Principal components of phenolics to characterize red Vinho Verde grapes: anthocyanins or non-coloured compounds?

Phenolic profile of 10 different varieties of red "Vinho Verde" grapes (Azal Tinto, Borraçal, Brancelho, Doçal, Espadeiro, Padeiro de Basto, Pedral, Rabo de ovelha, Verdelho and Vinhão), from Minho (Portugal) were studied. Nine Flavonols, four phenolic acids, three flavan-3-ols, one stilben and eight anthocyanins were determined. Malvidin-3-O-glucoside was the most abundant anthocyanin while the main non-coloured compound was much more heterogeneous: catechin, epicatechin, myricetin-3-O-glucoside, quercetin-3-O-glucoside or syringetin-3-O-glucoside. Anthocyanin contents ranged from 42 to 97%. Principal component analysis (PCA) was applied to analyse the date and study the relations between the samples and their phenolic profiles. Anthocyanin profile proved to be a good marker to characterize the varieties even considering different origin and harvest. "Vinhão" grapes showed anthocyanins levels until twenty four times higher than the rest of the samples, with 97% of these compounds.