LC-MS analysis and vasorelaxant effect of extracts from original habitat and ex-situ reproduced specimens of Flemingia faginea: roles of the endothelium and calcium channels

Abstract

Flemingia faginea leaves are used to treat hypertension. This study compared the vasorelaxant activities and phytochemical composition of extracts from leaves collected on ex-situ reproduced specimen (AEFf-ex) or original habitat specimen (AEFf-or). Endothelium-intact and endothelium-denuded rat aortic rings, receptor antagonists, channel blockers, and enzyme inhibitors were used to determine the mechanisms underlying the AEFf-or effect. LC–MS chromatographic profiles of AEFf-or and AEFf-ex appeared qualitatively similar, suggesting comparable polyphenolic composition. Crude extracts (3 × 10 -3 to 3 mg/mL) concentration-dependently caused relaxation of aortic smooth muscle pre-contracted with phenylephrine (EC 50 : 0.34 ± 0.06 mg/mL) or KCl (80 mM) (EC 50 : 0.85 ± 0.12 mg/mL). The relaxation was delayed in the presence of atropine or methylene blue, indicating the plausible implication of eNOS/NO/sGC/cGMP/signaling pathways. AEFf-or-induced relaxation was reduced in the presence of indomethacin, strengthening the hypothesis that endothelial-derived factors are involved. TEA attenuated the AEFf-or-induced relaxation. AEFf-or caused a rightward shift of the Ca 2+ cumulative concentration-response curves, suggesting changes in the mobilization of calcium, perhaps due to a direct effect on calcium channels. AEFf-or effect was similar to that of verapamil, a Ca 2+ channel blocker. Concentration-response curves to Phe or KCl shifted downwards in the presence of AEFf-or. It is possible that AEFf-or acts on Ca 2+ release from intracellular stores, as it produces a concentration-dependent reduction of the phenylephrine contractile response in calcium-free medium. Results suggested that AEFf produced vasorelaxation from the reduction of calcium mobilization through ion channels or internal stores that may be modulated by, or associated with, endothelial signaling pathways.