Protective effects of grape seed extract against oxidative and nitrative damage of plasma proteins.

Oxidative stress, vascular inflammation, endothelial dysfunction plays a crucial role in the pathogenesis of cardiovascular diseases. The aim of our in vitro study was to examine the antioxidative properties of grape seed extract, and its potential protective effect on the haemostatic function of human fibrinogen under oxidative stress conditions, induced by peroxynitrite (100 μM). The preincubation of plasma with the tested extract (0.5-50 μg/ml or 0.5-300 μg/ml) reduced the formation of 3-nitrotyrosine and diminished oxidation of thiol groups in plasma proteins. The low concentrations (0.5-50 μg/ml) of grape seed extract also decreased the level of carbonyl groups, however at higher concentrations (100-300 μg/ml) this effect was not observed. Furthermore, grape seed extract counteracted the inhibitory effect of peroxynitrite on human plasma clotting. The results obtained in this study indicate that components of the grape seed extract posses antioxidative properties and may be promising substances for the creation of new dietary supplements.