Degradation and metabolic profiling for benzene kresoxim-methyl using carbon-14 tracing.

Benzene kresoxim-methyl (BKM) is an effective strobilurin fungicide for controlling fungal pathogens but limited information is available on its degradation and metabolism. This study explored the degradation and metabolic profiling for BKM in soils by carbon-14 tracing and HPLC-TOF-MS analyzing. Results indicated that 88%-98% of C-BKM remained as parent or incomplete intermediates after 100 days. Three main radioactive metabolites (M1 to M3, ≥90%) and three subordinate radioactive metabolites (Ma to Mc, ≤2%) were observed, along with a non-radioactive metabolite M4. The main intermediates were further confirmed by self-synthesizing their authentic standards, and BKM was proposed to degrade via pathways including: 1) the oxidative cleavage of the acrylate double bond to give BKM-enol (M1); 2) the hydrolysis of the methyl ester to give BKM acid (M2); 3) the cleavage of M1 and M2 to yield Mc, which could be decarboxylated to give M3; and 4) the ether cleavage between aromatic rings to form M4. This study builds a solid metabolic profiling method for strobilurins and gives a deeper insight into the eventual fate of BKM by demonstrating its transformation pathways for the first time, which may also be beneficial for understanding the risks of other analogous strobilurins.