flavan-3-ol and epigallocatechin-gallate

Flavan-3-ol derivatives are common plant-derived bioactive compounds. In particular, (-)-epigallocatechin-3-O-gallate shows various moderate biological activities without severe toxicity, and its health-promoting effects have been widely studied because it is a main ingredient in green tea and is commercially available at low cost. Although various biologically active flavan-3-ol derivatives are present as minor constituents in plants as well as in green tea, their biological activities have yet to be revealed, mainly due to their relative unavailability. Here, I outline the major factors contributing to the complexity of functionality studies of flavan-3-ol derivatives, including proanthocyanidins and oligomeric flavan-3-ols. I emphasize the importance of conducting structure-activity relationship studies using synthesized flavan-3-ol derivatives that are difficult to obtain from plant extracts in pure form to overcome this challenge. Further discovery of these minor constituents showing strong biological activities is expected to produce useful information for the development of functional health foods.

Topics: Catechin; Flavonoids; Functional Food; Health Promotion; Humans; Molecular Structure; Polyphenols; Proanthocyanidins; Structure-Activity Relationship; Tea

Regular green tea consumption has been shown to reduce the risk of cancer and diabetes mellitus. These effects are attributed to tea flavan-3-ols, especially to epigallocatechin gallate; however, the molecular targets and mechanisms of action are still subject of extensive research. The special roles of the endoplasmic reticulum (ER) in biotransformation, protein synthesis, calcium homeostasis, and glucose production make this organelle a potential target of the antitumor and antidiabetic effects of tea flavan-3-ols. The purpose of this review is to present evidence for the biologic actions of tea flavan-3-ols on specific ER targets associated with normal function and disease. Reactivation of chemical carcinogens can be reduced by tea flavan-3-ols through inhibition of glucuronide transport across the ER membrane. Catechins modulate Ca(2+) release from the ER lumen and interfere with glycoprotein maturation, which can lead to decreased viability and increased drug sensitivity of tumor cells. Epigallocatechin gallate inhibits glucose transport across the ER membrane, which can underlie the reduction of hepatic glucose production by tea flavan-3-ols. These mechanisms likely contribute to the chemopreventive and glucose-lowering effects of tea catechins. Investigating the effects of flavan-3-ols on ER functions is a promising field of medical and biochemical research to understand disease and improve health.

Topics: Animals; Anticarcinogenic Agents; Antineoplastic Agents, Phytogenic; Biological Transport; Biotransformation; Calcium Signaling; Carcinogens; Catechin; Drug Resistance, Neoplasm; Endoplasmic Reticulum; Flavonoids; Gluconeogenesis; Glucuronides; Glycosylation; Humans; Hypoglycemic Agents; Protein Processing, Post-Translational; Tea

Dark teas are prepared by a microbial fermentation process. Flavan-3-ol B-ring fission analogues (FBRFAs) are some of the key bioactive constituents that characterize dark teas. The precursors and the synthetic mechanism involved in the formation of FBRFAs are not known. Using a unique solid-state fermentation system with β-cyclodextrin inclusion complexation as well as targeted chromatographic isolation, spectroscopic identification, and Feature-based Molecular Networking on the Global Natural Products Social Molecular Networking web platform, we reveal that dihydromyricetin and the FBRFAs, including teadenol A and fuzhuanin A, are derived from epigallocatechin gallate upon exposure to fungal strains isolated from Fuzhuan brick tea. In particular, the strains from subphylum Pezizomycotina were key drivers for these B-/C-ring oxidation transformations. These are the same transformations seen during the fermentation process of dark teas. These discoveries set the stage to enrich dark teas and other food products for these health-promoting constituents.

Topics: Bacteria; Camellia sinensis; Catechin; Fermentation; Flavonoids; Flavonols; Food Handling; Food Microbiology; Tea

Plant defense inducers (PDIs) are booming and attractive protection agents designed to immunostimulate the plant to reduce subsequent pathogen colonization. The structure-PDI activity relationships of four flavan-3-ols: Epicatechin (EC), Epigallocatechin (EGC), Epicatechin gallate (ECG), Epigallocatechin gallate (EGCG) and Gallotannic acid (GTA) were investigated in both whole plant and suspension cell systems. ECG, EGCG, and GTA displayed elicitor activities. Their infiltration into tobacco leaves induced hypersensitive reaction-like lesions with topical scopoletin and PR-target transcript accumulations. On the contrary, EC and EGC infiltrations fail to trigger the biochemical changes in tobacco tissues. The tobacco BY-2 cells challenged with ECG, EGCG, or GTA led to alkalinization of the BY-2 extracellular medium while EC and EGC did not trigger any pH variation. This work provides evidence that the esterified gallate pattern is as an essential flavonoid entity to induce plant defense reactions in tobacco. The phytoprotective properties of the esterified gallate-free EC and the esterified gallate-rich GTA were evaluated on the tobacco/

Topics: Catechin; Flavonoids; Molecular Structure; Nicotiana; Phytophthora; Plant Diseases; Plant Leaves

Several studies have demonstrated that flavan-3-ol/procyanidins are associated with biological functions in the prevention of various chronic diseases, including obesity and diabetes. Knowledge of their mechanisms, including bioavailability, has significantly progressed in the last decade. However, the differences of the metabolic signatures among flavan-3-ol/procyanidins remain ambiguous.. The metabolites in urine over time after acute administration of three typical flavan-3-ol/procyanidins ((epi)catechin [EPC], epigallocatechin gallate [EGCG], and procyanidin dimer [PC]) in view of the chemical structure were analyzed by HPLC-quadrupole TOF/MS. Several bile acid and amino acid derivatives including tryptophan and tyrosine, as well as flavan-3-ol/procyanidin conjugates and phenolic acid degradation products generated by the gut microbiota were observed in rat urine.. Multivariate statistical analyses suggest that the exogenous and endogenous metabolites of flavan-3-ol/procyanidins greatly differ, although the chemical structures of three typical flavan-3-ol/procyanidins-EPC, EGCG, and PC-are similar. Thus, metabolomic differences likely affect their biological functions and health benefits.

Topics: Animals; Biflavonoids; Catechin; Chromatography, High Pressure Liquid; Flavonoids; Male; Mass Spectrometry; Molecular Weight; Proanthocyanidins; Rats, Wistar

Three subtypes of white tea, Silver Needle (SN), White Peony (WP), and Shou Mei (SM), differ in their taste, aroma, bioactivity, and commercial value. Here, a metabolomics investigation on the chemical compositions combining taste equivalent-quantification and dose-over-threshold (DoT) determination on the taste qualities were applied to comprehensively characterize the white tea subtypes for the first time. Significant differences in the contents of catechins, dimeric catechins, amino acids, phenolic acids, flavonol/flavone glycosides, and aroma precursors were observed among these 3 white teas. Metabolite content comparison and partial least-squares (PLS) analysis suggest that theanine, aspartic acid, asparagine, and AMP were positively correlated with the umami taste in white tea, and flavan-3-ols, theasinensins, procyanidin B3, and theobromine had positive correlations with higher bitterness and astringency tastes. In addition, puckering astringent (-)-epigallocatechin gallate (EGCG), (-)-epicatechin gallate (ECG) and theogallin, bitter-tasting caffeine, and the mouth-drying/velvety-like astringent γ-aminobutyric acid (GABA) were identified as key taste compounds of white tea infusion by absolute quantification and DoT factor calculations. This work provided systematic and comprehensive knowledge on the chemical components, taste qualities, and sensory active metabolites for the subtypes of white tea.

Topics: Amino Acids; Astringents; Benzopyrans; Biflavonoids; Caffeine; Catechin; Flavones; Flavonoids; Flavonols; Gallic Acid; Glycosides; Hydroxybenzoates; Metabolomics; Odorants; Phenols; Plant Extracts; Polyphenols; Proanthocyanidins; Quinic Acid; Taste; Tea

Many studies have shown that flavan-3-ols inhibit mammalian alpha-amylases but the published IC

Topics: alpha-Amylases; Amylose; Animals; Catechin; Digestion; Flavonoids; Hydrolysis; Inhibitory Concentration 50; Models, Molecular; Oligosaccharides; Starch; Swine; Tea

The relatively low oral bioavailability of flavan-3-ols from acute doses is commonly highlighted as a limitation when considering the biological significance of these compounds. However, evidence suggests that the absorption of flavan-3-ols may be enhanced during periods of repeated exposure which is more representative of dietary patterns. To explore changes occurring in the upper small intestine from repeated exposure to dietary flavan-3-ols, Caco-2 human intestinal cells were cultured and differentiated in the presence of isolated flavan-3-ols epigallocatechin gallate (EGCG) and epicatechin (EC) or flavan-3-ol-rich green tea and grape seed extracts. Following differentiation, cellular accumulation, Phase II metabolism, and transcellular transport were assessed from a final acute dose of the respective pretreated compound or extract. 10 μM EGCG pretreatment significantly (P < 0.05) decreased the appearance rate of both sulfated and methyl sulfate EGCG metabolites compared to the control. In contrast, 10 μM EC pretreatment resulted in a significantly greater appearance of methylated EC from acute treatment. After 4 h, 10 μM green tea extract pretreatment resulted in a significant (P < 0.05) 38% greater cumulative transport of EC, in addition to 44-60% increased transport of EGCG and epicatechin gallate (ECG) at 60 min compared to the control. For monolayers pretreated with 10 μM grape seed extract, there was a significant (P < 0.05) 17-56% greater cumulative transport of C and EC after 4 h. Assessment of the mRNA expression of select xenobiotic and metabolizing genes revealed that pretreatment with green tea and grape seed extracts significantly (P < 0.05) increased the expression of COMT, ABCC2 and ABCB1. Overall, these results suggest that intestinal adaptation to both isolated flavan-3-ols and extracts rich in these compounds alters their intestinal transport and metabolism.

Topics: Biological Transport; Caco-2 Cells; Catechin; Catechol O-Methyltransferase; Cell Differentiation; Flavonoids; Humans; Intestinal Mucosa; Intestines; Multidrug Resistance-Associated Protein 2; Multidrug Resistance-Associated Proteins

Porphyromonas gingivalis is a pathogen strongly involved in chronic and aggressive forms of periodontitis. Natural products, mainly polyphenols, have been described for advanced treatment of periodontitis by inhibition of the bacterial adhesion of P. gingivalis to the epithelial host cells. An acetone:water extract (LBE) from the rhizomes of Limonium brasiliense (Boiss.) Kuntze was tested under in vitro conditions for potential antiadhesive effects against P. gingivalis to human KB cells and for inhibition of the proteolytic activity of gingipains, the main virulence factor of P. gingivalis. LBE≤100μg/mL had no cytotoxicity against the bacteria and did not influence the cell physiology of human epithelial KB cells. At 100μg/mL LBE reduced the adhesion of P. gingivalis to KB cells significantly by about 80%. LBE at 20μg/mL reduced the proteolytic activity of the arginin-specific Rgp gingipain by about 75%. Chemical profiling of LBE indicated the presence of gallic acid, epigallocatechin-3-O-gallate and samarangenins A and B as lead compounds. UHPLC by using MS and UV detection displays a suitable method for quality control of the extract for identification and quantification of the lead compounds.

Topics: Adhesins, Bacterial; Bacterial Adhesion; Benzopyrans; Catechin; Cysteine Endopeptidases; Epithelial Cells; Flavonoids; Gallic Acid; Gingipain Cysteine Endopeptidases; Humans; KB Cells; Plant Extracts; Plumbaginaceae; Porphyromonas gingivalis; Proanthocyanidins; Rhizome

Proanthocyanidins (PA) from shea (Vitellaria paradoxa) meal were investigated by thiolytic degradation with benzyl mercaptan and the reaction products were analysed by high performance liquid chromatography-mass spectrometry. These PA were galloylated (≈40%), contained only B-type linkages and had a high proportion of prodelphinidins (>70%). The mean degree of polymerisation was 8 (i.e. average molecular size was 2384Da) and epigallocatechin gallate (EGCg) was the major flavan-3-ol subunit in PA. Shea meal also proved to be a potentially valuable source for extracting free flavan-3-ol-O-gallates, especially EGCg (575mg/kg meal), which is known for its health and anti-parasitic benefits. Proanthocyanidins were isolated and tested for bioactivity against Ascaris suum, which is an important parasite of pigs. Migration and motility tests revealed that these PA have potent activity against this parasitic nematode.

Topics: Animals; Anthelmintics; Ascaris suum; Catechin; Chromatography, High Pressure Liquid; Ericaceae; Flavonoids; Gallic Acid; Molecular Structure; Proanthocyanidins; Seeds; Swine

Interactions between polyphenols and macromolecules may impact polyphenol stability and bioavailability from foods. The impact of milk on tea flavan-3-ol stability to thermal treatment was investigated. Single strength (36.2 protein per L), quarter strength (9.0 g protein per L) milk, and control model beverages were incubated with epigallocatechin gallate and green tea extract at 62 or 37 °C for 180 min. Intact flavan-3-ols and select auto-oxidation products [theasinesins (THSNs) and P-2 dimers] were quantified by LC-MS. Generally, greater polyphenol to protein ratios increased first order degradation rates, consequently decreasing formation of oxidation products. The presence of galloyl and hydroxy moieties was associated with higher stability of monomeric flavan-3-ols with increasing protein concentrations suggesting potential for protein affinity to stabilise flavan-3-ols to thermal treatment. Absence of these moieties led to no observable improvements in stability. These results suggest that protein interactions may be useful in stabilising flavan-3-ols through thermal processing.

Topics: Animals; Beverages; Catechin; Dietary Proteins; Flavonoids; Food Handling; Milk; Polyphenols; Tea

The principal green tea polyphenol, (-)-epigallocatechin-3-O-gallate (EGCg), may provide chemoprotection against conditions ranging from cardiovascular disease to cancer. Binding to plasma proteins stabilizes EGCg during its transport to targeted tissues. This study explored the details EGCg binding to bovine serum albumin. Both fluorescence lifetime and intensity data showed that the hydrophobic pocket between subdomains IIA and IIIA is the binding site for EGCg. Fluorescence and circular dichroism were used to establish the roles of the flavan-3-ol and galloyl moieties of the EGCg in binding and to demonstrate a binding-dependent conformational change in the protein. Competitive binding experiments confirmed the location of binding, and molecular modeling identified protein residues that play key roles in the interaction. This model of EGCg-BSA interactions improves the understanding of the likely physiological fate of this green tea-derived bioactive polyphenol.

Topics: Animals; Catechin; Cattle; Flavonoids; Kinetics; Molecular Structure; Protein Binding; Serum Albumin

The accumulation of flavan-3-ols in response to ultraviolet (UV) irradiation was investigated in grape berries with emphasis on the expression of three structural genes (VvANR, VvLAR1 and VvLAR2), and three regulatory genes (VvMYB5a, VvMYB5b and VvMYBPA1), and as well as the contents of flavan-3-ols. UV-A irradiation showed a promoting effect on the transcription of three structural genes at 3-week (flavan-3-ol accumulation period), 7-week (the end of flavan-3-ol accumulation) and 11-week (the beginning of anthocyanin synthesis) periods of berry development. UV-B irradiation also up-regulated all or part of the structural genes, but the activation effect of UV-C irradiation appeared only in the 7-week and 11-week grapes. The developmental stage-dependent activation by the three types of UV was also initiated for three regulatory genes, but the transcriptional up-regulation of the structural genes by UV irradiation was not entirely regulated by these transcription factors. The increase in the content of 2,3-trans-flavan-3-ols or 2,3-cis-flavan-3-ols by UV irradiation paralleled overall with the expression up-regulation of their corresponding structural genes in the 3-week and the 7-week grapes, but not in the 11-week grapes, indicating that the overexpression of structural genes by UV radiation does not translate into a higher content of flavan 3-ols at mature stage.

Topics: Analysis of Variance; Anthocyanins; Biosynthetic Pathways; Catechin; Flavonoids; Fruit; Gene Expression Regulation, Developmental; Gene Expression Regulation, Plant; Genes, Plant; Plant Proteins; Real-Time Polymerase Chain Reaction; Time Factors; Transcriptional Activation; Ultraviolet Rays; Vitis

Physiological studies on aging in perennials are mainly focused either on the primary metabolism or the hormonal regulation of the process. However, to our knowledge, the involvement of the secondary metabolism in this process has not yet been explored. Cistus clusii, a Mediterranean sclerophyllous evergreen bush, shows considerable amounts of flavan-3-ols in leaves. In the present study, we aimed at determining the impact of environmental conditions and plant aging in the flavan-3-ol content in C. clusii plants grown in field conditions, which included summer drought and recovery periods. Six-year-old plants suffered more from photo-oxidative stress, especially during excess light periods, and showed lower maximum photosynthetic rates than 1-year-old plants. C. clusii leaves accumulated (-)-epigallocatechin gallate in early summer, in a strong positive correlation with both the photon flux density and the photoperiod, but not with the plant water status. Moreover, C. clusii plants accumulated proanthocyanidins (polymeric flavan-3-ols) in leaves during summer. Older plants showed higher levels of proanthocyanidins and (-)-epicatechin, but only during late spring and summer. From the result of the present study, we conclude that excess light enhances flavan-3-ol content in C. clusii, a process enhanced as plants age due to increased excess light stress.

Topics: Catechin; Cellular Senescence; Cistus; Flavonoids; Light; Lipid Peroxidation; Proanthocyanidins

Because consumption of teas may be associated with potential health benefits due to its content in polyphenols and in Western countries the consumption of tea is equally divided between the hot and the ready-to-drink (RTD) cold versions of this typical beverage, the aim of this work was to study the absorption and metabolism of flavan-3-ols in human volunteers after the ingestion of a commercial RTD tea.. A feeding study was carried out in 20 healthy human volunteers and urine samples were collected for 24h after tea ingestion. Flavan-3-ols-derived molecules were identified and quantified in urine samples by high-performance liquid chromatography with tandem mass spectrometric detection.. Eight relevant metabolites were identified in urine, all modified flavan-3-ols with the exception of unmetabolized gallic acid. The urinary excretion of flavan-3-ols was equal to 7.2% of the intake with tea. Gallic acid, which was abundant in the RTD tea used in this study, reached a 4.5% of the drunken amount.. The bioavailability values observed are in agreement with previous reports, although the dosage of polyphenols ingested in this study is remarkably lower. Moreover, the use of a group of 20 volunteers, more than the average number of subjects used for usual human acute-feeding studies involving polyphenols, provides additional credibility to the results. After drinking the RTD ice tea used in this study, the internal compartments are exposed to non-marginal doses of flavanols and flavanol metabolites up to 24h.

Topics: Adolescent; Adult; Biological Availability; Catechin; Chromatography, High Pressure Liquid; Female; Flavonoids; Gallic Acid; Humans; Male; Middle Aged; Tandem Mass Spectrometry; Tea

Ten healthy human subjects consumed 500 mL of Choladi green tea, containing 648 mumol of flavan-3-ols after which plasma and urine were collected over a 24 h period and analysed by HPLC-MS. Plasma contained a total of ten metabolites, in the form of O-methylated, sulphated and glucuronide conjugates of (epi)catechin and (epi)gallocatechin, with 29-126 nM peak plasma concentrations (C(max)) occurring 1.6-2.3 h after ingestion, indicative of absorption in the small intestine. Plasma also contained unmetabolised (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate with respective C(max) values of 55 and 25 nM. Urine excreted 0-24 h after consumption of green tea contained 15 metabolites of (epi)catechin and (epi)gallocatechin, but (-)-epigallocatechin-3-gallate and (-)-epicatechin-3-gallate were not detected. Overall flavan-3-ol metabolite excretion was equivalent to 8.1% of intake, however, urinary (epi)gallocatechin metabolites corresponded to 11.4% of (epi)gallocatechin ingestion while (epi)catechin metabolites were detected in amounts equivalent to 28.5% of (epi)catechin intake. These findings imply that (epi)catechins are highly bioavailable, being absorbed and excreted to a much greater extent than most other flavonoids. It is also evident that flavan-3-ol metabolites are rapidly turned over in the circulatory system and as a consequence C(max) values are not an accurate quantitative indicator of the extent to which absorption occurs.

Topics: Catechin; Chromatography, High Pressure Liquid; Flavonoids; Humans; Intestinal Absorption; Spectrometry, Mass, Electrospray Ionization; Tea

Astringency is one of the major organoleptic properties of food and beverages that are made from plants, such as tea, chocolate, beer, or red wine. This sensation is thought to be due to interactions between tannins and salivary proline-rich proteins, which are natively unfolded proteins. A human salivary proline-rich protein, namely IB-5, was produced by the recombinant method. Its interactions with a model tannin, epigallocatechin gallate (EGCG), the major flavan-3-ol in green tea, were studied here. Circular dichroism experiments showed that IB-5 presents residual structures (PPII helices) when the ionic strength is close to that in saliva. In the presence of these residual structures, IB-5 undergoes an increase in structural content upon binding to EGCG. NMR data corroborated the presence of preformed structural elements within the protein prior to binding and a partial assignment was proposed, showing partial structuration. TOCSY experiments showed that amino acids that are involved in PPII helices are more likely to interact with EGCG than those in random coil regions, as if they were anchorage points for the ligand. The signal from IB-5 in the DOSY NMR spectrum revealed an increase in polydispersity upon addition of EGCG while the mean hydrodynamic radius remained unchanged. This strongly suggests the formation of IB-5/EGCG aggregates.

Topics: Amino Acid Sequence; Animals; Catechin; Flavonoids; Humans; Ligands; Molecular Sequence Data; Nuclear Magnetic Resonance, Biomolecular; Proline; Protein Conformation; Protein Folding; Salivary Proline-Rich Proteins; Sequence Alignment

Interactions between salivary proline-rich proteins and tannins are involved in astringency, which is one of the most important organoleptic sensations perceived when drinking wine or tea. This work aimed to study interactions between a recombinant human salivary proline-rich protein, IB-5, and a flavan-3-ol monomer, epigallocatechin gallate (EGCG). IB-5 presented the characteristics of natively unfolded proteins. Interactions were studied by dynamic light scattering, isothermal titration microcalorimetry, and circular dichroism. The interaction mechanism was dependent on protein concentration. At low concentrations, a three-stage mechanism was evidenced. Saturation of the interaction sites (first stage) was followed by protein aggregation into metastable colloids at higher EGCG/protein ratios (second stage). Further increasing this ratio led to haze formation (third stage). At low ratios, a disorder-to-order transition of IB-5 structure upon binding was evidenced. At high protein concentrations, direct bridging between proteins and EGCG was observed, resulting in significantly lower aggregation and turbidity thresholds.

Topics: Amino Acid Sequence; Catechin; Flavonoids; Glycosylation; Humans; Kinetics; Peptide Fragments; Peptides; Phenols; Polyphenols; Proline-Rich Protein Domains; Salivary Proteins and Peptides

Binding of flavan-3-ols to nuclei is characteristic of Tsuga canadensis (coniferous tree). This is achieved with the DMACA reagent (p-dimethylamino-cinnamaldehyde), which stains almost exclusively monomeric and oligomeric flavan-3-ols with an intense blue colour. Deep flavanol staining also occurred when calf cells of small intestine were enriched with added catechins. In order to detect the components of nuclei that may associate with catechins, the principal components of chromatin (DNA, histones) were subjected to UV-VIS spectroscopic titration. DNA or histone sulphate containing the histones H1, H2A, H2B, H3 and H4 were dissolved in cationic and anionic buffers (Tris, phosphate) at different pH values (pH 8.0, 7.4 and 7.0) and titrated with EGCG (epigallocatechin gallate) or catechin. The results show that DNA of calf thymus and the catechins investigated form no spectroscopically detectable association equilibria. However, strong association complexes are found between histone sulphate and EGCG or catechin by means of the Mauser diagrams (A and AD diagrams). The association equilibria can be accompanied by aggregation (precipitation) of histone proteins, especially initiated by EGCG. The titration equilibria are spectroscopically more pronounced in Tris buffers at higher pH values than at lower values, whereas in phosphate buffers the opposite trend is found. Surprisingly, catechin shows nearly no interactions with histone sulphate in phosphate buffers in the pH range 7.0-8.0, which is in contrast to EGCG. Fundamentally, the targets of chromosomes for catechins seem to be the histone proteins of chromatin.

Topics: Catechin; Cell Nucleus; Cells, Cultured; Chromatin; Chromosomes; DNA; Flavonoids; Histocytochemistry; Histones; Hydrogen-Ion Concentration; Mathematics; Mitosis; Spectrum Analysis; Titrimetry; Tsuga

In the present study, we investigated the free radical scavenging effects of green tea extract and green tea tannin mixture and its components using a nitric oxide (NO) and superoxide (O(2)(-)) generating system in vitro. Green tea extract showed direct scavenging activity against NO and O(2)(-) and green tea tannin mixture, at the same concentration, showed high scavenging activity. Comparison of the activities of seven pure compounds isolated from green tea tannin mixture showed that (-)-epigallocatechin 3-O-gallate (EGCg), (-)-gallocatechin 3-O-gallate (GCg) and (-)-epicatechin 3-O-gallate (ECg) had higher scavenging activities than (-)-epigallocatechin (EGC), (+)-gallocatechin (GC), (-)-epicatechin (EC) and (+)-catechin (C), showing the importance of the structure of flavan-3-ol linked to gallic acid for this activity. Among the gallate-free tannins, EGC and GC were more effective O(2)(-) scavengers than EC and C, indicating the O-trihydroxy structure in the B ring is an important determinant of such activity. However, this structure did not affect the NO scavenging activity. These findings confirm that green tea tannin has excellent antioxidant properties, which may be involved in the beneficial effect of this compound.

Topics: Catechin; Dose-Response Relationship, Drug; Flavonoids; Free Radical Scavengers; In Vitro Techniques; Nitric Oxide; Oxidants; Oxidation-Reduction; Structure-Activity Relationship; Superoxides; Tannins; Tea