Preparation of Citronella and Thyme Essential Oil Nanoemulsions and Their Insecticidal Efficiency Against Mosquitoes (Culex pipiens)

Abdelmawla, Nada A.; Mohafrash, Samia M. M.; El Sharkawy, Asmaa Z.; Farghaly, Doaa S.; Mossa, Abdel-Tawab H.

doi:10.21608/ejchem.2025.404022.12043

Preparation of Citronella and Thyme Essential Oil Nanoemulsions and Their Insecticidal Efficiency Against Mosquitoes (Culex pipiens)

Document Type : Original Article

Authors

¹ Pesticide Chemistry Department, Chemical Industries Research Institute, National Research Centre, 33 El Bohouth Street (former El Tahrir St.), P.O. 12622, Dokki, Giza, Egypt.

² Zoology and Entomology Department, College of Science, Al-Azhar University, P. O. 11765, Cairo 11865, Egypt

10.21608/ejchem.2025.404022.12043

Abstract

The objective of this study was to develop eco-friendly insecticides utilizing nanotechnology. Essential oils from citronella and thyme were extracted and analyzed using gas chromatography-mass spectrometry (GC-MS). The GC-MS analysis of citronella oil identified Z-Citral and E-Citral as the main chemical constituents, comprising 34.45% and 42.99% of the oil, respectively. In contrast, o-Cymene and Thymol accounted for 28.44% and 26.84% of thyme oil, respectively. A nanoemulsion of these oils was formulated and assessed for its efficacy against mosquitoes, Culex pipiens. The nanoemulsions were prepared using essential oil and Tween 80 in varying ratios under ultrasonic emulsification for durations of 2.5, 5, and 10 minutes. Our findings indicate that the droplet size of the nanoemulsion is influenced by the emulsification parameters. The stable nanoemulsion exhibited droplet sizes of 20.2 nm for citronella and 54.6 nm for thyme. The results demonstrated that both thyme and citronella essential oils exhibit significant adulticidal and knockdown effects on Culex pipiens. The citronella and thyme oils showed KC50 values for knockdown at 0.424 and 5.651 mg/ml for essential oils and 10.954 and 6.977 mg/ml for their respective nanoemulsions. Furthermore, the adulticidal LC50 of citronella and thyme oils against Culex pipiens after 24 hours was recorded as 6.038 and 5.619 mg/ml for essential oils and 20.245 and 11.048 mg/ml for their nanoemulsions. The findings suggest that nanoemulsions are formulated utilizing aqueous mediums, which are typically less toxic and more environmentally sustainable compared to traditional solvents. This attribute improves their safety for human use and promotes their application across various environments. Consequently, these eco-friendly nanoformulations can be regarded as viable alternatives to synthetic insecticides for the management of public health pests and vector-borne diseases.

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