Title : Chemical composition, antioxidant activity, cholinesterase inhibitor and in vitro insecticidal potentiality of essential oils of lippie multiflora moldenke and eucalyptus globulus labill on the main carpophagous pests of cotton plant in côte d' ivoire
Abstract:
In the face of the abusive and repeated use of synthetic insecticides that are harmful to human health and to the viability of the cotton production system in Côte d'Ivoire, finding alternatives becomes imperative. Thus, the objective of this study was to study the chemical composition and biological activity of essential oils of Lippia multiflora (Verbenaceae) and Eucalyptus globulus (Myrtaceae) and to evaluate their insecticidal potential in the laboratory on three main carp pests of cotton. After extraction of essential oils by the chemical composition of these was determined. Also, their antioxidant and anti-acetylcholinerase activities were evaluated. Subsequently, different concentrations of the two essential oils were prepared and applied by contact on batches of insects constituted by ten. The essential oil of L. multiflora was the most toxic for the three pests tested. Indeed, the lethal concentrations (LC50) determined were 1.74 %, 1.39 and 7.20 % respectively on Pectinophora gossypiella, Thaumatotibia leucotreta and Helicoverpa armigera. In contrast, the values obtained with E. globulus EO were nine to two times greater (16.05 %, 10.23 % and 16.32 % respectively on these pests). With respect to the chemical composition of the essential oils, E. globulus EO was the richest in oxygenated monoterpenes (65 %) with 1,8-cineole or eucalyptol as the majority compound (61.6 %). The EO of L. multiflora was distinguished by a lower proportion of oxygenated monoterpenes (44.3 %), but it contained more terpene elements (24 against 15 for the EO of E. globulus). The EOs of L. multiflora and E. globulus also showed significant inhibitors of acetyl (2.13 and 2.16 mg GALAE/g, respectively) and butyryl cholinesterase (4.03 and 3.61 mg GALAE, respectively). L. multiflora was differentiated by its good inactivation of tyrosinases (163.46 versus 58.95 Mg KAE/g in E. globulus). Better antioxidant activity was observed with L. multiflora EO relative to DPPH (7.05±0.34 mg TE/g). Biopesticides based on L. multiflora essential oil could be developed for the phytosanitary protection of cotton plant.
Keywords : Essential oils, Carpophagous insects, Antioxidant activity, Antiacetylcholinesterase activity, insecticidal activity
