Polyphenol-enriched fractions from Sicilian grape pomace: HPLC-DAD analysis and antioxidant activity

On the basis of a preliminary screening of seven different samples of Sicilian grape pomace, the 'Nerello Mascalese' sample NM2 was selected for an ethanol preparative extraction. The defatted NM2 EtOH extract was subjected to DPPH center dot and GAE assays, showing good radical scavenging activity (SC50 = 9.9 mu g/mL) and a GAE value of 397.7 mg/g extract. HPLC-DAD analysis of NM2 extract allowed a quantitative determination of the main anthocyanins (AN) and flavonols/flavonol glycosides (FL/FG). Aliquots of the NM2 extract were subjected to three different fractionation protocols (FP1, FP2 and FP3). The fractions were examined by DPPH center dot and GAE assays, and subjected to HPLC-DAD analysis for the quantitative determination of the main AN and FL/FG. FP3 allowed obtaining a polyphenol-enriched fraction with SC50 = 14.8 mu g/mL and GAE = 184.1 mg/g of fraction, accounting for only 1.3% in weight of the EtOH extract. Some considerations about the relationship between antioxidant activity and AN/FL/FG HPLC-DAD profiles are also reported. (C) 2007 Elsevier Ltd. All rights reserved.