Activity, toxicity, molecular docking, and environmental effects of three imidazolinone herbicides enantiomers

All imidazolinone (IMI) herbicides are chiral consisting of two enantiomers; however, studies on the enantioselectivities of their interactions are limited. This study is a systematic assessment of the enantiomers and racemates of IMI herbicides, including semi-preparation and determination of absolute configurations, stereoselective bioactivity toward target organisms (Echinochloa crus-galli and Microcystis aeruginosa), and toxicity toward Michigan Cancer Foundation-7 (MCF-7) cells. R-imidazolinones were found to be more active than S-IMIs in the inhibition of target organisms, and neither enantiomer had estrogenic activity. Moreover, the relationship between the molecular structures and the efficiency of target growth inhibition by the IMI herbicides was investigated. Molecular modeling provided the rational structural basis for the enantioselectivity of the acetohydroxyacid synthase (AHAS) activity of the IMIs. These findings encourage the application of enantiopure R-IMI herbicides to capitalize on their advantages over the racemates.