Effect of Thymus vulgaris L. (Lamiales: Lamiaceae) Essential Oil on Energy Reserves and Biomarkers in Culex pipiens L. (Diptera: Culicidae) from Tebessa (Algeria)

Abstract

The aim of this study was to assess the chemical composition of the leaf essential oil of Thymus vulgaris cultivated in Tebessa (Northeast Algeria) and to evaluate its potential larvicidal activity against fourth instar larvae of Culex pipiens L., 1758. A total of 20 fourth instar larvae of C. pipiens were exposed to a variety of concentrations (25-200 ppm) in laboratory according to the standard procedure portrayed by World Health Organization. The effects were examined on the mortality, the activities of acetylcholinesterase (AChE), glutathione S-transferase (GST), gluhatione (GSH) rate and the biochemical composition (proteins, lipids, carbohydrates) of larvae body, respectively. The EO yield calculated from the dry matter of the aerial part of the plant was 1.58 %. Its chemical composition has been analyzed by the GC and GC-MS systems. A chemical constituent of 18 compounds was identified in the oils of T. vulgaris compounds representing to 99.94 %. Bioassay test revealed that this essential oil exhibited larvicidal properties as they could induce 100 % mortality in the larvae of C. pipiens at the concentrations of 200 ppm. Biomarker measurments in treated larvae (LC25 and LC50) revealed no effect on AChE activity, activation of detoxification system as showed by an increase in GST activity and a decrease in GSH rate. The biochemical compositions show that the essential oil affected the energy reserves with a marked effect on proteins and lipids. Lastly, our results proved the potential use of this natural material as an alternative to synthetic insecticides for controlling mosquitoes.