Currants (Vitis vinifera L.) content of simple phenolics and antioxidant activity

Currant (Vitis vinifera L.) is a dried vine product, produced almost exclusively in Southern Greece and used in the Mediterranean diet. The three different commercial sub-varieties of currants, namely Vostizza, Gulf, and Provincial were investigated for their total polyphenol content, individual phenolic compounds, and total antioxidant capacity. Total polyphenol content was estimated with the Folin-Ciocalteau assay while identification and quantification of individual target polyphenolic compounds was performed by gas chromatography/mass spectrometry. Total polyphenol content ranged between 151 mg/100 g and 246 mg/100 g currants. Among the polyphenols studied, 17 were identified in Gulf and Provincial currants and 16 in Vostizza currants. The predominant polyphenolic compound in all currants was vanillic acid at mean concentration 1.21 ± 0.23 mg/100 g currants. Caffeic acid, gallic acid, syringic acid, p-coumaric acid, protocatechuic acid, ferulic acid, and quercetin also predominated. The antioxidant activity of currants was assessed by the 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. The amount of currants needed to scavenge 50% of DPPH radical (EC50) was similar for all sub-varieties ranging from about 4 mg to 6.5 mg. Total antioxidant capacity is in descending order Vostizza > Provincial > Gulf. By the present work, the consumption of currants is considered to contribute to the intake of antioxidants.