Comprehensive Assessment of Enantioselective Bioactivity, Toxicity, and Dissipation in Soil of the Chiral Herbicide Flurtamone

Flurtamone is a typical chiral pesticide with a pair of enantiomers. In this study, the enantioselective biological effects of flurtamone enantiomers were systematically investigated. The bioactivities of R-flurtamone were 6.3-35.6 and 1.7-9.9 times higher than S- and Rac-flurtamone, respectively. The contribution of the R-enantiomer to herbicidal activity was 86.3-97.3%. The carotenoid content in the R-flurtamone treatment group was 1.31-2.14 times lower than that in the S-flurtamone treatment group. Molecular docking found that flurtamone can form aromatic H-bonds with phenylalanine (PHE) 233 of phytoene desaturase (PDS), while R-flurtamone can form pi-pi stacking with PHE 202 and PHE 311. The binding energies of R- and S-flurtamone were -10.239 and -7.555 kcal/mol, respectively. Furthermore, the acute toxicity levels to Selenastrum capricornutum of R- and Rac-flurtamone were both highly toxic, and S-flurtamone has moderate toxicity. S-Flurtamone dissipated preferentially. Therefore, the development of R-flurtamone can decrease environmental risks and protect human health.