ANTIOXIDATIVE ACTIVITY OF MONOACYLATED ANTHOCYANINS ISOLATED FROM MUSCAT-BAILEY-A GRAPE

The antioxidative activity of four anthocyanins isolated from the Muscat Bailey A grape, which has a malvidin nucleus, was evaluated according to the amount of malonaldehyde formed by the autoxidation of linoleic acid in Trizma buffer (pH 7.4). Thiobarbituric acid derivatives of malonaldehyde were quantitatively analyzed by a spectrophotometer (at 535 nm). Malonaldehyde (20 nmol/mg of linoleic acid) was regularly detected after a 16-h inculation period without antioxidants. Malvidin 3-O-(6-O-p-coumaroylglucosido)-5-glucoside showed only 2.6 nmol/mg of linoleic acid malonaldehyde production. p-Coumaric acid attached to malvidin 3-glucoside and malvidin 3,5-diglucoside was found to play an important role in preventing malonaldehyde production from linoleic acid. The antioxidative activity of an acylated anthocyanin was compared with other chemicals. Malvidin 3-O-(6-O-p-coumaroylglucosido)-5-glucoside proved to be 2 times more effective than commercially available antioxidants such as (+)-catechin and alpha-tocopherol. From the results, ii was found that the monoacylated anthocyanins from the pericarps of grapes can be used as powerful antioxidants as well as for colorants.