In vitro Inhibition of Phosphodiesterase-5 Activities by Ethanol Extract of Rauwolfia vomitoria Stem Bark and its Therauptic Effect on Penile and Cardiac Tissue

Abstract

Abstract Rauwolfia vomitoria (swizzle stick) is known to possess aphrodisiac potentials which inhibits or reduce the activities of phosphodiesterase-5 hence promoting erectile functions. Phosphodiesterase-5 (PDE-5) is a marker for erectile dysfunction and vasodilation of coronary and pulmonary arteries. This study assesses the impact of Rauwolfia vomitoria stem bark ethanol-based extracts on the activity of phoshodiesterase-5 in cardiac and penile tissue. The penile and cardiac tissues of 20 male Wistar rats were removed and homogenized after they were sacrificed by cervical dislocation. The phosphodiesterase-5 activity of the tissue homogenate were evaluated at varying concentrations of cyclic GMP (cGMP) and in the presence of standard drug (sildenafil) and ethanol extract of Rauwolfia vomitoria. Ethanol extract of Rauwolfia vomitoria was discovered to uncompetitively inhibit phosphodiesterase-5 activities in these tissues as a result of it reduced Vmax and Km obtained. This uncompetitive inhibition indicates that at high concentration of substrate, the inhibition of PDE-5 activity cannot be reversible. Hence, ethanol extract of Rauwolfia vomitoria may be effective in the inhibition of Phosphodiesterase-5 and consequently, erectile dysfunction. It may also improve vasodilation and may help in the treatment of cardiovascular diseases