Stereoselective Separation of the Fungicide Bitertanol Stereoisomers by High-Performance Liquid Chromatography and Their Degradation in Cucumber

SFC-MS/MS enantioseparation, stereoselective behavior and risk assessment of the chiral pesticide bitertanol in four vegetables and soil

The stereoselective behavior and dietary risk of bitertanol in four vegetables and soil were studied. Firstly, the method for measuring bitertanol stereoisomers by SFC-MS/MS was established and optimized, and the analysis time was 5 min. In addition, cis-(+)-(1R,2S)-bitertanol and trans-(+)-(1R,2R)-bitertanol were preferentially dissipated in cabbage and pakchoi, while trans-(+)-(1S,2S)-bitertanol had a preferential dissipation in lettuce. For diastereoisomers, cis-bitertanol was dissipated with preference in the vegetables under test. The dissipation halflives of rac-bitertanol were as follows: pakchoi (0.57-0.74 days) < cabbage (0.87-1.07 days) < celery (1.32-1.63 days) < lettuce (1.75-2.37 days) < soil (22.5-24.7 days). Finally, the final residual concentrations of rac-bitertanol in lettuce (0.0128 mg/kg) and celery (0.0289 mg/kg) were higher than the maximum residue limit (MRL, 0.01 mg/kg), which should raise concern. The results of dietary risk assessment showed that both the chronic dietary risk and the acute dietary risk of rac-bitertanol in these test vegetables were negligible.

Comprehensive study of flusulfinam in paddy water-sediment microcosms: Enantioselective fate, degradation pathways, and toxicity assessment

Flusulfinam, a novel chiral herbicide, demonstrates effective weed control in paddy fields. Nevertheless, a comprehensive investigation into its environmental fate in paddy systems, particularly at the enantiomeric level, remains deficient. Herein, paddy water-sediment microcosms were constructed across four sites to explore the enantiomeric behavior of flusulfinam. Enantioselective environmental behavior results show S-flusulfinam was found to preferentially accumulate in sediment, while R-flusulfinam showed preferential degradation in water and the overall system. Following this, the metabolic pathway of flusulfinam in the microcosms was also proposed. Eight metabolites were identified for the first time, and the synthesis and quantification of main metabolites M299 and M100 further substantiated the proposed flusulfinam metabolic pathways. In addition, enantioselective of R-M299 was also found in the Anhui microcosms. As predicted by Toxicity Estimation Software Tool, acute toxicity assessments revealed that M299 and M100 exhibit lower toxicity toward Danio rerio larvae and Selenastrum capricornutumwere compared to flusulfinam. Then, Illumina sequencing revealed that the degradation of flusulfanam had a significant impact on the abundance of key microbial genera, including Anaeromyxobacter, Nitrospira, Reyranella, and Sphingomonas. Overall, this study offers novel insights into the enantioselective fate of flusulfinam in paddy water-sediment ecosystems, provides a valuable reference for the assessment of environmental and ecological risks associated with flusulfinam. Finally, the R-flusulfinam is considered the safer enantiomer, as evidenced by its preferential degradation in microcosms systems and our prior research highlighting the high efficacy and low toxicity characteristic of R-flusulfinam.

Enantioselective toxicity assessment of prothioconazole on earthworms (Eisenia foetida) in artificial soil environments

The chiral fungicide prothioconazole (PTZ) is extensively employed in agricultural practices, prompting serious concern due to its environmental impact. PTZ is prone to undergo metabolism, leading to the formation of chiral prothioconazole-desthio (dPTZ) in the environment. However, limited knowledge exists regarding its enantioselective behavior and toxicity towards invertebrate organisms in soil ecosystems. In this study, R-(-)- and S-(+)- PTZ enantiomers were individually synthesized, and their stereoselective toxicity effects on earthworms (E. foetida) were studied in artificial soil under environmentally relevant concentration exposures. The results showed a significant accumulation of dPTZ in earthworms, surpassing the levels of PTZ. Moreover, the concentration of S-(-)- dPTZ in earthworms was notably higher than that of R-(+)- dPTZ after exposure, reaching peak levels on day 14. Concurrently, oxidative stress induced by S-(+)- PTZ enantiomers in earthworms exhibited a substantial increase compared to R-(-)- enantiomers on day 14, indicating a higher ecological risk associated with the former in non-target organisms. Transcriptome analysis unveiled distinct impacts on earthworm physiology. S-(+)-PTZ exposure significantly affected energy metabolism, immune responses and digestive systems. In contrast, R-(-)-PTZ exposure influenced the synthesis of carbohydrates, proteins, and lipids. These insights contribute to understanding the complex interactions between PTZ enantiomers and soil-dwelling organisms, providing a scientific foundation for advancing the application of high efficiency, low toxicity PTZ monomer pesticides.

Immunochromatographic visualization detection platform for bitertanol in foods

As a widely used fungicide in agriculture, bitertanol (BIT) significantly affects hormone regulation leading to imbalance of homeostasis in vivo, which makes it necessary to monitor BIT residues in foods. In this research, a novel hapten derivation scheme was designed by analyzing the chemical structure of BIT to prepare an anti-BIT monoclonal antibody with high affinity, specificity and sensitivity (half inhibitory concentration of 4.78 ng/mL). Subsequently, a visualized gold immunochromatographic assay (GICA) platform was established based on antigen-antibody specific recognition, with a limit of detection of 0.06 mg/kg and 0.18 mg/kg in cucumber and tomato, respectively. GICA has spiked recoveries of 84.3 %-114.1 %, determines results are not significantly different from those of LC-MS/MS, and the complex purification treatments can be reduced during the detection process. Therefore, the developed GICA is a reliable, rapid, and sensitive method for on-site rapid monitoring of BIT in foods.

Dispersive magnetic solid phase extraction of triazole fungicides based on polybenzidine/magnetic nanoparticles in environmental samples

A polybenzidine-modified Fe3O4@SiO2 nanocomposite was successfully synthesized through a chemical oxidation method and employed as a novel sorbent in dispersive magnetic solid phase extraction (DMSPE) for the preconcentration and determination of three triazole fungicides (TFs), namely diniconazole, tebuconazole, and triticonazole in river water, rice paddy soil, and grape samples. The synthesis method involved a polybenzidine self-assembly coating on Fe3O4@SiO2 magnetic composite. Characterization techniques such as FT-IR, XRD, FESEM, EDX, and VSM were used to confirm the correctness of the synthesized nano-sorbent. The target TFs were determined in actual samples using the synthesized nanocomposite sorbent in combination with gas chromatography-flame ionization detection (FID). Several variables were carefully optimized , including the sample pH, sorbent dosage, extraction time, ionic strength, and desorption condition (solvent type, volume, and time). Under the optimized experimental conditions, the method exhibited linearity in the concentration range 5-1000 ng mL-1 for triticonazole and 2-1000 ng mL-1 for diniconazole and tebuconazole. The limits of detection (LOD) for the three TFs were in the range 0.6-1.5 ng mL-1. The method demonstrated acceptable precision with intra-day and inter-day relative standard deviation (RSD) values of less than 6.5%. The enrichment factors ranged from 248 to 254. Finally, the method applicability was evaluated by determining TFs in river water, rice paddy soil, and grape samples with recoveries in the range 90.5-106, indicating that the matrix effect was negligible in the proposed DMSPE procedure.

Isolation of Sphingomonas sp. AJ-1 and its enantioselective S-methylation of the triazole fungicide prothioconazole

Prothioconazole is a widely used chiral triazole fungicide, and its residue pollution has attracted wide attention in recent years. However, little is known about microbial metabolic processes of prothioconazole enantiomers. In this study, a prothioconazole-degrading strain, Sphingomonas sp. AJ-1, was isolated from activated sludge. The optimal temperature and pH for prothioconazole degradation by strain AJ-1 were 30 °C and 6.0, respectively, and the degradation rate of prothioconazole by strain AJ-1 was negatively correlated with the initial concentration. When supplemented with additional carbon source, the degradation rates of 10 mg/L (Rac)-/(S)-/(R)-prothioconazole by strain AJ-1 were 76.0 %, 100.0 % and 64.8 % within 6 d, respectively. The CS bond of prothioconazole was methylated to produce (S)-/(R)-prothioconazole-S-methyl by strain AJ-1, but the degradation rate of prothioconazole by strain AJ-1 with (S)-enantiomer was 2.54-fold of that with (R)-enantiomer. Moreover, the toxicity of (Rac)-prothioconazole-S-methyl was 5.57 times lower than that of (Rac)-prothioconazole to Pseudokirchneriella subcapitata. The results showed that strain AJ-1 had obvious enantioselective metabolism for prothioconazole, and this metabolism was a detoxification process. This study provides new insights into the enantioselective metabolism of the chiral fungicide prothioconazole in microorganisms.

Systematic evaluation of chiral pesticides at the enantiomeric level: A new strategy for the development of highly effective and less harmful pesticides

Over the past few decades, pesticides have been used in large quantities, and they pose potential risks to organisms across various environments. Reducing the use of pesticides and their environmental risks has been an active research focus and difficult issue worldwide. As a class of pesticides with special structures, chiral pesticides generally exhibit enantioselectivity differences in biological activity, ecotoxicity, and environmental behavior. At present, replacing the racemates of chiral pesticides by identifying and developing their individual enantiomers with high efficiency and environmentally friendly characteristics is an effective strategy to reduce the use of pesticides and their environmental risks. In this study, we review the stereoselective behaviors of chiral pesticide, including their environmental behavior, stereoselective biological activity, and ecotoxicity. In addition, we emphasize that the systematic evaluation of chiral pesticides at the enantiomeric level is a promising novel strategy for developing highly effective and less harmful pesticides, which will provide important data support and an empirical basis for reducing pesticide application.

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.

Ratiometric detection of p-nitrophenol and its derivatives using a dual-emissive neuron cell-like carbonized probe based on a ππ stacking quenching mechanism

p-Nitrophenol and its derivatives can cause serious harm to the health of mankind and the earth's ecosystem. Therefore, it is necessary to develop a novel and rapid detection technology for p-nitrophenol and its derivative. Herein, excellent water-soluble, large-size and dual-emissive neuron cell-analogous carbon-based probes (NCNPs) have been prepared via a solvothermal approach, using o-phenylenediamine as the only precursor, which exhibit two distinctive fluorescence (FL) peaks at 420 and 555 nm under 345 nm excitation. The NCNPs show a neuron cell-like branched structure, are cross-connected, and are in the range of 10-20 nm in skeleton diameter. Interestingly, their blue-green dual-colour fluorescence is quenched by p-nitrophenol or its derivative due to the specific mechanism of the ππ stacking interactions or internal filtration effect. Accordingly, a simple, rapid, direct and free-label ratiometric FL detection of p-nitrophenol is proposed. An excellent linear relationship shows linear regions over the range of 0.1-50 μM between the ratio of the FL intensity (FL555 nm/FL420 nm) and the concentrations of p-nitrophenol. The detection limit is as low as 43 nM (3σ). Importantly, the NCNP-based probe also shows acceptable repeatability and reproducibility for the detection of p-nitrophenol and its derivatives, and the recovery results for p-nitrophenol in real wastewater samples are favourable.

Enantioselective Detection, Bioactivity, and Degradation of the Novel Chiral Fungicide Oxathiapiprolin

Oxathiapiprolin is a novel chiral piperidine thiazole isooxazoline fungicide that contains a pair of enantiomers. An effective analytical method was established for the enantioselective detection of oxathiapiprolin in fruit, vegetable, and soil samples using ultraperformance liquid chromatography-tandem triple quadrupole mass spectrometry. The optimal enantioseparation was achieved on a Chiralpak IG column at 35 °C using acetonitrile and 0.1% formic acid aqueous solution (90:10, v/v) as the mobile phase. The absolute configuration of the oxathiapiprolin enantiomers was identified with the elution order of R-(-)-oxathiapiprolin and S-(+)-oxathiapiprolin by electron circular dichroism spectra. The bioactivity of R-(-)-oxathiapiprolin was 2.49 to 13.30-fold higher than that of S-(+)-oxathiapiprolin against six kinds of oomycetes. The molecular docking result illuminated the mechanism of enantioselectivity in bioactivity. The glide score (-8.00 kcal/mol) for the R-enantiomer was better with the binding site in Phytophthora capsici than the S-enantiomer (-7.50 kcal/mol). Enantioselective degradation in tomato and pepper under the field condition was investigated and indicated that R-(-)-oxathiapiprolin was preferentially degraded. The present study determines the enantioselectivity of oxathiapiprolin about enantioselective detection, bioactivity, and degradation for the first time. The R-enantiomer will be a better choice than racemic oxathiapiprolin to enhance the bioactivity and reduce the pesticide residues at a lower application rate.

A review on the stereospecific fate and effects of chiral conazole fungicides

The production and use of chiral pesticides are triggered by the need for more complex molecules capable of effectively combating a greater spectrum of pests and crop diseases, while sustaining high production yields. Currently, chiral pesticides comprise about 30% of all pesticides in use; however, some pesticide groups such as conazole fungicides (CFs) consist almost exclusively of chiral compounds. CFs are produced and field-applied as racemic (1:1) mixtures of two enantiomers (one chiral center in the molecule) or four diastereoisomers, i.e., two pairs of enantiomers (two chiral centers in the molecule). Research on the stereoselective environmental behavior and effects of chiral pesticides such as CFs has become increasingly important within the fields of environmental chemistry and ecotoxicology. This is motivated by the fact that currently, the fate and effects of chiral pesticides such as CFs that arise due to their stereoselectivity are not fully understood and integrated into risk assessment and regulatory decisions. In order to fill this gap, a summary of the state-of-the-art literature related to the stereospecific fate and effects of CFs is needed. This will also benefit the agrochemistry industry as they enhance their understanding of the environmental implications of CFs which will aid future research and development of chiral products. This review provides a collection of >80 stereoselective studies for CFs related to chiral analytical methods, fungicidal activity, non-target toxicity, and behavior of this broadly used pesticide class in the soil environment. In addition, the review sheds more light on mechanisms behind stereoselectivity, considers possible agricultural and environmental implications, and suggests future directions for the safe use of chiral CFs and the reduction of their environmental footprint.

Enantioseparation and stereoselective dissipation of the novel chiral fungicide pydiflumetofen by ultra-high-performance liquid chromatography tandem mass spectrometry

Pydiflumetofen is a novel and efficient broad-spectrum chiral fungicide consisting of a pair of enantiomers. A simple and sensitive chiral analytical method was established to determine the enantiomers of this chiral fungicide in food and environmental samples by ultra-high-performance liquid chromatography tandem triple quadrupole mass spectrometry (UHPLC-MS/MS) using QuEChERS method coupled with octadecylsilane-dispersive solid-phase extraction (C₁₈-dSPE) as extraction procedure. The specific optical rotation and the absolute configuration of the enantiomers were identified by polarimetry and electronic circular dichroism (ECD). The elution order of the pydiflumetofen enantiomers on Lux Cellulose-2 was S-(-)-pydiflumetofen and R-(+)-pydiflumetofen. The average recoveries of eleven matrices ranged from 71.3% to 107.4%. The intraday relative standard deviations (RSDs) were less than 11.8%, and the interday RSDs were less than 12.6% for the two enantiomers. Stereoselective dissipation in pakchoi and soil were observed: S-(-)-pydiflumetofen was degraded faster than R-(+)-pydiflumetofen in pakchoi, causing the enantiomer fraction (EF) of the enantiomers to change from 0.50 to 0.42 in 7 days. However, R-(+)-pydiflumetofen was degraded faster than S-(-)-pydiflumetofen in soil, causing the EF of the enantiomers to change from 0.49 to 0.52 in 21 days. This study provides a method for monitoring pydiflumetofen enantiomer residues, which is crucial for improving risk assessments and the development of chiral pesticides.

Size-controllable synthesis of zinc ferrite/reduced graphene oxide aerogels: efficient electrochemical sensing of p-nitrophenol

In this study, a nonaqueous method for the synthesis of size-controlled highly crystalline zinc ferrite/reduced graphene oxide (ZFO/rGO) aerogel was provided by using benzyl alcohol as the medium. In our findings, benzyl alcohol was introduced not only as the solvent, but the structure-directing agent and strong reducing agent during the nucleation and growth of ZnFe₂O₄ nanoparticles (NPs). The characterization analysis indicated that ZnFe₂O₄ NPs were immobilized on the multilayer rGO with a controllable size of 12 nm. Moreover, the 3D ZFO/rGO aerogel shows excellent electrochemical property as a facile electrochemical sensor for the detection of p-nitrophenol (p-NP). The ZFO/rGO electrochemical sensing offers the advantages of wide linear range (1-500 μmol l^-1), excellent sensitivity (23.985 mA mM^-1 cm^-2), good stability and selectivity (<8.8%). In addition, the possible reaction mechanism of 3D ZFO/rGO aerogel was explained during the detection process under acidic condition. Significantly, our results not only provided insight into the possible reaction mechanism of 3D ZFO/rGO nanocomposite, but proposed the way for the synthesis of highly crystalline materials through a benzyl alcohol-mediated method.

Stereoselective environmental behavior and biological effects of the chiral bitertanol

Bitertanol is a widely used chiral triazole fungicide. The stereoselective environmental behavior and biological effects of bitertanol are not clear. The present study evaluated the stereoselectivity of bitertanol, including its degradation in five typical soils (under laboratory controlled aerobic, anaerobic and sterilization conditions), metabolism in rat liver microsomes (RLM; in vitro), and the endocrine disruption effects on the estrogen receptor (ER) and thyroid hormone receptor (TR) using reporter gene assays. The results indicated that (1S,2R)-bitertanol and (1R,2S)-bitertanol had faster degradation rates in soil than the other stereoisomers. The half-lives of four bitertanol stereoisomers ranged from 9.1 d to 86.6 d in different soils under different conditions. (1S,2R)-bitertanol was preferentially metabolized in RLM. The molecular docking results confirmed the in vitro experiments that (1S,2R)-bitertanol had shortest binding distances and lowest energies with cytochrome P450 enzymes (CYPs). Four bitertanol stereoisomers showed stereoselective antagonistic effects on ER. Additionally, (1S,2R)-bitertanol and (1R,2S)-bitertanol exhibited antagonistic effects on TR. These results suggest that the use of pure (1S,2R)-bitertanol instead of the commercial stereoisomer mix, may help reduce environmental pollution and biological toxicity.

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.

Identification, Quantification, and Stereoselective Degradation of Triazole Fungicide Cyproconazole in Two Matrixes through Chiral Liquid Chromatography-Tandem Mass Spectrometry

Systematic investigation of cyproconazole, including absolute stereochemistry, fungicidal activity, quantification in two matrixes, and stereoselective degradation in cucumber, are conducted in this study. By virtue of vibrational circular dichroism (VCD) spectroscopy, absolute configurations of four stereoisomers were identified to be (2R,3R)-(+)-, (2R,3S)-(+)-, (2S,3S)-(-)-, and (2S,3R)-(-)-cyproconazoles. Then four stereoisomers exhibited stereoselective fungicidal activities against Fusarium graminearum Schw and Magnaporthe oryzae, and the order of fungicidal activity was (2S,3S)-(-)-stereoisomer > the stereoisomer mixture > (2S,3R)-(-)-stereoisomer > (2R,3R)-(+)-stereoisomer > (2R,3S)-(+)-stereoisomer. Moreover, chiral liquid chromatography-tandem mass spectrometry was used to identify and quantify cyproconazole stereoisomers in soil and cucumber matrixes. Good linearity (R² ≥ 0.99) and recoveries (86.79-92.47%, RSD ≤ 3.94%) for them were achieved, individually. Furthermore, stereoselective degradation of four cyproconazole stereoisomers was observed in cucumber and the order of degradation rate was (2R,3R)-(+)-cyproconazole > (2S,3S)-(-)-cyproconazole > (2R,3S)-(+)-cyproconazole > (2S,3R)-(-)-cyproconazole. We envision that such systematic assessments of chiral fungicides at an enantiomeric level would provide valuable information in future studies involving enantioselective physiological, metabolic, and toxicological activities.