Predicted interactions of GC–MS-detected metabolites from Trichoderma sp. LB1 with chemosensory protein 8 (CSP8) of Spodoptera litura : a blind molecular docking study

The common cutworm, Spodoptera litura (Fabricius), is a polyphagous pest that defoliates crops and rapidly develops resistance to synthetic insecticides. This study evaluated predicted interactions between metabolites putatively identified by gas chromatography–mass spectrometry (GC–MS) in the ethyl acetate extract of the entomopathogenic fungus Trichoderma sp. LB1 and chemosensory protein 8 (CSP8) of S. litura. Using blind docking in AutoDock Vina, we docked 13 test compounds and three reference ligands against the receptor structure (PDB ID: 7E8L). Among the test compounds, 1,2,4-benzenetricarboxylic acid, 1,2-dimethyl ester and 2-t-butyl-5-(dimethoxy-phosphoryl)−3-methyl-4-oxoimidazolidine-1-carboxylic acid, t-butyl ester received the most favorable docking scores (−5.7 and −5.5 kcal/mol, respectively), compared with −4.2 kcal/mol for the reference ligand bombykol. Their predicted poses involved hydrogen bonds, hydrophobic contacts, and van der Waals interactions. Our previous study reported antifeedant activity of the ethyl acetate extract and repellent activity of conidia of Trichoderma sp. LB1 against S. litura; the present computational results cannot establish that the docked compounds are responsible for these effects. These findings therefore identify candidate compounds for further investigation rather than demonstrating a mechanism. Biochemical binding, electrophysiological, and behavioral assays are needed to determine whether these compounds bind CSP8 and influence chemosensory responses in S. litura.