Cyanobacterial secondary metabolites as biocontrol agents: Targeting dengue vector larvae through histological and molecular pathways.

The increasing resistance of Aedes aegypti to conventional insecticides necessitates the development of eco-friendly alternatives. This study investigates the larvicidal efficacy of Lyngbya sp. SMC 069 extracts, particularly focusing on fatty acid-rich chloroform fractions. Among the solvents tested, the chloroform extract showed the highest activity with 90.58 % mortality at 500 ppm against third-instar larvae. Column chromatography yielded a fast-eluting fraction (FR) with superior potency achieving 98.21 % mortality at 50 ppm and an LC50 of 22.3 ppm. FT-IR analysis confirmed the presence of alkane, alkene, and ester functional groups, while GC-MS identified oleic acid derivatives as major constituents. Histopathological analysis revealed disruption of the larval midgut and cuticle. Molecular docking revealed that oleic acid binds strongly to larval targets, including fatty acid-binding protein (-6.6 kcal/mol) and acetylcholinesterase (-5.6 kcal/mol), suggesting dual mechanisms of metabolic disruption and neurotoxicity. These research findings demonstrate the potential of Lyngbya-derived fatty acids as sustainable larvicides. The bioactive fraction's efficacy at low concentrations supports its candidacy for inclusion in integrated mosquito management programs aimed at mitigating vector-borne diseases like dengue. This research advances SDG 3 (Good Health and Well-Being) by providing a sustainable biological alternative for reducing dengue transmission risk.