Natural Biocidal Potential of <i>Thymus vulgaris</i> Essential Oilfrom the Souk Ahras Region,Algeria: Chemical Compositionand Larvicidal Activity

The aim of the present study was to determine the chemical composition of the essential oil (EO) extracted from the aerial parts of Thymus vulgaris collected in the Souk Ahras region of northeastern Algeria to evaluate their insecticidal activity against Culex pipiens larvae. The EO was obtained by hydrodistillation, and its chemical composition was analyzed using Gas Chromatography-Mass Spectrometry (GC-MS). Thirty-eight (38) components have been identified in the T. vulgaris EO, corresponding to 99.98% of the total composition, where p-cymene (21.32%), carvacrol (19.85%), γ-terpinene (19.12%) and thymol (18.78%) are the main compounds identified. The larvicidal activity was assessed against Culex pipiens fourth instar larvae following World Health Organization (WHO) guidelines, with LC₅₀ (lethal concentration for 50% mortality) and LC₉₀ (lethal concentration for 90% mortality) values determined at different exposure times. The EO showed strong larvicidal activity, with LC₅₀ values of 3.01 ppm, 2.48 ppm, and 2.32 ppm at 24, 48, and 72 hours, respectively. Additionally, the EO significantly inhibited acetylcholinesterase (AChE) activity and enhanced glutathione S-transferase (GST) activity, indicating involvement of neurotoxic and detoxification pathways. These findings underscore the effectiveness of Thymus vulgaris EO as a potent natural biocide against mosquito larvae and highlight its potential as a sustainable, eco-friendly alternative to synthetic insecticides.