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

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 microg/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 microM). HEVe, the most potent extract (0.15-50 microg/ml), induced relaxation in aortic rings pre-contracted with KCl (80 mM), with an IC50 value of 34.61 +/- 1.41 microg/ml and E(max) value of 85.0 +/- 4.38%. Pretreatment with HEVe (30 microg/ml) also inhibited contractile responses to noradrenaline and CaCl(2). HEVe (9.98 +/- 2.0 microg/ml) reduced noradrenaline-induced transient contraction in Ca(2+)-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 microM), tetraethylammonium (5 mM), glibenclamide (10 microM) or 2-aminopyridine (100 microM).
Conclusions: Our results suggest that HEVe induces relaxation through an endothelium-independent pathway, involving blockade of Ca(2+) channels, and this effect could be related to the presence of valepotriates.