Assesment of the antioxidant activity and content of polyphenolic compounds in grapevine seeds

Our work was focused on the study of the antioxidant properties of grapevine seeds. We monitored the grapevine seeds of 6 cultivars of Vitis vinifera, L. (Nativa, Kofranka, Blaufränkish, Marlen, Cabernet Moravia and Italian Riesling). Antioxidant activity was determined by three principally different methods (DPPH, ABTS and FRAP), the content of the total polyphenolic compounds was determined by the Folin ciocalteu method, and the content of the total flavanols was determined by DMACA reagent (p-dimethylaminocinnamaldehyde). Results are presented as an equivalent of gallic acid in g.L-1, respectively were expressed as g.L-1 of catechin equivalents (DMACA method). The highest values of antioxidant activity were measured in the cultivar Nativa (DPPH - 7.75 g.L-1, ABTS - 4.888 g.L-1, FRAP - 4.25 g.L-1). Conversely, the lowest values of antioxidant activity were detected in the cultivar Kofranka (DPPH - 7.08 g.L-1, ABTS - 4.17 g.L-1, FRAP - 4.55 g.L-1). Cultivar Nativa also reached the highest content of flavonols (3.77 g.L-1). The highest measured values of the content of total polyphenolic compounds were identified in the cultivar Cabernet Moravia (15.2 g.L-1 of GAE). Conversely, the lowest values of the content of total polyphenolic compounds were detected in the cultivar Nativa (8.04 g.L-1). Pearson correlation coefficients were calculated for the existing values between antioxidant activity (DPPH, ABTS, FRAP), contents of flavonols, and contents of total polyphenols. The highest correlation coefficient was found between the DPPH and ABTS methods; specifically, it was 0.857.O