Abstract

Cytotoxicity and larvicidal properties of the leaf extracts of 3 Annonaceous plants, Annona muricata L., A. senegalensis Pers and A. squamosa L. were tested against brine shrimp larva and the late 3^rd instar of Culex quinquefascintus Say. The larval mortality was observed 24 h post-exposure. Based on the probit analysis, the LC₅₀ value for crude extracts of A. muricata, A. senegalensis and A. squamosa were observed to be 20.87, 0.67 and 0.64 µg/mL respectively for shrimp larvae and 56.47, 23.42 and 11.01 µg/mL respectively for C. quinquefascintus. Bioassay-guided fractionation of crude extracts indicated high activity of the ethyl acetate fractions with mortality of ≥ 90% at 50 µg/mL for both A. senegalensis and A. squamosa. However, further bioassay of sub-fraction of the 2 ethyl acetate fractions from the 2 plant species showed close dependent and a decreased activity (p ≥ 0.05) at the same concentration levels. 2 known aporphine alkaloids, (-)-roemerine and annonainewere identified as active principles from the ethyl acetate extracts of A. senegalensis and A. squamosa respectively. With the larvicidal properties of A. senegalensis being described here for the first time, its value together with that of A. squamosa may prove to be the best natural source of larvicidal agents.

Key words: Annona species, cytotoxic and larvicidal activities, isolation, aporphine alkaloids