Intrinsic Clearance and Metabolism Pathway of Fosthiazate in Rat and Cock Liver Microsomes: From Chiral Assessment View

Chiral fosthiazate enters the organisms via environmental exposure and food web enrichment. Liver subcellular fractions of rats (RLM) and cocks (CLM) were prepared to explore the stereoselective metabolism of fosthiazate in vitro. The results indicated that fosthiazate exhibited different stereoselective metabolism behaviors in RLM and CLM. The clearance rate order of RLM to four fosthiazate stereoisomers was (1R,3R)-fosthiazate > (1S,3R)-fosthiazate > (1R,3S)-fosthiazate > (1S,3S)-fosthiazate. However, CLM showed a faster clearance rate to (1S,3S)-fosthiazate and (1S,3R)-fosthiazate than the other two stereoisomers. The molecular docking results revealed that the stereoselectivity was partially due to the stereospecific binding between fosthiazate stereoisomers and cytochrome P450 proteins. The main metabolism pathways of fosthiazate in RLM and CLM were oxidation and hydrolysis with five common metabolites including M299, M243, M227, M103, and M197 being identified by LC-TOF-MS/MS. The present study provides the accurate data on risk assessment of chiral fosthiazate.