Study On Enantioselective Toxicology Of Chiral Pesticides Isocarbophosto Aquatic Organisms

Enantioselectivity differences of chiral pesticide including environmental chemical behavior and ecotoxicological aspects is ubiquitous in human and animal body.Isocarbophos(ICP)belongs to an organophosphorus pesticide and it is a thiophosphamide insecticide,acaricide.It is widely used to agriculture.Isocarbophos is a chiral compound,but there are few studies on the toxicity of different enantiomers of ICP.The preliminary work of this subject explored the effects of acetone on the photosynthetic activity of Microcystis flos-aquae and Chlorella pyrenoidsa,and found the sensitive algae and its no observation effect concentration.This result provided a more reliable data basis for the study of chiral pesticide toxicology.In this study,ICP pesticide was chiral split to obtain a single enantiomer.We determined the chlorophyll a content,photosynthesis parameters,antioxidase enzyme activity and Malondialdehyde(MDA)contentof M.flos-aquae,as well as the antioxidant enzyme activity and MDA content of Daphnia magna to reveal the toxic effects of ICP on aquatic organismsand to elucidate the enantioselective differences of aquatic toxicity.The purpose of the experiment is to provide technical support and scientific basis for environmental safety and human health risk assessment of chiral pesticide.The results indicated:(1)The NOEC values of acetone to M.flos-aquae and C.pyrenoidsa were 0.5%and 0.05%,respectively,which indicated that M.flos-aquae was more sensitive to acetone.(2)Toxicity of ICP and its enantiomers to the chlorophyll a content and photosynthetic activity of M.flos-aquae:(+)-ICP reduced chlorophyll a content,the strongest toxicity;Rac-ICP followed,(-)-ICP toxicity was the weakest.(+)-ICP also inhibited the photosynthetic activity of M.flos-aquae and decreased the light energy utilization,maximum electron transport rate and strong light tolerance of algal cells.Under(-)-ICP and Rac-ICP effected,M.flos-aquae was promoted the electron transport and light energy utilization of photosystem II,and enhanced the photosynthetic activity,so that algae cells had strong ability to withstand light.Therefore,this result showed that the effect of chiral isocarbophos on the chlorophyll a content and photosynthesis of M.flos-aquae was significant enantioselectivity.(3)The results showed that there was significant enantiomeric difference in the oxidative damage effect of M.flos-aquae.During the exposure period,Rac-,(+)-and(-)-ICP did not induce lipid peroxidation of the M.flos-aquae cell membrane.However,the MDA content in the(+)-ICP group was higher than that in the(-)-ICP,and effect of the SOD and CAT enzyme activities was hormesis effect.(-)-ICP treatment group had no effect on SOD activity,and CAT activity was also hormesis effect that the degree was less than(+)-ICP group.(4)The effect of ICP on D.magna produced the oxidative damage that showed significant enantiomeric differences.In the treatment group with high concentration(2.5~20 ?g/L),(+)-ICP resulted in lipid peroxidation in the D.magna,and the MDA content of(-)-ICP and ICP was significantly lower than that of the blank group.SOD activity in the(-)-ICP was higher than that in ICP and(+)-ICP at each concentration.The activity of(+)-ICP was higher than that of ICP and(-)-ICP at the concentration of2.5~20 ?g/L.