Vasorelaxant effect of Valeriana edulis ssp. procera (Valerianaceae) and its mode of action as calcium channel blocker

Abstract

Abstract Objectives The aim was to evaluate the relaxant effect of extracts from Valeriana edulis and determine the possible mechanism of action of the hexanic extract as vasorelaxant agent. Methods Extracts from rhizomes obtained by maceration (hexanic (HEVe), dichloromethanic (DEVe), methanolic (MEVe) and hydroalcoholic (HAEVe) (3.03–500 µg/ml)) were evaluated on aortic rat rings with and without endothelium. Key findings Extracts induced a significant concentration-dependent and endothelium-independent relaxation on isolated rat aorta pre-contracted with noradrenaline (0.1 µm). HEVe, the most potent extract (0.15–50 µg/ml), induced relaxation in aortic rings pre-contracted with KCl (80 mm), with an IC50 value of 34.61 ± 1.41 µg/ml and Emax value of 85.0 ± 4.38%. Pretreatment with HEVe (30 µg/ml) also inhibited contractile responses to noradrenaline and CaCl2. HEVe (9.98 ± 2.0 µg/ml) reduced noradrenaline-induced transient contraction in Ca2+-free solution, and inhibited contraction induced by KCl (80 mm). In endothelium-denuded rings, the vasorelaxant effect of HEVe was not modified by 1-H-[1,2,4]-oxadiazolo-[4,3a]-quinoxalin-1-one (1 µm), tetraethylammonium (5 mm), glibenclamide (10 µm) or 2-aminopyridine (100 µm). Conclusions Our results suggest that HEVe induces relaxation through an endothelium-independent pathway, involving blockade of Ca2+ channels, and this effect could be related to the presence of valepotriates.