Evaluation of the larvicidal and adult emergence inhibiting effects of Adonsonia digitata seeds n-hexane extract against Aedes aegypti and Culex quinquefasciatus mosquito

Abstract

Mosquito-borne diseases remain a significant global public health problem, necessitating the development of effective and environmentally friendly alternatives to synthetic insecticides. This research evaluated the larvicidal efficacy of Adansonia digitata L. seed oil extracted with n-hexane against Aedes aegypti and Culex quinquefasciatus under controlled laboratory conditions. Seeds obtained from Samaru Market, Zaria, were air-dried, ground, and Soxhlet-extracted using n-hexane. Adult mosquitoes collected from Ahmadu Bello University were reared and used for larval bioassays. Test concentrations (50–400 ppm) were prepared in accordance with WHO guidelines, with distilled water as control. Phytochemical screening revealed the presence of terpenoids, flavonoids, saponins, alkaloids, glycosides, phenolics, tannins, steroids, carbohydrates and anthraquinones. GC–MS analysis identified eleven compounds, with n-hexadecanoic acid, 9-octadecenoic acid and oleic acid as the major constituents. Larvicidal assays showed significant dose- and time-dependent mortality (p < 0.05) in both species. Higher concentrations (300–400 ppm) produced increased mortality and reduced pupation, indicating strong developmental inhibition. Ae. aegypti was more susceptible than Cx. quinquefasciatus, as evidenced by lower LC50 values over 24–72 h. The extract also caused marked suppression of pupal emergence, suggesting interference with normal growth and metamorphosis. The larvicidal and growth-regulatory effects observed in the research are attributed to the synergistic action of bioactive phytochemicals and fatty acids. These findings demonstrate that A. digitata aqueous and seed oil extract is a promising botanical larvicide and a safe, locally available alternative for sustainable mosquito control and resistance management