Abstract

Acacia nilotica is a natural forest tree with many traditional uses in Sudan. Preliminary laboratory studies were conducted to analyze the phytochemical constituents of three extracts (water, ethanol and petroleum ether) prepared from A. nilotica (leaves and fruits), and to evaluate their larvicidal effects against the malaria vector mosquito,Anopheles arabiensis. The knockdown and residual effects of the extracts were tested in separate bioassay experiments, compared with two standard insecticides. The results showed wide range of secondary metabolites in water and ethanol extracts, mainly alkaloids, saponins, flavones and tannins, while the petroleum ether extracts were dominated by triterpenes and sterols. The fruits extracts seemed to be richer in active compounds than the leaves extracts. Therefore, the petroleum ether extracts exerted better mortality effects than other extracts, with fruits treatments being superior to leaves in all cases. Moreover, the fruits petroleum ether extract (0.5%) showed similar mortality percent (90.0%) as those of the two insecticides at 24 h post exposure. This treatment also manifested significantly the best residual actions up to three weeks, but lied next in order to both insecticides. Hence, the extract was recommended for further studies to indicate its toxic compound(s) and their possible usage for A. arabiensis control.

Key words: Acacia nilotica, Anopheles arabiensis, extracts, phytochemical analysis, larvicidal effect.