| Research shows that catechin oligomers have biologic activities such as antiatherosclerotic and preventing skin cancer and so on. However, the pathway of formation of oligo-catechins is complex with unclear conditions. In the paper, with the evaluation index of consumption of catechins and formation amount of theaflavins (including theaflavin, theaflavin-3-gallate, theaflavin-3'-gallate and theaflavin-3, 3'-G), the enzymatic oligomerization reaction system was designed as follows: substrate (50mg) was dissolved in a mixture of acetone–pH 5 phosphate buffer (1:10 v/v,11 ml), which contained 0.8mg of horseradish peroxidase. While being stirred, 0.2ml of 3%(v/v) H2O2 was added in the system, sustaining over 1 hour with magnetic stiring (700rpm) before 2ml of citric acid (pH=1.87) was added to terminate the reaction. Besides theaflavin derivatives, unknown compounds with molecule weight between 200 and 1200 were detected by HPLC/MS.The ethyl estate fractions of black tea were separated and the bioability was analyzed in the article. Results showed that the combination of column chromatography, analyzing HPLC and preparative HPLC could provide good effect on separating and purifying fractons. 7 peaks were obtained, and a mixture of 2 flavonol glycosides (quercetin-3-β-D-glucoside and quercetin-3-β-D-galactoside) was further isolated from peak 3. With the controls of EGCG, TP, TF, TFMG and TFDG, the bioability of ethyl estate fractions on total antioxidation (T-AOC) and radicals scavenging of OH·, O2-·and DPPH·was tested. SAS with significant difference analysis shows that, the bioactivity of catechins monomers and oligomers was stronger than that of high polymers.
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