Preliminary Screening of Some Nigerian Medicinal Plants for Molluscicidal Activities

In a search for natural products that could be used to control the vectors of tropical diseases, four medicinal plants grown in Nigeria; Moringa oleifera, Senna alata, Caesalpinia pulcherrima, and Vernonia amygdalina were screened for molluscicidal effects. Serial dilutions of 1000, 625, 500, 375, 250, and 125ppm were prepared from the stock solution of the extracts. Adult Biomphalaria pfeifferi were exposed to the various graded concentrations. Mortalities were recorded after 24 hours. The results of mortality and the assessment of the lethal concentrations for 50% and 90% (LC50 and LC90) mortalities of snails were determined using probit analysis. There was a high degree of homogeneity between concentration and mortalities observed; R2= 0.919, 0.976, 0.963, 0.988 for ethanolic extracts of M. oleifera, Senna alata, C. pulcherrima and V. amygdalina respectively. There were positive correlations between mortalities observed in snails and extracts’ concentrations. Aqueous and ethanolic extracts of V. amygdalina had the lowest LC50 values (614.8 and 338.8ppm) making it the most potent of the plants used in this study. All extracts caused significant mortality of B. pfeifferi (P < 0.05). These plant extracts generally showed promising molluscicidal activity and are recommended for further studies.