Endothelium-independent vasorelaxant activity of Trachyspermum ammi essential oil on rat aorta

Abstract

ABSTRACTSeveral pharmacological activities of the essential oil of Trachyspermum ammi seeds (TAEO) have been previously studied. These include antitussive, antihypertensive, and antispasmodic effects. However, its action on isolated aorta has not yet been studied. This study was aimed to investigate the vasorelaxant activity of TAEO and characterize its mechanism of action. Extraction of TAEO was performed using Clevenger-type apparatus with the final content of 4.5% (v/w). To evaluate some probable mechanisms of action of TAEO, the action isometric tension was then measured in the aortic rings from Wistar rats which were precontracted with phenylephrine (PHE) (1 µM) or KCl (60 mM). The major constituents of TAEO included Thymol (38.1%), gamma-terpinene (33.3%), and p-cymene (23.1%), as was analyzed by GC-MS. The cumulative concentrations of TAEO reduced precontraction caused by PHE and KCl (p < 0.05) significantly, which was dose dependent. The vasorelaxation caused by TAEO was not influenced in the presence of methylene blue and L-NAME in the endothelium-intact and denuded aorta ring. The inhibitory effect of TAEO on the aortic rings precontracted with KCl and PHE was considerably reduced by nifedipine. These findings hypothesized that the vasorelaxation caused by TAEO is completely endothelium independent and the extracellular Ca2+ influx was also inhibited by TAEO.