Enantioselective Toxic Effects And Bioenrichment Of Chiral Pesticides Penflufen Against On Chlorella Pyrenoidosa

Up to now,40%of the pesticides used in our country market are chiral pesticides.The biological effects of chiral pesticide racemates and enantiomeric monomers in the environment are different.Penflufen is a new type of chiral amide fungicide.Rice and other crops have been widely registered and used,and it is particularly necessary to carry out the environmental safety assessment of penflufen from the enantiomeric level.The biological effects of penflufen and its enantiomers in water have not been reported.In this paper,taking the aquatic environment Chlorella pyrenoidosa as the research object,it is clear that penflufen and its enantiomers have an effect on Chlorella pyrenoidosa.The difference between the stereoselective toxicity and bioaccumulation of the chlorophyll was determined,and the reasons for the difference in toxicity were revealed through the determination of chlorophyll content,and the mechanism of its toxicity effect was preliminarily elucidated through metabolomic analysis.The research results provide scientific basis and technical support for the safe and rational use and evaluation of penflufen..The main findings are as follows:1.To study the differences in the toxicity of penflufen and its enantiomers to Chlorella pyrenoidosa.The results showed that the toxicity of penflufen and its enantiomers to Chlorella pyrenoidosa was inversely proportional to the exposure time and exposure concentration,and there was a certain stereoselective toxicity difference,but it was not obvious.The EC₅₀ of rac-penflufen,S-penflufen and R-penflufen are 5.32,5.13 and 6.11mg/L,respectively,and the order of their toxicity is:S-penflufen>rac-penflufen>R-penflufen2.By measuring the content of photosynthetic pigments in Chlorella pyrenoidosa cells by penflufen and its enantiomers,the reasons for the differences in their stereoselective toxicity were revealed.The results showed that with the increase of exposure concentration,the content of photosynthetic pigments in Chlorella pyrenoidosa decreased to varying degrees,and the higher the exposure concentration,the more obvious the difference in stereoselectivity of cell photosynthetic pigment content;at low exposure concentrations（1mg/L）,the content of chlorophyll did not change significantly;at the intermediate exposure concentration（3 mg/L）,the contents of chlorophyll a,chlorophyll b,carotenoids and total chlorophyll treated with rac-penflufen about 23%,22%,21%,and 32%,respectively,and the contents of chlorophyll a,chlorophyll b,carotenoids and total chlorophyll were reduced by about 35%,28%,and 37%,respectively,after exposure to S-penflufen.The contents of chlorophyll a,chlorophyll b,carotenoid and total chlorophyll were decreased by 17%,15%,13%and 24%,respectively,after exposure to R-penflufen.3.To explore the stereoselective bioaccumulation of Chlorella pyrenoidosa by the enantiomers of penflufen.The results showed that Chlorella pyrenoidosa had a certain stereoselective bioconcentration effect on penflufen,and reached the peak at 3 d.R-penflufen was preferentially enriched,and the maximum enrichment amount was 30 mg/kg.In the water without Chlorella,the enantiomers of penflufen were degraded slowly and there was no significant difference,in the water with Chlorella pyrenoidosa,the enantiomers of penflufen degraded rapidly and existed certain selectivity differences,S-penflufen and R-penflufen were degraded by 65.8%and 82.5%respectively at 7d.4.Through metabolomic analysis,the effect of penflufen on the metabolism of Chlorella pyrenoidosa was studied.The results showed that among the 157 differential metabolites,25 metabolites were up-regulated and 132 were down-regulated;the biosynthesis of plant secondary metabolites,pyrimidine metabolism,ABC transport and central carbon metabolism in cancer were all significantly affected;L-glutamine regulates the down-regulation of cytosine,uracil and thymine in vivo and affects cytosine metabolism;metabolites such as L-glutamine and D-fructose 1,6-bisphosphate are down-regulated,indicating that Chlorella pyrenoidosa is sensitive to glucose And glutamine has a high consumption,the metabolic pathway changes are mainly reflected in the central carbon metabolism.