Larvicidal and adulticidal activities of Purpureocillium lilacinum secondary metabolites against the malaria vector Anopheles gambiae

Malaria control is increasingly threatened by widespread resistance of Anopheles mosquitoes to conventional chemical insecticides, highlighting the urgent need for novel and environmentally sustainable vector control agents. The entomopathogenic fungus Purpureocillium lilacinum (Thom) Luangsa-ard et al. and its secondary metabolites, including leucinostatins and pulixin, are known to inhibit Plasmodium parasites. However, their direct effects on mosquito survival have not been investigated. Fourth-instar larvae were significantly more susceptible to the crude extract than second-instar larvae, with an LC 90 approximately 4-fold lower. Extended fermentation increased larvicidal potency, reducing the LC 90 from 129 μg/mL to 61 μg/mL. Most fractions showed larvicidal activity, with the two most polar fractions exhibiting significantly greater activity than the crude extract. Purified pulixin and leucinostatins displayed potent larvicidal effects. The LC 90 values of pulixin and leucinostatin A against fourth-instar larvae were 68 μg/mL and 9 μg/mL, respectively. The LD 90 of leucinostatin A against adult female mosquitoes was approximately 1 μg per mosquito. Secondary metabolites from P. lilacinum represent promising, cost-effective, and environmentally friendly larvicides against malaria vectors. Because leucinostatin A can inhibit parasite development in adult mosquitoes, kill larvae in aquatic habitats, and kill adult mosquitoes by contact, it may provide a dual-action strategy for blocking malaria transmission.