Antioxidant chemistry of green tea catechins: Oxidation products of (-)-epigallocatechin gallate and (-)-epigallocatechin with peroxidase

Tea catechins display possible antitumor activities which are believed to be mainly due to their antioxidative effects. However, the specific mechanisms of the antioxidant action of tea catechins remain unclear. In this study, (-)-epigallocatechin gallate (EGCG) and (-)-epigallocatechin (EGC) were reacted with peroxidase in the presence of H2O2 to produce two oxidation products. These two products were determined as the symmetric dimer of EGCG and EGC, respectively. Thus, the trihydroxyphenyl B-ring, rather than galloyl moiety, was the more active site of antioxidant reaction. Moreover, this study provided some insight into the specific mechanism of antioxidant reactions of tea catechins, and a possible mechanism is proposed.