FURTHER STUDIES ON THE PHARMACOLOGICAL AND TOXICOLOGICAL PROFILE OF CRUDE EXTRACTS OF H ELI OTR OP I UM I N DI CUM LINN

Abstract

Heliotropium indicum Linn has various medicinal uses in the treatment of disease conditions such as abdominal pains, amenorrhoea, dysmenorrhoea, skin rashes, wounds, hypertension, ocular infections, convulsion, dizziness and also used as a component of ‘’abemuduro’’ (a local herbal preparation used mostly by Asante women to manage post - labour inflammatory reactions). The purpose of this work was to evaluate the pharmacological activity of crude extracts of Heliotropium indicum on isolated smooth muscle preparations, the cardiovascular system of the anaesthetised cat, isolated rabbit and frog hearts and also the analgesic and some toxicological effects in in vivo and in vitro studies to explain some of its reported local uses. In vitro studies of the effects of the crude extracts on smooth muscle preparations ( Isolated guinea – pig ileum, isolated rabbit jejunum, and isolated rat uterus) showed contractile activity which was possibly mediated by stimulating muscarinic and nicotinic receptors, since the contractions were readily inhibited by atropine and hexamethonium. Two prostaglandin synthetase inhibitors indomethacin and diclofenac sodium could not modify the effects of the crude extracts and oxytocin on the isolated pregnant and non – pregnant rat uterus preparations. The crude extracts of Heliotropium indicum showed significant (P < 0.05) stability to plasma cholinesterase comparable to those of methylcholine and carbamylcholine. In vivo and in vitro studies of the effects of crude extracts on the cardiovascular system of the anaesthetized cat showed negative inotropic and chronotropic effects. The cardiovascular effects of the crude extracts could be mediated through M2 – receptor stimulation or by direct action on the heart muscle. Crude extracts of Heliotropium indicum (30 - 300 mg/kg-1) insignificantly [F 3,8 = 2.633, P = 0.5391, F 3, 8 = 8.633, p = 0.3321] inhibited both the first and second phases of formalin induced pain as compared to those of morphine and diclofenac sodium (1 – 10 mg/kg-1) [F3,8 = 2.699, P = 0.3926 and F3, 8 = 1.442, p = 0.9923; F3, 8 = 1.678, P = 0.9234, and F3, 8 = 2.344, p = 0.4121] respectively. Oral doses of 3 g/kg in mice and 5 g/kg in rats of the crude extracts were tolerated, however, in crude extract treated rats histopathological damages were observed in the liver, kidney, lungs, and heart.