Artemisia copa aqueous extract as vasorelaxant and hypotensive agent.

Abstract Ethnopharmacological relevance Artemisia copa Phil. (Asteraceae) is a medicinal plant commonly used in traditional medicine in Argentina. Aim of the study The vasorelaxant and hypotensive activities of the aqueous extract of Artemisia copa have been investigated. Materials and methods The in vitro effect of the extract and isolated compounds from Artemisia copa was investigated using isolated rat aortic rings. The acute effect caused by the intravenous (i.v.) infusion (0.1–300 mg/kg) on blood pressure and heart rate was evaluated in spontaneous hypertensive rats. In addition, a phytochemical analysis of the extract was performed by HPLC. Results Artemisia copa had a relaxant effect in endothelium-intact aortic rings that had been pre-contracted with 10 −7  M phenylephrine ( E max =96.7±1.3%, EC 50 =1.1 mg/ml), 10 −5  M 5-hydroxytriptamine ( E max =96.7±3.5%, EC 50 =1.5 mg/ml) and 80 mM KCl ( E max =97.9± 4.4%, EC 50 =1.6 mg/ml). In denuded aortic rings contracted by phenylephrine, a similar pattern was observed ( E max =92.7±6.5%, EC 50 =1.8 mg/ml). l -NAME, indomethacin, tetraethylammonium and glibenclamide were not able to block the relaxation induced by the extract. Nevertheless, the pre-treatment with Artemisia copa attenuated the CaCl 2 -induced contraction in a concentration-dependent manner (E max : 86% of inhibition for 3 mg/ml and 52% de-inhibition for 1 mg/ml). This pre-treatment also induced a significant attenuation of the norepinephrine-induced contraction in a concentration-dependent manner ( E max : 72.7% of inhibition for 3 mg/ml and 27% de inhibition for 1 mg/ml) in a Ca 2+ free medium. Upon analyzing the composition of the extract, the presence of p -coumaric acid, isovitexin, luteolin and chrysoeriol were found. Luteolin (CE 50 : 1.5 μg/ml), chrysoeriol (CE 50 : 13.2 μg/ml) and p -coumaric acid (CE 50 : 95.2 μg/ml), isolated from the aqueous extract, caused dilatation of thoracic aortic rings pre-contracted with phenylephrine. Artemisia copa administered i.v. also induced a decrease in the mean arterial pressure but did not affect the heart rate in hypertensive rats. Conclusions The aqueous extract of Artemisia copa proved to have vasorelaxing and hypotensive effects through the inhibition of Ca 2+ influx via membranous calcium channels and intracellular stores. The presence of luteolin, chrysoeriol and p -coumaric acid found in this plant could be involved in this effect.