Stereoselective behaviour of diclofop-methyl and diclofop during cabbage pickling

This experiment studied the behaviour of diclofop-methyl (DM) and its main metabolite, diclofop (DC), during the pickling process. DM showed obvious enantioselective degradation in the pickled cabbage in the pickling process, with a half-life of 4.95 days for (+)-(R)-DM but less than 12 h for (−)-(S)-DM. In addition, the stereoselective degradation of DM also led to the enantioselective formation of DC. Therefore, (−)-(S)-DC showed a higher residue level than (+)-(R)-DC in both pickled cabbage and its brine. Rac-DC was added into the cabbage used for pickling to study the behaviour of the enantiomers of DC; no enantioselective degradation was observed either in the pickled cabbage or in the brine. DM and DC were configurationally stable in the process, showing no interconversion of (−)-(S)- to (+)-(R)- enantiomer, or vice versa. This research provides information for evaluating the risk of food safety and environmental pollution at the enantiomer level.