveau endogene, seul 2% se retrouve a l'etat natif dans l'urine et 8% dans le caecum. La presence des formes glucuronidees et/ou sulfatees dans le caecum (4 mol/g ms) revele l'importance du cycle entero-hepatique. Dans l'urine et/ou les feces nous retrouvons egalement des formes methylees et, encore jamais decrites, des formes (ent) (ent)-epicatechine, 3-o-methyl-(ent)-epicatechine. Les etudes in vitro revelent la bioconversion de la catechine par la flore fecale du rfh dont nous isolons 13 souches actives : eggerthella lenta (n= 1), escherichia coli (n= 6) et enterococcus faecalis (n= 6). In vivo, au moins 10% de la catechine est transformee en plusieurs metabolites bacteriens : trois lactones la 5--(3, 4- dihydroxyphenyl)--valerolactone la 5--(3-hydroxyphenyl)--valerolactone, la 5--(4-hydroxy, 3-methoxyphenyl)--valerolactone et l'acide 3-hydroxyphenylpropionique, tous excretes par voie urinaire, temoignant de leur absorption massive. L'absence de metabolites endogenes fecaux temoigne de leur metabolisme secondaire par la flore. L'epicatechine se differencie de la catechine par une absorption superieure, l'emergence d'un nouveau metabolite endogene, l'epiafzelechine, et la stereospecificite des metabolites bacteriens. Les effets sante pourraient donc dependre d'un triple partenariat (absorption, transformation endogene, transformation bacterienne) s'exercant de facon locale et/ou systemique. Les activites biologiques de certains metabolites tels que les acides phenoliques et l'epiafzelechine ont deja fait l'objet d'etudes recentes, celles des formes (ent) restent a decouvrir.
2
Flôres, Maíra Frigo. "Efeitos do exercício físico e da suplementação com chá-verde sobre características bioquímicas e comportamentais associadas ao envelhecimento." Universidade Federal do Pampa, 2013. http://dspace.unipampa.edu.br:8080/xmlui/handle/riu/308.
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O envelhecimento causa rejuízos cognitivos e de memória que têm sido relacionados com o estresse oxidativo (EO). Descobrir formas de atenuar o EO é importante para minimizar perdas cognitivas. O exercício físico e as catequinas constituintes do chá verde são potenciais antioxidantes que podem auxiliar na proteção das funções cognitivas e de memória. Ao passo que evidências sugerem papel neuroprotetor do exercício, efeitos do chá verde durante o envelhecimento como estratégia para combater o EO ainda são bastante incipientes. Essa pesquisa verificou os efeitos do exercício físico e da suplementação com o chá verde sobre aspectos bioquímicos e comportamentais associados ao envelhecimento. Ratos Wistar com 9 meses de idade foram divididos em grupos, sendo eles: controle, exercício, chá verde, exercício e chá verde, além de um grupo controle jovem. As intervenções foram feitas por três meses, constando de exercício aeróbico e ingestão de chá verde de maneira isolada, e realização de exercício aeróbico com concomitante ingesta de chá verde. Em conclusão, o chá verde não evitou déficits cognitivos no envelhecimento, mas diminuiu as espécies reativas aumentando as defesas antioxidantes. O exercício melhorou diversos parâmetros bioquímicos e comportamentais. A falta de efeito do chá verde na cognição pode estar relacionada com as características da intervenção, ao passo que a diminuição nas espécies reativas sugere um papel de proteção do chá verde mesmo em um período curto de suplementação.
Aging is associated with cognitive and mnemonic deficits frequently reported as related to the oxidative stress (OS). There is continuous interest to minimize effects of OS in order to avoid cognitive deficits. Physical exercise and catechines from green tea are potential antioxidants helping to protect cognitive and memory functions. While there are evidences supporting the neuroprotective role of physical exercise, the effects of green tea supplementation during aging as strategy to combat OS still are quiet incipient. In this study the effects of physical exercise and green tea supplementation on biochemical and behavioral characteristics associated with aging were addressed. Wistar rats 9 months aged were organized in groups as follow: young control group; aged control group; exercise aged group; green tea supplementation aged group; exercise and green tea supplementation aged group. Interventions lasted 3 months composed by aerobic exercise and green tea, combined or not. Green tea was not effective in avoid cognitive deficits associated with aging, but significantly decreases ROS activity with significant improve in antioxidants defenses. Physical exercise improved all parameter in both biochemical and behavioral testing. The lack of effects of green tea on cognition may rely on the duration of the intervention, while decrease in the ROS suggests its effect role even during a short supplementation period.
3
Asim, Mohammed. "Metabolism and bioactivity of catechins." Thesis, University of Newcastle upon Tyne, 2017. http://hdl.handle.net/10443/3774.
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Green tea is widely consumed worldwide, second only to water. Its health effects have been attributed to its polyphenolic catechin content, which accounts for a significant percentage of its dry weight. Epidemiological studies have observed beneficial health effects of green tea catechins against some cancers, cardiovascular diseases, and neurodegenerative diseases. However most studies have also been carried out in vitro where the concentrations of catechins used are not obtainable in the human body. The in vivo situation is very complicated and relies on favourable absorption, metabolism, and excretion of the catechins. In this thesis it is reported, the potential health benefits of green tea catechins in tissues which are highly and most often in contact with catechins, the oral cavity and the intestine. In experiments modelling the oral cavity the four major catechins were extensively absorbed into H400 cells, and showed significant protection at physiological concentrations against H2O2 induced mitochondrial DNA damage. Thereafter the in vitro metabolism of catechins were measured using various intestinal and liver enzyme fractions. It was shown, that in these systems, glucuronidation was the main metabolism pathway. These enzyme fractions also provided mixtures of metabolites which were used to measure their comparative bioactivities in relation to their parent compounds. This was done via the assessment of their protective effects against H2O2 induced mtDNA damage in human intestinal cells. The metabolites were shown to be significantly bioactive; however the majority of the metabolites had lower bioactivities than the parent compound. In the final study the aim was to inhibit the glucuronidation of catechins to aid in the development of strategies to enhance catechin bioavailability. The two compounds chosen have previously been shown to inhibit intestinal glucuronidation. In this study it was determined that both piperine and quercetin significantly inhibited the metabolism of the catechins in intestinal microsomes. These studies taken together give a platform for future studies to be carried out which will be more detailed and rigorous.
4
Sheehan, James M. "The formation of catechists." Online full text .pdf document, available to Fuller patrons only, 2001. http://www.tren.com.
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Wollersen, Heike. "Bestimmung und Identifizierung von Flavonoiden in Gerste mit HPLC-DAD-MS/MS." [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=971821453.
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Cheung, Bernice. "Historical catechisms in the modern church." Online full text .pdf document, available to Fuller patrons only, 2002. http://www.tren.com.
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Mochizuki, Manabu. "Electrochemical and spectroscopic analysis on the oxidation of catechins." Kyoto University, 2005. http://hdl.handle.net/2433/145449.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第11239号
農博第1454号
新制||農||902(附属図書館)
学位論文||H17||N3984(農学部図書室)
22848
UT51-2004-U444
京都大学大学院農学研究科応用生命科学専攻
(主査)教授 池田 篤治, 教授 關谷 次郎, 教授 大東 肇
学位規則第4条第1項該当
8
Clarke, Kayleigh Anne. "Bioavailability and bioactivity of green tea catechins in skin." Thesis, University of Leeds, 2013. http://etheses.whiterose.ac.uk/6354/.
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Dietary flavonoids have been extensively researched in relation to health benefits in humans. The regular consumption of green tea catechins (GTC) has been associated with a reduction in the risk of developing diabetes, cardiovascular disease and cancer. Flavonoids are known to protect plants from the damage caused by exposure to UV radiation, and this effect has also been observed when flavonoids are applied topically to human skin cells. The effect of oral consumption of flavonoids on skin protection from UV exposure is not clear. The work presented within this thesis aimed to investigate the effect of GTC on the response of skin cells to UV induced-stress. Keratinocyte cells from an immortalised human skin cell line (HaCaT) were assessed after exposure to various stress conditions in vitro (FBS starvation, hydrogen peroxide and UV), in combination with a pre-treatment of green tea extract or a purified mixture of GTC. GTC reduced cell death induced by stress (decrease in LDH release), and maintained viability (increase in MTT uptake) in HaCaT cells, relative to control treatments. The uptake of vitamin C, a photo-protective agent depleted after UV exposure, was enhanced by treatment with GTC during stress conditions, as monitored by uptake of 14C-dehydroascorbic acid and evaluation of vitamin C transporters with qRT-PCR. In relation to in vivo conditions, GTC may provide protection and also enhance vitamin C uptake into skin cells undergoing stress. Bioavailability of GTC and metabolites in human skin cells after daily consumption of green tea and vitamin C supplements for 3 months was also investigated. Catechin metabolites in a range of tissues (plasma, interstitial blister fluid, skin biopsies and urine) were identified with LC-MS-MS in unconjugated and conjugated (sulphate, methyl and glucuronide) forms. For the first time, conjugated catechin metabolites were identified in skin tissue samples and extracellular fluid surrounding skin cells; including M6/M6'-O-sulphate, O-methyl-EC-O-sulphate,EC-O-sulphate and EGC-O-glucuronide, with metabolites identified in urine and plasma post-consumption similar to data reported in the literature. The work presented in this thesis provides new knowledge on bioavailability of GTC and metabolites in human skin, which together with vitamin C, may exert UV protection and other health benefits. Further research is required in vitro using pure conjugated standards (methyl, glucuronide and sulphate moieties), and data corresponding to the inflammatory biomarkers post-UV exposure (analysis at the University of Manchester and University of Bradford) is also required before a conclusive relationship can be drawn between oral consumption of flavonoids and UV protection.
9
McEvilly, Christine A. (Christine Ann). "Catechisms and cataclysms : communication in the Reformation." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/59489.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Humanities, Arts, and Social Sciences [SHASS], History Section, 2007.Includes bibliographical references (leaves 87-88).
How does belief shape lived experience? This is a central question of existence that all people confront, be they philosophers or farmers. It is not simply a matter of religious belief but a problem that stems from the very core of what it means to be human. Who could decide how to spend their lives without defining priorities? Yet such profound choices are necessarily based on implicit beliefs, valuations of worth and existence. The Reformation period in early modem Europe shines a particularly bright light upon these fundamental questions. Once Martin Luther nailed his Thesis to the church door in Wittenberg in 1517, and in the religious turmoil of the sixteenth and seventeenth centuries that followed, no one could avoid considering basic questions about their faith, even if only to defend what had been the status quo. Furthermore, the personal beliefs of Martin Luther and his German princes became a subject that could change the political course of nations. It was in Martin Luther's crucible of religious turmoil that personal belief and government began to shape each other in drastic and visible ways, an interaction which not only emphasizes the importance of belief, but also highlights the problem of popular beliefs, which are difficult to discern in times of religious quietude. But why examine belief? Are there not other more visible expressions of historical change? Ultimately, history is about individuals. One can examine the great political and economic trends of nations, but they only have meaning as they relate to individual existence. What is a modern nation state, if not a collection of its citizens and of how they live, work, interact, and think? Examining the religious beliefs of a society allows one to look at thought and actions in those who were far removed from "high" intellectual culture; for the thoughts of those who composed the massive majority of European society cannot be ignored simply because they were not always expressed in easily retrieved written discourses. Luckily, since theologians, politicians, and activists tried to influence popular belief, their records can be examined. The methods used to influence belief and practice, suggest not only what was in fact believed, but also what topics were of central concern to society's dialogue on religious change. Belief can have power over forces and institutions far larger than any single believing individual. Indeed, the very idea that religion is an issue of concern to individuals and not defined at the level of a city or nation was a novel one in the early modem era. Not surprisingly, and such a fundamental change in the concept of the individual had widespread consequences. This work examines the transmission of reformation ideas from scholars and theologians to lay parishioners in both the Protestant and Catholic traditions. It considers how large scale revolutions in religious thought affected the lives, piety, and religious practice of ordinary individuals. Yet the examination of this theme of transmission and communication is ultimately just a small part of one of the questions that historians have debated: Can the Reformation period be seen as offering up a true division into two different religions, or should it be seen as a moment during which both Catholic and Protestant traditions modernized in parallel to each other? Of course, both views contain some elements of truth; both churches managed to modernize, but nevertheless had fundamental differences in both theology and practice. However, an equally vital question is, perhaps, whether the churches' interactions with society were characterized by the differences between them or by the similar, modern forms both churches shared. This work ultimately suggests that the differences that had developed between Catholic and Protestant traditions by the mid seventeenth century are dwarfed by the changes in both that converted medieval practice to a more modem system. These modem religious traditions would come to co-exist with modern nation states, evolving economic practice, re-defined communities, and the secularization of Europe. Similarities in Protestant and Catholic communication of new theology and reformed practice can be identified and traced, lending support to the theory of parallel reform with similar outcomes, particularly in terms of community and state, even if their respective theologies contained real differences. Communication provides a useful lens for examining this question of difference and modernization since it involves many elements of the two reformed traditions. The choice of what information was to be transmitted, suggests which new theologies the churches thought significant and which were important to the contentious dialogues of the period. The forms of communication speak to the regular functioning of the church as an organization, and suggest how authority figures interacted with their laity. The composition of the audience suggests the new community definitions of each church. This essay will examine three mediums for communicating the agenda of reform in the late sixteenth and early seventeenth centuries: architecture and visual art, education, and discipline and charity, insofar as they defined community ...
by Christine A. McEvilly.
S.B.
10
Mehra, Anisha. "The effects of green tea derived catechins upon adipocyte metabolism." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/12115/.
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Tea, from the plant Camellia Sinensis, is after water, the most consumed drink in the world. Green tea, produced by steaming freshly harvested leaves to prevent fermentation, is high in polyphenols known as catechins or flavanols. The major flavanols found in green tea include (-) epigallocatechin-3-gallate (EGCG) and (-) epicatechin. Literature reports suggest that green tea flavanols have the potential to exert anti-obesity effects by modulating weight gain and other factors such as lipogenesis, β-oxidation and adipokine release. Key features of obesity and associated insulin resistance are adipokine dysregulation, decreased sensitivity of adipocytes to insulin and subsequently, changes in glucose uptake by cells. The aims of this thesis were firstly to establish an efficient system of differentiated adipocytes and secondly to use this to investigate the effects of the flavanols EGCG and epicatechin on physiological outcomes such as adipokine release and glucose uptake. Thirdly, the question of whether these processes might be regulated by the ERK1/2 pathway and what may be happening upstream of this was explored. Finally, the effect of flavanol treatment on adipocyte gene expression of genes known to be modulated in obesity was investigated. Using the well established cell culture model of 3T3-L1 adipocytes, the studies from this thesis show that EGCG and epicatechin are able to modulate the release of the adipokines adiponectin and resistin, dependent on the media glucose concentration. This modulation may be mediated by the ERK1/2 pathway, since flavanol treatment increased ERK1/2 phosphorylation. Uptake of glucose was not altered by any time or concentration of EGCG or epicatechin, and there were no significant changes in adipocyte gene expression following EGCG or epicatechin treatment. A thorough investigation of adipokine release, ERK signalling, glucose uptake and gene expression, under the influence of flavanol treatment, showed that although molecular changes occurred in the 3T3-L1 system, these did not translate into functional readouts. Therefore, it appears unlikely that these have major direct effects on adipocyte function.
11
余詩德 and Sze-tak Yu. "Effects of Chinese green tea and tea catechins on lipolysis." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31969677.
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Yu, Sze-tak. "Effects of Chinese green tea and tea catechins on lipolysis." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21106137.
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Locher, Sanja Verfasser], and Peter [Akademischer Betreuer] [Schreier. "Analytische und Effektor-Studien von Catechinen / Sanja Locher. Betreuer: Peter Schreier." Würzburg : Universitätsbibliothek der Universität Würzburg, 2011. http://d-nb.info/101493284X/34.
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Beyer, Birgit [Verfasser]. "Untersuchungen zur Bioverfügbarkeit von Catechinen und Quercetin beim Rind / Birgit Beyer." Kiel : Universitätsbibliothek Kiel, 2015. http://d-nb.info/1076038360/34.
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Bursill, Christina. "Green tea and its catechins upregulate the low-density lipoprotein receptor /." Title page and abstract only, 1996. http://web4.library.adelaide.edu.au/theses/09SB/09sbb972.pdf.
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Salerno, Joseph A. "The approbation of catechisms in the 1983 Code." Theological Research Exchange Network (TREN), 1986. http://www.tren.com.
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Bernet, Ernest. "Sanctification as confessed by Luther in his catechisms." Theological Research Exchange Network (TREN), 1994. http://www.tren.com.
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Lindsay, Karen Martin. "Types, metaphors and symbols for baptism in the catechetical, artistic and liturgical genres of the early Church : a literary-aesthetic approach to the study of typology in early Christian hermeneutics." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368225.
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In the historico-critical paradigm typology was defined in terms of prefiguration and identified with corresponding events in `salvation history. ' In contrast, Frances Young identifies typology as a hermeneutic which has its roots in the literary structure of texts. The object of this thesis is to explore the phenomenon of typology within the hermeneutics of the early Church and to assess typology's contribution to the formation of Christian identity and culture. The thesis proposes an integrated approach to the study of type, metaphor and symbol across literary and aesthetic genres, and within a limited context, i. e., Christian initiation. The introduction to the thesis surveys typology within the historical and literary paradigms. Section one considers varied uses of typology in the catechetical homilies of the Fathers. Section two looks at typology in the artistic programmes of some early Christian baptisteries. Section three surveys uses of typology in some prayers of early baptismal liturgies. By redefining typology in terms of mimesis, multi-valence and multi-culturalism we are able to demonstrate the way in which early Christians forged imaginative links between their own worshipping community and the world of Scripture, through typology.
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Quesada, Isabel Maria. "Effects of dietary catechins and proanthocyanidins on zinc homeostasis in hepatic cells." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8695.
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Les catequines i els seus polímers, les procianidines, són flavonoids presents en hortalissesi fruits amb efectes beneficiosos sobre la salut. Actuen com a antioxidants segrestant
espècies reactives d'oxigen (ROS) i quelant els metalls ferro i coure. També es comporten
com a molècules senyalitzadores, modulant múltiples vies de senyalització i metabòliques i
l'expressió gènica, incloent-hi la d'enzims antioxidants. Resultats previs del Grup de Recerca
en Nutrigenòmica mostren que una dosi oral aguda d'un extracte de procianidines de llavor
de raïm (GSPE) reprimeix l'expressió de les metal·lotioneïnes (MT), proteïnes lligadores de
zinc, a fetge de rates, i tanmateix incrementa l'expressió del receptor nuclear orfe small
heterodimer partner.(SHP/Nr0b2) (Del Bas et al., 2005). Igualment, es va demonstrar que les
procianidines actuen com a coactivadors transcripcionals del receptor nuclear d'àcids biliars
Farnesoid X Receptor (FXR), el qual es responsable de la sobre-expressió de SHP causada
per GSPE a cèl·lules hepàtiques, i de l'efecte hipotrigliceridèmic de les prociandines effect
(Del Bas et al., 2008; Del Bas et al., 2009).
Els objectius d'aquesta Tesi van ser determinar si les catequines i procianidines
interaccionen amb el zinc, avaluar el seu efecte sobre l'homeòstasi del zinc en cèl·lules
hepàtiques -incloent l'efecte sobre l'expressió de genes MT, utilitzats aquí com a
biomarcadors de l'activitat de les procianidines a cèl·lules hepàtiques-, i disseccionar els
mecanismes pels quals les procianidines afecten l'homeòstasi del zinc, en particular
confirmar si els gens MT són dianes de SHP i FXR.
Els resultats obtinguts mostren que GSPE, així com diverses catequines i procianidines
pures, incloent-hi el flavonoid del te verd (-)-epigallocatechin-3-gallate (EGCG), lliguen
cations de zinc en solució amb una afinitat més gran que el quelant específic de zinc
Zinquin. En cèl·lules d'hepatocarcinoma humanes HepG2, GSPE inhibeix l'acumulació
intracel·lular de zinc i contraresta els efectes tòxics de dosis elevades de zinc sobre la
viabilitat cel·lular. GSPE reprimeix l'expressió de gens de MTs i d'exportadors de zinc mentre
que estimula l'expressió d'importadors de zinc. L'expressió dels importadors de zinc de la
xarxa Trans-Golgi és estimulada per GSPE. A més a més, GSPE bloqueja la inducció de
l'expressió de MTs per la citoquina proinflamatoria IL-6, pel generador de ROS tBOOH, per
l'agonista de receptors de glucocorticoids dexametasona, i pels metalls coure i zinc.
EGCG reprodueix els efectes de GSPE sobre l'homeòstasi del zinc en HepG2, reprimint
l'expressió de MTs i d'exportadors de zinc, estimulant l'expressió d'importadors de zinc, i
UNIVERSITAT ROVIRA I VIRGILI
EFFECTS OF DIETARY CATECHINS AND PROANTHOCYANIDINS ON ZINC HOMEOSTASIS IN HEPATIC CELLS
Isabel Maria Quesada
ISBN:978-84-694-1258-9/DL:T-322-2011
inhibint l'acumulació de zinc intracel·lular i la toxicitat de dosis elevades de zinc. La
procinidina dimèrica B1 i la trimèrica C1 es comporten tenen efectes contraris als de GSPE i
EGCG pel que fa a l'expressió de MT i l'acumulació de zinc total en cèl·lules HepG2.
Pel que fa al zinc làbil citoplasmàtic, la minúscula fracció del total del zinc cel·lular que
modula múltiples vies metabòliques i senyalitzadores, tant GSPE com EGCG i C1 eleven en
gran manera els nivells de zinc làbil detectable per Zinquin a cèl·lules HepG2.
Experiments amb ratolins KO per SHP o per FXR han demonstrat que GSPE reprimeix
l'expressió postprandrial de gens MT a fetge per una via que no depen de SHP però que és
depenent de FXR. A més, l'àcid biliar CDCA, un lligand fisiològic i activador de FXR,
reprimeix l'expressió de gens MT a cèl·lules HepG2. Per tant, els gens MT són diana de FXR
i, conseqüentment, FXR apareix com un receptor nuclear que modula l'homeòstasi del zinc.
Per explicar aquests resultats, proposem que catequines i procianidines poden actuar tant
com a segrestadors de zinc -evitant la seva entrada a la cèl·lula a través dels transportadors
de zinc de membrana plasmàtica-, com d'ionòfors de zinc -cotransportant cations zinc a
través de la bicapa lipídica i incrementant així els nivells de zinc làbil citoplasmàtic. La
repressió de gens MT induïda per l'activació de FXR per GSPE podria també contribuir a
l'increment de zinc làbil, en impedir que els cations zinc siguin segrestats per apo-tioneïna
sintetitzada de novo.
Donat el paper del zinc làbil com a modulador de múltiples víes de senyalització i
metabòlics, formulem la hipòtesi que la quelació extracel·lular de cations de zinc i l'elevació
de zinc làbil citoplasmàtic són mecanismes subjacents a l'activitat biològica de catequines i
procianidines i, per tant, que les vies metabòliques i de senyalització afectades pel zinc làbil,
ho seràn també per aquests flavonoids.
Effects of dietary catechins and proanthocyanidins on zinc homeostasis in
hepatic cells.
Catechins and their polymers procyanidins are health-promoting flavonoids found in edible
vegetables and fruits. They act as antioxidants by scavenging reactive oxygen species and
by chelating the redox-active metals iron and copper. They also behave as signaling
molecules, modulating multiple cell signaling and metabolic pathways and gene expression,
including that of antioxidant enzymes. Previous results of the Nutrigenomics Reseach Group
showed that an oral acute dose of a grape-seed procyanidin extract (GSPE) represses the
expression of the zinc-binding protein metallothionein (MT) genes in rat liver, and enhances
the expression of the orfan nuclear receptor small heterodimer partner (SHP/Nr0b2) (Del Bas
et al., 2005). In addition, it was shown that procyanidins act as transcriptional coactivators of
the nuclear bile acid receptor Farnesoid X Receptor (FXR), which in turns upregulates SHP
expression, thereby exerting an hypotrygliceridemic effect (Del Bas et al., 2008; Del Bas et
al., 2009).
The objectives of this Ph.D. Thesis were to determine whether catechins and procyanidins
interact with the redox-inactive metal zinc, to evaluate their effect on zinc homeostasis in
hepatic cells -including the expression of MT genes, used here as a biomarkers of
procyanidin activity in hepatic cells-, and to disect the mechanisms by which procyanidins
affect cellular zinc homeostasis, in particular to asses whether MT genes are targets of SHP
and FXR.
Our results show that GSPE, as well as individual catechins and procyanidins tested,
including the green tea flavonoid (-)-epigallocatechin-3-gallate (EGCG), bind zinc cations in
solution with higher affinity than the zinc-specific chelator Zinquin. In human
hepatocarcinoma HepG2 cells, GSPE inhibits intracellular zinc accumulation and counteracts
the toxic effects of excess zinc on cell viability. At the mRNA expression level, GSPE
downregulates MTs and zinc-efflux transporters while upregulating zinc-influx transporters.
Zinc importers of the Trans-Golgi network are upregulated by GSPE. In addition, GSPE
blocks the induction of MTs expression by the proinflammatory cytokine IL-6, the ROS
generator tBOOH, the glucocorticoid receptor agonist dexamethasone, and the metals
copper and zinc.
EGCG reproduces the major effects of GSPE on zinc homeostasis in HepG2, downreguling
the expression of MTs and zinc-efflux transporters, while upregulating the expression of zincinflux
transporters, concomitantly inhibiting intracellular zinc accumulation and the toxicity of high zinc doses. Procyanidin dimer B1 and trimer C1 behave opposite to GSPE and EGCG
with regard to MT expression and intracellular zinc accumulation in HepG2 cells.
Concerning cytoplasmic labile zinc, the tiny fraction of total cellular zinc that modulates
signaling and metabolic pathways, we found that GSPE, EGCG and trimeric procyanidin C1
greatly elevate Zinquin-detectable labile zinc in HepG2 cells.
Experiments with SHP-null and FXR-null mice demonstrate that GSPE downregulates
postprandial expression of MT genes in the liver, in a SHP-independent but FXR-dependent
manner. In addition, chenodeoxycholic acid, a physiological ligand and activator of FXR,
represses the expression of MT genes in HepG2 cells. Thus, MT genes are targets of FXR
and, consequently, FXR is revealed as a modulator of zinc homeostasis.
To explain these results, we postulate that catechins and procyanidis may act both as
sequestrants of zinc -thereby impeding the entrance of zinc cations to the cell through
plasma membrane zinc transporters-, and as zinc ionophores -thereby cotransporting zinc
cations through the lipid bilayer and increasing the levels of cytoplasmic labile zinc.
Repression of MT expression by procyanidin-activated FXR might also contribute to the
increment of the labile pool of zinc, by hindering the sequestration of zinc-cations by de novo
synthesized apo-thionein.
Given the role of labile zinc as modulator of multiple intracellular signaling and metabolic
pathways, we forward the hypothesis that extracellular complexation of zinc cations and
subsequent elevation of cytoplasmic labile zinc may be relevant mechanisms underlying the
health-promoting activity of catechins and procyanidins and, therefore, that the signaling and
metabolic pathways modulated by labile zinc will be aslo a target of these flavonoids.
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Kafley, Suvash. "Distribution of catechins, epicatechins and methylxanthines in caffeinated and decaffeinated green tea." Online version, 2008. http://www.uwstout.edu/lib/thesis/2008/2008kafleys.pdf.
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Peng, Zhongkui. "Feeding determinants in aphids with special reference to the Rose Aphid Macrosiphum rosae (L.)." Title page, table of contents and introduction only, 1991. http://web4.library.adelaide.edu.au/theses/09PH/09php398.pdf.
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Bibliography: leaves 170-189. This thesis looks at aphid feeding determinants by type and location. It examines the role of leaf surface chemicals in the discrimination of host plants and the deterrent effect of catechin and its oxidative condensation products.
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Ehrnhöfer, Dagmar Elisabeth. "Green tea catechins change the aggregation behavior of proteins associated with neurodegenerative disease." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2007. http://dx.doi.org/10.18452/15624.
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Eine Gemeinsamkeit verschiedener neurodegenerativer Erkrankungen ist die abnormale Ansammlung von Proteinen im Gehirn, wie z. B. von alpha-Synuclein (Syn)-Aggregaten bei der Parkinson''schen Krankheit (PD) oder von Huntingtin (Htt)-Aggregaten bei Chorea Huntington (HD). Am Anfang dieser Studie wurde eine Bibliothek von ca. 5000 natürlichen Substanzen nach Inhibitoren der Htt-Aggregation durchsucht. Eine der wirksamen Substanzen war (-)-Epigallocatechingallat (EGCG), eine Verbindung, die in grünem und schwarzem Tee vorkommt. Die antioxidativen Eigenschaften von EGCG wurden bereits mit einer neuroprotektiven Wirkung in Verbindung gebracht, was EGCG zu einem vielversprechenden Kandidaten für die Entwicklung einer neuen Behandlungsmethode macht. Eine inhibierende Wirkung auf Proteinaggregation wurde jedoch bis jetzt noch nicht nachgewiesen. Diese Studie zeigt, dass EGCG die Aggregation von Htt und Syn hemmt, indem es dosisabhängig eine oligomere Proteinkonformation stabilisiert. Diese Oligomere wirken jedoch nicht als Keime in Aggregationsreaktionen. Zusätzlich verändert EGCG die Exposition bestimmter Epitope, die von konformationsspezifischen Antikörpern im Laufe der Aggregation erkannt werden. Daher könnte die Substanz Proteine, die zur Aggregation neigen, auf einen alternativen Faltungspfad in der Missfaltungskaskade führen. Weiterhin legen die Ergebnisse nahe, dass eine direkte Wechselwirkung zwischen EGCG und Proteinen in einer ungefalteten Konformation stattfindet. In verschiedenen Zellkultur-Modellsystemen verringerte EGCG die Toxizität, die von missgefalteten Proteinen ausgeht, was nahelegt, dass die neu geformten oligomeren Spezies nicht toxisch sind. EGCG könnte daher ein chemisches Chaperon darstellen, das die Missfaltung und Toxizität von Proteinen, die mit neurodegenerativen Krankheiten assoziiert sind, verringert. Die Substanz könnte daher die Basis zur Entwicklung einer neuen Therapie für diese unheilbaren Krankheiten darstellen.A common feature of neurodegenerative disorders is the abnormal accumulation of aggregated protein the brain, such as alpha-Synuclein (Syn) aggregates in Parkinson''s disease (PD) and Huntingtin (Htt) aggregates in Huntington''s disease (HD). In this study, a library of approximately 5000 natural compounds was screened for inhibitors of Htt aggregation. One of the hits was (-)- Epigallocatechin gallate (EGCG), a compound present in green and black tea. The antioxidant properties of this substance have been linked to neuroprotection before, making it a promising candidate for the development of a treatment for neurodegenerative diseases. Inhibition of protein aggregation by EGCG, however, has not been demonstrated so far. This study shows that EGCG inhibits the aggregation of Htt and Syn by stabilizing an oligomeric conformation of the respective proteins in a dose-dependent manner. These oligomers do not seed the aggregation of Htt and Syn. Also, EGCG modifies the exposure of different epitopes recognized by conformation-specific antibodies during the aggregation process. The compound might therefore lead aggregation-prone proteins on an alternative folding pathway in the misfolding cascade. The results furthermore suggest that direct interaction occurs between EGCG and proteins in an unfolded conformation. EGCG also reduces toxicity caused by misfolded Htt or Syn in cell culture model systems, suggesting that the oligomeric protein species formed in the presence of EGCG are not toxic to living cells. EGCG might therefore represent a chemical chaperone that can modulate misfolding and toxicity of proteins associated with neurodegenerative diseases and could provide the basis for the development of a novel pharmacotherapy for these fatal disorders.
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Botten, Dominic Frith. "A computational exploration of green tea catechins and their interaction with cardiac proteins." Thesis, King's College London (University of London), 2015. https://kclpure.kcl.ac.uk/portal/en/theses/a-computational-exploration-of-green-tea-catechins-and-their-interaction-with-cardiac-proteins(21113980-000f-4c0a-b760-4336e7ef3ee3).html.
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Green tea catechins have been in use for some time as a curative for a number of disorders and illnesses, however their direct benefits are still disputed. In this thesis several computational techniques have been applied to systems involving green tea catechins in order to study their properties and better ascertain their supposed health benefits. Based on first principles data, classical force fields of four selected green tea catechins (-)-Epigallocatechin 3-Gallate (EGCg), (-)-Epicatechin 3- Gallate (ECg), (-)-Epigallocatechin-3-O-(3-O-Methyl)-Gallate (EGCmg) and (-)-Epigallocatechin (EGC) have been parametrised in order to examine their behaviour under different conditions. Classical Molecular Dynamics coupled with Metadynamics has been used to explore the potential energy surface of these molecules as a function of selected torsions deemed crucial to the conformation of the system. In depth analysis of their interactions under classical conditions has been carried out in gas phase, water and chloroform. The catechins EGCg and EGC were further examined using Density Functional Theory (DFT) to determine their radical properties which are closely linked to their antioxidant activity. By calculating their ionisation potentials, bond dissociation enthalpies and acidity in gas phase, water and benzene solution we find little difference in their energies, despite large structural differences, and we investigate the limit of DFT in accurately describing these systems. Classical simulations of the cardiac protein Troponin C (a protein known to be crucial to the process of heart contraction), in complex with EGCg, were carried out from the basis of previous experimental work and it was found that EGCg exerts a stabilising effect on the calcium ion mobility present in the system and may help regulate calcium signalling in the cardiac sarcomere. Using sparse experimental data as a guide, alternative proteinligand binding possibilities were uncovered and used to help validate and expand the current experimental knowledge on the troponin C - troponin I system, giving rise to two low affinity, non-specific binding sites for EGCg which also affect calcium mobility.
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Ahn, Jinsoo. "Characterization of (+)-Catechin and Quercetin from Pawpaw Pulp." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1307045912.
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Charoenchon, Nisamanee. "Can green tea catechin supplement protect against photoageing?" Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/can-green-tea-catechin-supplement-protect-against-photoageing(64eefb5f-ef37-4900-9c03-3477c8a74e50).html.
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Photoaged skin caused by chronic ultraviolet radiation (UVR) is characterised clinically with hyperpigmentation, coarse skin texture and deep wrinkles; the worst outcome is skin cancer. Histological investigation of the alteration within major extracellular matrices (ECM; elastic fibres, fibrillar collagens) is essential study to understand the cellular effect on skin structure from UVR. This thesis used an acute dose of radiation to examine in humans in vivo the effect of UVR on ECM components before assessing whether a dietary intervention could protect skin from UVR damage. Green tea catechins (GTCs) have anti-oxidant properties and may be an interesting option as a systemic photoprotection agent. Hence this thesis assesses: 1) the effect of acute irradiation of skin on dermal ECM damage to see whether it mimics the changes observed in photoageing and; 2) whether dietary supplementation with GTC will provide dermal ECM protection. UV-induced change in elastic fibre network. Initially, the effect of two different UV light sources on elastic fibre protein (elastic fibres, fibrillin-rich microfibrils and fibulin-2 and -5 microfibrils) remodelling was performed. The effect of ultraviolet B vs full-spectrum solar simulated radiation (SSR) were investigated in a small sample of healthy Caucasian volunteers (n = 6 per group). At 24 hour after 3× MED irradiation, Weigert's resorcin–fuchsin stained elastic fibres showed a significant reduction regardless of irradiation protocol (UVB, P<0.01; SSR P<0.05). Specific components were identified by immunohistochemistry; a significant reduction in fibrillin-rich microfibrils (FRM) was observed in UVB-irradiated skin (P<0.05), whilst fibulin-5-positive microfibrils were only affected by SSR (P<0.05). The data revealed, therefore, differential effects on UV wavelength on ECM remodelling. SSR, the more physiologically relevant light source was used in subsequent studies Supplement effect in SSR-induced damage in elastic fibre. Fifty healthy volunteers were recruited to this randomised control trial to investigate whether GTC can protect skin from photodamage. Volunteers were randomized to GTC (1080 mg plus 100 mg vitamin C; n=25) or placebo (maltodextrin; n = 25) daily for 12-weeks with compliance assessed biochemically in urine samples. Of the n = 50 recruited, 44 volunteers completed the study. In baseline, UVR challenge resulted in a significant remodeling of the cutaneous elastic fiber system (P<0.001), particularly fibulin-2 and fibulin-5-positive microfibrils at 24-hr after 3×MED irradiation. In post-supplementation, fibulin-5 positive microfibrils were protected from UVR remodeling (% staining, mean ± SE; no UV, 18.1±0.89; UVR, 17.1±0.61; P=0.30) whilst no protection was seen in the placebo group (no UVR, 19.41±0.79; UVR, 17.69±0.61; P<0.05). Supplement effect in SSR-induced damage in collagenous matrix. In the identical experiment, collagenous matrices including synthesis of procollagen I was also examined as fibrillar collagens are the major ECM components providing strength within dermis. The fibrillar collagen and newly synthesised procollagen I were stained by Picrosirius red and immunohistochemistry respectively. At baseline, acute irradiation significantly reduced papillary dermal fibrillar collagens (P<0.001) and induced deposition of newly synthesised pro-collagen I (P=0.02). In post-supplementation, GTC enhanced the deposition of thin collagen fibres in the dermis. Whilst placebo showed no effect on the altered organisation of fibrillar collagens or deposition of pro-collagen I following the irradiation challenge, GTC protected the organisation of fibrillar collagens in the papillary dermis (P=0.97).This novel in vivo human study may be used to recapitulate elastic fibre and collagen changes associated with photoageing and may be useful for dissecting out the mechanisms underlying extracellular matrix damage in response to chronic sunlight exposure. Furthermore, in a randomized control trial, dietary GTC protected fibulin-5 microfibrils and collagen fibres in the papillary dermis from UV-mediated degradation. The mechanism by which this protection occurs requires further study.
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Sheibani, Ershad. "Effects of water chemistry and panning on flavor volatiles and catechins in teas (Camellia sinensis)." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/71287.
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In the first experiment, effects of brewing time, chlorine, chloramine, iron, copper, pH and water hardness were investigated for their effects on extraction of epigallocatechine gallate (EGCG) and caffeine in green tea and oolong tea aqueous infusions. The extraction of EGCG and caffeine were lower when green tea was brewed in hard water compared to distilled water. Brewing green tea and Oolong tea in tap water resulted in higher extraction of caffeine but had no effect on EGCG compared to distilled water. The extraction of EGCG and caffeine were significantly increased (P<0.05) when green tea and Oolong tea were brewed in the chlorinated water at 4.0 mg free chlorine per liter.
The purpose of the second experiment was to optimize SDE conditions (solvent and time) and to compare SDE with SPME for the isolation of flavor compounds in Jin Xuan oolong tea using Gas Chromatography- Mass Spectrometry (GC-MS) and Gas Chromatography- Olfactrometry (GC-O). The concentration of volatile compounds isolated with diethyl ether was higher (P<0.05) than for dichloromethane and concentration was higher at 40 min (P<0.05) than 20 or 60 minutes. For SDE, 128 volatiles were identified using GC-MS and 45 aroma active compounds using GC-O. The number of volatiles identified using GC-MS was lower in SPME than SDE. For SPME, 59 volatiles and 41 aroma active compounds were identified. The composition of the volatiles isolated by the two methods differed considerably but provided complementary information.
The goal of the third experiment was to determine effects of panning on flavor volatile compositions of oolong using GC-MS and GC-O. Simultaneous Distillation and Extraction (SDE) and Solid Phase Microextraction (SPME) techniques were applied for extraction of volatiles in panned and unpanned teas. A total of 190 volatiles were identified from SDE and SPME extractions using GC-MS and GC-O. Trans-nerolidol, 2- hexenal, benzaldehyde, indole, gernaiol, and benzenacetaldehyde contents were significantly decreased (P<0.05) by panning; however, panning increased (P<0.05) contents of linalool oxide, cis jasmone, methyl salicylate in oolong tea. Overall, panning significantly changes the volatile compositions of the tea and created new aroma active compounds.Ph. D.
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Jiang, Dian Dong. "Potential chemo-prophylactics effect of green tea catechins in pre-malignant and malignant prostate." Thesis, University of Nottingham, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.580302.
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Green tea catechins have been recognized as a potential chemopreventive agent for prostate. Prostatic intraepithelial neoplasia (PIN) lesion is widely accepted as the pre-invasive stage of adenocarcinoma and a predictive marker of prostate cancer development. This study confirmed that novel catechin-derivatives showed a greater inhibitory effect on proliferation in PIN cells than in PCa cells. In addition, two minor existing catechins, (-)-epigallocatechin (EGC) and (-)- epicatechin (EC) showed a synergistic inhibitory effect on PIN cell growth, invasion, migration and progression of PIN to a mesenchymal-like invasive phenotype by inhibition of Epithelial Mesenchymal Transition (EMT)-associated transcriptional factors such as Twist, Snail, Slug and Zeb-l. In this study, a carcinoma-associated fibroblast (CAF)-like human bone marrow- derived mesenchymal stem cells (hMSCs) was established via exposing hMSCs to human prostate tumour-conditioned medium (TCM). TCM-exposed hMSCs exhibited the ability to promote tumour cell growth of prostate and colon cancer and PIN cell invasion. Green tea catechin treatment inhibited PIN cell invasion by reversal of EMT. A chemo-resistant (CR) prostate cell line (CR-PC3M) was established and exhibited a greater resistance to several chemotherapeutic drugs such as 5- fluorouacil, Taxotere and Doxorubicin, and expressed a high level of a drug resistance-associated transporter ABCG2 and the cancer stem cell (CSC) marker
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Kim, Mihye. "Studies on potential side-effects of green tea catechins on colitis and colon carcinogenesis." Kyoto University, 2007. http://hdl.handle.net/2433/136570.
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Kyoto University (京都大学)0048
新制・課程博士
博士(農学)
甲第13403号
農博第1658号
新制||農||948(附属図書館)
学位論文||H19||N4299(農学部図書室)
UT51-2007-Q804
京都大学大学院農学研究科食品生物科学専攻
(主査)教授 入江 一浩, 教授 吉川 正明, 教授 伏木 亨
学位規則第4条第1項該当
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Forrest, Neil David. "Studies on new approaches for the radiolabelling of (+)-catechin." Thesis, University of Glasgow, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410656.
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Ryle, Peter Robert. "Ethanol-induced fatty liver : protective action of (+)-catechin compounds." Thesis, University of Surrey, 1986. http://epubs.surrey.ac.uk/847975/.
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The aim of the work presented in this thesis was to assess the protective properties of the bioflavanoid drug, (+)-catechin, and its palmityl ester, 3-palmitoyl-(+)-catechin, against ethanol hepato-toxicity (ie: fatty liver) in the rat. In initial experiments, both (+)-catechin compounds were found to protect against the hepatic lipid accumulation (mainly triglyceride) after acute ethanol dosing, and after long-term feeding of ethanol in a liquid diet. In the latter situation, 3-palmitoyl-(+)-catechin was significantly more effective than (+)-catechin itself at preventing fatty liver, probably as a result of its greater lipid solubility and longer half-life in the liver tissue. Published work suggested two possible mechanisms of action for the (+)-catechin compounds against ethanol hepatotoxicity. Firstly, the ability of the drugs to correct the elevated hepatic NADH:NAD ratio (redox-state) after ethanol dosing may limit steatosis. Secondly, free radical scavenging properties may prevent liver injury occurring as a result of ethanol-induced lipid peroxidation. Acute experiments were performed which confirmed that the (+)-catechin compounds corrected the redox-state change after acute ethanol administration, but subsequent studies in which correction of the redox-state by Naloxone or Methylene Blue was found to have little influence on ethanol-induced steatosis, suggested that this was not the mechanism of action of the drugs. Synthetic antioxidants (free radical scavengers) were found to prevent both acute and chronic ethanol-induced fatty liver, under the same experimental conditions as those under which the (+)-catechin compounds afforded protection, without reversing the redox-state change after ethanol dosing. 3-Palmitoyl-(+)-catechin was then shown to prevent ethanol-induced hepatic lipid peroxidation (measured as mitochondrial diene conjugates and liver malonaldehyde levels) after acute ethanol dosing, at the same time as preventing triglyceride accumulation. As other effects of the compounds which might influence fat accumulation after ethanol were excluded (eg: inhibition of ethanol metabolism or lowering of liver acetaldehyde concentrations), it was concluded that the (+)-catechin compounds protect against alcoholic fatty liver in rats by inhibiting ethanol-induced lipid peroxidation, and the possible consequence of the latter (ie: mitochondrial damage and impaired fatty acid oxidation), rather than acting through modulation of the redox-state. The findings here cast doubts on the commonly-quoted 'redox-state' mechanism for fatty liver production by ethanol, and support the lipid peroxidation hypothesis for alcoholic liver injury.
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Rocha, Biff. ""De Concilio's Catechism," Catechists, and the History of the Baltimore Catechism." IMRI - Marian Library / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1386154475.
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Chung, Du Sung. "The importance of catechism for the Presbyterian Church in South Korea." Thesis, University of Wales Trinity Saint David, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.683023.
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Sirk, Timothy Wayne. "A Molecular Dynamics Study on the Interaction of Tea Catechins and Theaflavins with Biological Membranes." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26946.
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Molecular dynamics simulations were performed to study the interactions of bioactive catechins and theaflavins commonly found in tea with lipid bilayers, as a model for cell membranes. Previously, multiple experimental studies rationalized the anticarcinogenic, antibacterial, and other beneficial effects of these compounds in terms of physicochemical molecular interactions with cell membranes. To contribute toward understanding the molecular role of tea polyphenols on the structure of cell membranes, simulation results are presented for seven catechins and three theaflavins in lipid bilayer systems which are both pure (POPC) and representative of HepG2 cancer cells (POPC and POPE). Our simulations show that the catechins and theaflavins evaluated have a strong affinity for the lipid bilayer \textit{via} hydrogen bonding to the bilayer surface, with many of the catechins able to penetrate beneath the surface. Epigallocatechin-gallate (EGCG) and Theaflavin-3,3'-digallate showed the strongest interaction with the lipid bilayers based on the number of hydrogen bonds formed with lipid headgroups. The simulations also provide insight into the functional characteristics of the tea compounds that distinguish them as effective compounds to potentially alter the lipid bilayer properties. The results on the hydrogen-bonding effects may contribute to a better understanding of proposed multiple molecular mechanisms of the action of catechins and theaflavins in microorganisms, cancer cells, and tissues.Ph. D.
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Lee, Suk-ching. "Effect of green tea derived compounds on the growth of androgen independent prostate cancer in vivo /." View the Table of Contents & Abstract, 2006. http://sunzi.lib.hku.hk/hkuto/record/B36404640.
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Kopaniszen, Malgorzata. "Protective effect of green tea polyphenols on dinitrobenzene sulphonic acid (DNBS)-induced colitis in mice." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B40687466.
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Chen, Jie Jack. "Growth inhibition effects of green tea and epigallocatechin gallate in bladder tumors." Click to view the E-thesis via HKUTO, 2003. http://sunzi.lib.hku.hk/hkuto/record/B4257772X.
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Bannister, Magdalien. "Comparison of free and immobilized polyphenol oxidase enzymes for the biocatalytic conversion of catechins into theaflavins." Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/30922.
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The reusability of active enzyme is important in industrial bio-catalysis applications. This is not
readily accomplished with free enzymes. The project investigated a new enzyme immobilization
matrix, ReSynTM, and compared it to three widely used matrixes, Eugergit C, Eupergit C 250 L
and DEAE Sephadex A-25. Initial comparative immobilization performed with BSA, determined
ReSynTM (covalent immobilization) to have an approximate 8 fold higher protein loading
efficiency than the other support. The enzymes selected for immobilization were polyphenol
oxidase (PPO) (first reported purification of PPO from Forelle pear) and laccase
(Novozyme (Pty) Ltd) based upon their application potential. From the comparative assessment
of immobilization based on BSA and the activity (units/mg support) attained by ReSynTM
immobilized laccase, it was deduced that ReSynTM demonstrated performance superiority over the
other supports.
The project aim was the application of immobilized PPO in the ice tea industry to increase the
value of black iced tea based upon an increased theaflavin content. The unusually rich sub-group
of polyphenols known as flavanols or catechins, may constitute up to 30% of the dry tea leaf
weight. The oxidation of green leaf polyphenols is precluded in the preparation of green tea in
contrast to the promotion of oxidation in the production of black tea. PPO catalyzes the
controlled aerobic oxidation of catechins producing various quinones which undergo condensation
reactions resulting in dimeric compounds known as theaflavins, whereas a peroxidase (PO)
enzyme produces polymeric substances, known as thearubigins, during the fermentation stage of
black tea production (Graham 1992). The production of theaflavins from flavan-3-ols (catechins),
is catalysed by PPO (Bonnely et al. 2003). The black tea theaflavins are a mixture of theaflavin,
theaflavin-3-gallate, theaflavin-3'-gallate and theaflavin-3,3'-digallate.
The project focussed on the bioconversion of green tea leaf catechins into theaflavins, as the
original method employed to acquire theaflavins, the extraction of theaflavins from black tea
(only 0.4-1.85% of the dry weight of black tea), doesn’t provide a cost-effective manner of
recovering theaflavins, and amounts to an industrially unfeasible approach (Sharma et al. 2009,
Wang & Li 2006). Preliminary exploratory investigation into the theaflavin synthesis capacity of
Forelle pear and Yacon (Smallanthus sonchifolius) leaf homogenates, respectively determined a
136% and 98% theaflavin content to that present in Lipton® Yellow label black tea, after an hour
of fermentation utilizing Lipton® Green tea as starting material. The homogenates of ForelleDissertation (MSc)--University of Pretoria, 2013.
Biochemistry
MSc
Unrestricted
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Chang, Cheng, and 張捷. "Variety Selection of Higher Methylated Catechin Content Germplasm Resources and Studies of the Diversity of Taiwan Tea Cultivars Based on Total Catechins and Their Fractions." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/96333988107416093288.
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碩士大葉大學
生物產業科技學系
98
Using pan-fried green teas made from Taiwan as main teas in spring and autumn seasons, analysis and comparison their contents of catechins and catechin methyl ester, identify tea varieties containing high levels of catechin methyl ester, establishment the data of Taiwan's tea of catechins. According to principal component analysis and UPGMA method, evaluate season, suitability, catechins of tea varieties such as relevance. Evaluate content in distribution of catechins when selection breeding at different times of extension station of Taiwan and all teas species varieties.The results indicated that the autumn tea catechins were higher than the spring tea, but other than EGCG；Teas of Taiwan Tea Extension Station (TTES) No. 1 to 20, all have higher EGCG and total catechins contents than that from other tea varieties; partially fermented tea varieties have a higher content of catechin methyl ester. For TD004 (TTES No.4), its catechin methyl ester in spring and autumn has the average content of 3.3(g/100g d.w.). The highest mean average content of EGCG3 "Me was TD064 (Woan Joong), which has the highest concentrations of 1.6 (g/100g dw). Using the UPGMA method MVSP software to do cluster analysis on the tea species. The catechin profiles for TD007, TD085, TD093, TD100 are unique and not able to be grouped with most of the other tea varieties based on principal component analysis (PCA) and cluster analysis. PCA results also indicated that the parameters such as tea manufacturing suitability, the type of tea varieties released by TTES along the timeline, catechin content are related. Our results also indicated that wild teas in Taiwan have very different catechins content profiles in cluster analysis.The results in present research have established a germplasms database of teas in Taiwan and those data can be used to better serve the future of tea breeding.
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Locher, Sanja. "Analytische und Effektor-Studien von Catechinen." Doctoral thesis, 2011. https://nbn-resolving.org/urn:nbn:de:bvb:20-opus-65143.
Full textAbstract:
Catechine gehören als Flavan-3-ole zur Gruppe der Polyphenole. Aufgrund deren vielfältiger positiver Effekte auf den menschlichen Organismus nehmen sie in der Ernährungsforschung einen hohen Stellenwert ein. Dabei hat man bei den Flavan-3-olen meist nur die in der Natur vorherrschenden Isomere (+)-Catechin und (-)-Epicatechin untersucht, doch auch (-)-Catechin und (+)-Epicatechin sind Naturstoffe. Letztere findet man z.B. in Guarana oder in verarbeiteten Lebensmitteln, wie z.B. Kakao- und Kakaoerzeugnissen. Sie entstehen durch Epimerisierung unter den technologischen Bedingungen beim Rösten der Kakaobohnen und der Alkalisierung der Kakaomasse. Bei der Kakao-Verarbeitung werden ferner auch Catechin-C-Glykoside gebildet. Im ersten Teil dieser Arbeit wurden Stabilitätsstudien mit (+)-Catechin bei unterschiedlichen pH-Werten und Temperaturen durchgeführt. Der zweite Teil dieser Arbeit umfasst Untersuchungen von Catechin-Isomeren und zwei Catechin-C-Glykosiden auf ihren Einfluß auf die Lipoxygenase (LOX)- und Xanthinoxidase (XOD)-Aktivität. Für die Catechin-C-Glykosidbildung ist von uns eine neue Vorstellung zu deren Entstehungsmechanismus im Laufe der Lebensmittelverarbeitung entwickelt worden. Abschließend wurden anhand von Modelling-Studien die Effekte auf die Enzymsysteme erklärtAs flavan-3-ols, catechins belong to the group of polyphenols. Due to their manifold positive effects on the human organism, catechins are of important significance in food research. Although only the two most abundant isomers in nature, (+)-catechin and (-)-epicatechin, have been studied in most cases; however, (-)-catechin and (+)-epi-catechin occur in nature as well. The latter are found i.e. in guarana or in processed food, as cacao and cacao products as the result of epimerization due to technological processing, i.e. while roasting the cocoa beans and alkalisation of the cacao mass. Catechin-C-glycosides are also formed during cacao processing. In the first part of this thesis stability studies with (+)-catechin at different pH values and temperatures were carried out. The second part of this work comprises analysis of catechin isomers and two catechin-C-glycosides on their influence on lipoxygenase (LOX)- and xanthinoxidase (XOD)-activity. For the building mechanism of catechin-C-glycosides during food processing a new hypothesis was developed. Finally the effects on enzyme systems were explained by means of modelling studies
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Ong, David, and 王志偉. "The Physiological Activities of Tea Catechins." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/71105157874479841323.
Full textAbstract:
碩士國立臺灣海洋大學
食品科學系
93
Abstract This study mainly reviews the antioxidative, antimicrobial and anticancer activities of the catechins, the dominant polyphenol components in tea. The scanvanging activity for hydroxy radical ranks in order as epicatechin gallate (ECG) ＞epigallocatechin gallate(EGCG)＞epicatechin（EC）＞gallic acid（GA）＞gallocatechin（GC）＞epigallocatechin（EGC）, all of which are greater than that of Vit C. The scanvanging activity of ECG and EGCT for superoxide and hydrogen peroxide is greater than that of Vit C and Vit E by 8.32 times. Catechins can inhibit the oxidation of the low density lipoproteins and accordingly, decrease the risk for arteriosclerosis. The antibacterial activity of EGCG is greater than that of EC. Both EGCG and EC have stronger effect on G（＋）bacteria than G（－）bacteria. The minimal inhibition concentration（MIC）of EGCG for S. aureus.and E.coli are 73 and 573 �慊/ml, respectively, while the MIC for EC are 183 and ＞1145 �慊/ml, respectively. The data from the action on liposome demonstrate that both EGCG and EC can damage the cell membrane and result in the leakage of the cell. The presence of the negative residues in membrane deaease the actions of EGCG and EC on the membrane. Catechins can inhibit the propogation of cancer cell by inducing the aptosis of cell and inhibiting the functions of tumor promoters, hormones, cytokines and growth factors. In the presence of 50 �慆 and 100 �慆 of EGCG the ratio for cells in G2-M phase was increased from 13.8﹪to 15.6﹪and 24.1﹪, respectively. The animal models used for the anticancer / antitumor study of catechins include: （1）N-nitrosodiethylamine injection to in A/J mice induce cancer production;（2）N-nitrosomethylbenzylamine induced the cancer of esophagus of Wistar rats;（3）treatments by 7,12-dimethylbenz[a]anthracene and 12-0-tetrade canoylphorbol-13-acetete to induce skin cancer in SENCAR rats; （4）induction of colon cancer in rats by N-ethyl-N’-nitro-N-nitroguanidine and azoxymethane.
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Lin, Chun-Yao, and 林俊曜. "Antioxidant Effects of Catechins and Soluble Fiber." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/99775730042935360110.
Full textAbstract:
碩士實踐大學
食品營養研究所
92
Reactive oxygen species (ROS) with high oxidative reactivity can oxidize lipids, proteins, and DNA molecules and consequently lead to cellular and organic injury. We examined the possible mechanisms of ROS on oil smoke induced lung injury and excess metal ion induced atherosclerosis. We evaluated the antioxidant activity and the prevention role of two natural extracts, catechins and soluble fiber, on oil smoke induced lung injury and FeCl3 induced arterial atherosclerosis. Our in vitro results found that both catechins and soluble fiber are efficient antioxidants to scavenge O2─•, H2O2, and HOCl. When compared to vitamin C, the antioxidant ability is in an order of catechins＞vitamin C＞soluble fiber. In the first experiment, we found that the amount of whole blood ROS measured by a chemiluminescence analyzer was increased (320.8±154.8 counts/10sec) after 30 min of exposure to oil smoke. The enhanced ROS level was still maintained at a similar value after 60-120 min of oil smoke exposure. Dietary catechins significantly reduced oil smoke enhanced whole blood ROS (76.0±15.5 counts/10sec) and lung larvage ROS (157.4±10.9 counts/10sec). The protective mechanism by catechins could be due to upregulation of protective Bcl-2 and HSP-70 protein and downregulation of proapoptotic Bax protein expression in the lung. In the second experiment, we evaluated the effect of soluble fiber on on blood lipid profile and FeCl3 induced arterial atherosclerosis in high fat-diet fed hamsters. We found that high fat-diet increased plasmas total cholesterol (from 72.9±2.8 to 110.5±7.1 mg/dl) and low-density lipid protein levels (from 18.5±1.3 to 39.3±5.7 mg/dl) and accelerated the atherosclerotic formation (from 342.0±58.4 to 287.0±17.5 sec). Dietary soluble fiber decreased total cholesterol and low-density lipid proteins and elongated the time for arterial atherosclerosis (from 287.0±17.5 to 378.8±34.6 sec). By western blot, the increased Bax protein and decreased Bcl-2 and HSP-70 protein expression was found in the liver and kidney of high fat-diet fed hamsters. However, soluble fiber decreased Bax expression and increased Bcl-2 and HSP-70 protein expression. Based on the results, we conclude that dietary catechins or soluble fiber can increase antioxidant protein expression and thus decrease oxidative stress induced lung injury and atherosclerosis.
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Yang, Meei-Ju, and 楊美珠. "Metabolic Mechanism and Bioactivity of Tea Catechins." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/t6jx5p.
Full textAbstract:
博士國立臺灣大學
園藝暨景觀學系
107
Catechins and its polymers offer various health benefits. Therefore, it is very important to realize catechin metabolic process and its physiological activity during manufacturing and storage process. This result will support for future various functional tea production. Catechin is unstable and easily oxidized in water solution. Non-enzymatic browning of tea was due to photooxidation, temperature and pH variation. Hence catechin chemical transformation at different environmental conditions is an important issue in tea drink manufacture. In this study, first, we try to figure out the change of catechin under blue light irradiation in alkaline solution by chromatography and mass spectrometry techniques. Catechin is colorless in water solution. However, it was turn into yellow color under blue light irradiation in alkaline condition. The yellow substance was characterized as catechin dimer (proanthocyanidin) and it can be prevented by ascorbic acid addition. It showed that ascorbic acid will inhibit catechin photooxidation. A superoxide anion was produced through catechin photooxidation under blue light irradiation in alkaline condition. This free radical can cause inactivation of multidrug-resistant Acinetobacter baumannii and support as solution for environmental microbial safety. Furthermore, different fermented tea from the same resource of tea leaves was produced and was analyzed by chromatography and mass spectrometry techniques to understand correlation of catechin metabolic pathway during different fermented process. As the degree of fermentation (oxidation) increases, metabolic reaction of catechin was increased and catechin was decreased followed by increasing of theasinensins (TSB and TSC), theaflavins (TF and TF3G) and gallic acid. Non-fermented tea (green tea) and semi-fermented tea (pouchong and oolong tea) have high DPPH scavenging effect, reducing power and ABTS free radical scavenging ability, owing to high catechin concentration. Completely fermented tea (black tea) has high ferrous ion chelating ability because of high theasinensins, theaflavin and gallic acid concentration. Forty-six compounds were characterized for three different fermented tea by analytical liquid chromatograph tandem mass spectrometer with collision-induced dissociation (CID). It showed that variation of molecular composition after tea fermentation. Catechins and flavonol aglycones were significantly decreased followed by formation of organic acid, theasinensins and theaflavin. In addition, a lot amount of catechin dimers were detected in green tea, and decreasing when fermentation. Chemical composition was analyzed from different age of strip type partial fermented tea to explore the effects of storage on the metabolism of catechins. The mechanism of tea inhibited inflammatory response was discussed by immune response was stimulated by foreign substances lipopolysaccharide (LPS) in macrophages RAW 264.7 and trigger nitric oxide (NO) generate. As the results, as the time go by, total polyphenol, total catechin, total catechin dimer and total theasinensin were reduced without theaflavin production. It showed that metabolic mechanism is difference between manufacture process and tea storage. The phenomenon of pH value first drops and then rise of tea was cause by combination of catechin metabolic products “gallic acid” and other organic acids change. Anti-inflammatory ability of tea was enhanced with rising of storage time and test dose. The bioactivity test of tea storage time indicating a positive correlation between metabolic compounds: gallic acid, pyrogallol, caffeoyl tartaric acid derivative, quinine derivative, bayberry flavonoid glycoside, kaempferol and ellagic acid and anti-inflammatory ability.
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"Pharmacokinetics of tea catechins in the rat." 2001. http://library.cuhk.edu.hk/record=b5890905.
Full textAbstract:
Chen Yu.Thesis submitted in: November 2001.
Thesis (M.Phil.)--Chinese University of Hong Kong, 2001.
Includes bibliographical references (leaves 98-112).
Abstracts in English and Chinese.
Acknowledgements --- p.I
List of publications --- p.II
Abstract --- p.III
Abstract (Chinese) --- p.IV
Abbreviations --- p.V
Chapter Chapter 1 --- Introduction --- p.1
Chapter 1.1 --- Tea --- p.1
Chapter 1.2 --- Green tea --- p.3
Chapter a) --- Chemical composition of green tea --- p.3
Chapter b) --- Pharmacological activities of green tea polyphenols --- p.6
Chapter c) --- Pharmacokinetics of green tea polyphenols --- p.10
Chapter 1.3 --- Objective --- p.14
Chapter Chapter 2 --- Validation of analysis method for tea catechins --- p.15
Chapter 2.1 --- Materials and methods --- p.16
Chapter a) --- Preparation of a catechin-mixture from tea --- p.16
Chapter b) --- Preparation of stock solutions --- p.18
Chapter c) --- Preparation of biofluid samples --- p.18
Chapter d) --- HPLC analysis of tea catechins --- p.19
Chapter 2.2 --- Results --- p.21
Chapter a) --- Catechin-mixture (tea extracts) --- p.21
Chapter b) --- "Extraction from plasma, urine and feces" --- p.21
Chapter c) --- HPLC analysis of biofluid samples --- p.23
Chapter 2.4 --- Discussion --- p.26
Chapter Chapter 3 --- Pharmacokinetics of tea catechins following administration of different doses of the catechin-mixture --- p.32
Chapter 3.1 --- Materials and methods --- p.33
Chapter a) --- Surgery and animal maintenance --- p.33
Chapter b) --- Dosing and sample collection --- p.33
Chapter c) --- Pharmacokinetics analysis of tea catechins --- p.35
Chapter 3.2 --- Results --- p.36
Chapter 3.3 --- Discussion --- p.50
Chapter Chapter 4 --- Pharmacokinetics of tea catechins following administration of different doses of individual catechins --- p.52
Chapter 4.1 --- Materials and methods --- p.53
Chapter a) --- Chemicals and reagents --- p.53
Chapter b) --- Pharmacokinetic study of tea catechins and the HPLC analysis --- p.53
Chapter c) --- Pharmacokinetic analysis of tea catechins --- p.54
Chapter 4.2 --- Results --- p.55
Chapter 4.3 --- Discussion --- p.67
Chapter Chapter 5 --- Plasma protein binding of tea catechins --- p.69
Chapter 5.1 --- Introduction --- p.69
Chapter 5.2 --- Materials and methods --- p.72
Chapter a) --- Ultrafiltration --- p.72
Chapter b) --- Preparation of stock solution --- p.73
Chapter c) --- Determination of nonspecific binding of the catechins --- p.73
Chapter d) --- Determination of ultrafiltration conditions --- p.74
Chapter e) --- In vitro plasma protein binding assay --- p.74
Chapter f) --- Statistical analysis --- p.75
Chapter 5.3 --- Results --- p.76
Chapter a) --- Nonspecific binding in ultrafiltration --- p.76
Chapter b) --- Protein binding of the catechins --- p.76
Chapter c) --- Statistical analysis --- p.76
Chapter 5.4 --- Discussion --- p.80
Chapter Chapter 6 --- Partition of tea catechins in red blood cell --- p.82
Chapter 6.1 --- Materials and methods --- p.83
Chapter a) --- Prepare of stock solution --- p.83
Chapter b) --- In-vitro erythrocyte partition --- p.83
Chapter c) --- Data Analysis --- p.83
Chapter 6.2 --- Results --- p.85
Chapter a) --- Selection of experiment conditions --- p.85
Chapter b) --- Partition of catechins to RBC --- p.85
Chapter 6.3 --- Discussion --- p.87
Chapter Chapter 7 --- Comparison of pharmacokinetics of tea catechins in mixture form versus pure compound --- p.89
Chapter Chapter 8 --- Conclusion --- p.95
References --- p.98
44
"Catechins against sodium iodate-induced retinal degeneration." 2013. http://library.cuhk.edu.hk/record=b5884367.
Full textAbstract:
Yang, Yaping.Thesis (Ph.D.)--Chinese University of Hong Kong, 2013.
Includes bibliographical references (leaves 156-165).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts also in Chinese.
45
"The antioxidative and hypolipidemic activities of tea catechins." 1997. http://library.cuhk.edu.hk/record=b5889150.
Full textAbstract:
by Chan Ping Tim Timothy.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.
Includes bibliographical references (leaves 129-141).
ACKNOWLEDGMENTS --- p.I
ABSTRACT --- p.II
LIST OF ABBREVIATIONS --- p.IV
TABLE OF CONTENTS --- p.VI
Chapter CHAPTER 1 --- GENERAL INTRODUCTION --- p.1
Chapter 1.1 --- History of tea --- p.1
Chapter 1.2 --- Botany and agriculture of tea --- p.1
Chapter 1.3 --- Classification of tea --- p.2
Chapter 1.4 --- Composition of tea --- p.4
Chapter 1.5 --- Tea processing --- p.8
Chapter 1.5.1 --- Manufacture of green tea --- p.8
Chapter 1.5.2 --- Manufacture of black tea --- p.8
Chapter 1.5.3 --- Manufacture of oolong tea --- p.10
Chapter 1.6 --- Pharmacological effects of tea catechins --- p.13
Chapter 1.6.1 --- Antioxidative activity --- p.13
Chapter 1.6.2 --- Hypolipidemic activity --- p.14
Chapter 1.6.3 --- Antimutagenic activity --- p.15
Chapter 1.6.4 --- Anticarcinogenic activity --- p.15
Chapter 1.6.5 --- Antibacterial activity --- p.16
Chapter CHAPTER 2 --- ANTIOXIDATIVE ACTIVITIES OF TEA ETHANOL EXTRACTS AND GTC ON OXIDATION OF CANOLA OIL --- p.18
Chapter 2.1 --- Introduction --- p.18
Chapter 2.1.1 --- Lipid oxidation in food --- p.18
Chapter 2.1.2 --- Phenolic antioxidants --- p.19
Chapter 2.1.2.1 --- Major phenolic antioxidants used in food --- p.19
Chapter 2.1.2.2 --- Mechanism of action of phenolic antioxidants --- p.20
Chapter 2.1.2.3 --- BHA and its safety --- p.22
Chapter 2.1.2.4 --- BHT and its safety --- p.24
Chapter 2.1.3 --- Natural antioxidants --- p.24
Chapter 2.2 --- Objectives --- p.26
Chapter 2.3 --- Materials --- p.28
Chapter 2.4 --- Methods --- p.28
Chapter 2.4.1 --- GTC extraction --- p.28
Chapter 2.4.2 --- "HPLC analysis of GTC," --- p.29
Chapter 2.4.3 --- Isolation and purification of individual epicatechin isomers --- p.30
Chapter 2.4.4 --- Ethanol extraction of tea --- p.30
Chapter 2.4.5 --- Effect of tea ethanol extracts on oxygen consumption of canola --- p.31
Chapter 2.4.6 --- Effect of GTC on oxygen consumption of canola oil --- p.32
Chapter 2.4.7 --- Fatty acid analysis --- p.32
Chapter 2.4.8 --- Thermal loss of BHT --- p.33
Chapter 2.4.9 --- Thermal loss of GTC --- p.33
Chapter 2.4.10 --- Statistics --- p.35
Chapter 2.5 --- Results --- p.37
Chapter 2.5.1 --- Antioxidative activities of tea ethanol extracts --- p.37
Chapter 2.5.2 --- The yield and composition of GTC from jasmine tea --- p.51
Chapter 2.5.3 --- Antioxidative activity of GTC --- p.55
Chapter 2.5.4 --- Antioxidative activities of individual epicatechin isomers --- p.55
Chapter 2.5.5 --- Thermal loss of GTC --- p.60
Chapter 2.6 --- Discussion --- p.62
Chapter 2.6.1 --- Contribution of catechins to the antioxidative effects of tea ethanol extracts --- p.62
Chapter 2.6.2 --- Antioxidaitve activities of different types of teas --- p.62
Chapter 2.6.3 --- Proposed mechanisms for the relative activity of epicatechin isomers --- p.63
Chapter 2.6.4 --- Loss of BHT via volatilization --- p.66
Chapter 2.6.5 --- Potential of tea catechins as food antioxidants --- p.67
Chapter 2.6.5.1 --- Safety of GTC --- p.67
Chapter 2.6.5.2 --- Solubility of GTC --- p.68
Chapter 2.6.5.3 --- Effects of GTC on food quality --- p.68
Chapter CHAPTER 3 --- INHIBITORY EFFECTS OF GTC AND EPICATECHIN ISOMERS ON IN VITRO CU2+-MEDIATED LDL OXIDATION --- p.70
Chapter 3.1 --- Introduction --- p.70
Chapter 3.1.1 --- Mechanisms of LDL oxidation --- p.71
Chapter 3.1.1.1 --- Nature and sources of oxidants underlying LDL oxidation --- p.71
Chapter 3.1.1.2 --- Structural changes of ox-LDL --- p.72
Chapter 3.1.2 --- Biological effects of ox-LDL --- p.74
Chapter 3.1.3 --- Antioxidants and atherosclerosis --- p.76
Chapter 3.2 --- Objectives --- p.78
Chapter 3.3 --- Materials and methods --- p.79
Chapter 3.3.1 --- LDL isolation --- p.79
Chapter 3.3.2 --- LDL oxidation --- p.79
Chapter 3.3.3 --- Thiobarbituric acid-reactive substance (TBARS) assay --- p.80
Chapter 3.3.4 --- Lipid analysis --- p.80
Chapter 3.3.5 --- Statistics --- p.81
Chapter 3.4 --- Results --- p.82
Chapter 3.4.1 --- Protective effects of GTC against LDL oxidation --- p.82
Chapter 3.4.2 --- Varying protective effects of individual epicatechin isomers --- p.82
Chapter 3.4.3 --- Protective effects of GTC against oxidative degradation of PUFAs in LDL --- p.86
Chapter 3.5 --- Discussion --- p.88
Chapter 3.5.1 --- Tea catechins as anti-atherogenic agents --- p.88
Chapter 3.5.2 --- Mechanisms of the protective effects of tea catechins against Cu2+-induced LDL oxidation --- p.88
Chapter 3.5.3 --- Relative antioxidative activities of epicatchin isomers --- p.89
Chapter 3.5.4 --- Absorption of tea catechins --- p.90
Chapter 3.5.5 --- Pro-oxidant activities of tea catechins --- p.91
Chapter CHAPTER 4 --- HYPOLIPIDEMIC ACTIVITY OF GTC --- p.93
Chapter 4.1 --- Introduction --- p.93
Chapter 4.1.1 --- High serum cholesterol as a risk factor of CHD --- p.93
Chapter 4.1.2 --- Serum TG and CHD --- p.94
Chapter 4.1.3 --- Hypolipidemic effect of tea --- p.95
Chapter 4.1.4 --- Hamster as an animal model of cholesterol metabolism --- p.96
Chapter 4.2 --- Objectives --- p.97
Chapter 4.3 --- Materials and methods --- p.98
Chapter 4.3.1 --- Animals --- p.98
Chapter 4.3.2 --- Experiment 1 --- p.98
Chapter 4.3.3 --- Experiment 2 --- p.100
Chapter 4.3.4 --- Experiment 3 --- p.101
Chapter 4.3.5 --- "Serum lipid, lipoprotein and apolipoprotein determinations" --- p.101
Chapter 4.3.6 --- Lipid analysis of liver and carcass --- p.102
Chapter 4.3.7 --- Analysis of fecal lipid content --- p.102
Chapter 4.3.8 --- Determination of hepatic cholesterol content --- p.103
Chapter 4.3.9 --- Assay of fatty acid synthase activity --- p.105
Chapter 4.3.10 --- Statistics --- p.105
Chapter 4.4 --- Results --- p.106
Chapter 4.4.1 --- Growth and food intake --- p.106
Chapter 4.4.2 --- Effects of different levels of dietary GTC on serum TG and cholesterol --- p.106
Chapter 4.4.3 --- Time course study of the hypolipidemic effects of dietary GTC --- p.109
Chapter 4.4.4 --- Effects of GTWE on serum lipid and apolipoprotein profiles --- p.113
Chapter 4.4.5 --- "Effects of dietary GTC on hepatic TG, FFA and cholesterol contents" --- p.113
Chapter 4.4.6 --- "Effects of dietary GTC on carcass TG, FFA and cholesterol contents" --- p.118
Chapter 4.4.7 --- Effects of dietary GTC on fatty acid synthase activity --- p.118
Chapter 4.4.8 --- Effects of dietary GTC on fecal lipids content --- p.118
Chapter 4.5 --- Discussion --- p.120
Chapter 4.5.1 --- Hypolipidemic effect of GTC --- p.120
Chapter 4.5.2 --- Effects of GTC on serum apolipoproteins --- p.120
Chapter 4.5.3 --- Implication of GTC intake in humans --- p.121
Chapter 4.5.4 --- Mechanisms for the hypolipidemic activity of GTC --- p.122
Chapter 4.5.5 --- Reduction in hepatic TG and FFA contents in GTC-fed hamsters --- p.123
Chapter 4.5.6 --- Suppression of body lipid accumulation by dietary GTC --- p.124
Chapter 4.5.7 --- Mechanisms for the hypocholesterolemic activity of GTC --- p.124
Chapter CHAPTER 5 --- CONCLUSIONS --- p.126
REFERENCES --- p.129
46
"Antioxidative activities of green tea catechins (Jasmine tea)." 1999. http://library.cuhk.edu.hk/record=b6073186.
Full textAbstract:
Thesis (Ph.D.)--Chinese University of Hong Kong, 1999.Includes bibliographical references (p. 218-235).
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Mode of access: World Wide Web.
Abstracts in English and Chinese.
47
蕭廷宇. "Anti-glycation effects of polyphenol catechins in green tea." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/5yu287.
Full textAbstract:
碩士國立嘉義大學
食品科學系研究所
106
Taking excess food often causes obesity, diabetes mellitus, hypertension and other chronic diseases. The main reason for the above is carbonhydrate’s carbonyl group and protein’s amino group occur glycation reaction and form advanced glycation end-products (AGEs). Accumulation of AGEs in the body would cause oxidative stress, inflammation and other phenomena accompanied by cell or tissues damage, and then trigger these diseases.Therefore, it’s worth to find natural anti-glycation foods against chronic diseases. Green tea is one of the most consumed beverage in today's tea market. Green tea was made through withering, blanching, drying and other steps. Because it has not been fermented so it is also called non-fermented tea, which preserves a variety of tea polyphenols and vitamins. Green tea’s catechins have been proved having anti-oxidation, anti-free radical and other benefits. However, whether catechins have anti-glycation ability remains to be elucidated. Thus, the aim of this study was to investigate catechins’s anti-glycation ability. In AGEs inhibition test, the IC50 values for ECG and EGCG were 446.60 ± 74.2 μM and 315.79 ± 6.0 μM, respectively. It showed that these two were much better than postive-control aminoguanidine (AG) (IC50 value 6760.36 ± 72.3 μM) in suppression of AGEs formation. From the results, ECG and EGCG also demonstrated higher inhibitory effect on glycation marker β-amyloid, carbonyl and fructosamine, with the decreasing rates of 66%, 69%, 47% (ECG), and 76% 70% 43% (EGCG), respectively. Based on this results EGCG has the highest anti-glycation ability among the four catechins, presumably related to the structure of gallate and the number of hydroxyl group. Based on the previous reports and the results of this study, we can speculate that green tea possesses not only the anti-oxidant effect but also the ability to inhibit the glycation index. Among them, EGCG has the best anti-glycation ability.
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Lin, Ru-Wei, and 林儒緯. "Effects of Green Tea Catechins and Ipriflavone Derivatives on Osteoclastogenesis." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/45508645744098309768.
Full textAbstract:
博士高雄醫學大學
藥學研究所
97
Abstract Osteoporosis is a significant disease in geriatrics. A nutritional approach to reduce bone loss would be a future goal to achieve an inexpensive way for managing osteoporosis. Previous epidemiological studies found that people with a habit of tea drinking have higher bone mineral density and less chance to get hip fracture. Green tea catechin, (−)-epigallocatechin gallate (EGCG), increased the osteogenic function in mesenchymal stem cells was reported. The effect of EGCG on osteoclastogenesis remains to be elucidated. In this study, we investigated the influence of EGCG on osteoclasts and found that treatment of EGCG (10–100 μM) significantly suppressed nuclear factor-kB ligand-induced osteoclast differentiation and pit formation in murine RAW 264.7 cells, the precursor cells of osteoclasts, and primary bone marrow macrophages cells (BMMs). We also identified that EGCG targets at the early stage of osteoclastic differentiation while having no cytotoxic effect on osteoclast precursors. Analysis of the inhibitory mechanisms revealed that EGCG significantly inhibited RANKL-induced NF-κB transcriptional activity by reducing nuclear transport of NF-κB. The results demonstrate that EGCG is a potent inhibitor of osteoclastogenesis via a mechanism involving NF-κB and TRAP gene. Our results also indicate that the possibility of EGCG to become a new strategy against bone resorption. Ipriflavone is a synthetic isoflavone derivative, which has been suggested to be an inhibitor of bone resorption in vitro and in vivo. Several clinical studies suggested that ipriflavone is able to prevent bone loss. We have screened over 150 ipriflavone derivatives by the tartrate resistant acid phosphatase (TRAP) activity of RAW 264.7 cells after RANKL induction for osteoclastogenesis. The results indicated that 3-(3,4-dimethoxyphenyl)-7-(oxiran-2-ylmethoxy)-4H-chromen-4- one (19) and 3-{4-[3-(cyclohexylamino)-2-hydroxypropoxy]phenyl}- 7-methoxy- 4H-chromen-4-one (20a) exhibited significant inhibitory effects on osteoclast activity (TRAP activity in RAW 264.7 with an IC50 of 0.56 and 2.28 μM, respectively). The results imply that these two compounds can be candidates for the discovery of anti-osteoporotic drug.
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Chang, Yu-min, and 張愉敏. "Preparative Isolation and Separation of Catechins from Green Tea Powders." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/48132773821746744268.
Full textAbstract:
碩士國立雲林科技大學
工業化學與災害防治研究所
94
Green tea (non-fermented) is a popular, no alcoholic beverage in the world, and it is recognized for its high content of tea polyphenols, in particular tea catechins. The four represented catechins of green tea are, epigallocatechin(EGC), epicatechin(EC), epigallocatechin gallate(EGCG), and epicatechin gallate(ECG). Nevertheless, epigallocatechin gallate(EGCG) is the most abundant and biologically active compound in green tea. Many researches in the past found that green tea polyphenols have physiological effects in anti-oxidant, anti-tumorgenic, anti-mutagenic, anti-pathogenic, anti-inflammation, and anti-fungus, etc. Many health foods and products containing green tea polyphenols are already in markets, such as toiletries, cosmetics, foods, and beverages.The objective of this study is to develop an efficient and scalable isolation and separation technique, from which tea catechins can be produced with high purity and high recovery using green tea powers as the raw material. The results show that, first, the purity of the four catechins was about 16.0% in the green tea powders analyzed by HPLC. In the first stage of isolation, the method of liquid-liquid extraction and the method of solid-phase extraction were included. For the liquid-liquid extraction method operated in a batch mode, the procedure is simple and easy to proceed. Under the optimal extraction conditions (water/oil ratio as 1：1, extraction temperature as 30℃ and extraction time as 2 hours), the purity of the four catechins was raised to be about 57.0% and recovery of the four catechins was about 70.0%. For the solid-phase extraction method operated in a continuous mode, the procedure is more complicated and tedious. Using the intermediate polar XAD-7 HP resins as the packing material and operated under the optimal adsorption and desorption conditions, the purity of the four catechins were raised to be about 45.4% and the recovery of the four catechins were 74.9%. In the second stage, four catechins were separated and purified directly from the concentrate after the first stage by using elution chromatography with a preparative C-18 column operated under an optimal elution condition (mobile phase compositions of Methanol/water (1% acetic acid)). EGC, EGCG+EC and ECG were about 48.0%, 70.0% and 60.0%, respectively, the recoveries of the four catechins were collected in three separated regions and their purities were about 80+%, and after five times injection (about 88.6 mg the concentrate injected), the yields of EGC, EGCG+EC and ECG were about 5 mg, 28mg and 1 mg, respectively.
50
Hou, Chia-Hung, and 侯佳宏. "Extraction and functional study of catechins from old tea leaf." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/00904554362981656492.
Full textAbstract:
碩士南台科技大學
生物科技系
93
Catechins are the major functional compound in the tea leaf. They can br used in healthy articles and healthy foods because of their preventive and inhibitory effects for many diseases including cancer, coronary artery disease, liver trouble and infectious diseases. There are more catechins contanted in old leaf than in the tender leaf that was used for manufacturing tea. In this study, we propose a process to extract the catechins from the waste old tea leaf, eliminate the caffeine from the extract and assess the functional effects of the product. In our process, we could obtain the methanol extracts with 17.12 % catechins in it by extracting crushed tea leaf with tea/extractant ratio (w/v) of 1:10 at 60℃ for 3 hours. The methanol extracts are concentrated to a liquor, and the liquor was then extracted with the same volume of dichloromethane and ethyl acetate for eliminating the caffeine and extracting catechins, respectively. Finally, the product, which contains 52.62 % catechins and less than 1% caffeine is dried by lyophilization. The product showed higher antioxidant activity at the DPPH-scavenging capacity than EC and EGC. In anti-tumor activity test, the product could inhibit the growth of A549 and HCT-8 cell but not Chang Liver cell at the concentration range of 50-200 g/mL.