Evaluation of Mosquito Repellent Activity of Essential Oils from Nigerian Cymbopogon citratus Against Anopheles gambiae

The escalating resistance of Anopheles gambiae to synthetic pyrethroid insecticides and the adverse health effects of DEET-containing repellents have renewed global interest in plant-derived mosquito repellents. Cymbopogon citratus, lemongrass, is widely cultivated and used as a mosquito deterrent across South West and South South Nigeria. This study evaluates the repellent activity of essential oils extracted from Cymbopogon citratus sourced from Ekiti State against laboratory-reared Anopheles gambiae. Essential oil was obtained by hydrodistillation using a Clevenger apparatus and characterised by GC-MS analysis. Repellent bioassays were performed using the arm-in-cage method with serial dilutions of the oil formulated in ethanol at concentrations of 5%, 10%, 20%, and 30%. DEET (20%) served as the standard comparator. Complete protection time and the effective concentration providing 50% repellency (EC50) were determined. GC-MS identified citral (geranial and neral), myrcene, and limonene as the dominant constituents. The 20% and 30% concentrations provided complete protection times of 4.1 and 5.6 hours respectively, compared to 6.2 hours for DEET. EC50 was 11.2% v/v. These results support the development of standardised Cymbopogon citratus essential oil-based repellent formulations as safer, locally derived alternatives for malaria vector control in Nigeria. Keywords: Cymbopogon citratus, mosquito repellent, Anopheles gambiae, essential oil, lemongrass