HPLC Separation and Characterization of Flavonols in the Skins of Vitis vinifera var. Cinsault

Abstract

A high performance liquid chromatography (HPLC) method to investigate the flavonol composition of grape skins was developed using Cinsault grapes. In addition to the expected main grape flavonols, several unknown compounds were separated. They were isolated by semi-preparative HPLC and identified by means of ultraviolet spectrophotometry, mass spectrometry, proton nuclear magnetic resonance (NMR), and thin layer chromatography (TLC) analysis of the sugars released from the glycosides by acidic and enzymic hydrolysis. The main flavonols were quercetin-3-glucoside, quercetin-3-glucuronide, and myricetin-3-glucoside. Minor compounds included kaempferol-3-glucoside, kaempferol-3-galactoside, and isorhamnetin-3-glucoside. The kaempferol- and myricetin-3-glucuronides and three diglycosides were also tentatively identified. Evidence was obtained that six additional pigments consisted of the chalcone forms of anthocyanins.