In vitro antioxidant activity of red grape skins

Phenolic antioxidants seem to be partly responsible for the protective effects against cardiovascular diseases attributed to moderate wine consumption. Grape skins greatly contribute to the phenolic composition of red wine. In this paper, the in vitro antioxidant activity of red grape (Vitis vinifera) skins is determined. We show that the radical scavenging activity (C-50 values) against 2,2-diphenyl-1-picrylhydrazyl (DPPH.) of grape skin extracts is relatively high (3.2-11.1 mg dried skin/mg DPPH.) in relation to other foodstuffs and, as expected, is influenced by grape variety, stage of grape ripening and vintage. The antioxidant potential of grape skins seems to be transferred into wine since grape varieties with skins exhibiting high antioxidant potential also resulted in wines with high antioxidant activity. Statistically significant correlations were found between antioxidant activity and phenolic content (total polyphenols, proanthocyanins, catechins and anthocyanins) for both grape skins and wines.