Vasodilating properties of the stem bark extract of Mitragyna ciliata in rats and guinea pigs.

Mitragyna ciliata is commonly used in traditional medicine for the treatment of inflammation, hypertension, headache, rheumatism, gonorrhoea and broncho-pulmonary diseases. In the present study, the vascular relaxant effect in the rat and guinea-pig was investigated. The extract induced aortic relaxation in a concentration-dependent manner, with an EC(50) of 1.3 and 7 microg/mL for the noradrenaline- and KCl-induced contractions, respectively. The relaxant effect of the extract on KCl-induced contractions was fi ve times greater than on noradrenaline-induced contractions. Moreover, the relaxant effect of the extract was higher in rat aortic rings with endothelium (104.67%) than without endothelium (49.44%). Chemical analysis of the extract showed the presence of alkaloids and flavonoids which may be responsible for the antihypertensive properties. Copyright 2004 John Wiley & Sons, Ltd.