Abstract

Total protein extract of the leaves of Morinda morindoïdes were investigated for rabbit blood pressure and mechanical activity of isolated rat heart. Total proteins of M. morindoïdes (PT-Mm) were extracted according the saturation related to Dawson method. The blood pressure was analysed using the mercury manometer of Ludwig. The mechanical activity of the heart was realized with the Langendorff method. PT-Mm produced a reversible hypotension at doses ranging from 5.55 to 27.77 mg/kgBw, and irreversible hypotension to 55.55 mg/kg resulting in the death of the animal. PT-Mm showed a significant decrease (31.77 ± 2.72%) in average of the arterial blood pressure in a dose-related manner. Also, PT-Mm (10^-8 to 10^-1mg/ml) decreased both the force and rate of myocardial contraction, respectively (28.58 ± 2.47 and 33.35% ± 2.35) in a concentration dependent manner. The hypotensive effect of PT-Mm was inhibited by atropine sulfate. The hypertensive effect of adrenaline was strongly reduced by PT-MN extract (77.44 ± 2.23%). In conclusion, total proteins extract of M. morindoïdes has blood pressure lowering effect which would result from the combined actions of myocardial depression and activation of muscarinic cholinergic receptors mediated by vascular smooth muscle relaxation. 

Key words: Cardiovascular activity, Morinda morindoïdes, Total proteins, Blood pressure, Heart rate.