Assessment of Mosquito Repellent Potentials of Ocimum gratissimum and Cymbopogon citratus Essential Oil and In silico Determination of Bioactive Compounds

Abstract

Aims: To evaluate the repellency and in silico activities of bioactive compounds from Ocimum gratissimum and Cymbopogon citratus essential oils against Anopheles gambiae, and to determine their potential as eco-friendly alternatives to synthetic mosquito repellents. Study Design: The laboratory-based experimental study involved integrating essential oil extraction, physicochemical characterization, repellency bioassays, and molecular docking analysis. Place and Duration of Study: The research was carried out in the Department of Medical Biochemistry and Animal and Environmental Biology Department, Delta State University, Abraka, between May and July, 2025. Methodology: Essential oils from O. gratissimum and C. citratus were extracted using the hydro-distillation method and incorporated into topical ointments at varying concentrations. Skin-friendliness was verified through physicochemical assessments including pH, viscosity, spreadability, and stability tests. Repellency assays followed WHO standard arm-in-cage protocols. In silico molecular docking was performed on major phytochemicals—particularly γ-Muurolene and Copaene—against An. gambiae glutathione S-transferases and odorant-binding proteins to assess binding affinities and potential mechanisms of repellency. Results: Both essential oils demonstrated statistically significant repellency compared to untreated controls (p < 0.05). C. citratus showed stronger protection than O. gratissimum. The combined formulation produced the highest repellency, exceeding the efficacy of DEET at equivalent concentrations. Docking studies indicated strong binding affinities of γ-Muurolene and Copaene to GSTs and odorant-binding proteins, suggesting possible interference with mosquito detoxification pathways and host-seeking behavior. Conclusion: Synergistic formulations of O. gratissimum and C. citratus essential oils show strong potential as sustainable, plant-based alternatives to synthetic repellents such as DEET. Further field trials in malaria-endemic regions are recommended to validate their safety, long-term stability, and real-world applicability for community-level malaria prevention.