文摘
The flavonol profiles of a wide set of Vitis vinifera white grape cultivars were determined by HPLC–DAD–ESI-MSn 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 Ximxe9;nez, Gewürztraminer, Verdejo, Albillo, and Riesling) were characterised by relatively high and significantly different proportions of the newly reported, usually very minor, isorhamnetin-type flavonols.