Ethanol extract of Daucus carota seeds exhibits stomach toxicity and disrupts multiple physiological processes in Spodoptera litura

Spodoptera litura Fabricius is a notorious agricultural pest worldwide. Currently, the use of insecticides is an important and effective approach for managing S. litura , however, it has developed resistance to multiple insecticides. Therefore, exploring and identifying novel, efficient, and environmentally safe natural bioactive substances is highly important for controlling this pest. In this paper, the stomach toxicity and growth inhibitory effects of an ethanol extract from Daucus carota seeds were studied. The main components of the extract were identified, and their mechanisms of action were explored through RNA-seq analysis and qPCR techniques. The results showed that the LC50 of the extract was 3.5 mg/mL. The larval survival rate, pupation rate, pupal and larval weight, female adult longevity and hatching rate were significantly reduced, and the larval stage was significantly prolonged when the larvae were fed artificial diets supplemented with extracts at the concentrations of LC15, LC20, and LC50. A total of 1305 compounds were detected in the extract by GC‒MS. Phenyl isothiocyanate and 2,6-dimethylaniline showed the highest stomach toxicity among the 12 compounds with the highest contents in the extracts, with adjusted mortality rates of 100% and 94.87 ± 2.96%, respectively, at 1 mg/mL. The LC50 values of phenyl isothiocyanate and 2,6-dimethylaniline were 0.60 mg/mL and 2.13 mg/mL, respectively. KEGG analysis and real time PCR revealed that treatment with both components (phenyl isothiocyanate and 2,6-dimethylaniline) affected mainly the cytochrome P450 pathway, glutathione metabolism pathway, xenobiotic metabolism pathway, hormone biosynthesis pathway, and fatty acid metabolism pathway. Our study provides a foundation for the development of novel, efficient, and environmentally safe natural bioactive compounds to control S. litura .