PHARMACOLOGICAL PROFILE OF EPIYANGAMBIN - A FUROFURAN LIGNAN WITH PAFANTAGONIST ACTIVITY

The ability of a furofuran lignan, epiyangambin, to inhibit PAF-induce d rabbit platelet aggregation in vitro and thrombocytopenia in rats wa s investigated. Epiyangambin dose-dependently inhibited PAF-induced pl atelet aggregation without modifying the amplitude of the maximal resp onse, indicating a competitive antagonism. The IC50 value of epiyangam bin for 10(-9) M PAF-induced aggregation was 6.1 X 10(-7) M and the Sc hild analysis provided a pA2 of 6.91 +/- 0.2 with a slope of 0.98 +/- 0.25 (n = 4) and a pK(b) of 6.94 +/- 0.19. Epiyangambin had no effect upon the platelet aggregation induced by collagen, thrombin or ADP. Th e in vivo administration of the lignan at 20 mg/kg significantly inhib ited PAF-induced thrombocytopenia in rats. These data indicate that ep iyangambin is a potent and selective antagonist of PAF both in vitro a nd in vivo.