Stereoselective environmental behavior and biological effect of the chiral organophosphorus insecticide isofenphos‑methyl

Abstract

The enantiomeric environmental behaviors, bioactivities and toxicities of isofenphos‑methyl enantiomers were characterized systematically in this study. (R)‑Isofenphos‑methyl was degraded preferentially in Yangtze River water and different types of vegetables with an enantiomeric fraction (EF) of 0.6 to 0.96. However, (R)‑isofenphos‑methyl was amplified in both Nanjing (EF = 0.32) and Nanchang (EF = 0.27) soil. Our investigations found that there no bidirectional chiral inversion occurred in either Yangtze River water or soils. The bioactivity of (S)‑isofenphos‑methyl was higher than that of its (R)‑enantiomer against different insect targets, such as Meloidogyne incognita, Nilaparvata lugens, Plutella xylostella and Macrosiphum pisi (3.7 to 149 times). (S)‑Isofenphos‑methyl showed higher toxicity for the nontarget organism (1.1 to 32 times). However, (R)‑isofenphos‑methyl possesses 4.0 times more potency than the (S)-form for the nontarget soil organism Eisenia foetida. This study generally could provide more scientific guidance for the corresponding risk assessments of pesticides in addition to providing a new theoretical basis for scientifically and rationally using isofenphos‑methyl.