Antioxidant and Vasorelaxant Properties of Phaseolus vulgaris Linn (Fabaceae) Immature Pods Extract on the Thoracic Aorta of NMRI Mice

Abstract

Introduction: Oxidative stress, through the increased bioavailability of reactive oxygen species (ROS), is a major cause of hypertension. The resulting endothelial remodeling promotes the production of vasoconstrictor substances leading to an increase in blood pressure. This study aimed to evaluate the antioxidant and vasorelaxant properties of the decoction (PAD), ethyl acetate (EAP), and residual aqueous (ARP) fractions of immature Phaseolus vulgaris pods on NMRI mice thoracic aorta rings. Methods: Phytochemical screening was performed by high-performance thin-layer chromatography. Folin-Ciocalteu and aluminum trichloride colorimetric methods were used to quantify total polyphenol compounds (TPC) and total flavonoids (TFC), respectively. Antioxidant activities of the extracts were determined by 2,29-azinobis-3-ethylbenzothiazoline-6-sulfonic (ABTS●), 2,2-Diphenyl-1-picrylhydrazyl (DPPH●), and ferric ion (FRAP) radical reduction methods. The DMT 620M ADInstruments myograph technique was used to evaluate the ex-vivo vasodilatory effects of Phaseolus vulgaris extracts on aortic rings. Results: Chromatographic fingerprints showed the presence of flavonoids, coumarins, tannins, steroids, triterpenes, and saponins in the extracts studied. The TPC (61.07±0.04 mgGAE/g) and TFC (6.16±0.03 mgQE/g) of EAP were statistically significant compared to that of PAD and ARP (p<0.001). The antioxidant power of Trolox was statistically significant compared to all studied extracts (p<0.05). It should be noted that among these extracts, EAP showed the better antiradical capacities for ABTS (IC50=71.87±0.30 µg/mL) and DPPH (IC50=9.93±0.00 µg/mL). However, for FRAP activity, it was the PAD extract (T=170.68±0.11 µgAAE/g) that obtained the best score. In terms of vasorelaxant activity, all extracts induced concentration-dependent relaxation of aortic rings precontracted with U46619. Pharmacodynamic parameters were significantly in favor of EAP [EAP(E+)=(Emax=100.06±0.00%; pD2=1.24±0.01) and EAP(E-)=(Emax=101.01±0.00%; pD2=0.84±0.02)] followed by PAD and then ARP. Conclusion: Phaseolus vulgaris immature pod extracts possess concentration-dependent vasorelaxant effects on isolated mouse aorta. These preliminaries results were scientific evidence to support the use of this plant in traditional and complementary medicine for the treatment of hypertension.