Platelet Anti-Aggregating Plant Materials

The smear method developed by Velaskar and Chitre was modified to allow the screening of plant extracts and/or fractions for platelet anti-aggregating activity. The modified smear method was also found suitable for massive screening of pure compounds. Sample fractions prepared from various plant extracts were examined for their effects against ADP, arachidonic acid (AA) or collagen induced platelet aggregations. Several solvent fractions of plant extracts including water fraction prepared from the methanol extract of Acanthopanax sp. was inhibitory against rat platelet aggregations. The activity guided treatments and fractionations of the water fraction from A. senticosus Max yielded two anti-platelet aggregatory substances, 3, 4-dihydroxybenzoic acid (I) and its artefact ethyl 3, 4-dihydroxybenzoate(II). The inhibitory activities of I and II against rat platelet aggregation were compared with that of aspirin, a known inhibitor of platelet aggregation. Discussions also included the results of the investigations on the structural activity relationships among the various dihydroxybenzoic acid derivatives against platelet aggregations induced by either one of ADP, AA or collagen.