The stereoselective bioactivity and mechanism of indoxacarb against Spodoptera frugiperda.

Background: Indoxacarb, a type of chiral pesticide, is used to control Lepidoptera insects. Most studies had focused on the environmental behavior and selective toxicity of indoxacarb enantiomers, and the mechanism behind its selective biological activity against target organisms is not well understood.

Results: Spodoptera frugiperda was selected as the target insect. The lethal concentrations (96 h) of indoxacarb enantiomers on S. frugiperda were 2.61 mg/kg (S-indoxacarb) and 463.52 mg/kg (R-indoxacarb). S-Indoxacarb resulted in stronger oxidative damage to S. frugiperda than R-indoxacarb, and catalase and malondialdehyde were upregulated by 40.46% and 68.64% respectively after treatment with S-indoxacarb. Furthermore, cytochrome P450 and carboxylesterase were activated by S-indoxacarb, increasing by 39.62% and 63.68% respectively. Decarbomethoxyllated JW062 (DCJW), a metabolite of indoxacarb, has insecticidal activity. The concentration of DCJW in the S-indoxacarb treatment group was 2.73 times that in the R-indoxacarb treatment group. Molecular docking results demonstrated that S-indoxacarb could spontaneously bind to metabolic enzymes and be metabolized.

Conclusions: Enantiomeric bioactivity of indoxacarb enantiomers against on S. frugiperda was observed. S-Indoxacarb demonstrated remarkable insecticidal efficacy. Upon ingestion by S. frugiperda, it induced oxidative damage. Furthermore, S-indoxacarb was metabolized to DCJW, which has a significant role in its insecticidal properties. The selective bioactivity of indoxacarb enantiomers in S. frugiperda might be attributed to the enantiomeric metabolites. These findings offer a new perspective on the selective mechanisms of chiral pesticides. © 2025 Society of Chemical Industry.