Larvicidal and adulticidal activities of Purpureocillium lilacinum Secondary Metabolites against the Malaria Vector Anopheles gambiae

Background 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. Results Fourth-instar larvae were significantly more susceptible to the crude extract than second-instar larvae, with an approximately four-fold lower LC ₉₀ . 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. Conclusion 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.