Bidens pilosa L. (Asteraceae) is routinely used in African pharmacopoeia for the management of inflammations, diarrhoea and cardiovascular disorders including hypertension. The implication of β-adrenomimetic agonist substances in the hypotension and vasodilatation induced by a chromatographic active fraction F2 of the leaves aqueous extract (BpF2) were investigated. BpF2 induced a dose-dependent hypotension (1 mg/kg b.w.- 25 mg/kg b.w.) in the rabbit. It caused a concentration dependent (10-12 mg/ml- 10-1 mg/ml) decrease in the force of contraction of the isolated guinea-pig aorta. The hypotension and vasodilatation elicited by BpF2 were attenuated in the presence of propranolol (a β-adrenoceptor antagonist). The results suggest that BpF2 could contain β-adrenomimetic agonist substances that may be partly responsible for the hypotension and the vasodilatation. This would therefore justify the use of the plant to treat hypertension.
Keywords: β-adrenomimetic agonists, propranolol, hypotension, vasodilatation
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