Chemical composition and activity of an Ocimum basilicum essential oil on Culex pipiens larvae: Toxicological, biometrical and biochemical aspects

The present study was undertaken in order to determine the chemical composition of the leaf essential oil of Ocimum basilicum (Lamiaceae) cultivated in Tebessa (Algeria) and to assess their potential larvicidal activity against the most abundant and investigated mosquito species, Culex pipiens L., 1758 (Diptera, Culicidae). The essential oil extracted from O. basilicum was tested at different concentrations ranging between 50 and 150 ppm on newly molted fourth-instar larvae under standard laboratory conditions according to the World Health Organization recommendations. The effects were examined on the mortality, the activities of acetylcholinesterase (AChE) and glutathione-S-transferase (GST), the morphometric measurements and the biochemical composition of body of larvae, pupae and adults, respectively. O. basilicum essential oil which is extracted from dried leaves with an output of 1.56 ± 0.15%, is yellow pale. Its chemical composition has been investigated by GC/MS. Thirty eight compounds have been identified. The major compounds were: linalyl acetate (53.89%) and linalool (22.52%). The larval mortality was observed after 24 h of exposure. The LC50 and LC90 values were 73.45 and 101.20 ppm, respectively. The enzymatic measurements performed in LC50 treated larvae revealed a neurotoxic activity and a stimulation of the detoxification system as evidenced by an inhibition of AChE and an increase in GST activity, respectively. The morphometric study shows that the essential oil tested was found to decrease the growth of different developmental stages. Moreover, it reduces significantly the body contents of proteins, carbohydrates and lipids of the different stages studied (larvae, pupae, adult male and female). Overall, our results indicate that O. basilicum essential oil has potential for the development of new and safe control products against mosquitoes.