Search

Grünem und schwarzem Tee werden zahlreiche gesundheitsfördernde Wirkungen auf das Herz-Kreislauf-System zugeschrieben. Insbesondere wird der Schutz vor Arteriosklerose, Bluthochdruck und die positive Wirkung auf die Gefäßfunktion diskutiert. Darüber hinaus wurden auch antioxidative Effekte der Teepolyphenole beschrieben. In vitro wurden aber auch prooxidative Effekte von Teepolyphenolen beobachtet. Diese können selbst oxidiert werden und dadurch reaktive Sauerstoffspezies (ROS) wie Wasserstoffperoxid (H2O2) und Hyperoxidanionen (O2.-) bilden. Einige Arbeitsgruppen gehen von einer Autooxidation mit Bildung von Dimeren/Chinonen der Teepolyphenole aus, was bislang nur in vitro gezeigt werden konnte. In diesem Zusammenhang ist bislang nur teilweise verstanden, wie die beschriebenen vasodilatorischen Effekte der Polyphenole vermittelt werden. Es ist unklar, ob rezeptorvermittelte Signalwege involviert sind oder ob Autooxidation mit Bildung von ROS eine Rolle spielt. Bisher ist bekannt, dass Epigallocatechin-3-gallat (EGCG) in den Endothelzellen über Proteinkinasen die endotheliale Stickstoffmonoxid-Synthase (eNOS) durch Phosphorylierungen aktiviert und dadurch zu steigender Stickstoffmonoxid (NO.)- Produktion und nachfolgender Vasodilatation führt. Als involvierte Proteinkinasen konnten die Phosphatidylinositol-3-OH-Kinase (PI3-Kinase), cAMP-abhängige Proteinkinase (PKA) und Proteinkinase B (AKT) identifiziert werden. Es wird diskutiert, ob die NO-vermittelte Relaxation der Gefäße eine redoxempfindliche Reaktion ist, die die Anwesenheit von H2O2 und O2.- benötigt. Diese könnten als frühes Signal die PI3-Kinase/AKT-abhängige eNOS-Phosphorylierung auslösen. In der vorliegenden Arbeit sollte eine mögliche Autooxidation unter Bildung von ROS als übergeordneten Auslöser des PI3/AKT-Kinase-Signalweges untersucht werden. Studienergebnisse zur Autooxidation von EGCG wurden in der vorliegenden Arbeit auf grünen und schwarzen Tee, sowie Theaflavin-3,3´-digallat (TF3) als Bestandteil des schwarzen Tees, erweitert und somit auf verschiedene Teepolyphenole übertragen. Die Untersuchungen erfolgten in mehreren Schritten, um die Ergebnisse mit verschiedenen Methoden zu verifizieren. Basis aller Untersuchungen bildete das Aortenringmodell aus der Ratte, welches als ex vivo Versuchsmodell die in vivo Situation im Blutgefäß nachstellt. Um die Beteiligung der ROS H2O2 und O2.- an der Vasodilatation durch Teepolyphenole zu untersuchen, wurde zu Beginn eines jeden Experimentes als Einmalgabe Superoxiddismutase (SOD, 500 U/ml), Katalase (200 U/ml) oder Mangan(III)tetrakis(1-methyl-)porphyrin (MnTMPyP, 10 μM) dem Organbad zugegeben. Mitgeführt wurden Kontrollringe, die nur mit Wasser behandelt wurden. Zur Messung der Vasodilatation erfolgte alle 30 Minuten die Gabe von EGCG (0,1 - 10 μM), TF3 (0,02 - 2 μM), sowie grünem oder schwarzem Tee (5 -50 μl, was bei 50 μl ca. 5 μM EGCG bzw. 0,06 μM TF3 entsprach) in die Organbäder. Die Teepolyphenol-induzierte Vasodilatation wurde bei allen Interventionen durch Katalase vollständig verhindert, bei schwarzem Tee durch SOD hingegen signifikant verstärkt. Eine nicht signifikante Verstärkung der Vasodilatation durch SOD war auch bei EGCG, TF3 und grünem Tee zu beobachten. Die Ergebnisse deuten darauf hin, dass H2O2 maßgeblich die Vasodilatation auslöst. Die Stabilitätsmessungen von EGCG und TF3 gaben Aufschluss über eine mögliche Autooxidation der Teepolyphenole. EGCG (1 und 10 μM) und TF3 (0,5 und 2 μM) wurden als Einmalgabe dem Organbad zugegeben und nach 1, 15 und 30 Minuten Proben entnommen. Die Messungen von EGCG und TF3 mittels Ultrahochdruckflüssigkeitschromatographie zeigten einen raschen Konzentrationsabfall im zeitlichen Verlauf und unterstützen damit die These der Autooxidation. Dies kann auch für die Teepolyphenole im grünen und schwarzen Tee vermutet werden. Katalase und SOD hatten einen stabilisierenden Effekt auf EGCG und TF3, so dass beide Polyphenole zum Teil in höheren Konzentrationen nachweisbar waren als ohne Antioxidantien. Des Weiteren wurde mit dem Amplex Red Wasserstoffperoxid Test die durch EGCG und TF3, sowie grünen und schwarzen Tee generierte Menge an H2O2 gemessen. EGCG (1 und 10 μM), TF3 (0,5 und 2 μM), sowie grüner und schwarzer Tee (50 μl) wurden als Einmalgabe dem Organbad zugegeben und nach 1, 15 und 30 Minuten Proben entnommen. Bei grünem und schwarzem Tee sowie EGCG und TF3 war nach kurzer Zeit H2O2 nachweisbar, dessen Entstehung nach Vorbehandlung mit Katalase und SOD stark vermindert wurde. Es gibt darüber hinaus auch die Möglichkeit der Beteiligung weiterer ROS an der Vasodilatation. Aus den vorhandenen Ergebnissen kann auf einen extrazellulären Zerfall/Autooxidation der Teepolyphenole unter H2O2-Bildung geschlossen werden. Das extrazellulär gebildete H2O2 kann in die Zellen diffundieren und intrazellulär den PI3/AKT-Signalweg mit nachfolgender Phosphorylierung der eNOS und Vasodilatation auslösen. Die hier vorliegende Arbeit stützt damit die Vermutung, dass Teepolyphenole auch prooxidativ wirken können und trägt zum Verständnis der Mechanismen der Vasodilatation durch Teepolyphenole bei. Aufgrund der widersprüchlichen Ergebnisse bezüglich prooxidativer und antioxidativer Effekte von Teepolyphenolen bedarf es jedoch weiterführender Untersuchungen. Zudem muss der Frage nachgegangen werden, ob andere Inhaltsstoffe oder Metaboliten im grünen und schwarzen Tee die Vasodilatation vermitteln., Green and black tea are attributed to numerous health promoting effects on the cardiovascular system. In particular, the protection against arteriosclerosis, hypertension and the positive effect on vascular function is discussed. In addition, antioxidant effects of tea polyphenols have been described. In vitro, however, prooxidative effects of tea polyphenols have also been observed. They can be oxidized themselves and thereby form reactive oxygen species (ROS) like hydrogen peroxide (H2O2) and superoxide (O2.-). Some studies assume autooxidation of tea polyphenols with the formation of dimers/quinones, which has been demonstrated in vitro only. In this context, it is still unclear how the described vasodilatory effects of polyphenols are mediated. It is unknown if receptor-mediated signaling pathways are involved or if autooxidation with the formation of ROS takes place. In endothelial cells, epigallocatechin-3-gallate (EGCG) activates the endothelial nitric oxide synthase (eNOS) by phosphorylation of protein kinases that results in increased nitric oxide (NO) production and vasodilatation. Phosphatidylinositol-3-OH-kinase (PI3-kinase), cAMP-dependent protein kinase (PKA) and protein kinase B (AKT) were identified as protein kinases involved in this process. It is discussed whether the NO-mediated relaxation of the vessels is a redox-sensitive reaction that requires the presence of H2O2 and O2.-. These could trigger the PI3-kinase/AKT-dependent eNOS phosphorylation as an early signal. In the present work, the possible autooxidation with the formation of ROS as a trigger of the PI3/AKT kinase signaling pathway was investigated. Previous results on the autooxidation of EGCG were extended to green and black tea, as well as to theaflavin-3,3´-digallate (TF3) as a component of black tea. The investigations were carried out in several steps in order to verify the results with different methods. All investigations were done with the rat aortic ring model, an ex vivo experimental model, which simulates the in vivo situation in the blood vessels. To investigate the involvement of the ROS H2O2 and O2.- in the vasodilation of tea polyphenols, a single dose of superoxide dismutase (SOD, 500 U/ml), catalase (200 U/ml) or mangan(III)tetrakis(1-methyl-)porphyrine (MnTMPyP, 10 μM) was added to organ baths at the beginning of each experiment. Control rings were treated with water only. To measure vasodilation, every 30 minutes EGCG (0.1 - 10 μM), TF3 (0.02 - 2 μM), green or black tea (5 -50 μl, which correspond to about 5 μM EGCG or 0.06 μM TF3 at 50 μl) were given to organ baths. Tea polyphenol-induced vasodilatation in the aortic ring model was completely prevented by catalase, but was significantly enhanced by SOD in black tee and not significantly enhanced in EGCG, TF3 and green tea. The results suggest that H2O2 is a major cause of vasodilatation. The stability measurements of EGCG and TF3 revealed a possible autooxidation of tea polyphenols. EGCG (1 and 10 μM) and TF3 (0.5 and 2 μM) were added as a single dose to organ bath and sampled after 1, 15 and 30 minutes. Measurements of EGCG and TF3 concentrations through ultra-high-pressure liquid chromatography revealed a strong reduction over time and thus support the hypothesis of autooxidation. This may also be suspected for the tea polyphenols in green and black tea. Catalase and SOD had a stabilizing effect on EGCG and TF3, so that both polyphenols were partly detectable in higher concentrations than without antioxidant. Furthermore, the Amplex Red Hydrogen Peroxide Assay was used to measure the amount of H2O2 induced by EGCG and TF3, as well as green and black tea. EGCG (1 and 10 μM), TF3 (0.5 and 2 μM), as well as green and black tea (50 μl) were added as a single dose to the organ bath and sampled after 1, 15 and 30 minutes. By using green and black tea, as well as EGCG and TF3, H2O2 was measured within a short time, that was diminished by pretreatment with catalase and SOD. However, the involvement of further ROS in the process of vasodilatation cannot be excluded. From the present results, an extracellular decay/autooxidation of tea polyphenols with concurrent formation of H2O2 is concluded. These extracellular generated H2O2 can diffuse into the cells and trigger the PI3/AKT signaling pathway followed by phosphorylation of eNOS and vasodilatation. The present work thus supports the assumption of prooxidative effects of tea polyphenols and contributes to the understanding of the mechanisms of vasodilatation by tea polyphenols. However, due to the contrary results regarding the prooxidative and antioxidant effects of tea polyphenols, further investigations are needed. In addition, the question must be investigated whether other ingredients or metabolites in green and black tea mediate vasodilation.

Tea is cultivated in diverse environments causing yield and quality differences in its beverages. To maximise yields and quality, agronomic practices should be optimised. But agronomic recommendations are uniform in different environments in Kenya despite variations in the growth factors responsible for changes in yields and quality. Plucking is labour intensive and a costly agronomic input in tea production. Trials were conducted for ten years in five tea growing regions in Kenya to assess yields and quality responses of clone BBK 35 tea to location of production and harvesting intervals. There were different (P ⩽ 0.05) yields in the various locations, with significant (P ⩽ 0.05) interaction effects between locations and harvesting intervals. Yields declined in three out of five regions but increased in one location with longer plucking intervals. Yields in a geographical area of production can not be used to estimate its expected yields in other tea growing areas. Black tea theaflavins varied significantly (P ⩽ 0.05) with geographical area of production, but other plain tea quality parameters did not vary with location. It is therefore possible to make similar black teas with similar plain tea quality parameters except theaflavins from all tea growing regions of Kenya. Tea quality improved with short plucking rounds. One way to maximise tea quality is through shortening harvesting intervals. It is necessary to establish optimal harvesting rounds in the different tea growing regions in Kenya to maximise yields and quality.

Background/Aims: The polyphenols catechins and theaflavins in black tea have been shown to possess many medicinal properties, including anticancer activity and some antifungal characteristics, but there have been few studies of their anti-Candida activity. In this paper we report the results of our study of the anti-Candida activity of tea polyphenols. Methods: The effects of 4 different concentrations of catechins and theaflavins were evaluated on 5 isolates each of 5 Candida species employing an agar diffusion growth inhibition assay. The minimum inhibitory concentration (MIC) of the polyphenols against C. albicans was determined. The post-antifungal effect (PAFE) of the polyphenols for C. albicans was investigated. C. albicans cells exposed to polyphenols were studied using a scanning electron microscope (SEM). Results: Both polyphenols showed anti-Candida activity against all tested Candida species and demonstrated a MIC of 6.25 mg/ml for C. albicans. C. glabrata was found to be the most sensitive species followed by C. parapsilosis, C. albicans, C. krusei and C. tropicalis (p < 0.05 for all). Significant intraspecies variations in sensitivity were noted among C. parapsilosis and C. tropicalis (p < 0.001) for both polyphenols. Theaflavins displayed standard PAFE while catechins showed a paradoxical PAFE with all isolates of C. albicans. SEM revealed considerable cell wall damage of C. albicans cells exposed to the polyphenols. Conclusion: The study reveals for the first time the anti-Candida properties of black tea polyphenols that may find therapeutic applications in future.

Black teas are known for their characteristic brown colour, bitter taste and astringent mouth feel. These sensory characteristics are mainly influenced by the phenolic oxidation products present in black tea. The oxidation of phenolics from green tea leaves during black tea manufacturing is an uncontrolled process. With the objective to make tea oxidation a more controlled process, the aim of this thesis was to understand the enzymatic oxidation reactions occurring during tea oxidation, and to enable more rapid analysis of complex mixtures of phenolics. By incubating green tea catechins with an exogenous tyrosinase, a black tea-like phenolic profile was obtained, enriched in theaflavins, which are important for quality of tea. Further oxidation of theaflavins yielded theatridimensins, in which an epicatechin is coupled to the benzotropolone ring of theaflavin. By using MS/MS on selected ions these theatridimensins were shown to occur in black tea. This MS method could also be used to distinguish isomeric procyanidins and dehydrocatechins based on MS2 fragments, as well as the different interflavanic configurations occurring in dehydrodicatechins. The dehydrocatechins were shown to occur in black tea as well. Besides these oligomerization reactions mediated by tyrosinase, oxidation of tea phenolics also comprised hydroxylation. The enzymatic activity from tea leaves responsible for this hydroxylation reaction, was found to be peroxidase. All findings were condensed into a new version of the ‘oxidative cascade hypothesis’, describing the oxidation reactions towards formation of a black tea.

Phenolic compounds constitute 50-70% of tea water extract and are the main quality parameters for teas. Theaflavins (TF), thearubigins (TR) and theabrownins (TB) are the major polyphenols that determine the quality of black tea. These compounds were measured in 56 leaf teas and teabags sampled from Australian supermarkets in Queensland. The various quantities of TF, ranging from 0.29% to 1.25%, indicate a quality difference that exists among the teas studied. Low TF content in black tea may be due to over-fermenting and/or long periods of storage. The solubility of TR and TB from teabags ranged from 82% to 92%, indicating that the permeability of teabags was variable. Variable quantities of TF in Australian teas show instability and a tendency of TF to oxidize during storage. Total polyphenols in green teas ranged from 14% to 34%, indicating a large variation, which was not reflected in price. The solubility of total polyphenols from teabags has been proposed as a useful quality index of the filtering paper used for the teabags. This chemical analysis of phenolic compounds in commercial teas may be a potential tool for the quality control of Australian manufactured and imported teas in Australian markets. (C) 2005 Elsevier Ltd. All rights reserved.

significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of significantly affect measured levels of tea compounds and (2) there was a wide variation in the composition of the tea compounds both within each tea category and among categories: black teas contained both theaflavins the tea compounds both within each tea category and among categories: black teas contained both theaflavins the tea compounds both within each tea category and among categories: black teas contained both theaflavins the tea compounds both within each tea category and among categories: black teas contained both theaflavins the tea compounds both within each tea category and among categories: black teas contained both theaflavins and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained and catechins, green and white teas contained catechins and trace amounts of theaflavins, herbal teas contained very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, very low amounts of all tea compounds. A statistical profile of the distribution of catechins, theaflavins, caffeine, and theobromine in the evaluated teas offers consumers a choice of teas containing high levels of healthand theobromine in the evaluated teas offers consumers a choice of teas containing high levels of healthand theobromine in the evaluated teas offers consumers a choice of teas containing high levels of healthand theobromine in the evaluated teas offers consumers a choice of teas containing high levels of healthand theobromine in the evaluated teas offers consumers a choice of teas containing high levels of healthpromoting compounds. promoting compounds. promoting compounds. promoting compounds.

Ein gesundheitlicher Zusatznutzen von Tee, der im Sinne eines „Functional Food” uber die Nahrstoffversorgung hinausgeht, ist aufgrund von In-vitro- und Tierstudien vor allem fur kardiovaskulare Krankheiten und Krebs zu erwarten. Zudem konnte Tee in der Pravention von Zahnkaries, Osteoporose und Adipositas eine Rolle spielen. Aufgussgetranke der Teepflanze Camellia sinensis sind reich an Polyphenolen. Insbesondere Katechine, wie EGCG, Flavonole, Thearubigine und Theaflavine konnten z. B. uber antioxidative Mechanismen praventiv wirken. Polyphenole beeintrachtigen andererseits die Resorption von Nichtham-Eisen, was bei Personen mit schlechter Eisenversorgung zu Anamien fuhren konnte. Gute epidemiologische Studien inklusive Interventionsstudien zu Zusammenhangen zwischen Teekonsum und Gesundheit fehlen aber noch weitgehend und/oder die Resultate sind widerspruchlich. Ungenaue Erhebungsmethoden und ungenugende Kontrolle fur Storfaktoren sind mogliche Grunde fur Letzteres. Dies sollte fur die weitere Forschung berucksichtigt werden. In vitro studies and animal trials provide evidence that tea produced from the leaves of Camellia sinensis may prevent cardiovascular disease and cancer of various sites. There is also some evidence of an inverse relationship between tea consumption and dental caries, bone density and obesity. Tea is an important source of polyphenols. Especially catechins and for example EGCG respectively, flavonols, theaflavins and thearubigins may be of importance in the prevention of chronic diseases by their antioxidant capacity or other mechanisms. On the other hand, polyphenols inhibit nonheme iron absorption and may lead to iron deficiency anemia in people with marginal iron stores. However, the findings from epidemiological studies on the association between tea and chronic diseases are inconsistent or missing. Conflicting results may arise from inadequate assessment of tea preparation and intake as well as from incomplete control for confounding factors. This should be taken into account in future research on this topic.

Increase in coarser plucking standards significantly (P

The chemistry underlying the changes which occur during tea leaf fermentation is reviewed and used as a basis for proposals for the structure of thearubigins, the major pigments of black teas.

Separation factor is an important index for judging the eluotropic sequence of solutes in countercurrent chromatography (CCC). This paper has proven that the contribution of the common basic agglomerate can be eliminated when calculating the separation factor for analogues and introduced a computational equation based on UNIFAC. According to the equation, the estimation of separation factors needs only a few different groups of analogues. Eleven kinds of analogues, such as phytosterol, chlorinated s‐triazines, flavonoids, theaflavins, anthocyanins, sporaviridins, etc., have been tested with the method. Though the solvent systems used are different from each other, the estimated eluotropic sequences are all consisted well with the literatures except for two chlorinated s‐triazines.

Variations in the black tea quality of high-yielding clone S15/10 in response to rates of NPKS 25:5:5:5 fertiliser of 200 and 400 kg Nha ˇ1 year ˇ1 , plucking intervals of 7, 14 and 21 days and a selective plucking standard of up to two leaves and a bud or an unselective plucking standard were studied. Generally, quality declined with longer plucking intervals and unselective plucking. Although there was a general decline in quality with increasing nitrogen rate, only the black tea total colour declined significantly on increasing the nitrogen rate from 200 to 400 kg Nha ˇ1 year ˇ1 . For each nitrogen rate and each plucking interval, unselective plucking reduced the black tea quality. No significant interactions between any two of the three (nitrogen rate, plucking interval and plucking standard) or all three factors were noted, indicating that the patterns of response were similar. The results demonstrate that black tea quality changes due to the factors studied occur in the same pattern with variations in treatments. Poor black tea quality due to any of the factors studied cannot therefore be corrected by varying the other factors. # 2000 Society of Chemical Industry

Although most clones are selected for quality and yields, there are clones in production with superior yields but producing inferior black tea quality and vice versa . Some of these clones with superior yield give very poor black tea quality characteristics. Such clones are normally not progressed in selection programmes. Blending the clonal leaf prior to maceration results in the production of black teas with average quality relative to the amount of the clonal leaf in the mixture. There is no evidence of clonal incompatibility. Slow fermenting clones with superior yields may therefore be selected and planted, provided they are not planted in single stands. ©

In recent years, Turkish black tea has been manufactured by a combination of orthodox + rotorvane + orthodox systems, especially developed for the conditions of Turkey. The optimum fermentation time of black tea manufactured by this system was investigated at the factory level by measuring the theaflavin contents during the fermentation step, which starts with rolling and ends with drying processes. Optimum fermentation times from the start of rolling in the ORO system were determined to be 83 min and 80 min for coarse tea and sieved fine tea, respectively, by theaflavin analysis. Low levels of theaflavin in Turkish black tea were attributed to the very low quality of the fresh tea leaves and of the plucking standards.

The phenolic constituents of 95 black teas, from nine countries, were analysed by HPLC. The procedure resolved 38 coloured phenolic components which were classified as theaflavins (4), thearubigins (22) and flavonol glycosides (11). One of the thearubigin constituents was unresolved chromatographically, but nevertheless quantified as a hump. The relative levels of these substances for different regions and countries of origin were compared. Statistical analysis of the HPLC results with discriminant analysis or canonical variant analysis and ANOVA, highlighted the characteristic differences in phenolic substance levels which contributed most powerfully to the discrimination between origins. Discriminant analysis revealed a discrimination rule based on phenolic composition which achieved a country of origin classification success of 94%. This type of approach highlights which substances are most important in defining origin in terms of tasters' assessments.

HPLC analysis of Kenya clonal black tea liquors revealed the presence of four major theaflavins in the following order: theaflavin > theaflavin-3-gallate > theaflavin-3,3′-digallate > theaflavin-3′gallate. The total amounts and the ratios of the individual theaflavins varied with clones resulting in variations in the astringency of the teas as measured by theaflavin digallate equivalent. Theaflavin digallate and theaflavin digallate equivalent showed a better relationship with sensory evaluation than did total (Flavognost) theaflavins.

Flavour index and Group I1 volatile flavour compounds of clonal black tea progressively decreased while Group I compounds increased during fermentation process. However, theaflavins in made black tea and tasters' evalu- ation of such tea changed in a quadratic manner with fermentation time. The rate of production of the individual theaflavins varied within a clone and between different clones as fermentation progressed. The results explain the errors obtained when only one quality parameter is used to estimate optimum fermentation time in black tea manufacture.

Both theaflavins and sensory evaluations vary in a quadratic manner with fermentation duration in the process of black tea manufacture. The rate of formation of total (Flavognost) theaflavins varies with clones, and within a clone the individual theaflavins form at different rates with resultant changes in the theaflavin ratios as fermentation progresses. The astringency of black tea also varies with composition and total amounts of the theaflavins, as individual theaflavins have different astringencies. The measurement of total theaflavins may therefore not correctly predict total astringency and hence value of tea.

This communication describes the routine use of small inexpensive C18 cartridges for rapid separation and accurate measurement of both thearubigins (TR) and theaflavins (TF) in a liquor brewed from black tea. The slow, traditional method overestimates TR content because of interference from flavonol glycosides. Comparison is also made favourably with other methods available for estimating total TF and sometimes TR in tea.

Thearubigins are the most abundant group of phenolic pigments found in black tea accounting for an estimated 60% of the solids in a typical black tea infusion. Fifty years ago the term thearubigins was first introduced and up to now the chemical nature of the thearubigins remains largely unresolved if not mysterious despite many efforts clarifying their structure. This paper summarizes some of our attempts to clarify and elucidate the chemical nature of the thearubigins, presenting for 15 commercially representative teas data obtained using combustion analysis, IR spectroscopy, NMR spectroscopy, Diffusion NMR spectroscopy, UV–vis spectroscopy, Circular Dichroism spectroscopy and atomic force microscopy, MALDI-TOF-MS and ESI-FT-ICR-MS. The thearubigin fractions from these 15 teas are remarkably similar with respect to their spectroscopic fingerprint. The data obtained are consistent with the thearubigins being structures of not more than 2000 Da with more than 5000 individual chemical entities detected that are susceptible to concentration-driven aggregation in aqueous solution, and that retain the chiral properties of the flavanols and theaflavins. By applying petrolomics-style data interpretation strategies and by developing novel data interpretation strategies a structural model for the thearubigins was developed.

Though tea production continues throughout the year in Kenya, there ere monthly variations in yields and chemical composition attributable to the changes in environmental conditions. Total volatile flavour compounds (VFC), group I VFC, group II VFC and caffeine ere higher throughout the experimental period in black teas manufactured from plants here fertilisers ere applied than here fertiliser as not applied. Levels of thearubigins (TR) and flavour index (FI) ere generally high hen there as no fertiliser application. Theaflavins (TF) levels varied ith the time of the year but there as no clear trend due to fertiliser.

Artykuł recenzowany / peer-reviewed article We hypothesized that among reproductive-age women consuming large quantities of tea, the production of estradiol would be suppressed. It has been shown that catechins and theaflavines, the major constituents of tea, inhibit aromatase, an enzyme which catalyses the conversion of androgens to estrogens. Our study included Polish women living in urban (N=61) and rural (N=48) areas. Women collected daily saliva samples for one complete menstrual cycle and filled out dietary questionnaires. Saliva samples were analyzed by radioimmunoassay for concentration of 17-β estradiol (E2). Women with high (above the median) average daily consumption of black tea had reduced levels of salivary E2, in comparison with women who drank less black tea (below median). This effect was observed within the whole study group, as well as separately within urban (p = 0.0006) and rural (p = 0.013) groups. High intake of the sum of subclasses of tea catechins and epigallocatechin gallate, assessed using the USDA database [http://www.nal.usda.gov], was also associated with lower concentrations of E2 within all women (p = 0.01 and p = 0.0001, respectively) and within the urban group (p = 0.0001 and p = 0.004, respectively). Similar relationships were observed between the sum of subclasses of theaflavines and thearubigines and E2 levels for the whole group (p = 0.002) and for urban women (p = 0.02). Women with high consumption of tea had lower levels of E2 concentration throughout the entire menstrual cycle. These results may have implications for reducing hormone-related cancer risk by a relatively easy dietary intervention. the State Committee for Scientific Research, Warsaw, Poland, project No. 3 P05E 016 25 and 6 P05D 112 20, the Radcliffe Institute of Advanced Study, Harvard University and the Norwegian Cancer Society.

Dietary antioxidants might prevent oxidative damage to tissues and therefore protect against cardiovascular disease and cancer. Dietary phenols are strong antioxidants in vitro but their role in vivo is uncertain. Furthermore, there are only limited data on their bioavailability in humans. The aim of this thesis was to investigate whether bioavailability data on flavonoids and cinnamic acids support the hypothesis that they can affect health in humans . Because the group of phenols in foods is huge, we focussed our research on major phenols in foods; the flavonol quercetin, black tea phenols and chlorogenic acid (5-caffeoylquinic acid). We studied their bioavailability and effect on plasma homocysteine in humans, a potential risk factor for cardiovascular disease.The bioavailability of quercetin and chlorogenic acid depends upon their conjugated moieties. Hollman et al. found that the bioavailability of quercetin-3-rutinoside, a major flavonol in tea, was only 20% of that of quercetin-4'-glucoside. We found that transformation of quercetin-3-rutinoside into quercetin-3-glucoside will improve its bioavailability because the 3-glucoside had the same high bioavailability as the 4'-glucoside. Caffeic acid is a major phenol in coffee, but it is present as a conjugate with quinic acid, called chlorogenic acid. We found that the conjugation of caffeic acid with quinic acid hinders absorption in humans: absorption of chlorogenic acid was only 30% of that of its caffeic acid moiety.Furthermore, we found that chlorogenic acid, black tea solids and quercetin-3-rutinoside are extensively metabolized in the human body, mainly before they reach the circulation. Their metabolites have no, or less, antioxidant activity in vitro than their parent phenols. Therefore the role of dietary phenols as antioxidants in vivo might be less important than suggested by their in vitro antioxidant activity.Coffee consumption increases plasma homocysteine, a potential risk factor for cardiovascular disease. Chlorogenic acid from coffee is partly responsible for the homocysteine-raising effect of coffee, because we found that it increased plasma homocysteine. Black tea solids also raised plasma homocysteine, whereas quercetin-3-rutinoside did not. Furthermore, we found that glycination of metabolites of phenols in the body is not involved in the homocysteine-raising effect of phenols.In conclusion, chlorogenic acid, tea phenols and quercetin are available in the human body, but their effects on health are uncertain. Further research on bioavailability and health effects of dietary phenols is needed.

Dietary antioxidants might prevent oxidative damage to tissues and therefore protect against cardiovascular disease and cancer. Dietary phenols are strong antioxidants in vitro but their role in vivo is uncertain. Furthermore, there are only limited data on their bioavailability in humans. The aim of this thesis was to investigate whether bioavailability data on flavonoids and cinnamic acids support the hypothesis that they can affect health in humans . Because the group of phenols in foods is huge, we focussed our research on major phenols in foods; the flavonol quercetin, black tea phenols and chlorogenic acid (5-caffeoylquinic acid). We studied their bioavailability and effect on plasma homocysteine in humans, a potential risk factor for cardiovascular disease.The bioavailability of quercetin and chlorogenic acid depends upon their conjugated moieties. Hollman et al. found that the bioavailability of quercetin-3-rutinoside, a major flavonol in tea, was only 20% of that of quercetin-4'-glucoside. We found that transformation of quercetin-3-rutinoside into quercetin-3-glucoside will improve its bioavailability because the 3-glucoside had the same high bioavailability as the 4'-glucoside. Caffeic acid is a major phenol in coffee, but it is present as a conjugate with quinic acid, called chlorogenic acid. We found that the conjugation of caffeic acid with quinic acid hinders absorption in humans: absorption of chlorogenic acid was only 30% of that of its caffeic acid moiety.Furthermore, we found that chlorogenic acid, black tea solids and quercetin-3-rutinoside are extensively metabolized in the human body, mainly before they reach the circulation. Their metabolites have no, or less, antioxidant activity in vitro than their parent phenols. Therefore the role of dietary phenols as antioxidants in vivo might be less important than suggested by their in vitro antioxidant activity.Coffee consumption increases plasma homocysteine, a potential risk factor for cardiovascular disease. Chlorogenic acid from coffee is partly responsible for the homocysteine-raising effect of coffee, because we found that it increased plasma homocysteine. Black tea solids also raised plasma homocysteine, whereas quercetin-3-rutinoside did not. Furthermore, we found that glycination of metabolites of phenols in the body is not involved in the homocysteine-raising effect of phenols.In conclusion, chlorogenic acid, tea phenols and quercetin are available in the human body, but their effects on health are uncertain. Further research on bioavailability and health effects of dietary phenols is needed.

Modern chromatographic techniques such as high-performance liquid chromatography are currently the most helpful approach to the routine analysis of and research of non-volatile tea constituents. Using these techniques some errors in the more classical analytical techniques could be detected. Unfortunately, some of these methods of analysis are still in widespread use, even as official methods. However, knowledge of especially the polyphenols in tea is still lacking, and for many of the minor polyphenols no chromatographic methods for the determination exist.

Correlation between theaflavins content and tasters' valuations of Kenyan black teas generally give positive but statistically non-significant correlation coefficients. In 105 correlations using 12 samples each, only eight analyses gave statistically significant (P⩽0.05) correlations. Theaflavins contributed positively towards valuations but Kenyan black plain teas have high and possibly above optimum theaflavins content. Consequently other factors appear to play major roles in tea pricing, for example the generally higher prices realised by Kenyan black plain teas compared to Malawi black plain teas can only be partly attributed to the higher theaflavins content of the Kenyan teas.

There are several critical stages in the Flavognost method for theaflavin analysis in black tea. These have been identified and their significance determined experimentally. During sample preparation, the particle size of the ground material, and the type of grinder used to produce it, directly influence the level of extracted theaflavin. The temperature of the water used and the time over which infusion is carried out are also very significant as is the method of shaking. Failure to control conditions at these critical stages can give rise to a fourfold variation in results. Recommendations are given for possible incorporation into standard protocols.

Concentrations of theaflavin and caffeine were determined in whole Kapchorua Pekoe Fannings and in six of its sieved fractions, as well as in Kapchorua Pekoe Dust, Betjan Flowery Broken Orange Pekoe and Rupai Flowery Orange Fannings and in one sieved fraction of each. The partition constants of theaflavin and caffeine between these leaves and water at 80°C were also determined. Neither property varied significantly with leaf size but did depend on leaf origin and manufacture. The concentration and partition constants for caffeine were greater than for theaflavin. As a corollary, the ratio of caffeine to theaflavin is larger in tea initially drawn from the teapot than in the beverage prepared after topping up with fresh hot water.

Black tea clones have different contents of theaflavins, thearubigins and caffeine. The amounts vary with localities and the patterns of variations change from clone to clone. There was no significant relationship between altitude and theaflavins (except in clones 6/8, 31/8 and 31/11), or thearubigins or caffeine. Tea breeding programmes for high quality need to evaluate the clones in areas of intended release, as chemical composition—and hence quality—vary with localities.

The Flavognost assay for measurement of theaflavin in black tea is discussed, and experimental evidence presented to explain why some parts of the assay can cause within and between laboratory variation. The major problems raised are concerned with the temperature of the infusion, and with the proportion of the total theaflavin present in the tea leaf that is actually extracted. The role of the leaf's endogenous aluminium in theaflavin analysis is discussed, and it is shown that it might be possible to replace the expensive Flavognost reagent with aluminium chloride, which is less than 1% of the price.

A comparative study using in-line theaflavins analysis (ILTF), theaflavins of made-tea analysis (TFMT) and tasters' evaluations, to optimise fermentation during tea manufacture, was carried out. All methods obeyed a quadratic relationship with time. On average, the optimum fermentation times were 107.7, 135.3, 136.2 and 147.4 min for ILTF, TFMT, taster D and taster E, respectively. Linear relationships between different methods had good correlation coefficients but TFMT and tasters' evaluations related best. In the absence of a taster, TFMT can be used to optimise fermentation time in tea processing.

Comparaison de l'activite polyphenoloxydasique et peroxydasique et de la teneur en theaflavine de feuilles de theiers obtenus par clonage ou par semis, en relation avec la couleur du the-boisson et donc sa qualite