Blood Pressure-lowering and Vascular Modulator Effects of Acorus calamus Extract Are Mediated Through Multiple Pathways

Abstract

This investigation was aimed to provide a pharmacologic basis to the medicinal use of Acorus calamus in cardiovascular disorders. In normotensive anesthetized rats, crude extract of Acorus calamus and its ethylacetate and nHexane fractions caused a fall in mean arterial pressure. In rabbit aorta rings, crude extract was more potent against high K⁺ (80 mM), ethylacetate against phenylephrine (1 μM), whereas nHexane fraction was equipotent against both precontractions. Crude extract exhibited a vasoconstrictor effect on baseline. Pretreatment of aortic rings with crude extract and its fractions shifted Ca⁺² concentration-response curves to the right, similar to verapamil. Crude extract and ethylacetate fraction suppressed phenylephrine peak formation in Ca⁺²-free medium. In rat aorta preparations, crude extract exhibited endothelium-independent relaxation with a vasodilatory effect against high K⁺. nHexane fraction caused an endothelium-dependent Nω-nitro-l-arginine methyl ester-sensitive vasorelaxant along with ryanodine-sensitive vasoconstrictor effect on baseline tension and partially inhibited high K⁺, although ethylacetate fraction caused an endothelium-independent relaxant and endothelium-dependent vasoconstrictor effect. These data indicate that crude extract possesses a combination of effects, relaxant effects mediated possibly through Ca⁺² antagonism in addition to a nitric oxide pathway, although the associated vasoconstrictor effects may be meant by nature to offset excessive vasodilatation, thus providing a pharmacologic rationale to its cardiovascular medi-cinal uses.