Differential Effects of Grape (Vitis vinifera) Skin Polyphenolics on Human Platelet Aggregation and Low-Density Lipoprotein Oxidation

Antioxidant and antiplatelet properties of grape products are thought to be responsible for observed antiatherosclerotic effects. Diverse classes of phenolics are derived from the seed and skin (GSK) of grapes. The relative contributions of the classes of phenolics to observed properties of grape products are unknown. In this paper, GSK fractions were used to examine effects on platelet aggregation, low-density lipoprotein (LDL) oxidation in vitro, and relative binding of phenolics to LDL. GSK was separated into six fractions (fractions 1-6), and primary phenolics were characterized using high-performance liquid chromatography and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Fractions 4, 5, and 6, enriched in polygalloyl polyflavan-3-ols (PGPFs) with 3-6, 4-8, and 6-15 degrees of polymerization, respectively, inhibited platelet aggregation. Fractions 1-3, containing various amounts of oligosaccharides, hydroxycinnamic acids, anthocyanins, flavanols, and low molecular weight PGPFs, significantly increased platelet aggregation. Fractions 4-6 were most effective in binding LDL and inhibiting LDL oxidation. Fractions 5 and 6 exhibited the greatest inhibition of platelet aggregation and LDL oxidation, suggesting that polymeric PGPFs are responsible for the beneficial effects of grape products. Conversely, phenolics in fractions 1-3 may reduce the net biological potency of the grape products and have undesirable effects on cardiovascular disease risk factors.