Comparison of TLC and spectro photo metric methods for evaluation of the antioxidant activity of grape and berry anthocyanins

Variation of antioxidant activity was measured for differently prepared extracts of pressed residues (mare) from red wine making and production of blackcurrant and redcurrant juice. On the basis of previous tests ethanol and water were chosen as suitable solvents for preparing phenolic extracts from selected samples. Antioxidant activity was also measured for commercially available standards of the anthocyanins present in grapes and red- and blackcurrants, for example malvidin 3-glucoside (Mv3G), cyanidin 3-glucoside (Cy3G), delphinidin 3-glucoside (Dp3G), peonidin 3-glucoside (Pe3G), and petunidin 3-glucoside (Pt3G). Each standard and a mixture of all standards (concentration 250 mug mL(-1)) were analyzed. Two different analytical methods were used, spectrophotometry and TLC. In both methods DPPH was used as a source of stable free radicals with which components with antioxidant activity react. The strongest antioxidant activity was found for Cy3G, then for Pe3G and Mv3G, and the lowest was for Pt3G and Dp3G (both methods). Relatively high antioxidant activity was determined for all samples. The most effective was blackcurrant extract prepared with 70% aqueous ethanol and the least effective were redcurrant extracts. Correlations between TLC and spectrophotometry were calculated for standards and for extracts. The results showed that the methods correlated well for pure standards (r = 0.979) whereas for crude extracts the correlation was slightly lower (0.857) but still acceptable. Press residues from red wine making and from production of blackcurrant and redcurrant juice are rich sources of phenolic antioxidants and so could be used as natural antioxidants in the food industry.