Determination of the phenolic composition of sherry and table white wines by liquid chromatography and their relation with antioxidant activity

The purpose of this work is to study possible relationships between the antioxidant activity (AA) of 13 table white and 9 sherry wines and their phenolic composition. Twenty phenolic compounds were determined by liquid chromathography (LC). AA has been determined by different methods, including 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) and Oxygen Radical Absorbance Capacity (ORAC). The AA of pure phenolic standard compounds has also been measured. Statistical study has been performed using multiple regression analysis and artificial neural networks to ascertain if a specific phenolic composition accounts for a higher AA. Certain phenolic compounds exhibit a high linear correlation with the overall AA of wines. For example, gallic acid, glucoside of cutaric acid and tyrosol as determined by the ORAC method. If we study AA values obtained by ABTS and DPPH methods, a good correlation is obtained with (−)-epigallocatechin gallate and ethyl caffeate. The contribution of each phenolic compound to the AA was also examined. Gallic acid, protocatechuic acid, caffeic acid and tyrosol are the main contributors to the ORAC value. If we use ABTS and DPPH methods, the main contributors are gallic, caffeic and caftaric acids and (−)-epigallocatechin gallate.An equation calculated by Multiple Regression Analysis correlates (r = 0.9028) ORAC values of wines with concentration of certain phenolic compounds (gallic acid, protocatechuic acid, tyrosol, caffeic acid, (−)-epigallocatechin gallate, coumaric acid and 2-furaldehyde).