The potency of nanoemulsion of Clove oil and their main component Eugenol on some biochemical and histological aspects on Spodoptera littoralis (Boisd) (Lepidoptera: Noctuidae)

Abstract

Although synthetic insecticides are most effective for controlling insects, their extensive application has hazardous effects on the environment and human health. Recently, nanotechnology techniques are open up novel applications in the field of agrochemical formulations. Nanoemulsion (NEs) attracted great attention in delivering and enhancing essential oils many poorly soluble in water. In this study, we evaluated the larvicidal activity of the clove oil and its main component eugenol, and both NE formulations against 4th instar larvae of S. littorals under laboratory conditions. NEs of clove oil and eugenol were prepared by high-energy ultrasonication, 5% EO was the optimal concentration for preparations. The droplet sizes of clove oil and eugenol NEs were 207nm and 54.68 nm and the
polydispersity index (PDI) were 0.33 and 0.26, respectively. Generally, eugenol was more effective than clove oil, where the LC50 gradually decreased from 4.64 to 1.65 and 11.97 to 2.18 % after 1and 5days of exposure. Clove NE exhibited more toxicity than clove oil emulsion,the LC50 values were 1.77 and 2.18% at the end of the experiment. Besides, the eugenol NE formula demonstrated significant
toxicity compared to the eugenol emulsion. Results noticed that all tested materials decreased protein levels in larvae of S. littorals by 46.31% and 31.91% with clove oil and clove NE. increases in aspartate aminotransferase (AST) activity were recorded with clove oil and clove NE but decreased activity with eugenol and eugenol NE. As well, alanine aminotransferase (ALT) and alkaline phosphatase (ALP)
activity decreased with all treatments. Also, the histological disturbance was estimated in this study as ultrastructural alterations in the midgut of the 4th instar larvae. histological examination showed a high distribution of this larvae's midgut after treatments with LC50 values of all tested materials, especially with NE. Midgut epithelial cells showed more deformation and have many vacuoles, some columnar and goblet cells were destroyed, and the peritrophic membrane was destroyed in many parts.