PS-BPB03-2: VASORELAXANT-MEDIATED ANTIHYPERTENSIVE EFFECT OF THE SEED AQUEOUS EXTRACT OF AFRAMOMUM PRUINOSUM GAGNEP. (ZINGIBERACEAE)

Abstract

Objective: Despite the existing therapies, arterial hypertension is still a prevalent and a worldwide major public health concern, prompting the search for new therapeutic alternatives. The present study investigated the antihypertensive and the related mechanisms of action of the seed aqueous extract of Aframomum pruinosum (AEAP), a plant used in Cameroon traditional medicine against cardiovascular ailments. Design and method: Male Wistar rats were rendered hypertensive by chronic oral administration of L-NAME (30 mg/kg/day) for three consecutive weeks, and hypertensive rats were selected and treated with L-NAME alone or in combination with AEAP at doses of 75 or 150 mg/kg/day for an additional 3 consecutive weeks. Captopril (25 mg/kg/day, p.o) was used as reference drug. Blood pressure and heart rate were monitored weekly. At the end of the experiment, the heart was harvested, weighed, and sections of cardiac tissue were stained with hematoxylin and eosin for histological analysis. Cumulative concentrations of the aqueous extract (3, 10, 30, 100, and 300 μg/mL) were tested on intact or endothelium-denuded aorta rings precontracted with norepinephrine (NE; 1 μM) or KCl (90 mM) in absence or presence of L-NAME (a nitric oxide synthase inhibitor, 100 μM), indomethacin (a prostaglandin synthesis inhibitor; 10 μM), methylene blue (a guanylate cyclase inhibitor, 1 μM), tetraethylammonium (TEA; a non-specific potassium channel blocker; 5 μM) or glibenclamide (an ATP-sensitive potassium channel blocker; 10 μM). The contractile response to NE, or CaCl2 was also assessed in the presence or absence of the plant extract. Results: AEAP completely reversed (p < 0.001) L-NAME-induced elevated systolic and diastolic blood pressure, and increased heart rate. AEAP partially reversed cardiac hypertrophy, leucocyte infiltration, and prevent cardiac necrosis. AEAP induced a concentration-dependent vasorelaxant effect on NE- and KCl-evoked contraction with EC50 values of 13.46 and 49.37 μg/mL, respectively. Removal of the endothelium and the preincubation of aorta rings with L-NAME significantly (p < 0.05) reduced the vasorelaxant effect of the plant extract, while indomethacin and methylene blue had no effect (p > 0.05). Glibenclamide, similar to TEA, significantly (p < 0.001) inhibited the vasorelaxant response to AEAP. Also, the extract significantly (p < 0.01 and p < 0.001) inhibited NE- and CaCl2-induced contraction. Conclusion: AEAP possesses antihypertensive effects that are at least partially mediated by its vasorelaxant activity. Nitric oxide release, opening of KATP channels, blockade of alpha-1 receptors, and inhibition of Ca2+ influx account for this vasorelaxant activity.