タンパク質酸化を指標とした茶飲料の抗酸化および酸化促進作用

Abstract

The ready-to-drink tea beverages from the market were examined to assess their pro-oxidant activities by incubating with bovine serum albumin in the presence of 10 mM 2,2'-azobis (2-amidinopropane) dihydrochloride (AAPH), a water-soluble free radical initiator, or 0.1 mM CuC12 in sodium phosphate buffer (pH 7.4) at 37°C for 90 mM. Protein carbonyl was measured as an index of protein oxidation. In the presence of AAPH, several green tea beverages reduced the formation of protein carbonyl possibly by scavenging free radicals, whereas oolong tea and black tea enhanced the protein carbonyl formation. In the presence of Cu^2+ ions, all tea beverages examined in this study largely increased protein carbonyl content. Additionally catechins oxidized by tyrosinase increased the protein carbonyl formation. These results indicate that oxidized catechins and their derivatives, which are rich in oolong tea and black tea, may be responsible for the protein carbonyl formation