Cardiovascular effects of mollic acid glucoside, a 1α-hydroxycycloartenoid saponin extractive from Combretum molle R Br ex G Don (Combretaceae) leaf

SUMMARY: The cardiovascular effects of mollic acid glucoside (MAG), a 1α-hydroxycycloartenoid saponin extractive from Combretum molle R Br ex G Don (Combretaceae) leaf, have been investigated in some experimental animal paradigms. The plant extract (MAG, 5–80 μg/ml) produced concentration-dependent, significant (p < 0.05–0.001) negative inotropic and negative chronotropic effects on guinea pig isolated electrically driven left, and spontaneously beating right atrial muscle preparations, respectively. MAG also significantly reduced (p < 0.05–0.001) or abolished, in a concentration-dependent manner, the rhythmic, spontaneous contractions of portal veins isolated from healthy, normal Wistar rats. Like acetylcholine (ACh, 10(-8)–10(-5) M), the plant extract (5–80 μg/ml) produced concentration-related relaxations of rat isolated endothelium-containing thoracic aortic rings pre-contracted with noradrenaline (NA, 10(-10)–10(-5) M). The vasorelaxant effects of MAG in the aortic rings were markedly inhibited or annulled by N(G)-nitro-L-arginine methyl ester (L-NAME, 10(-5) M), a nitric oxide synthase inhibitor. Furthermore, MAG (2.5–40 mg/kg iv) caused dose-related, transient but significant reductions (p < 0.05–0.001) in the systemic arterial blood pressures and heart rates of anaesthetised normotensive and hypertensive rats. The results of this laboratory animal study indicate that MAG caused bradycardia, vasorelaxation and hypotension in the mammalian experimental models used. The vasorelaxant action of MAG was endothelium dependent, and was therefore possibly dependent on the synthesis and release of nitric oxide (NO). The findings of this study suggest that Combretum molle leaf may be used as a natural supplementary remedy in essential hypertension and in certain cases of cardiac dysfunctions in rural African communities.