Comparative assessment of the behaviour and potential ecological risks of pretilachlor and its metabolites in contrasting soil environments

Abstract

A comparative evaluation of degradation behaviour and possible ecological risks associated with pretilachlor and its metabolites was conducted. Five metabolites (M1–M5) were synthesized and characterized. Pretilachlor and the metabolites were applied at 0.25 and 0.50 µg/g in different soils. Despite having shorter half-lives (t_1/2 = 1.18.1 days) than pretilachlor (t_1/2 = 5.313.7 days), metabolites residues persisted in soil from 3 to 45 days. Based on the conservative and first-tier screening of measured soil residues, some compounds showed risk quotients, RQ > 1 for earthworms, fish and honeybees; whereas the RQ for algae, birds and rats ranged from moderate to negligible. M2 and M3 reduced soil dehydrogenase activity by 1.11.5 times, while pretilachlor and remaining metabolites enhanced it. M2 and M3 bound strongly to the catalytic site of the dehydrogenase near Zn^2 + ion with docking scores of −5.45 and −5.22 kcal/mol, respectively. The overall stability of the docked complexes was also established through 100 ns molecular dynamics simulations. The root mean square deviation (RMSD) and root mean fluctuations (RMSF) remained within the acceptable limits (less than 2.5 Å), indicating stable protein-ligand interactions. In summary, pretilachlor metabolites may persist in the environment with potential risk implications to different non-target species.