Polymeric Proanthocyanidins in Skins and Seeds of 37  Vitis vinifera  L. Cultivars: A Methodological Comparative Study

The polymeric proanthocyanidins (PAs) composition of skins and seeds from different Vitis vinifera L. cv. was evaluated, sampling 37 cultivar, preserved in the grapevine collection of Grinzane Cavour (Piedmont, Italy). PAs were quantified using both spectrophotometric (n-butanol and vanillin assay) and chromatographic (high-performance liquid chromatography [HPLC]) methods, and the evaluation of their antioxidant activity was performed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging assay. Results of PAs quantification with the different methods were significantly correlated. A strong correlation pointed out between anthocyans and PAs content (particularly regarding HPLC method; r = 0.9359, P = 0), and the antioxidant activity was not dependent on the polymeric PAs content, but negatively correlated with the degree of polymerization (r =-0.6102, P = 1 × 10⁻⁴). The hierarchical clustering on principal components analysis allowed grouping the samples in 3 different clusters, observing a direct association between the cluster classification and the anthocyans/PAs content.