Chemical Profiling and Bioactivity of <i>Plectranthus amboinicus</i> Essential Oil Against <i>Spodoptera littoralis</i> by Targeting <i>N</i>‐Acetylglucosamine Kinase (NAGK)

Abstract

Abstract This study investigated the chemical composition of Plectranthus amboinicus essential oil and their impact on the Egyptian cotton leafworm, Spodoptera littoralis , an herbivorous lepidopteran insect. Accordingly, twenty‐eight compounds (96.8%) were found comprising monoterpenes and sesquiterpenes made up 39.34% and 56.82% of the mixture, respectively. Among the monoterpenes, carvacrol (19.38%) and O ‐cymene (8.22%) represent the main components, whereas the main components of sesquiterpenes were τ ‐muurolol (13.08%) and isospathulenol (7.52%). Further, substantial malformations were observed in both the pupal and adult stages at the applied concentrations which did not impact adult survival rate, however the survival rate of pupae was significantly lower at 75 mg/L. The findings elucidate the effects of P. amboinicus essential oil on moths, especially S. littoralis , presenting a viable method to reduce reliance on synthetic chemical insecticides and promote the adoption of natural substances for pest control. Molecular docking was used to evaluate the binding of 28 identified phytochemicals to N ‐acetylglucosamine kinase (NAGK, PDB ID: 2CH5), an important enzyme for the chitin metabolism of S. littoralis . Longifolol, humulene, and terpinen‐4‐ol showed potent inhibition of NAGK, surpassing the co‐crystallized ligand. Therefore, the optimization of these compounds may lead to the development of effective, environmentally friendly insecticides for S. littoralis .