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.
From the *Drug Discovery and Natural Products Research Division, Department of Biological and Biomedical Sciences, Aga Khan University Medical College, Karachi, Pakistan; and †Department of Pharmaceutical Sciences, COMSATS, Institute of Information Technology, Abbottabad, Pakistan.
Received for publication January 23, 2009; accepted April 15, 2009.
This study was supported by funds made available by the Pakistan Science Foundation and the Higher Education Commission of Pakistan.
The authors report no conflicts of interest.
Reprints: Anwarul Hassan Gilani, PhD, National Professor of Pharmacology, Department of Biological and Biomedical Sciences, Aga Khan University Medical College, Karachi-74800, Pakistan (e-mail: firstname.lastname@example.org).