thromboxane-b2 and helenalin

This study investigates the effect on human platelet function of two sesquiterpene lactones from Arnica montana L., helenalin (H) and 11 alpha,13-dihydrohelenalin (DH). Both compounds inhibited collagen-induced platelet aggregation, thromboxane formation and 5-hydroxytryptamine secretion in a concentration-dependent manner at 3-300 microM. When arachidonic acid was used as stimulus, thromboxane formation remained unaffected despite of inhibition of platelet aggregation. Both H and DH reduced the number of acid-soluble sulfhydryl groups in platelets, by up to 78% at anti-aggregatory concentrations. Moreover, H- and DH-induced platelet inhibition could be prevented by the thiol containing amino acid cysteine. It is concluded that H and DH inhibit platelet function via interaction with platelet sulfhydryl groups, probably associated with reduced phospholipase A2 activity.

Topics: Arachidonic Acid; Arachidonic Acids; Blood Platelets; Cysteine; Humans; Phospholipases A; Phospholipases A2; Platelet Aggregation; Platelet Aggregation Inhibitors; Serotonin; Sesquiterpenes; Sesquiterpenes, Guaiane; Sulfhydryl Reagents; Thromboxane B2