225793-49-7Relevant articles and documents
Antioxidant chemistry of green tea catechins. New oxidation products of (-)-epigallocatechin gallate and (-)-epigallocatechin from their reactions with peroxyl radicals
Valcic,Burr,Timmermann,Liebler
, p. 801 - 810 (2000)
The green tea catechins (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) react with peroxyl radicals generated by thermolysis of the azo initiator 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN) to produce several oxidation products. Structure elucidation of these products can provide insights into specific mechanisms of antioxidant reactions. We isolated and identified a previously unreported reaction product of EGCG and three reaction products of EGC. In the EGCG product, the B-ring was transformed into a ring-opened unsaturated dicarboxylic acid moiety. The EGC products include a seven-membered B-ring anhydride and a symmetrical EGC dimer, both analogues of previously described EGCG oxidation products. The third EGC product was an unsymmetrical dimer. In all identified products, changes occurred solely in the B-ring of EGCG or EGC. This confirmed our previous observation that the principal site of antioxidant reactions in EGCG and EGC is the trihydroxyphenyl B-ring, regardless of the presence of a 3-galloyl moiety. A stoichiometric factor n of 4.16 ± 0.51 was measured for EGCG, whereas factors of 2.20 ± 0.26 was found for EGC and 2.33 ± 0.18 measured for methyl gallate. These values represent the net peroxyl radical trapping per catechin molecule by several competing reactions. EGCG and EGC oxidation involves addition of oxygen, which is not derived from water, but most likely from atmospheric oxygen via peroxyl radicals. Characteristic oxidation products may be useful markers for antioxidant actions in living systems.
Plasma‐induced oxidation products of (–)‐epigallocatechin gallate with digestive enzymes inhibitory effects
Jeong, Gyeong Han,Kim, Tae Hoon
, (2021/09/28)
(?)‐Epigallocatechin gallate (EGCG), the chief dietary constituent in green tea (Camellia sinensis), is relatively unstable under oxidative conditions. This study evaluated the use of non‐thermal dielectric barrier discharge (DBD) plasma to improve the anti‐digestive enzyme capacities of EGCG oxidation products. Pure EGCG was dissolved in an aqueous solution and irradiated with DBD plasma for 20, 40, and 60 min. The reactant, irradiated for 60 min, exhibited improved inhibitory properties against α‐glucosidase and α‐amylase compared with the parent EGCG. The chemical structures of these oxidation products 1–3 from the EGCG, irradiated with the plasma for 60 min, were characterized using spectroscopic methods. Among the oxidation products, EGCG quinone dimer A (1) showed the most potent inhibitory effects toward α‐glucosidase and α‐amylase with IC50 values of 15.9 ± 0.3 and 18.7 ± 0.3 μM, respectively. These values were significantly higher than that of the positive control, acarbose. Compound 1, which was the most active, was the most abundant in the plasma‐irradiated reactant for 60 min according to quantitative high‐performance liquid chromatography analysis. These results suggest that the increased biological capacity of EGCG can be attributed to the structural changes to EGCG in H2O, induced by cold plasma irradiation.
Production and degradation mechanism of theacitrin C, a black tea pigment derived from epigallocatechin-3-O-gallate via a bicyclo[3.2.1]octane-type intermediate
Matsuo, Yosuke,Li, Yan,Watarumi, Sayaka,Tanaka, Takashi,Kouno, Isao
experimental part, p. 2051 - 2059 (2011/04/18)
Black tea is rich in polyphenols and has been shown to have various health benefits; however, its components have not yet been clarified in detail. Enzymatic oxidation of epigallocatechin-3-O-gallate, the most abundant polyphenol in tea, is thought to con
A novel black tea pigment and two new oxidation products of epigallocatechin-3-O-gallate
Tanaka, Takashi,Matsuo, Yosuke,Kouno, Isao
, p. 7571 - 7578 (2007/10/03)
During tea fermentation, oxidation-reduction dismutation of a number of quinone metabolites of tea catechins yields numerous minor products, which make it difficult to separate and purify black tea polyphenols. In this study, epigallocatechin-3-O-gallate
Production of theasinensins A and D, epigallocatechin gallate dimers of black tea, by oxidation-reduction dismutation of dehydrotheasinensin A
Tanaka, Takashi,Watarumi, Sayaka,Matsuo, Yosuke,Kamei, Midori,Kouno, Isao
, p. 7939 - 7947 (2007/10/03)
Theasinensins A and D are B,B′-linked dimers of (-)-epigallocatechin 3-O-gallate connected through R and S biphenyl bonds, respectively, and are major constituents of black tea. Enzymatic oxidation of epigallocatechin 3-O-gallate produced dehydrotheasinensin A, and the structure was shown to be equivalent to an o-quinone of theasinensin A. When the aqueous solution of dehydrotheasinensin A was heated, theasinensin D was produced along with galloyl oolongtheanin. On the other hand, dehydrotheasinensin A was converted to theasinensins A and D along with oxidation products in phosphate buffer at pH 6.8 at room temperature. The results strongly suggested that theasinensins in black tea were produced by oxidation-reduction dismutation of dehydrotheasinensin.
