Larvicidal and Antifungal Properties of Picralima nitida (Apocynaceae) Leaf Extracts

Abstract

The larvicidal and antifungal activities of ethanolic and aqueous leaf extracts of Picralima nitida were evaluated in static bioassays on 4th instar larvae of Anopheles gambiae and three fungal species: Aspergillus flavus, Candida albicans and Microsporum canis. All extractions were done using distilled water and 50% ethanol. Larvicidal assays were carried out at extract concentrations of 0.15, 0.30, 0.45, 0.60 and 0.75% w/v, for 72h. For the antifungal studies extract concentrations used were 200, 100, 50 and 25mg/ml. At the end of larvicidal assay the highest concentration recorded mortality of 57.60% and 38.40% for ethanolic and aqueous leaf extracts respectively. 72h LC50 values obtained from Probit analysis, using SPSS version 17 were 0.660% and 1.057% w/v for ethanolic and aqueous leaf extracts respectively. Larvae in the control experiments registered no death throughout the period of experiment, rather they were actively wriggling and some even metamorphosed into pupae. For the antifungal studies the agar well diffusion technique was employed. Antifungal effects were determined using measurements of inhibition zone diameter (IZD). Results obtained revealed that both the aqueous and ethanolic leaf extracts exerted antifungal effect on A. flavus and C. albicans, but no antifungal effect was exhibited against M. canis, at the extract concentrations used in this study, rather a steady growth in the test plates seeded with M. canis was observed. The same was applicable with the negative controls. The drug, ketoconazole exerted antifungal effect on all test organisms. Phytochemical screening of the leaf revealed the presence of alkaloids, cardiac glycosides, saponins and terpenes. The leaf of P. nitida possesses larvicidal and antifungal potential and therefore warrants a more thorough exploitation.