Abstract: Tea catechin oxidation products(TCOP) with the retention time of 9.825 min were separated from H2O2 model oxidation system using multistage column chromatography and they were identified to be two products with m/z 471 and m/z 939 using HPLC/ESI-MS/MS. The oxidation product with m/z 471 is found to be a product from epigallocatechin gallate(EGCG) by eliminating two hydrogen atoms and adding one oxygen atom,and the product with m/z 939 is its dimer. The antioxidant activities of the oxidation products were measured in different systems. The results showed that the tea catechin oxidation products have very strong antioxidant activity in all tested systems. The scavenging rates of the oxidation products on hydroxyl free radical(·OH) generated in methyl violet color metric system,2-deoxy-D-ribose system and salicylic acid system are 96.46%,84.8% and 81.9%,respectively,and the scavenging rate on superoxide anion(O2·) generated in luminescence of pyragollic acid-Luminol system is 97.0%. The antioxidant activities of the oxidation products are much stronger than those of tea polyphenol at the same concertration in all tested systems.

Key words: catechin oxidation products, separation, identification, antioxidant activity