Identification of Oxidation Products of (−)-Epigallocatechin Gallate and (−)-Epigallocatechin with H2O2

Abstract

(−)-Epigallocatechin gallate (EGCG) and (−)-epigallocatechin (EGC) are two important antioxidants in tea. They also display some antitumor activities, and these activities are believed to be mainly due to their antioxidative effects. However, the specific mechanisms of antioxidant action of tea catechins remain unclear. In this study are isolated and identified two novel reaction products of EGCG and one product of EGC when they were reacted separately with H₂O₂. These products are formed by the oxidation and decarboxylation of the A ring in the catechin molecule. This study provides unequivocal proof that the A ring of EGCG and EGC may also be an antioxidant site. This study also indicates an additional reaction pathway for the oxidation chemistry of tea catechins. Keywords: Catechins; EGCG; EGC; antioxidants; H₂O₂