Context: Chromolaena odorata (L.) R.M.King & H.Rob. (Asteraceae) or Siam weed has long been used to stop bleeding in Thailand and many countries. Only the aqueous leaf extract was investigated in in vivo and there have been conflicting results of in vitro hemostatic mechanisms of this plant.
Objective: The most appropriate C. odorata leaf extract that promoted the highest hemostatic activity and the hemostatic mechanisms of these plant extracts will be investigated.
Materials and methods: The lyophilized aqueous leaf extract and alcoholic (50, 70, and 95% ethanol) extracts from the fresh and dried leaves were investigated both in vivo and in vitro. The bleeding time in male Wistar rats was measured to investigate the hemostatic effect. The hemostatic mechanisms were tested using in vitro platelet aggregation and blood coagulation tests in sheep plasma.
Results: All extracts displayed significantly reducing bleeding time (<2.5 min) in rats but did not induce platelet aggregation or blood clotting in the in vitro study. The in vitro blood clotting times of all extracts were >0.6 min. Ethanol extract (70%) from the dried leaves proved to be the extract producing the highest hemostatic activity in vivo with the bleeding time of 1.85 min.
Discussion and conclusion: The in vivo study with rats confirmed the significant ability of this plant extract to stop bleeding. However, the sufficient amount of calcium and active compounds which are aggregating and clotting agents to enhance blood coagulation and platelet aggregation in in vitro tests should be further studied.