Antithrombotic activities of green tea catechins and (-)-epigallocatechin gallate

The antithrombotic activities and mode of action of green tea catechins (GT C) and (-)-epigallocatechin gallate (EGCG), a major compound of GTC, were i nvestigated, Effects of GTC and EGCG on the murine pulmonary thrombosis in vivo, human platelet aggregation in vitro, and ex vivo, and coagulation par ameters were examined. GTC and EGCG prevented death caused by pulmonary thr ombosis in mice in vivo in a dose-dependent manner. They significantly prol onged the mouse tail bleeding time of conscious mice. They inhibited adenos ine diphosphate- and collagen-induced rat platelet aggregation ex vivo in a dose-dependent manner. GTC and EGCG inhibited ADP-, collagen-, epinephrine -, and calcium ionophore A23187-induced human platelet aggregation in vitro dose dependently. However, they did not change the coagulation parameters such as activated partial thromboplastin time, prothrombin time, and thromb in time using human citrated plasma. These results suggest that GTC and EGC G have the antithrombotic activities and the modes of antithrombotic action may be due to the antiplatelet activities, but not to anticoagulation acti vities. (C) 1999 Elsevier Science Ltd. All rights reserved.