Characterization of Bioactive Compounds and Assessment of Insecticidal Potentials of Aspergillus Myco-Metabolites against Anopheles gambiae (Diptera: Culicidae)

Abstract

The increasing resistance of Anopheles gambiae to synthetic insecticides has necessitated the search for sustainable, bio-based alternatives. This study investigated the characterization of bioactive compounds and insecticidal potential of Aspergillus myco-metabolites isolated from soil samples collected within the Federal University Dutse (11°45′N, 9°20′E), Jigawa State, Nigeria. The fungus, designated Aspergillus FUD-AS1, was cultured in potato dextrose broth for ten days, and secondary metabolites were extracted using ethyl acetate. The crude extract was analyzed using GC–MS and FTIR spectroscopy to determine its chemical composition and functional groups. GC–MS identified thirteen compounds dominated by fatty acids and terpenoids, including hexadecanoic acid (19.6 ± 0.5%), 9,12-octadecadienoic acid (16.8 ± 0.4%), and oleic acid (13.2 ± 0.3%) with significant differences (p < 0.001). Larvicidal bioassay results revealed a dose- and time-dependent mortality, with 100% larval death achieved at 80 mg/L after 48 h and an LC₅₀ of 26.8 ± 1.1 mg/L. Adulticidal assays showed complete mortality at 80 mg/L within 24 h and an LC₅₀ of 3.0 ± 0.2 µg/mosquito (p < 0.001). Glutathione S-transferase (GST) activity increased significantly from 1.18 ± 0.05 to 1.96 ± 0.08 U/mg protein (p < 0.001), indicating metabolic stress. Storage stability tests demonstrated >90% retention of insecticidal activity after four weeks at 25 °C and eight weeks at 4 °C (p = 0.004).  These findings confirm that Aspergillus FUD-AS1 metabolites possess potent, temperature-stable insecticidal properties suitable for integrated vector management. The study highlights the potential of fungal bioactive compounds as eco-friendly alternatives to chemical insecticides for controlling malaria vectors.