Effects of α-tocopherol, l-arginine, and quercetin on aggregation of human platelets

Some nutrients such as vitamin E, l-arginine, and flavonoids inhibit platelet aggregation; however, the effects of these compounds separately are weak. In food, these compounds may be presented all together. The aim of this work was to study the antiplatelet effect of vitamin E in combination with l-arginine or the flavonoid quercetin and also with prostacyclin, an endogenously formed antiplatelet agent of the human being. The inhibition of adenosine diphosphate-induced platelet aggregation was measured photometrically in human platelet-rich plasma. α-Tocopherol alone inhibited platelet aggregation at a concentration of 1 mmol/L and higher. The combination of 100 μmol/L of l-arginine with 200 μmol/L of α-tocopherol caused a significant decrease of adenosine diphosphate-induced platelet aggregation. At these concentrations, neither of the compounds were effective alone. In addition, quercetin, at a concentration of 2 μmol/L, was ineffective alone. However, in combination with 200 μmol/L of α-tocopherol, quercetin reduced platelet aggregation. Furthermore, α-tocopherol at a subthreshold concentration potentiated the antiplatelet effect of prostacyclin. Thus, α-tocopherol at a subthreshold concentration enhanced the inhibitory activity of other natural agents of platelet aggregation.