Cardiovascular properties of aqueous extract from Mitragyna inermis (wild).

Aqueous extracts of Mitragyna inermis (AEMI) used traditionally as antihypertensive agents produced a concentration-dependent (0.1-3 mg/ml) ex vivo increase in cardiac contractile response and coronary flow but did not modify heart rate in the rat. Interestingly, AEMI produced relaxation in isolated porcine coronary artery at concentration up to 3 mg/ml that was exclusively dependent on the presence of endothelium. This relaxation involved partial depolarization (KCl 20, 40 mM) and NO synthase inhibitor-sensitive mechanisms but was not sensitive to the blockade of cyclo-oxygenase pathway. In contrast, the relaxant effect of AEMI was not dependent on the presence of endothelium in rat tail artery. Taken together, the present study demonstrates hypotensive, cardiotropic and vasodilatory properties of AEMI that contribute to better understanding of its beneficial effect against cardiovascular diseases.