Toxicity Difference And Mechanism Of Flufiprole Enantiomers To Eisenia Foetida

Enantiomers of chiral pesticides have similar physical and chemical properties in nonchiral environments,but the biological activity,toxicity and environmental behavior of racemic and enantiomers of some chiral pesticides tend to show significant differences in chiral environments.Exploring pesticides with chiral structures as a mixture may result in inaccurate environmental risk assessments.Therefore,more and more scholars are exploring the toxicity mechanism of chiral pesticides from the chirality level.In order to provide theoretical support for the use and development of chiral pesticides,this paper systematically studied the toxicity mechanism of flufiprole enantiomers to earthworms from different aspects.The main contents are as follows:Individual level:Artificial soil method was used to measure the 14 day half lethal concentration of flufiprole enantiomers on earthworms.The result was:the LC₅₀of Rac-flufiprole,R-flufiprole,S-flufiprole to earthworm respectively were3633.98 mg/kg,1485.76 mg/kg,4555.86 mg/kg.The results showed that the order of enantiomeric toxicity was R-flufiprole>Rac-flufiprole>S-flufiprole.Cell level:Paraffin section and H.E staining were used in testing to observe the tissue structure of earthworm after exposure.The results showed that under the three dose levels of 303?454?727mg/kg,the tissue structure of earthworm cells under R-(+)-flufiprole was damaged first and most seriously,followed by Rac-(±)-flufiprole,and the earthworm under S-(-)-flufiprole was the least damaged.Tissue level:To explore the effect of flufiprole enantiomers on the antioxidant enzymes and malondialdehyde of Eisenia foetida.The results showed that the activities of SOD,CAT,POD and MDA were first inhibited and then activated at three dose levelsof 303?454?727mg/kg,with the extension of exposure time,the inhibition was lower than that of the control group.Compared with the three agents,R-(+)-flufiprole had significant inhibitory effect on the enzyme activities of three oxidative stress classes,followed by Rac-(±)-flufiprole,while S-(-)-flufiprole had the lowest inhibitory effect.Molecular level:A single cell gel electrophoresis test(comet assay)was used to investigate the damage size and difference of DNA on earthworm cavity by flufiprole enantiomers.The results showed that the DNA damage degree(olive tail distance,tail length,tail DNA content)first increased and then decreased with the increase of exposure time and concentration,and reached the maximum at 14 days,then decreased gradually after 14 days,and the higher the concentration,the slower the decrease.Compared with the three chemicals,the damage degree of R-(+)-flufiprole to earthworm DNA was the largest,followed by Rac-(±)-flufiprole,and S-(-)-flufiprole.Gene expression level:Changes of gene expression in earthworms measured by q RT-PCR method.The results showed that the expression level of SOD and CAT in the enzyme system of oxidative stress system and TCTP gene controlling earthworm metabolism increased first and then decreased,except that the expression level of TCTP gene was lower than that of the control group at 28d,and the expression level of other genes was higher than that of the control group.TCTP and l-r RNA gene expression was down regulated,which was lower than that of the control group.The inhibition of l-r RNA and HSP90 gene expression was the least under the treatment of S-(-)-flufiprole,indicating that the toxicity of S-(-)-flufiprole was less than that of R-(+)-flufiprole and Rac-(±)-flufiprole.The toxicity of flufiprole enantiomers to earthworms was studied systematically by molecular,cytological and biological methods.It was found that the toxicity of R-(+)-flufiprole>Rac-(±)-flufiprole>S-(-)-flufiprole.