Vernolepin: an antiplatelet compound of natural origin.

Vernolepin, a natural compound isolated from Vernonia amygdalina Del., shows platelet anti-aggregating properties. In this paper some of its pharmacological activities towards rabbit platelets are studied. Vernolepin has a "stabilizing" effect during freeze-thawing of platelets, it inhibits arachidonic acid, ADP and collagen-induced platelet aggregation and interferes with ATP-release. Electromicroscopy shows a protection of platelets by the drug against adhesion and a desaggregating effect. All these activities are time dependent; a steep dose response relationship is seen. A concentration of 1 X 10(-5) g/ml seems to be optimal.