PHYTOCHEMICAL ANALYSIS AND EFFECTS OF AQUEOUS EXTRACT OF WITHANIA SOMNIFERA ON ISOLATED SMOOTH MUSCLE, PERFUSED HEART, BLOOD PRESSURE AND DIURESIS IN RATS

The plant Withania somnifera has many acclaimed medicinal uses. This work aims to explore the efficacy of the aqueous extract (AE) of W. somnifera on the isolated trachea and aorta rings, perfused heart, blood pressure and diuresis in rats. Phytochemical analysis of the whole plant of W. somnifera was carried out using standard extraction procedures followed by column chromatography. An aqueous extract (AE) was also prepared by boiling the whole plant material in water followed by evaporation under reduced pressure. The smooth muscle relaxant effect of AE of W. somnifera (10^-4 – 3×10^-1 mg/mL) was tested on isolated rat tracheal and aortic rings. The effect of AE on heart rate and contractility of the isolated perfused heart were recorded. The hypotensive effect of AE (0.4-120 mg/kg) was recorded from the carotid artery in anesthetized normotensive rats. The diuretic activity of AE was evaluated in rats at two different doses (800 and 1600 mg/kg), and urine volume was measured throughout 24 h. Phytochemical analysis of the Jordanian locality of W. somnifera resulted in the isolation of the four known compounds: withanone, withaferin A, β-sitosteryl glucoside, and 5, 6, 17, 27-tetrahydroxy withanolide. AE (10^-4 – 3×10^-1 mg/mL) caused modest relaxation of the carbachol-precontracted trachea but significant concentration-dependent relaxation of the phenylephrine precontracted aorta. Although AE doses (10^-3 – 3 mg) had a negligible effect on the rate or the contractility of the isolated perfused heart, intravenous doses of AE (0.4-120 mg/kg) caused dose-dependent fall of systolic and diastolic blood pressure of anesthetized rats. When AE was administered orally at a dose of 1600 mg/kg, it significantly increased the rate of urine excretion measured in conscious rats. These observations provide scientific support for using W. somnifera in traditional medicine as a hypotensive, anti-asthmatic, and diuretic agent.