Antioxidative properties of curcumin in the protection of blood platelets against oxidative stress in vitro.

The present in vitro study was designed to estimate the antioxidative activity of curcumin in the protection of human blood platelets and plasma against peroxynitrite (ONOO(-))-induced oxidative stress. The effects of curcumin (12.5-50 µg/ml) on ONOO(-)-induced damage of proteins and lipids were determined by the estimation of protein carbonyl groups, 3-nitrotyrosine formation, and thiobarbituric acid reactive substance (TBARS) generation. Exposure of blood platelets and plasma to 100 µM ONOO(-) resulted in an increased level of carbonyl groups, nitration of protein tyrosine residues, and enhanced lipid peroxidation. Curcumin inhibited carbonyl group formation in plasma and in platelet proteins. The highest dose of curcumin (50 µg/ml) reduced blood platelet protein carbonylation by approximately 40%. In the protection of blood plasma protein, the lower doses of curcumin (12.5 and 25 µg/ml) were more effective. Curcumin partially prevented 3-nitrotyrosine formation in plasma proteins; the effect of curcumin was only statistically significant in blood platelets at the highest dose (50 µg/ml). The antioxidative action of curcumin in the protection against lipid peroxidation caused by ONOO(-) was also observed. Curcumin suppressed the formation of TBARS both in blood platelets and in plasma samples. The highest concentration of curcumin (50 µg/ml) decreased the TBARS level by approximately 35% in both blood platelets and plasma samples. In conclusion, the present study demonstrates the antioxidative properties of curcumin and its protective effects against oxidative/nitrative changes of blood platelets and plasma components, especially proteins and lipids.