[Polyphenols and anthocyanins in fruits, grapes juices and wines, and evaluation of their antioxidant activity].Medicina (Kaunas). 2003; 39 Suppl 2:104-12.M
The objective of this study was to produce grape (Vitis vinifera L.) extracts using efficient solvents and to compare antioxidant activity, polyphenol and anthocyanin content and composition in the produced extracts to the same characteristics of grape juices and wines. Methanolic and aqueous extracts of red and blue grapes were produced. Total amounts of polyphenols and anthocyanins in grape extracts, juices and wines were determined. Total polyphenols were spectrophotometrically determined measuring absorption after using Folin-Ciocalteau reagent. Total anthocyanins were determined by pH-differential method. Antioxidant activity of all those grape products was analyzed in 2,2-diphenyl-1-picrylhydrazil (DPPH) and 2,2'-azine-bis-(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) free radical binding model systems. The results obtained by both antioxidant activity determination methods were comparable and permitted to evaluate the ability to inactivate free radicals. Individual polyphenols and anthocyanins were separated by high performance liquid chromatography. Compounds of malvidine, delphinidine and petunidine were identified as main anthocyanins present in grape products demonstrating antioxidant activity. The determined amounts of polyphenols and anthocyanins in red wines were relatively higher than in other investigated objects. The wines possessed the highest antioxidant activity, which correlated with the determined amounts of total polyphenols. Correlation between total anthocyanins contents and antioxidant activity of appropriate objects was not established.