Flavonols in skins of wild grapes (Vitis vinifera L., subsp. sylvestris (Gmelin) Hegi)

Abstract

Flavonols are a group of grape phenolics that play an important role in young red wines, as they are involved in copigmentation of the flavylium form of anthocyanins. A study on the flavonol composition of grape skins in several wild grapevine genotypes from different Iberian natural populations, preserved at El Encin Germoplasm Bank, has been carried out in 2012. Flavonol glycosides contained in grape skins were determined by HPLC-DAD and HPLC-MS, through a previous phase of purification, using ion exchange chromatographic columns to retain anthocyanins and other phenolic compounds, so that flavonols do not suffer co-elution with other components, improving HPLC analysis. Thus, it was possible to separate 12 flavonol glycosides, and eight of them were successfully identified. The major flavonols were quercetin-3-O-glucoside, quercetin-3-O-glucoronide and myricetin-3-O-glucoside. The diversity and number of flavonols differed for each genotype. The total content of flavonols ranged from 25 to 350 mg/kg grapes; the richest genotype was three times richer than Tempranillo grapes, used as a reference. The most significant difference between wild genotypes and reference cultivars was that, in many cases, myricetin-3-O-glucoside or quercetin-3-O-glucuronide predominated in wild genotypes.