Free radical scavenging capacity and inhibition of lipid oxidation of wines, grape juices and related polyphenolic constituents

The antioxidant activity of grape juices, wines made from the same lot as j uices and their major polyphenolic constituents was measured by the inhibit ion of lipid oxidation (ferric-thiocyanate) and free radical scavenging (2, 2-diphenyl-1-picrylhydrazyl) methods. DL-alpha-Tocopherol and 3-tertiary-bu tyl-4-hydroxyanisole (BHA) were used as references. The inhibition of lipid oxidation of the standards followed the order: rutin = ferulic acid > tann ic acid = gallic acid = resveratrol > BHA = quercetin > DL-alpha-tocopherol > caffeic acid. Meanwhile, the free radical scavenging activity of gallic acid was the highest, tannic acid, caffeic acid, quercetin, BHA and rutin a ctivities were intermediate and that for ferulic acid, DL-alpha-tocopherol and resveratrol were the lowest. Wines had higher activity than the corresp onding grape juices and red wine showed the strongest activity among the gr ape products tested. The antioxidant activity of the samples seems to be ba sed on their free radical scavenging capacity. (C) 1999 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All righ ts reserved.