Abstract: The present study was done to evaluate the hypotensive properties and the mechanisms action of the leaf aqueous extract in anaesthetized normotensive rats through a direct blood pressure measurement. The results showed that the extract caused a dose dependent fall in mean arterial pressure. Bilateral vagotomy did not abolished the hypotension induced by S. birrea. Pretreatment of rats with atropine, piperoxan and practolol did not abolished hypotension and suggests that muscarinic, α2 and β2 receptors are not involved in the induction of hypotension. These results suggest that the hypotensive effect of the extract is likely to be mediated through other factors like nitric oxide release or intracellular calcium decrease.