Hypotensive effect of an aqueous extract of Heliotropium indicum Linn (Boraginaceae)

Abstract

Heliotropium indicum Linn (Boraginaceae) has been used widely in the treatment of hypertension in Ghana. This study therefore was aimed at investigating the effects of an aqueous extract of H. indicum Linn on the heart and blood pressure of some laboratory animals as a means of establishing its hypotensive effect and verifying its traditional medicinal use as an antihypertensive. The extract was applied in vitro to an isolated frog and rabbit heart to investigate its effect on the force and rate of cardiac contraction, and administered to an anaesthetized cat to establish its effect on blood pressure. The extract had a dose-dependent negative inotropic and chronotropic effect on the frog and rabbit hearts similar to that observed for acetylcholine and histamine. These effects were inhibited by atropine but not mepyramine suggesting a muscarinic-receptor mediated effect. In vivo, the H. indicum aqueous extract produced a dose-related reduction in blood pressure of the anaesthetized cat. Findings reveal that H. indicum has hypotensive effect suggesting its usefulness in the treatment/management of hypertension and other cardiovascular diseases.