Study of three new p-coumaroyl glycoside flavonoids in some Italian red grape varieties

Main flavonols in grape are myricetin, quercetin and kaempferol present in glucoside and glucuronide forms [1]. Recently, also laricitrin, isorhamnetin and syringetin glucoside, galactoside and glucuronide were found [2]. In general, they are antioxidant compounds contained in dietary plants used for human nutrition [3]. A “suspect screening analysis” method by high-resolution mass spectrometry to study grape metabolomics was developed [4]. By this approach, three new p-coumaroyl flavonoids were putatively identified in Raboso Piave grape extract. Compounds were identified by overlapping various analytical methods according to recommendations in the MS-based metabolomics: accurate mass measurement provided the structural characterization of functional groups and literature data their probable position in the molecule. Compounds identified are a dihydrokaempferide-3-O-p-coumaroylhexoside-like flavanone, isorhamnetin-3-O-pcoumaroylglucoside, and a chrysoeriol-p-coumaroylhexoside-like flavone (Figure 1) [5]. In the present work, the study of these compounds was extended to other red grape varieties to evaluate their use as varietal markers. Correlation between p-coumaroyl derivatives and the anthocyanins was also studied to investigate the existence of possible common biosynthetic pathways.