Pharmacologic & Phytochemical characterization of the hypotensive action of Rhazya Stricta

Rhazya stricta Decne is a medicinal plant that is commonly used in the United Arab Emirates folk medicine as an antidiabetic agent. During our investigation of its pharmacological properties, R. stricta (5-100 mg/kg, iv) caused a dose-dependent decrease in mean blood pressure (maximal effect 40% reduction) and an inconsistent effect on the heart rate of urethane-anesthetized rats. On the isolated heart, the lyophilized extract reduced the rate and force of contraction by approximately 25% Phytochemical analysis of the lyophilized extract revealed the presence of a number of alkaloids and electrolytes. Atomic absorption analysis showed the presence of calcium, magnesium, sodium and potassium at concentration of 14.4, 9.2, 6.3 and 34.5 mg/g lyophilized extract, respectively. In a separate experiment, it was found that the electrolyte component accounted for 50% of the hypotensive activity of the lyophilized extract. An electrolyte-free fraction containing several alkaloids, obtained by liquid-liquid extraction of an ethanolic plant extract (2-6 mg/kg, iv), retained the hypotensive activity and was as effective as the lyophilized extract Yohimbine (3 mg/kg) partially blocked the hypotensive effect.