Abstract
Juniperus excelsa Bieb. is used in folk medicine for lowering blood pressure (BP). Its BP-lowering effect, endothelium-dependent and endothelium-independent vasodilator effects, and cardio-modulatory effect are reported here. The crude extract of J. excelsa (Je.Cr) which tested positive for the presence of anthraquinone, flavonoids, saponins, sterols, terpenes, and tannins induced a dose-dependent (10-300 mg/kg) fall in the arterial BP of anesthetized rats. In isolated rabbit aorta, Je.Cr (0.01-5.0 mg/mL) inhibited high K+ (80 mM)- and phenylephrine (1 μM)-induced contractions, like that caused by verapamil and papaverine. In endothelium-intact rat aortic preparations, Nω-nitro-l-arginine methyl ester hydrochloride-sensitive vasodilator activity was noted from Je.Cr, which also relaxed the endothelium-denuded aorta tissues. In guinea pig atria, Je.Cr initially caused mild cardiac stimulation, followed by inhibition, like that exhibited by papaverine. Je.Cr prolonged the R-R interval in electrocardiogram of rats under anesthesia. These results reveal that cardiovascular effects of J. excelsa are mediated possibly through a combination of Ca++ antagonism, nitric oxide-modulating mechanism, and phosphodiesterase inhibitory mechanism, which explain its medicinal use in hypertension.