Assessment on the stereoselective behavior of cyflumetofen to earthworms (Eisenia foetida): Degradation, bioaccumulation, toxicity mechanism, and metabolites

Abstract

In this study, environmental behavior and toxicity of cyflumetofen (CYF) enantiomers were evaluated comprehensively in a soil-earthworm system. In the earthworm (Eisenia foetida), (+)-CYF was preferentially accumulated, and acute toxicity of Rac-CYF was greater than that of (+)-CYF and (-)-CYF, indicating that the combination of CYF enantiomers increased the toxicity. As a measure of chronic toxicity, compared with (-)-CYF-treated earthworms, malondialdehyde accumulation was higher in (+)-CYF-treated earthworms, indicating a more severe oxidative stress response. In a DNA comet plot, the trailing distance in the (+)-CYF treatment was 1.97 times greater than that in the (-)-CYF-treated, revealing more severe genotoxicity with (+)-CYF. However, (-)-CYF was more likely than (+)-CYF to activate the earthworm detoxification enzyme pathway. With (+)-CYF treatment, the number of differentially expressed genes (DEGs) involved in the pathogenic pathway increased significantly, whereas with (-)-CYF-treatment, more DEGs were involved in P450 and glutathione S-transferase (GST) detoxification metabolic pathways, including high expression of the genes chi-III, GST-S-1, and GST-alpha-5. The main metabolites of the CYF enantiomers were A-2, A-12, B-1, AB-1, AB-7, and B-3, which exhibited potential ecotoxicity. In general, CYF was stereoselective in the soil-earthworm ecosystem, with (+)-CYF causing a higher genotoxicity risk than that of (-)-CYF. The study provides insight into the selective toxicity mechanisms of chiral CYF and contributes to a theoretical basis for risk assessment of low-risk pesticides.

Keywords: CYF enantiomers; Ecotoxicological metabolism; Eisenia foetida; Metabolites; Selective toxicity.