Cardiovascular effects of the n-butanol extract from Kalanchoe crenata leaves

Abstract

The present work examined the effects of the n-butanol extract from the leaves of Kalanchoe crenata (Andrews) Haworth (Crassulaceae) on rat blood pressure and guinea pig papillary muscle contraction and action potential. When administered intravenously at doses of 2, 5, and 10 mg/kg, the n-butanol extract of K. crenata leaves induced a significant transient fall in blood pressure and significantly reduced the cardiac rate for about 10 min. Concomitantly, the extract significantly increased the PR, QRS, and QT intervals of the electrocardiogram (ECG). At concentrations of 300 and 1,000 μ g/ml, the n-butanol extract was found to increase the amplitude of electrical contraction of papillary muscle by 137.6 and 223.0%, respectively. When tested on the ventricular myocardiac cell action potential, the extract (100 μ g/ml) significantly and time dependently delayed the repolarization without affecting the amplitude. Indeed, the 10%, 60%, and 90% repolarization times were respectively increased by 131.6%, 78.6%, and 52.7%. The bradycardic effect of the n-butanol extract may result from the increase of the PR, QRS, and QT intervals which are in accord with the delay in action potential repolarization observed in in vitro studies. The data obtained in the in vitro studies suggest that K. crenata possess potassium channel blockade properties that may account for its cardiac properties. © 2008 Informa UK Ltd.