Identification of new flavonols in hybrid grapes by combined liquid chromatography-mass spectrometry approaches

Grape flavonols are involved in the phenomenon of copigmentation in red wines. These compounds are characterised by nutraceutical properties, have antioxidant activity and are studied for chemotaxonomy of grapes. In general, hybrid grapes are characterised by presence of polyphenols often qualitatively and quantitatively different from Vitis vinifera varieties. In this work, flavonols of 34 hybrid grape varieties (22 red and 12 white) produced by crossing of V. vinifera, Vitis riparia, Vitis labrusca, Vitis lincecumii and Vitis rupestris species, were studied. Compounds were characterised by combining different liquid chromatography/mass spectrometry (LC/MS) methods: precursor-ion and neutral-loss multiple-reaction-monitoring (MRM), and high-resolution mass spectrometry. Twenty-four glycoside flavonols were identified, including 4 quercetin, 5 myricetin, 4 kaempferol, 3 isorhamnetin, 2 laricitrin, 3 syringetin and 3 dihydroflavonol derivatives; myricetin hexoside-glucuronide, myricetin O-di-hexoside, syringetin O-di-hexoside, isorhamnetin rutinoside and kaempferol rutinoside were found in grape for the first time. Statistical analysis (PCA and cluster analysis) divided the samples in four groups on the basis of their flavonol profiles.