RESUMO
Ardisia elliptica Thunberg (Myrsinaceae) is a medicinal plant traditionally used for alleviating chest pains, treatment of fever, diarrhoea, liver poisoning and parturition complications. The objectives of the study were to investigate the effect of A. elliptica on collagen induced platelet aggregation and to isolate and purify potential antiplatelet components. Fresh A. elliptica leaves were extracted using methanol (70% v/v) by Soxhlet extraction and the extract was analysed for its inhibition of collagen-induced platelet aggregation. Inhibition of platelet aggregation was assessed by incubating the extracts with rabbit blood and collagen in a whole blood aggregometer and measuring the impedance. The leaf extract was found to inhibit platelet aggregation with an IC50 value of 167 µ/ml. Using bioassay guided fractionation, β-amyrin was isolated and purified. The IC50 value of -amyrin was found to be 4.5 µ/ml (10.5 µM) while that of aspirin was found to be 11 µ/ml (62.7 µM), indicating that β-amyrin was six times as active as aspirin in inhibiting platelet aggregation. This paper is the first report that β-amyrin isolated from A. elliptica is more potent than aspirin in inhibiting collagen-induced platelet aggregation. In conclusion, A. elliptica leaves were found to inhibit collagen-induced platelet aggregation and one of the bioactive components responsible for the observed effect was determined to be β-amyrin.