Evaluation of the Repellency and Larvicidal Efficiency of Pulicaria undulata Extracts against Culex pipiens (L.) Mosquito Larvae: Phytochemical Profile and In-Silico Studies

Replacing synthetic insecticides with bioactive botanicals is essential for sustainable and eco-friendly mosquito control, addressing health risks from mosquito-borne diseases. This study evaluates the larvicidal, repellent, and biochemical effects of Pulicaria undulata extracts (water, ethanol, and petroleum ether) against Culex pipiens. The extracts were tested following WHO protocols, showing time- and concentration-dependent larvicidal activity. The petroleum ether extract exhibited the highest potency, with LC50 values of 221.60, 157.99, and 103.98 ppm at 24, 48, and 72 hours, respectively. Additionally, it demonstrated superior antifeedant and repellency effects, achieving 82% repellency at a concentration of 3.33 mg/cm². Biochemical analysis of larvae treated with LC50 doses of each extract revealed significant enzyme activity changes. Acetylcholinesterase, acid phosphatase, and alkaline phosphatase levels were reduced, with the petroleum ether extract showing the greatest effect. Glutathione S-transferase activity increased across all treatments, while protein, carbohydrate, and lipid contents declined, most prominently in larvae treated with petroleum ether extract. Gas Chromatography-Mass Spectrometry (GC-MS) analysis revealed a distinct chemical profile for each extract. The water extract was rich in monoterpenes and sesquiterpenes, with linalool being the major compound. Ethanol extracts contained fatty acid esters and flavonoids, dominated by hexadecanoic acid. Petroleum ether extracts were abundant in fatty acid esters and phenylpropanoids, with eugenol as the principal component. Molecular docking studies of the major compounds in the petroleum ether extract revealed strong binding for Oleic acid and Eugenol to AChE and GST, supporting its role in the observed bioactivities. These findings highlight the potential of Pulicaria undulata extracts, particularly petroleum ether extract, as eco-friendly alternatives for sustainable mosquito control.