Phenolic antioxidants in red wine : content and activity
Sensitive and selective methods were applied to the analysis of two batches of bottled wines. The relationship between the antioxidant activity, based on the reduction in Fremy's radical, vasodilation activity (batch 1 only), and phenolic content was investigated. Wines were selected to provide a range of origins, grape varieties and vinification methods. Batch 1 wines were sourced mainly from the Old World, while those in batch II were predominantly from the New World. The total phenolic content was determined by the Folin-Ciocalteu colorimetric assay and by the cumulative measurements obtained by HPLC. Total anthocyanins were determined using a spectral assay. While the wines exhibited a wide range in values in all parameters, with both batches the total phenol content, determined by both the Folin-Ciocalteu assay and HPLC, was very closely correlated with the ESR-derived antioxidant activity. Likewise a strong correlation was noted between the phenolic content and the vasodilation activity of Batch I wines. The antioxidant activity of Batch I wines was significantly correlated with the gallic acid, total stilbene and total flavin-3-ol content. Similarly with Batch II wines, gallic acid and total flavan-3-ols, along with polymeric pigments were significantly correlated with the ESR-derived antioxidant activity. Batch I and II had significantly different phenolic profiles though in both cases the flavin-3-ols and anthocyanins were quantitatively the major skin-derived phenolics present. However, in thirteen of the sixteen Batch I wines the major phenolics present were the flavin-3-ols compared with only five of the twenty-two Batch II wines. This discrepancy may be attributed to the viticultural practices of the Southern Hemisphere where many of these wines originated.