Phytol from Sphaeranthus indicus: A Natural Insecticide Against Aedes aegypti and Culex quinquefasciatus

Mosquitoes, as blood-feeding ectoparasites, are primary vectors for numerous pathogens that cause diseases such as dengue, lymphatic filariasis, malaria, chikungunya, and Japanese encephalitis in India. Due to the increasing resistance to synthetic insecticides, there is growing interest in developing phytochemical-based insecticides. This study aimed to evaluate the mosquitocidal potential of the hexane leaf extract of Sphaeranthus indicus, isolate its bioactive compound, and assess its ovicidal, larvicidal, and pupicidal efficacy against Aedes aegypti and Culex quinquefasciatus.

Phytochemical extraction, fractionation, and spectroscopic techniques were employed to isolate bioactive constituents from S. indicus. Ten fractions were obtained, and bioassays were conducted on mosquito eggs, larvae, and pupae. The most active compound was identified and compared with the reference insecticides azadirachtin and temephos.

Among the fractions, fraction 5 exhibited strong mosquitocidal activity, with phytol identified as the active compound. Phytol achieved ovicidal activity of 30% and 33% at 2 ppm against Ae. aegypti and Cx. quinquefasciatus, respectively. Larvicidal LC₅₀ values were 2.30 ppm (Ae. aegypti) and 2.29 ppm (Cx. quinquefasciatus), while pupicidal LC₅₀ values were 2.64 ppm and 2.57 ppm, respectively. Although phytol was less effective than azadirachtin and temephos in ovicidal assays, its larvicidal and pupicidal efficacy was comparable.

The study highlights phytol's mosquitocidal potential, showing comparable efficacy to conventional insecticides such as azadirachtin and temephos. The findings support phytol's integration into vector management programs, offering a promising natural alternative for environmentally sustainable mosquito control.