Stereoelective Degradation And Biological Effect Of Chiral Fungicide Bromothalonil

The use of chiral pesticides is becoming more and more common.After being applied to nature,these pesticides is generally regarded as single compounds with the metabolism and transformation in the environment.Although the enantiomers of chiral pesticides have similar physicochemical properties,the digestion and attribution of these enantiomers are always different.There may be significant differences in environmental behaviors,bioactivities and toxicities of chiral pesticides after applied to the environment.Based on gas chromatography,the method of detecting the enantiomer level of bromothalonil was established with the QuEChERS method of sample pretreatment and solid phase extraction.The stereoselective degradations of bromothalonil in different crops and soils were further studied.The stereoselective bioactivities to pathogenic fungi and toxicities to organisms-earthworms of bromothalonil were conducted a preliminary survey.This study fulfills gap of related researches and lays a theoretical foundation for the fine production of bromothalonil.This study also provides an important theoretical basis for the safe use and safety evaluation of bromothalonil.The main contents are as follows:1.The effects of chromatographic parameters such as inlet temperature,column temperature and heating procedure on the isolation and detection of the bromothalonil enantiomers were studied by gas chromatography.The residue analysis methods of bromothalonil enantiomers in tomatoes,cucumbers,chieh-quas and soil samples were established with the solid phase extraction columns,extraction and purification nethods.The average recovery rates of this method were from 73%to 110%.The daily RSD value is between 0.93%and 13%,while the daytime RSD value is between 0.49%and 12%.All results were in accordance with the pesticide residue test criteria.2.The stereoselective degradation of bromothalonil in tomato,cucumber,chieh-qua and soil was studied,and the results showed that the degradation of bromothalonil enantiomers was in line with the kinetic equation of primary reaction.The stereoselective degradation was found in tomato,cucumber,chieh-qua and soil.The degradation half-lives of(-)-bronothalonil in tomatoe,cucumber,chieh-qua and soil were 24.75,9,00,16.12 and 1034 d,while the degradation half-lives of(+)-bromothalonil were 14.14,7.14,13.33 and 8.25 d,respectively.The degradation rates of(+)-bromothalonil in tomato,chieh-qua,cucumber and soil were greater than those of(-)-brornothalonil(EF>0.5),suggesting that the degradation of(+)-bromothalonil was preferred.According to the degradation grade of pesticide,bromothalonil enantiomers are easily degradable pesticides.3.The biological activities of ten kinds of pathogenic fungi by rac-bromothalonil and its enantiomers were determined with the mycelium growth rate method.In addition to Colletotrichum orbiculare,(+)-bromothalonil has greater inhibitory effects against other nine species than rac-bromothalonil and(-)-bromothalonil.In addition to Botryotis cinerea and Sclerotinia sclerotiorum,(+)-bromothalonil and(-)-bromothalonil have significantly different inhibitory effects.In particular,the difference between the EC50 values of Curvularia lunat and Colletotrichum siamense were 3.28 and 10.77 times,respectively.4.The differences of bromothalonil and its enantiomers on the acute toxicities of earthworm,the cell rate of earthworm cavityand the lysosomal body were studied by using filter paper contact method.With the increase of time and concentration,the mortality rates of earthworms were increased.The LD50 of rac-bromothalonil,(-)-bromothalonil and(+)-bromothalonil were 14.72,11.99 and 17.53 ?g/cm2 after 48 h treatment.(-)-bromothalonil and(+)-bromothalonil were significantly different in the acute toxicities to earthworms.In the range of certain concentrations,the micronucleus rates of earthworm cavity cells increased with the increase of concentrations.(-)-bromothalonil was more likely to induce micronucleus in earthworm body cavity cells than rac-bromothalonil and(-)-bromothalonil.(-)-bromothalonil and(+)-bromothalonil have significant differences in the ability to produce micronucleus of earthworm cavity cells.With the increase of time,the toxic effects of bromothalonil and its enantiomers on lysosomes were enhanced.The order of the damage to the lysosomal membrane of body cavity cells was(+)-bromothalonil>rac-bromothalonil>(-)-bromothalonil.The toxicities of(-)-bromothalonil and(+)-bromothalonil to lysosomes were significantly different.The following conclusions are drawn from the above results:1.The residue analysis method of bromothalonil in the test samples conformed to the requirements of the pesticide residue test criterion.2.Chiral pesticide bromothalonil existed stereoselective degradation differences in tomato,cucumber,chieh-qua and soil.(+)-bromothalonil was degraded faster than(-)-bromothalonil in tomato,cucumber,chieh-qua and soil.3.There were selective differences in the bioactivity of rac-bromothalonil and its enantiomers on 9 test strains,and the activity of(+)-bromothalonil to the 8 test strains in addition to the Colletotrichum orbiculare were higher than that of rac-bromothalonil and(-)-bromothalonil.4.There were stereoselective differences in the acute toxicity,genotoxicity and lysosomal injury to earthworms.The toxicity of(+)-bromothalonil to earthworms was lower than that of rac-bromothalonil and(-)-bromothalonil.5.(+)-bromothalonil had greater fungicidal activities and was more environmentally friendly than rac-bromothalonil and(-)-bromothalonil,indicating that(+)-bromothalonil should be used as the main product in production.