SCREENING OF SOME MEDICNAL PLANTS OF ETHIOPIA FOR THEIR MOLLUSCICIDAL ACTIVITIES AND PHYTOCHEMICAL CONSTITUENTS

Schistosomiasis infection is on the rise in Ethiopia, affecting a substantial portion of the productive force. The transmission and life cycle of the schistosome parasite is effected between the molluscan intermediate host and the definitive host, i.e. man. Medicinal plants with molluscicidal properties have paramount importance for the local control of snails. This study was focused on the preliminary phytochemical and laboratory investigation of the molluscicidal properties as well as evaluation of the acute toxicity of the aqueous extracts of 19 different medicinal plants belonging to 23 families on mice. The effect of the aqueous extracts of 19 medicinal plants on experimental snails, Biomphalaria pfeifferi, Bulinus sp. and Physa acuta were evaluated. Portions of the same extracts were used for the identification of the major class of secondary metabolites. Determination of the LD50 of the extracts also carried out. Out of the tested plant extracts belonging to these plant families, four plants, viz., Albizia gummifera, Balanites aegyptica, Hedera helix and Warbrugia ugandensis exhibited promising molluscicidal activities against Biomphalaria pfeifferi, Bulinus sp. and Physa acuta. The chemical profile of the crude aqueous extracts showed the presence of some secondary metabolites viz., polyphenols, alkaloids, tannins, saponins and glycosides. Acute toxicity studies of the promising plant on mice showed medium lethal dose (LD50) values ranging from 150 mg per Kg – 450 mg per Kg when the aqueous extracts were administered intraperitonealy. The crude extracts of the plants demonstrating stronger molluscicidal effect and safety on non-target organism stresses the need for extended laboratory and field evaluation, which could then be employed to play an important role in schistosomiasis control.