FOOD. Science. Technology. Quality

Food. SCIENCE. Technology. Quality

Food. Science. TECHNOLOGY. Quality

Food. Science. Technology. QUALITY




Changes of (+) catechin antioxidant activity during enzymatic oxidation


The effect of enzymatic oxidation of (+) catechin on its antioxidant activity was investigated. Enzymatic oxidation of (+) catechin in the presence of apple polyphenol oxidase (PPO) and tyrosinase was studied at 25°C and in solution at pH 4 and 7. The antioxidant activity was determined by two methods: ABTS•+ and DPPH radical scavenging. (+) Catechin and the reaction products were monitored by HPLC and TLC. The rate of reaction in the presence of PPO at pH 7 was higher than at pH 4. The reaction products of catechin oxidation were dimers and tetramers. The rate of oxidation of catechin in the presence of tyrosinase was slower than in the presence of PPO. Antioxidant activity of catechin after two hours oxidation (PPO at pH 7) was reduced about 25% in DPPH method (expressed as IC50) and only about 12% in ABTS•+ method (expressed as TEAC), in spite of big decrease content of monomer catechin (57%). This finding indicates that as a result of (+) catechin enzymatic oxidation the compounds with antioxidant activity are formed.