Endothelium-dependent and independent effect of Guibourtia tessmannii (Caesalpiniaceae) on vascular contractility of rat

Abstract

The stem barks of Guibourtia tessmannii (Caesalpiniaceae) are used in traditional Gabonese medicine as antihypertensive remedies. In the present study, we investigated vasorelaxant properties effect of aqueous extract from G. tessmannii and fuller understanding these mechanisms of action in vitro. The activity of Guibourtia tessmannii was evaluated on isolated aorta rings of rat constricted with KCl (80 mM) and norepinephrine (10-4 M). Cumulative concentrations (1 mg/mL - 100 mg/ml) of G. tessmannii provoked a dose-dependent relaxation of the thoracic aorta precontracted by norepinephrine or KCl (95.69 ± 0.6% and 91.34 ± 4.90%, respectively). The vasorelaxant effect induced by G. tessmannii on the aorta precontracted by KCl was significant decreased in presence of Nω-nitro-L-arginine methyl ester (11.30 ± 4.3 %, p<0.05), tétraéthylammonium (52.2 ± 9.20 %, p<0.01). Indomethacin and atropine modify the vasorelaxant effect of plant extract (57.13± 6.9 %, p<0.01 and 58.83± 5.9 %, p<0.01, respectively. These results suggest that the vasorelaxant action of G.tessmannii was mediated via the muscarinic receptors. The direct effect of G.tessmannii to be mediated by alpha-adrenergic receptors and potassium channels.