Relations between polyphenols content and antioxidant activity in vine grapes and leaves

The occurrence and content of some polyphenols and the antioxidant activity of compounds present in grape berries, stems and leaves of Vitis vinifera L. were evaluated. Three white and three blue varieties of grapevine were investigated. The contents were determined of trans-resveratrol, trans-piceid, caftaric acid, tryptophan, catechin, epicatechin, total polyphenols, and flavanols, both in healthy material and in the samples of the plant material infested with microorganisms (Botryotinia fuckeliana Whetzel anamorph Botrytis cinerea Pers.; Uncinula necator (Schw.) Burr; Plasmopara viticola (Berk. & M.A. Curtis) Berl & De Toni). The antioxidant activity of the extracts obtained was determined by different methods: FRAP (Ferric Reducing Antioxidant Power), DPPH (2,2-diphenyl-1-picrylhydrazyl radical) and TAC-PCL (Total Antioxidant Capacity of Photochemiluminescence). The content of trans-resveratrol varied between 0.3-2.3 mg/kg and 0.7-12.1 mg/kg in non-infested and infested grape berries, respectively. The content of trans-piceid between 0.6-2.9 mg/kg and 1.5-6.3 mg/kg in non-infested and infested grape berries, respectively. The content of trans-resveratrol varied between 2.5-10.3 mg/kg and 3.7-20.9 mg/kg in healthy and in infected leaves, respectively. The content trans-piceid varied between 11.3-58.4 mg/kg and 18.5-60.9 mg/kg in the healthy and in the infected leaves, respectively. The highest content of trans-resveratrol was found in stems (16.3-276.3 mg/kg). In young lateral shoots, the highest levels of trans-piceid (12.6-99.7 mg/kg) and caftaric acid (474-2257 mg/kg) were determined. The infested grape berries showed a higher antioxidant activity, which was most closely correlated with the content of total polyphenols (correlation coefficient = 0.8336-0.9952).