Larvicidal Efficacy of Chloris virgata Extracts Against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus with Insights into Mode of Action via Molecular Docking.

Abstract

The indiscriminate use of synthetic insecticides for mosquito control has resulted in significant challenges, such as environmental pollution and growing insecticide resistance. In response, there is increasing interest in eco-friendly alternatives like plant-based larvicides. This study assesses the larvicidal efficacy of Chloris virgate (Poales: Poaceae) extracts against Aedes aegypti (Diptera: Culicidae), Culex quinquefasciatus (Diptera: Culicidae), and Anopheles stephensi (Diptera: Culicidae), and investigates the bioactive chemical compounds responsible for this activity. Soxhlet individual extraction was performed using n-hexane, chloroform, and ethanol, and methanol solvents are used separately to extract bioactive compounds from C. virgata. This approach allows for the selective extraction of specific compounds based on their solubility in each solvent. The extracts were tested on fourth instar larvae, and lethal concentrations (LC₅₀ and LC₉₀) were calculated via probit analysis. The methanol extract exhibited the lowest LC50 and LC90 values against Culex quinquefasciatus, with LC50 at 80.11 ppm and LC90 at 176.22 ppm, suggesting higher toxicity and effectiveness in larvicidal activity. Methanol extracts significantly affected mosquito larvae midguts, causing cytoplasmic thinning, muscle fiber disorganization, and brush border disruption. Gas chromatography-mass spectrometry (GC-MS) analysis identified major compounds such as stigmasterol, campesterol, and γ-sitosterol. Campesterol, 4.alpha.,14-Dimethyl-5.alpha, and Lanosterol showed strong binding affinities with acetylcholine esterase (5X61), exhibiting multiple hydrophobic interactions with key residues, including TRP 441, TYR 282, and CYS 447. Campesterol also displayed significant binding to Sterol Carrier Protein-2 (1PZ4) and Odorant-Binding Protein (3OGN) with several hydrophobic interactions, achieving binding affinities of - 10.1 kcal/mol and - 9.7 kcal/mol, respectively. This study highlights the potential of C. virgata methanol extracts as a promising eco-friendly larvicide for mosquito population management.