Stereoselective Behavior Of Chiral Pesticides In Animals

In this paper, we investigated the metabolism of the chiral pesticides in animal models.The enantioselective disappearance of tebuconazole and hexaconazole were incestigated in rat liver microsomes system and the cytotoxicity to the rat primary hepatocytes were determinedby the MTT assay. The degradation of rac-tebuconazole and the enantiomer followed first-order kinetics. The result demonstrated that rac-tebuconazole (15μmol L-1) degradation in vitro assay was selective, but no significant difference between the enantiomers was found in the respective incubation (7.5μmol L-1for each). The interaction results revealed that there was competitive inhibition between S-and R-form, and the inhibition was a significant difference. This means that the interaction effect between the two enantiomers contributed to the selective degradation in the rat liver microsomes. The metabolism rate of hexaconazole in male and female rat hepatic microsomes was enantioselective and the degradation rate of hexaconazole metabolism in male rat hepatic microsomes was faster than that in female. The inhibition experiments with CYP inhibitors showed that the inhibitory effect of inhibitors was enantioselective and affected by sex, suggesting that the enantioselective metabolism of hexaconazole was determined by the amount of hepatic cytochrome P450and the expression of individual isoforms of CYPs.The enantioselective pharmacokinetics and degradation of flutriafol enantiomers in rabbits were investigated by a single ear intravenous (i.v.) administration at doses of5.0mgkg-1b.w. of racemate. At the beginning the concentration of S-flutriafol in plasma was higher than its antipide, but it became lower than its antipide gone with time. The protein binding was an important factor in modulating the disposition of flutriafol. The pharmacokinetic parameters showed that the metabolism, distribution and elimination were gender-related and stereoselective.The enantioselective metabolism, distribution and elimination of alpha-HCH in hens were studied through the oral route. The results showed that processes of the absorption and distribution were quickly and the excretion process was one of the important causes of the stereoselectivity. The organic modified montmorillonite showed a good adsorption capacity to alpha-HCH and used as feed additive to reduce the alpha-HCH uptake.An analysis method was developed to analyse a-cypermethrin and its main acid metabolites. In this method, the isomerization of a-cypermethrin was reduced to an acceptable level. This method was very sensitive for the quantitative determination of a-CP and its major acid metabolites in animal foods.Baesed on this method, the behavior of a-CP in the plasma of hens after oral exposure. The results showed that the a-CP was mainly distributed in plasma and only cis-DCVA was detected in the experiment.Two novel pretreatment methods was developed based on the magnetic separation technology. First we a prepared a new magnetic material based on montmorillonite (MMT) through a two-step reaction. In this work, a MSPE method was developed for the extraction of five triazole pesticides residues in water samples to evaluate the applicability of this new material. The second method was low-density magnetofluid dispersive liquid-liquid microex-traction. Comparing with the existing low density solvents micro-extractionmethods, no special devices and complicated operations were required during the whole extraction process. Under the optimal extraction condition, the two novel pretreatment methods offered good LOD, as well as good linearity and acceptable repeatability.