Chemical characterisation of Malvar grape seeds (Vitis vinifera L.) by ultrafiltration and RP-HPLC-PAD-MS

A combination of fast ultrafiltration clean-up procedure and enhanced resolution RP-HPLC-PAD-MS analytical technique is proposed for the characterisation of low molecular mass extractable phytochemicals from Malvar grape seeds (Vitis vinifera L.). This methodology offers satisfactory resolution of the main procyanidin dimers and some trimers and tetramers. Thirty-nine peaks were identified. Seventeen of them contained 17 unambiguously identified compounds: 3 flavan-3-ol monomers (C, EC and ECG), 6 procyanidin dimers (B1, B2, B3, B4, B5 and B6), 1 procyanidin trimer (C1), 1 procyanidin tetramer ([EC-(4α-8)-EC-(4α-8)-EC-(4α-8)-EC]), 4 hydroxybenzoic derivatives (gallic and protocatechuic acids, protocatechuic aldehyde and methyl gallate*), 1 amino acid (tryptophan)* and ellagic acid*. The remaining 22 peaks, and 1 of the first 17 contained 26 compounds which were tentatively identified as: 2 procyanidin dimers (A- and B-type), 7 trimers, 3 tetramers, 7 monogalloylated dimers, 2 monogalloylated trimers and 1 digalloylated dimer, besides 1 gallotannin, 1 dihydroflavonol* and 2 ellagitannins, some of them described for first time in V. vinifera species. Flavan-3-ols represented 62.4% of all grape seed constituents, absorbing at 280 nm, whereas the non-flavan-3-ol species accounted for more than one-third of the total extractable grape seed constituents.