Radical Scavenging and Inhibition of Platelet Function by a Polyphenol-Rich Fraction from Salvia miltiorrhiza Bunge

A diet rich in polyphenols has previously been shown to be associated with a lower risk for cardiovascular dis- ease. Specifically, inhibition of platelet hyperactivation by polyphenols decreases platelet-dependent thrombosis, reducing the risk for cardiovascular disease. However, whether polyphenols in Salvia miltiorrhiza Bunge (SMB) affect platelet functions has not been clearly determined. Here, we investigated the effects of methanol and ethyl acetate (EtOAc) ex- tracts from SMB on free radical scavenging activities, and platelet aggregation and adhesion. We found that the EtOAc fraction was the most effective at scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azinobis(3- ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radicals (concentration for 50% reduction, RC50 = 2.4 ± 1.5 and 27.9 ± 1.4 μg/mL, respectively), and that, especially for DPPH radicals, the EtOAc fraction showed better scavenging activity than butylated hydroxyanisole (BHA, RC50 = 5.5 ± 0.1 μg/mL). Measurements with a turbidimetric aggregometer revealed that the EtOAc fraction was the most potent inhibitor of ADP- and collagen-induced rat platelet aggregation. In addition, the methanol and EtOAc fraction dose-dependently inhibited thrombin-stimulated platelet adhesion to collagen or fibrino- gen. Collectively, these results suggest that the polyphenol-rich EtOAc fraction from SMB can reduce platelet hyperacti- vation by scavenging free radicals. Thus, the EtOAc fraction of SMB is a potential source of inhibitors of platelet- dependent thrombosis.