Enantioselective Toxicity and Potential Endocrine-Disruptive Effects of the Insecticides Flufiprole and Ethiprole on Danio rerio.

Phenylpyrazole insecticides are widely used as chiral pesticides. However, the enantioselective toxicity and potential endocrine-disrupting effects of these insecticides on aquatic organisms remain unclear. Herein, the enantioselective toxicity and potential endocrine-disrupting effects of flufiprole and ethiprole were investigated by using zebrafish embryos/larvae as a model. The acute toxicity of R-flufiprole and R-ethiprole toward zebrafish embryos and larvae was 1.8-3.1-fold higher than that of the S-configuration. Additionally, R-flufiprole and R-ethiprole had a greater effect on the expression of genes related to the hypothalamus-pituitary-gonad axis in zebrafish compared with the S-configuration. Nevertheless, both S-flufiprole and S-ethiprole exhibited a greater interference effect on the expression of genes related to the hypothalamus-pituitary-thyroid axis and a greater teratogenic effect on zebrafish than the R-configuration. Thus, this study demonstrates that both flufiprole and ethiprole exhibit enantioselective acute toxicity and developmental toxicity toward zebrafish. Furthermore, those pesticides potentially possess enantioselective endocrine-disrupting effects.

Enantioselective endocrine-disrupting effects of the phenylpyrazole chiral insecticides in vitro and in silico.

The phenylpyrazole chiral insecticides, including the widely used fipronil, ethiprole, and flufiprole, have generated a worldwide interest due to their environmental toxicity. However, up to now,only few studies focused on their their potential endocrine-disrupting effects (EDEs). In this study, we investigated the endocrine hormonal disorder caused by the fipronil, ethiprole, and flufiprole enantiomers in vitro and in silico approach. Results of the luciferase reporter assay indicated that the enantiomers of fipronil, ethiprole, or flufiprole have shown stereoselective endocrine-disrupting effects. S-(-)-ethiprole and S-(-)-flufiprole have anti-thyroidal disorder effects whereas R-(-)-fipronil, R-(+)-ethiprole, and R-(+)-flufiprole showed anti-estrogenic disorder effects. The results of the molecular dynamics simulations revealed that the happened EDEs could be partially attributed to the enantioselective specific receptor binding affinities. It also suggested that Vander Waals interactions plays an important role in the binding procedure. This study could provide helpful information for the explanation of enantioselectivity in the EDEs of chiral phenylpyrazole pesticides at the molecular level.

Separation and detection of cyproconazole enantiomers and its stereospecific recognition with chiral stationary phase by high-performance liquid chromatography.

Cyproconazole, a chiral triazole fungicide, has been diffusely used and analyzed. The development of an effective analytical method for cyproconazole enantiomers can support their residual monitoring and risk assessment. In the present study, the absolute configuration of the cyproconazole enantiomers was confirmed by electronic circular dichroism and time-dependent density functional theory. The enantioseparation parameters were optimized by the response surface methodology using the Box-Behnken design on Lux Cellulose-2. The elution order of (2S,3R)-(+)-, (2S,3S)-(+)-, (2R,3S)-(-)-, and (2R,3R)-(-)-cyproconazole was simulated with molecular docking. The enantiomers were completely separated primarily via halogen bond and hydrogen bond interactions with the chiral stationary phases. The mean recoveries of the cyproconazole enantiomers in the four matrices were 71.8-102.0% with intraday relative standard deviations (RSDs) of 0.3-11.9% and interday RSDs of 0.9-10.6%. The results showed the chiral recognition mechanism clearly and confirmed that the method was accurate and convenient for the simultaneous detection of cyproconazole enantiomers in environmental and food matrices.

Stereoselective endocrine-disrupting effects of the chiral triazole fungicide prothioconazole and its chiral metabolite.

The wide use of chiral fungicides has generated interest in the stereoselectivity of their ecotoxicological effects. However, there are few studies about the potential endocrine-disrupting effects (EDEs) of chiral fungicides. This study evaluated the hormone receptor activities of the chiral triazole fungicide prothioconazole and its metabolite using reporter gene assays. The results indicated that prothioconazole and its metabolite possessed EDEs, and the metabolite exerted more activities than the activities of the parent compound, suggesting that the metabolic process is toxification. Stereoselective EDEs were observed, and the S-enantiomers possessed greater hormonal effects than those possessed by the R-enantiomers; the REC20 values ranged from 7.9 × 10-10 to 6.4 × 10-7 M for the thyroid hormone effects and from 3.2 × 10-9 to 7.8 × 10-8 M for the estrogenic effects. The molecular docking results revealed that the stereoselective EDEs of prothioconazole and its metabolite were partially attributed to enantiospecific receptor binding affinities. Overall, our results reveal that prothioconazole and its metabolite might disrupt the balance of the endocrine system by affecting the function of multiple nuclear hormone receptors and that they have the potential to affect the developmental and reproductive systems in humans.

A potential biomarker of isofenphos-methyl in humans: A chiral view.

Isofenphos-methyl (IFP) is a very active and persistent chiral insecticide. However, IFP has lower activity against acetylcholinesterases (AChEs). Previously, it was confirmed that phosphorothioate organophosphorus pesticides with N-alkyl (POPN) require activation by oxidative desulfuration and N-dealkylation. In this work, we demonstrated that IFP could be metabolized in human liver microsomes to isofenphos-methyl oxon (IFPO, 52.7%), isocarbophos (ICP, 14.2%) and isocarbophos oxon (ICPO, 11.2%). It was found that (R)-IFP was preferentially degraded compared to the (S)-enantiomer, and the enantiomeric fraction (EF) value reached 0.61 at 60 min. However, (S)-enantiomers of the three metabolites, were degraded preferentially, and the EF values ranged from 0.34 to 0.45. Cytochrome P450 (CYP) isoforms CYP3A4, CYP2E1, and CYP1A2 and carboxylesterase enzyme have an essential role in the enantioselective metabolism of IFP; but, the enzymes that participate in the degradation of IFP metabolites are different. The AChE inhibition bioassay indicated that ICPO is the only effective inhibitor of AChE. The covalent molecular docking has proposed that the metabolites of IFP and its analogs after N-dealkylation and oxidative desulfuration will possess the highest inhibitory activity against AChE. This study is the first to demonstrate that ICPO can be regarded as a potential biomarker for the biomonitoring of IFP and ICP exposure in humans.