ANTIOXIDANT ACTIVITY OF GRAPE EXTRACTS IN A LECITHIN LIPOSOME SYSTEM

Extracts of 14 different grapes were tested for their antioxidant acti vities in a copper-catalyzed lecithin liposome oxidation assay and ana lyzed for their phenolic components by high-performance liquid chromat ography (HPLC). The total phenolic contents of the grape extracts vari ed from 176 to 1236 mg garlic acid equivalents (GAE)/L. Extracts of re d wine grape varieties contained higher concentration of phenolics tha n other varieties. When compared at the same 20 mu M GAE basis, the gr ape extracts inhibited formation of conjugated diene hydroperoxides by 25.1 to 67.9%, and hexanal formation by 49.3 to 97.8%. Extracts of re d table grape varieties Red Globe and Emperor and white wine grape Var ieties Chardonnay and Sauvignon Blanc gave the highest antioxidant act ivities. The relative percentage inhibition of conjugated dienes and h exanal correlated with total phenols (r = 0.86 and 0.89). HPLC analyse s showed that anthocyanins were the most abundant phenolic compounds i n extracts of red grapes, and flavonols were most abundant in extracts of white grapes.