Chiral Insecticide α‑Cypermethrin and Its Metabolites: Stereoselective Degradation Behavior in Soils and the Toxicity to Earthworm Eisenia fetida

• Published in: Journal of agricultural and food chemistry 2015-09, Vol.63 (35), p.7714-7720
• Main Authors: Yao, Guojun, Jing, Xu, Peng, Wang, Liu, Xueke, Zhou, Zhiqiang, Liu, Donghui
• Format: Article
• Language: English
• Subjects: Animals; Insecticides - chemistry; Insecticides - toxicity; Kinetics; Molecular Structure; Oligochaeta - drug effects; Oligochaeta - growth & development; Pyrethrins - chemistry; Pyrethrins - toxicity; Soil Pollutants - chemistry; Soil Pollutants - toxicity; Stereoisomerism
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/acs.jafc.5b03148

The enantioselective degradation of the widely used chiral insecticide α-cypermethrin in soils has been investigated, and its main metabolites cis-3-(2′,2′-dichlorovinyl)-2,2-dimethylcyclopropane carboxylic acid (cis-DCCA) and 3-phenoxybenzoic acid (3-PBA), which have potential environmental problems, have also been determined. The enantiomers of α-cypermethrin were separated on Chiralcel OD chiral columns by high-performance liquid chromatography (HPLC) under normal phase, and the metabolites were detected by gas chromatography (GC) after derivatization. The results of the degradation showed that α-cypermethrin dissipated in soils with relatively long half-lives of 12.70–47.08 days and obvious stereoselective degradation of the two enantiomers was observed in the five soils, with enantiomeric fraction (EF) from 0.55 to 0.61 after 42 days, indicating that (+)-(1R,cis,αS) enantiomer was preferentially degraded. cis-DCCA and 3-PBA were formed in all of the soils, and it was found that the amount generated was related to the soil pH. cis-DCCA was easily generated in the acidic soils, while more 3-PBA tended to be generated in the soil of pH over 7. To evaluate the impact on soil animals, the toxicity, including the combined toxicity of cis-DCCA, 3-PBA, and α-cypermethrin, to earthworm (Eisenia fetida) was studied. The results of enantioselective transformation of α-cypermethrin in soils and the toxicity of α-cypermethrin and its metabolites to earthworm have some implications for environmental risk and food safety evaluations.