Studies On Enantioselective Biological Effect And Degradation Of Fenobucarb Enantiomers

Chirality exists in nature.Chiral compounds which have the same construction,physical and chemical properties but may have remarkably and selectively affect a number of crucial properties,such as biological effect,toxicity effect and environmental behavior.It is obviously not accurate to evaluate chiral pesticides at racemic levels.Fenobucarb,as a typical carbamate insecticide,can effectively control rice thrips,leaf hoppers and plant hoppers in paddy fields and have a good activity of sanitary insect pest.Until now,research about the enantioselective behavior of fenobucarb was not referred.This paper determined the enantioselective behavior of fenobucarb for provide a dependable reference data of fenobucarb enantiomers for the more accurate environmental and human health risk assessments.The results about this paper are followed:1.The fenobucarb enantiomers were baseline separated on a Daicel IG-3 chiral column using acetonitrile and 0.1%formic acid water(60:40,v/v),20℃ of column temperature and 0.3 mL/min of flow rate as mobile phase.The absolute configuration of fenobucarb enantiomers were confirmed as R-(+)-fenobucarb and S-(-)-fenobucarb by experimental and calculated electronic circular dichroism spectra.Meanwhile,the specific optical rotation of the two individuals were also conducted.Thus,the first eluted peak was R-(+)-fenobucarb and the second one was S-(-)-fenobucarb in IG-3 column.2.A reliable and sensitive method was developed and validated for the determination of chiral pesticide fenobucarb enantiomers in vegetables and environmental samples.Good linearity(R2>0.9962)was obtained for the four matrix calibration curves within the range of 0.5-50 mg/L.The limit of detection of the two enantiomers were in the range of 0.07-0.16 μg/kg.The mean recoveries of the two enantiomers ranged from 80.4%to 102%with intra-day relative standard deviations(RSDs,n=5)from 1.8%to 6.6%and inter-day RSDs(n=15)from 3.0%to 5.7%in four matrices.3.The stereoselective bioactivity and inhibiting acetylcholin esterase activity about fenobucarb enantiomers was studied.The results were similar that the R-iso is more efficient,2.7～3.0 times higher than that of S-iso for Nilaparvata lugens and Culex pipiens pallens larva.And S-fenobucarb shows nearly no insecticidal activity and inhibiting acetylcholin esterase activity for Musca domestica L.As to the inhibiting acetylcholin esterase activity of Nilaparvata lugens and Culex pipiens pallens larva,the R-iso is more efficient shows 3.0-3.2 times.4.The stereoselective toxicity about fenobucarb enantiomers was studied.The study showed that S-fenobucarb has the higher toxicity of the non-target organisms(Chlorella pyrenoidesa,Danio rerio embryo and HepG2 cell)at 1.3-1.7 times.5.Stereoselective degradation in cucumber and soil were studied in this paper.R-(+)-fenobucarb degraded 1.6 times faster than S-(-)-fenobucarb in cucumber.While no significant difference was observed in three kinds of soils.And fenobucarb enantiomers degraded faster in the normal soil than waterlogging soil.This indicated that aerobic microorganisms play an important role during the degradation.And fenobucarb degraded fastest in Jilin soil,degraded the most slowly in Jiangxi soil,which indicated that the degradation rate may be related to the content of organic carbon and nitrogen in soil.In the soil incubation experiment of a single enantiomer in Jiangsu soil,the degradation rate of enantiomers was almost the same as that of racemes,and there was no transformation between the two enantiomers.6.Stereoselective metabolism of fenobucarb enantiomers in the rat liver microsome was determined in this paper.The analytical method of rat liver microsome was reliable and precise with a recovery of 97.2～99.3%and RSDs of 1.0～1.8%.The two enantiomers had similar metabolic degradation rate.The fenobucarb was found no significant difference in the two enantiomers of fenobucarb in the metabolism of rat liver microsome.Also,there was no transformation between the two enantiomers.