Antithrombotic activities of aspalathin and nothofagin via inhibiting platelet aggregation and FIIa/FXa

Aspalathin (Asp) and nothofagin (Not) are two major active dihydrochalcones found in green rooibos tea (Aspalathus linearis; family, Fabaceae; tribe, Crotalarieae), which have been reported for their anti-oxidant activity. Here, the anticoagulant activities of Asp and Not were examined by monitoring activated partial thromboplastin time (aPTT), prothrombin time (PT), and the activities of thrombin (Factor IIa, FIIa) and activated factor X (FXa). And, the effects of Asp and Not on expression of plasminogen activator inhibitor type 1 (PAI-1) and tissue-type plasminogen activator (t-PA) were evaluated in tumor necrosis factor (TNF)-α activated human umbilical vein endothelial cells (HUVECs). Treatment with Asp and Not resulted in prolonged aPTT and PT and inhibition of the activities of thrombin and FXa, as well as inhibited production of thrombin and FXa in HUVECs. In addition, Asp and Not inhibited thrombin-catalyzed fibrin polymerization and platelet aggregation. Asp and Not also elicited anticoagulant effects in mice. In addition, treatment with Asp and Not resulted in significant reduction of the PAI-1 to t-PA ratio. Collectively, Asp and Not possesses antithrombotic activities and offers a basis for development of a novel anticoagulant.