Flavonol profiles of Vitis vinifera white grape cultivars

The flavonol profiles of a wide set of Vitis vinifera white grape cultivars were determined by HPLC-DAD-ESI MS in order to confirm the presence of isorhamnetin type flavonols and also to evaluate their ability for cultivar authenticity and differentiation Only 3 O glycoside derivatives of kaempferol quercetin and isorhamnetin were identified as grape flavonols The 3 O glucosides and 3 O galactosides of kaempferol quercetin and isorhamnetin and also the 3 O glucuronides of kaempferol and quercetin were detected in all the grape varieties In addition traces of isorhamnetin 3 O glucuronide and rutin (quercetin 3 O (6 rhamnosyl) glucoside) were detected in some cases Flavonol profiles of white grapes are dominated by quercetin type flavonols However the preliminary results have shown remarkable differences (Principal Component Analysis) in the contribution of kaempferol type flavonols to the characteristic white grape flavonol profiles which could suggest their use for cultivar authenticity and differentiation purposes In addition some white grape cultivars (e g Pedro Ximenez Gewurztraminer Verdejo Albino and Riesling) were characterised by relatively high and significantly different proportions of the newly reported usually very minor isorhamnetin type flavonols (C) 2010 Elsevier Inc All rights reserved