Analysis and tentative structure elucidation of new anthocyanins in fruit peel of Vitis coignetiae Pulliat (meoru) using LC-MS/MS: Contribution to the overall antioxidant activity

Abstract

The skin of Vitis coignetiae Pulliat (meoru) grown wild in the Republic of Korea was analyzed for anthocyanins via HPLC coupled to ESI-MS/MS in positive ion mode. Chromatographic separation was conducted via RP HPLC using a C(18) column, with a 50-min gradient from 0 to 80% methanol in water containing 0.5% formic acid. A total of 18 anthocyanins were identified. Among them, nine compounds were newly determined by comparing the retention time (t(R)) and mass fragmentation patterns with those of the previously reported anthocyanins for other grape varieties: malvidin hexose, peonidin 3-galactoside, malvidin 3-galactoside, cyanidin, petunidin, petunidin 3-(6''-coumaroyl)-5-diglucoside, peonidin, malvidin, and malvidin 3-(6''-coumaroyl)-5-diglucoside. The antioxidant activity of the V. coignetiae Pulliat anthocyanins was determined via 2,2-diphenyl-2-picrylhydrazyl radical scavenging and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation assays in a range of concentration from 25 to 500 mg/L. The capacity increased with concentration. The IC(50) values, defined as the concentration of sample required to scavenge 50% of free radicals, were calculated as follows: 189.63+/-11.31 mg/L and 141.29+/-6.70 mg/L for 2,2-diphenyl-2-picrylhydrazyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) radical cation, respectively. The antioxidant activity of the V. coignetiae Pulliat anthocyanins is substantially higher than that of ascorbic acid and is similar to the effects of the extracts obtained from other grape varieties.