Enantioselective uptake, translocation, and biotransformation of pydiflumetofen in wheat (Triticum aestivum L.): Insights from chiral profiling and molecular simulation.

Pydiflumetofen (PYD), a highly effective and broad-spectrum fungicide, is commonly employed for the control of fungal diseases. In this study, the uptake, translocation, and biotransformation of PYD by wheat (Triticum aestivum L.) were firstly investigated at a chiral level. The findings revealed that the residue concentration of R-PYD in wheat was higher than that of S-PYD, because of its higher uptake rate (k1 = 0.0421 h-1) and lower elimination rate (k2 = 0.0459 h-1). Additionally, R-PYD exhibited higher root bioconcentration factors and translocation factors compared with S-enantiomer, indicating R-PYD was more easily accumulating in roots and translocating to shoots. Furthermore, a total of 9 metabolites, including hydroxylated, demethylated, demethoxylated, dechlorinated, hydrolyzed, and glycosylated-conjugated products, were detected qualitatively in wheat roots or shoots. Symplastic pathway-mediated uptake, which predominantly relied on aquaporins and anion channels, was confirmed by root adsorption and inhibition experiments, without displaying any enantioselective effect. Molecular simulations demonstrated that R-PYD exhibited stronger binding affinity with TaLTP 1.1 with a lower grid score (-6.79 kcal/mol), whereas weaker interaction with the metabolic enzyme (CYP71C6v1) compared to the S-enantiomer. These findings highlight the significance of plant biomacromolecules in the enantioselective bioaccumulation and biotransformation processes. Importantly, a combination of experimental and theoretical evidence provide a comprehensive understanding of the fate of chiral pesticides in plants from an enantioselective perspective.

Fosthiazate exposure induces oxidative stress, nerve damage, and reproductive disorders in nontarget nematodes.

As a forceful nematicide, fosthiazate has been largely applied in the management of root-knot nematodes and other herbivorous nematodes. However, the toxicity of fosthiazate to nontarget nematodes is unclear. To explore the toxicity and the mechanisms of fosthiazate in nontarget nematodes, Caenorhabditis elegans was exposed to 0.01-10 mg/L fosthiazate. The results implied that treatment with fosthiazate at doses above 0.01 mg/L could cause injury to the growth, locomotion behavior, and reproduction of the nematodes. Moreover, L1 larvae were more vulnerable to fosthiazate exposure than L4 larvae. Reactive oxygen species (ROS) production and lipofuscin accumulation were fairly increased in 1 mg/L fosthiazate-exposed nematodes. Treatment with 0.1 mg/L fosthiazate significantly inhibited the activity of acetylcholinesterase (p < 0.01). Furthermore, subacute exposure to 10 mg/L fosthiazate strongly influenced the expression of genes related to oxidative stress, reproduction, and nerve function (e.g., gst-1, sod-1, puf-8, wee-1.3, and ace-1 genes). These findings suggested that oxidative stress, reproduction and nerve disorders could serve as key endpoints of toxicity induced by fosthiazate. The cyp-35a family gene was the main metabolic fosthiazate in C. elegans, and the cyp-35a5 subtype was the most sensitive, with a change in expression level of 2.11-fold compared with the control. These results indicate that oxidative stress and neurological and reproductive disorders played fundamental roles in the toxicity of fosthiazate in C. elegans and may affect the abundance and function of soil nematodes.

Stereoselective toxicity, bioaccumulation, and metabolic pathways of triazole fungicide cyproconazole in zebrafish.

Cyproconazole (CPZ) is a broad-spectrum fungicide that is widely used around the world. CPZ can persist in water which raised concerns about its potential adverse effects on aquatic life. In this study, the stereoselective toxicity, bioaccumulation, elimination, and kinetic biotransformation in zebrafish were investigated. The LC50 of 96 h acute toxicity was 15.88, 19.68, 26.99, and 17.10 mg/L for SR-, SS-, RS-, and RR-CPZ, respectively. The uptake and elimination experiment showed the bioconcentration factor in order of SR- > RR- > SS- > RS-CPZ at the exposure concentration of 0.1 and 1 mg/L. In the depuration stage, CPZ isomers were rapidly eliminated by 99% within 24 h. Moreover, the oxidative stress responses (POD, SOD, and CAT) were stereoselectively induced by CPZ stereoisomers, the activity of POD was significantly increased in all CPZ treatment groups compared to the control while the activity of CAT exhibited a concentration-dependent decrease in the CPZ treatment group. Multiple metabolic pathways of CPZ in zebrafish were proposed for the first time and 7 phase I metabolites and 25 phase II conjugates were found. This study determined the potential toxicity of CPZ to zebrafish and provided a strategy for the risk evaluation of CPZ stereoisomers in aquatic ecosystems.

Comprehensive Enantioselectivity Evaluation of Insecticidal Activity and Mammalian Toxicity of Fenobucarb.

To comprehensively evaluate the efficiency and risk of the chiral pesticide fenobucarb, the bioactivity, toxicity, and environmental behavior of fenobucarb (FNC) enantiomers were investigated. The results showed that R-FNC possesses 1.8-2.7 times more bioactivity than S-FNC but 1.3-3.0 times lower toxicity than S-FNC against four nontarget organisms: Chlorella pyrenoidosa, HepG2, and Danio rerio and its embryos. The corresponding enzyme inhibitory activity showed consistent results; the acetylcholinesterase inhibitory activity of target organisms was ordered as R-FNC > rac-FNC > S-FNC, while the reduction in catalase activity after exposure to R-FNC was 2.5 times that after exposure to S-FNC in zebrafish. The enantioselective bioactivity mechanism of FNC enantiomers was further explored in silico. No significant enantioselective degradation was found in soils or rat liver microsomes. In sum, R-FNC possesses higher insecticidal activity and lower toxicity. The development of R-FNC as a commercial agrochemical is beneficial for reducing pesticide inputs.

Enantioselective Bioactivity, Toxicity, and Degradation in Vegetables and Soil of Chiral Fungicide Mandipropamid.

Mandipropamid (MDP) is a widely used chiral fungicide to control oomycete pathogens with two enantiomers. In this study, the enantioselective bioactivity, toxicity, and degradation of MDP were investigated for the first time. The bioactivity of S-MDP was 118-592 times higher than that of R-MDP and 1.14-1.67 times higher than that of Rac-MDP against six phytopathogens. Molecular docking found that S-MDP formed a strong halogen bond with HIS 693 of cellulose synthase and possessed a lower binding energy, which validated the results of the bioactivity assay. S-MDP showed lower toxicity toward Spirodela polyrhiza, while it exhibited higher toxicity in Danio rerio embryo and larva. S-MDP preferentially degraded in cowpea and pepper, while R-MDP preferentially degraded in soil. There is no significant difference between the two enantiomers in the toxicity of adult D. rerio and in cucumber degradation. Therefore, the development of the S-enantiomer was considered as a better option to exhibit high efficiency, which could reduce the residual risk of the pesticide and ensure environmental safety.

Deoxynivalenol in Fusarium graminearum: Evaluation of Cyproconazole Stereoisomers In Vitro and In Planta.

Cyproconazole (CPZ), a representative chiral triazole fungicide, is widely used to control Fusarium head blight (FHB). In this study, the stereoselective efficiency of CPZ was investigated in vitro and in planta. Consistent results were observed between the in vitro bioassay and the in planta visual disease rating, with the control efficacy ordered RS-CPZ > RR-CPZ > SR-CPZ > SS-CPZ. Unexpectedly, the in planta deoxynivalenol level was in the order RR-CPZ > RS-CPZ > SS-CPZ > SR-CPZ, while RS-CPZ inhibited the deoxynivalenol production and ergosterol biosynthesis in Fusarium graminearum. We further investigated that the Tri genes were upregulated in Fusarium graminearum of the RS-CPZ group, and SR-CPZ preferentially degraded in wheat. An extra action mode of CPZ was inferred to stimulate the production of deoxynivalenol. These findings revealed the stereoselective efficiency of CPZ stereoisomers against FHB and provided new insights into the mechanism of action of triazole fungicides against FHB and deoxynivalenol.

Evaluation of exploitive potential for higher bioactivity and lower residue risk enantiomer of chiral fungicide pydiflumetofen.

BACKGROUND: Pydiflumetofen, as a new succinate dehydrogenase inhibitor (SDHI) chiral fungicide, has been used in crop production because of its broad-spectrum and high-efficiency antifungal activity. However, little is known about pydiflumetofen at the chiral level. The stereoselective bioactivity and degradation of pydiflumetofen enantiomers were therefore investigated. RESULTS: Pydiflumetofen presented effective bioactivity against the eight tested phytopathogens, and its enantiomers showed significant differences in activity. The bioactivity of R-pydiflumetofen was 9.0-958.8 times higher than that of the S enantiomer. Treatment with R-pydiflumetofen increased the cell membrane permeability of Sclerotinia sclerotiorum and decreased exopolysaccharide and oxalic acid production more than treatment with S-pydiflumetofen. Furthermore, R-pydflumetofen exhibited better inhibitory activity against the succinate dehydrogenase enzyme of S. sclerotiorum than S-pydiflumetofen by 584-fold. According to homology modeling and molecular docking studies, the binding affinities of the R and S enantiomers were -7.0 and -5.3 kcal mol-1 , respectively. Additionally, the degradation half-lives of S- and R-pydiflumetofen in three vegetables (cucumber, eggplant, and cowpea) under field conditions were 2.56-3.12 days and 2.48-2.76 days, respectively, which reveals that R-pydiflumetofen degrades faster than S-pydiflumetofen. CONCLUSION: Based on the results obtained, R-pydiflumetofen not only exhibited a higher bactericidal activity, but also posed fewer residual risks in the environment. The mechanism of the stereoselective bioactivity was correlated with the stereoselective inhibition activity of the target enzyme and affected the cell membrane permeability and the production of exopolysaccharide and oxalic acid. This research could provide a foundation for the systematic evaluation of pydiflumetofen from an enantiomeric view. © 2021 Society of Chemical Industry.

Stereostructure-activity mechanism of cyproconazole by cytochrome P450 in rat liver microsomes: A combined experimental and computational study.

Cyproconazole (CPZ), representing the chiral triazole fungicides, is widely used in the pharmaceutical and agricultural fields. To clarify its potential adverse effects on the generalized CYP-mediated processes within mammalian, a comparative experimental and computational approach was employed to investigate the CYP-mediated metabolism processes of CPZ stereoisomers in rat liver microsomes (RLMs). The depletion rate of CPZ stereoisomers in vitro incubation system with RLMs followed the order RR-> SS-> SR-> RS-CPZ. The results of kinetic assays were in line with the depletion rate results. Further inhibition assay confirmed the stereoselective metabolism of CPZ stereoisomers by different CYP isoforms. Molecular dynamics (MD) simulation revealed the stereoselective metabolism mechanism. Several hydrogen bonds and π-stacking restrict the position of CPZ isomers in the active cavity of CYPs so that the 4'-nitrogen on the triazole ring can bind closely to the heme of CYP, which results in the metabolism of CPZ isomers. By combining the computational and experimental approaches, the structure-activity relationship of CPZ and CYP was elucidated, and this method can be further applied to predict the degree of uncertainty in the process of xenobiotic biotransformation of triazole fungicides and serve as a basis for risk assessment.

Changes in soil and rat gut microbial diversity after long-term exposure to the chiral fungicide epoxiconazole.

In previous articles, it was found that epoxiconazole enantiomers can persist for a long time in the environment, causing severe environmental damage. Herein, we investigated alterations in the soil microbial community and rat gut microbiota after six weeks of treatment with rac-epoxiconazole or one of its enantiomers. The selected concentrations were 1, 2, and 6 times greater than the maximum residue limits (MRLs). The rat gut microbiota relative abundance in the feces significantly changed following exposure to rac-epoxiconazole or one of its enantiomers. At the phylum level, in the R,S-, S,R-epoxiconazole, and rac-treated groups, Firmicutes presented the greatest decrease in abundance; however, Spirochaetes presented the greatest increase in abundance in the rac- and S,R-epoxiconazole-treated groups. In response to R,S-epoxiconazole, Epsilonbacteraeota presented the greatest increase in abundance. In soil samples treated with epoxiconazole, the relative abundance of the soil bacterial community also changed. Proteobacteria presented the greatest decrease in abundance in the S,R- and rac-treated samples. However, Firmicutes presented the greatest increase in abundance. In the R,S-treated soil samples, the situation was the opposite. In general, prolonged exposure to epoxiconazole at high concentrations could initiate noticeable alterations in rat gut microbiota and soil microbial diversity. R,S-epoxiconazole had improved bioactivity and less toxic effects at relatively low concentrations. Therefore, we recommend using R,S-epoxiconazole at a relatively low concentration, which is better for environmental safety.

Enantioselective disposition and metabolic products of isofenphos-methyl in rats and the hepatotoxic effects.

Isofenphos-methyl (IFP), a chiral organophosphorus pesticide, is one of the main chemicals used to control underground insects and nematodes. Recently, the use of IFP on vegetables and fruits has been prohibited due to its high toxicity. In this study, we investigated the enantioselective distribution and metabolism of IFP and its metabolites, namely, isofenphos-methyl oxon (IFPO) and isocarbophos oxon (ICPO), in male Sprague Dawley (SD) rats. Forty eight hours (48 h) after exposure, ICPO was the main detectable compound in blood (up to 75%) and urine (up to 77%), and we found that (S)-ICPO was significantly more stable than (R)-ICPO (p < 0.05). Therefore, (S)-ICPO was proposed as a suitable candidate biomarker for the biomonitoring of IFP in human urine and blood. After 48 h exposure, 21.2-41.0%, 4.1-15.1%, and 8.6-18.7% of dosed IFP was detected in the liver of racemic, R and S enantiomer-exposed rats, respectively, and R-IFP and R-IFPO showed a faster degradation (p < 0.05). Our results showed that after one week of consecutive exposure to IFP, ICPO was accumulated in the liver of rats in both racemic and enantiopure groups (no difference between the groups, p > 0.05). We found that cytochrome P450 (CYP) (i.e. CYP2C11, CYP2D2 and CYP3A2 enzymes and carboxylesterases) is responsible for the enantioselective metabolism of IFP in liver. In addition, rats exposed to (S)-IFP exhibited hepatic lipid peroxidation, liver inflammation and hepatic fibrosis. This study provides useful information and a reference for the biomonitoring and risk assessment of IFP and organophosphorus pesticide exposure.

A novel mutation Asp-2078-Glu in ACCase confers resistance to ACCase herbicides in barnyardgrass (Echinochloa crus-galli).

Multiple-herbicide resistance (MHR) in barnyardgrass (Echinochloa crus-galli) is a threat to rice production. The Ala-205-Val mutation in acetolactate synthase (ALS) conferred resistance to several ALS inhibitors in the E. crus-galli population AXXZ-2; consequently, ALS-inhibitors were unable to control this noxious weed species. In the present study, the sensitivity to acetyl-coenzyme A carboxylase (ACCase) herbicides and other herbicides having different modes of action was evaluated to determine an effective strategy for chemical weed control. Compared with that of the reportedly sensitive population JLGY-3, the AXXZ-2 population showed differential resistance to three ACCase-inhibitors (cyhalofop-butyl, fenoxaprop-P-ethyl, and pinoxaden), in addition to quinclorac and pretilachlor. A novel substitution (Asp-2078-Glu) in ACCase was detected as the main target-site resistance mechanisms in the AXXZ-2 population. Structural modeling of the mutant ACCase protein predicted that Asp-2078-Glu confers resistance to three ACCase inhibitors by reducing the binding affinity between them and the ACCase protein. To the best of our knowledge, this is the first study to report that the novel Asp-2078-Glu mutation confers resistance to several ACCase inhibitors. Target-site mutations in ALS and ACCase were detected in this MHR population. Except for quinclorac, pretilachlor, ALS inhibitors, and the three ACCase inhibitors, a number of herbicides remain effective in controlling this MHR E. crus-galli population.

Stereoselective uptake and metabolism of prothioconazole caused oxidative stress in zebrafish (Danio rerio).

Prothioconazole (PTA) is a novel, broad-spectrum, chiral triazole fungicide that is mainly used to prevent and control the disease of cereal crops. However, the adverse effects of PTA and its major metabolite on nontarget organisms have aroused wide concern. In the present work, the acute toxic of the metabolite prothioconazole-desthio (PTA-desthio), with an LC50 of 1.31 mg L-1, was 3.5-fold more toxic than the parent compound, indicating that the metabolism of PTA in zebrafish was toxic. The stereoselective uptake and metabolism of PTA and PTA-desthio in zebrafish was firstly investigated using LC-MS/MS. Remarkable enantioselectivity was observed: S-PTA and S-PTA-desthio were preferentially uptake with the uptake rate constants of 8.22 and 8.15 d-1 at exposure concentration of 0.5 mg L-1, respectively, and the R-PTA-desthio were preferentially metabolized. PTA-desthio was rapidly formed during the uptake processes. The antioxidant enzyme activities in the zebrafish changed significantly, and these effects were reversible. A metabolic pathway including 13 phase I metabolites and 2 phase II metabolites was firstly proposed. A glucuronic acid conjugate and sulfate conjugate were observed in zebrafish. The results of this work provide information that highlights and can help mitigate the potential toxicity of PTA to the ecological environment and humans health.

Detrimental Effects of Multiple Mutations in Position 240 of Fusarium graminearum ß2-Tubulin.

Fusarium graminearum causes Fusarium head blight (FHB), a destructive disease of cereal crops worldwide. Carbendazim (methylbenzimidazol-2-ylcarbamate [MBC]) is widely used for controlling FHB. A previous study showed that the F240L mutation in the ß2-tubulin of F. graminearum (Fgß2-tubulin) confers hypersensitivity to MBC. Whether the substitution of phenylalanine by other amino acids in position 240 of the Fgß2-tubulin gene also confers hypersensitivity to MBC is unknown. Moreover, the biological fitness of these mutants is poorly understood. In this study, we substituted position 240 of Fgß2-tubulin with other amino acids. We found that the F240A, F240E, F240I, and F240Y mutations in Fgß2-tubulin could also confer F. graminearum hypersensitivity to MBC, although the effective concentration resulting in 50% inhibition (EC50) differed among the mutations. The F240G mutation, in contrast, decreased the sensitivity to MBC. In addition, a molecular docking assay indicated that the binding affinity between Fgß2-tubulin and MBC were increased by the F240A, F240E, F240I, and F240Y mutations but decreased by the F240G mutation. All mutants had normal conidial morphology, but the growth rates and pathogenicity of the F240A, F240E, F240G, F240I, and F240Y mutants were significantly decreased. Moreover, the F240A and F240G mutants produced twisted hyphae. In addition, microtubules were sparse and rarely observed in ß2F240A-EGFP, ß2F240E-EGFP, and ß2F240G-EGFP. These results indicate that position 240 (phenylalanine) is not only vital to the function of Fgß2-tubulin but also plays an important role in regulating the sensitivity of F. graminearum to MBC. Any mutation in this site would be detrimental to survival.

Enantioselective bioactivity, toxicity, and degradation in different environmental mediums of chiral fungicide epoxiconazole.

To clarify the environmental behaviour and bioactivity of epoxiconazole enantiomers, an integrated assessment has been done. The degradation in soil, water, and river-sediments were studied. The toxicity to Chlorella vulgaris and Daphnia magna was also examined. The bioactivity to plant-pathogens and molecular docking to CYP51 were investigated. The obtained results showed that the half-lives of R,S-(+)- and S,R-(-)-epoxiconazole were 38.8 and 21.2 days in Jiangsu soil, 43.2 and 22.7 days in Jiangxi soil, 29.1 and 21.3 days in Jilin soil, 43.5 and 32.7 days in anaerobic Jilin soil, 12.3 and 10.1 days in river sediments, and 33.2 and 9.3 days in river water, respectively. Maximum EF was 0.36 in Yangzi-river water. No enantioselective degradation was found in sterilized conditions. The EC50 to C. vulgaris after 48 h was 27.78 mg L-1, and 18.93 mg L-1 for R,S-(+)-, and S,R-(-)-epoxiconazole, respectively. The LC50 to D. magna was 4.16 mg L-1, and 8.49 mg L-1 for R,S-(+)-, and S,R-(-)-epoxiconazole, respectively. R,S-(+)-epoxiconazole bioactivity was 1.3-7.25 times higher than S,R-(-)-epoxiconazole. In conclusion, R,S-(+)- has higher bioactivity and higher environmental toxicity. In opposite, S,R-(-)- has lower environmental toxicity and lower bioactivity. R,S-(+)-epoxiconazole use is recommended with lower concentrations, which is appropriate for environment safety.

Stereoselective bioactivity, toxicity and degradation of the chiral triazole fungicide bitertanol.

BACKGROUND: The chiral pesticide bitertanol has been widely used in the prevention and treatment of fungal diseases on many crops. However, research on bitertanol at the stereoisomer level has not been reported. Here, we study the stereoselective bioactivity, toxicity, and degradation of this pesticide under laboratory and field conditions. RESULT: (1S,2R)-Bitertanol was the most effective stereoisomer, showing 4.3-314.7 times more potent bioactivity than other stereoisomers against eight target pathogenic fungi. (1S,2R)-Bitertanol showed 10.2 times greater inhibition of Botrytis cinerea spore germination than (1R,2S)-bitertanol. According to the receptor-drug docking results, the distances from the nitrogen atom in the heterocycle of (1S,2R)-, (1R,2S)-, (1R,2R)-, and (1S,2S)-bitertanol to the central Fe + atoms in the ferriporphyrin were 2.5, 3.8, 2.6, and 3.8 Å, respectively. (1S,2S)-Bitertanol was 1.6-2.7 times more toxic than (1R,2R)-bitertanol to Chlorella pyrenoidosa. The half-lives of (1R,2S)-, (1S,2R)-, (1R,2R)-, and (1S,2S)-bitertanol were 3.7, 4.1, 4.1, and 4.8 d, respectively, in tomato. CONCLUSION: The stereoselective bioactivity, toxicity, and degradation for bitertanol were first studied here. (1S,2R)-Bitertanol was a high efficiency and low toxicity stereoisomer. Moreover, the stereoselective bioactivity among all stereoisomers correlated with the binding distances and calculated energy differences between stereoisomers and the target protein. This study also provides a foundation for a systematic evaluation of bitertanol at the stereoisomer level. © 2019 Society of Chemical Industry.

Novel Liquid Chromatography-Tandem Mass Spectrometry Method for Enantioseparation of Tefluthrin via a Box-Behnken Design and Its Stereoselective Degradation in Soil.

A simple and eco-friendly dispersive solid-phase extraction method coupled with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was developed for the determination of the chiral pesticide tefluthrin in food and environmental samples. The response surface methodology was applied to optimize separation conditions. The elution order of tefluthrin enantiomers was Z-cis-(1S,3S)-(-)-tefluthrin and Z-cis-(1R,3R)-(+)-tefluthrin on a Lux Cellulose-1 chiral column was identified via a polarimeter and vibrating circular dichroism. The average recoveries in five matrices ranged from 76.9 to 107.6%, with intraday relative standard deviations (RSDs) less than 15.6% and interday RSDs less than 12.5% for two enantiomers. The enantioselective degradation was investigated via laboratory incubation experiments. Slightly enantioselective degradation was observed under aerobic conditions; (1S,3S)-tefluthrin degraded preferentially with the enantiomer fraction value of 0.57 at 120 days of incubation. No remarkable enantioselective degradation was observed under anaerobic and sterile conditions. It was the first time that pyrethroid pesticides were determined at the enantiomer levels via UPLC-MS/MS. This novel method was successfully applied for the enantioselective analysis of tefluthrin enantiomers in authentic samples, indicating its efficacy in investigating the environmental stereochemistry of tefluthrin in the food web and environment. It is of crucial importance to improve risk assessment and regulation of chiral pesticides in an agricultural system.

Stereoselective bioactivity of the chiral triazole fungicide prothioconazole and its metabolite.

Chiral triazole fungicides have played a significant role in plant pathogen control. Although their enantiomers often exhibit different bioactivity, the mechanism of the stereoselectivity has not been well studied. The stereoselective bioactivity and mechanisms of prothioconazole and its chiral metabolite against plant pathogenic fungi were investigated. The results indicated that the metabolite exerted more fungicidal activities than the activities of the parent compound. R-Prothioconazole and R-prothioconazole-desthio were 6-262 and 19-954 times more potent against pathogenic fungi than the S-enantiomers, respectively. The R-enantiomers were more effective than in inhibiting the biosynthesis of ergosterol and deoxynivalenol the S-enantiomer. Homology modeling and molecular docking suggested that the R-enantiomers of prothioconazole and prothioconazole-desthio possessed better binding modes than S-enantiomers to CYP51B. Moreover, exposure to prothioconazole and its metabolite enantiomers significantly changed the transcription levels of the CYP51 (CYP 51A, CYP51B, CYP 51C) and Tri (Tri5, Tri6, Tri12) genes. The results showed that application of the R-prothioconazole could require a smaller application amount to eliminate the carcinogenic mycotoxins and any environmental risks.

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.