In vitro screening of the vasorelaxant activity of Diospyros discolor Willd. (ebenaceae) leaf extracts
Diospyros discolor Willd., an endemic Philippine tree, is used in traditional medicine for managing various ailments like heart problems and hypertension. Because of its potential benefit to cause vascular smooth muscle relaxation, the present study aimed to investigate the methanol, hexane, ethyl acetate, n-butanol and aqueous leaf extracts of D. discolor for their vasorelaxant activity and total phenolic content. Vasorelaxant screening was carried out on isolated rat aortic rings. Using an automated polygraph data acquisition system and chart recorder, acetylcholine was used to determine the integrity of endothelium by relaxing the phenylephrine precontracted rings. Test rings were treated with the extracts and fractions in cumulative manner. Among the leaf extracts of D. discolor, Ethyl acetate fraction exhibited 52% relaxation at a concentration of 500µg/mL while methanol extract almost produced a 100% relaxation at the same concentration. Hexane and n-butanol fractions exhibited 28% and 47% respectively at the highest concentration. Removal of the endothelium and incubation with N G-nitro-L-arginine methylester (L-NAME) almost diminished the relaxant effects of the extract and its fractions. This study indicated that the extracts possess endothelium-dependent and NO-mediated vasorelaxant effects. Folin-Ciocalteau method also showed that all the extracts and fractions contained polyphenols expressed as gallic acid equivalent.