Enantioselective metabolism of triadimefon and its chiral metabolite triadimenol in lizards.

Chinese lizards ( Eremias argus ) were exposed to separated R -(-)-triadimefon, S -(+)-triadimefon and racemic triadimefon to evaluate enantioselective accumulation of triadimefon. After single oral administration of R -(-)-triadimefon, S -(+)-triadimefon and racemic triadimefon, the time-concentration curves in different tissues were found to be different. Triadimefon enantiomers crossed the blood-brain barrier and brain is a main target organ. The residues of triadimefon enantiomers in fat were highest after 24 h indicating that fat was the main tissue of accumulation. In racemic triadimefon exposure group, the enantiomer fractions of R -(-)-triadimefon in different tissues showed that the differences between R -(-)-triadimefon and S -(+)-triadimefon were significant in absorption and metabolism, but the differences became smaller in exclusion and accumulation. From the results of mathematical models, S -(+)-triadimefon was absorbed and eliminated faster than R -(-)-triadimefon, and R -(-)-triadimefon was easily distributed in the tissues and more easily converted into its metabolites. Furthermore, among the four enantiomers of triadimenol, SR -(-)-triadimenol produced by S -(+)-triadimefon may have the highest fungicidal activity and the strongest biological toxicity, RR -(+)-triadimenol produced by R -(-)-triadimefon was most likely to bioaccumulate in lizard. Identifying toxicological effects and dose-response relationship of SR -(-)-triadimenol and RR -(+)-triadimenol will help fully assess the risk of TF enantiomers use in the future. The results enrich and supplement the knowledge of the environmental fate of triadimefon enantiomers. [ABSTRACT FROM AUTHOR]