Effects of leaf extracts from Croton zambesicus Muell. Arg. on hemostasis

Ethnopharmacological relevance: The leaf decoction of Croton zambesicus Muell. Arg. (Euphorbiaceae; syn. Croton amabilis Muell. Arg., Croton gratissimus Burch) is traditionally used in Benin to treat hypertension. Aim of the study: As hypertension and thromboembolism are often associated in several cardiovascular diseases, we studied the potential effects of leaf extracts from Croton zambesicus on hemostasis. Materials and methods: We prepared the dichloromethane and aqueous extracts from the air-dried leaves of Croton zambesicus and separated the aqueous extract in its aqueous and dichloromethane fractions. The potential effects of these four extracts/fractions were investigated on red blood cells integrity using spectrophotometric lysis assays, on primary hemostasis using platelet aggregation studies and on secondary hemostasis using calibrated automated thrombin generation assays and coagulation factors inhibition tests. Results: In the in vitro testing, we found that none of the tested extracts/fractions exhibit hemolytic or antiplatelet activity. However, they display a moderate but significant anticoagulant activity which would be mediated through the direct inhibition of thrombin, FXa and TF/FVIIa. The active anticoagulant compound(s) seem to be mainly in the aqueous extract and especially in its aqueous fraction. Conclusions: This experimental work reported for the first time the anticoagulant effect of leaf extracts from Croton zambesicus. These findings are of particular interest as the leaves from Croton zambesicus are commonly used in infusion by local population and may provide a new natural source for the development of original anticoagulant agents. Furthermore, this activity, associated with the vasorelaxant properties of some of its diterpenes may prove to be interesting for the prevention of cardiovascular diseases in traditional medicine. (C) 2010 Elsevier Ireland Ltd. All rights reserved.