Comprehensive evaluation of novel fungicide benzovindiflupyr at the enantiomeric level: Bioactivity, toxicity, mechanism, and dissipation behavior

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.

Enantioselective Metabolism of Chiral Fungicide Prothioconazole by Mycobacterium sp. Y-3 and Its Bioaugmentation

Prothioconazole (PTC) is a kind of chiral triazole fungicide widely used in agricultural production, which can easily cause residual contamination and chiral selective toxicity. Microorganisms are the main participants involved in pollutant degradation in the environment. However, studies on the microbial enantioselective degradation of PTC and bioaugmentation of PTC-contaminated soil are still scarce. Herein, we isolated an efficient PTC-degrading strain, Mycobacterium sp. Y-3. Strain Y-3 preferentially metabolized (R)-PTC over (S)-PTC; the degradation rate of (R)-PTC was 2.5 times that of (S)-PTC. The T1/2 values of 20-80 μM (Rac)-/(S)-/(R)-PTC after treatment with strain Y-3 were 4.1-7.1 h at 37 °C and pH 5.0. The addition of glutamine could significantly enhance the PTC degradation ability of strain Y-3. Strain Y-3 metabolized PTC via methylation to form prothioconazole-S-methyl, the detoxification pathway for PTC. In bioaugmentation experiments, strain Y-3 eliminated PTC residues in the soil within 12 days. High-throughput sequencing analysis indicated that strain Y-3 colonized well in the soil. Inoculation with strain Y-3 reduced soil microbial community diversity and richness, while the bioaugmentation treatment enhanced the soil microbial community associations. These findings provide new insights into the enantioselective microbial metabolism of chiral PTC and in situ bioaugmentation of PTC-contaminated soils.

One-Pot Synthesis of Chiral Succinate Dehydrogenase Inhibitors and Antifungal Activity Studies

In this work, a series of novel chiral succinate dehydrogenase inhibitors (SDHIs) are synthesized through a one-pot Rh-catalyzed asymmetric hydrogenation-condensation strategy. This method exhibits high efficiency (up to 1000 Ton, 94% yield over two steps), high stereoselectivity (up to 99% ee), and broad substrate scope (68 examples in total), providing a superior pathway for the synthesis of such chiral fungicides. Mechanistic studies indicate that the amino group at the 2-position of the phenyl ring acts as an activating group, enhancing the reactivity and stereoselectivity control of the reaction. Furthermore, these molecules exhibit broad-spectrum and highly effective antifungal biological activity. Notably, enantiomers show significant differences in both in vitro and in vivo fungi-inhibiting experiments. Especially, (S)-5f showcases an antifungal activity against Botrytis cinerea (EC50 = 0.48 µm) that is much higher than that of its R enantiomer (EC50 = 36.7 µm). Molecular docking calculations, molecular dynamic simulation, enzyme activity assays, and ligand-target interaction experiments demonstrate that (S)-5f (ΔGMM-PBSA = -18.86 kcal mol-1, KD = 6.04 µm) inhibits succinate dehydrogenase more effectively than its R enantiomer (ΔGMM-PBSA = -13.01 kcal mol-1, KD = 8.5 µm). Moreover, the two enantiomers have significantly different effects on spore germination and the destruction of fungal phenotype.

Ecotoxicological impact of succinate dehydrogenase inhibitor (SDHI) fungicides on non-targeted organisms: a review

As the global population continues to grow, the use of pesticides to increase food production is projected to escalate. Pesticides are critical in plant protection, offering a powerful defense against fungal diseases such as apple scab, leaf spot, sclerotinia rot, damping off, sheath blight, and root rot, which threaten crops like cereals, corn, cotton, soybean, sugarcane, tuberous vegetables, and ornamentals. Succinate Dehydrogenase Inhibitor (SDHI) fungicides represent a novel class essential for controlling fungal pathogens and bolstering food security. However, the impact of SDHIs on non-target organisms, including freshwater and terrestrial invertebrates, crustaceans, and oligochaetes, remains insufficiently understood. Empirical studies indicate that SDHIs can induce mortality, mitochondrial dysfunction, oxidative stress, and developmental delays in non-target organims. Additionally, the environmental persistence of these compounds raises concerns about their potential for ecological disruption. The effects of SDHIs on pollinating species and the possible transgenerational transmission of harmful effects warrant further investigation. Comprehensive transcriptomic analyses are necessary to elucidate the molecular disturbances and adverse outcome pathways triggered by SDHIs. Furthermore, there are emerging concerns about the endocrine-disrupting potential of SDHIs in aquatic organisms. For the first time, this review aims to synthesize existing knowledge on the ecotoxicological impacts of SDHIs on non-target organisms and identify critical research directions to address the ecological challenges posed by their use.

Evaluation of Chiral Pesticide Chlorbufam at the Enantiomeric Level: Absolute Configuration, Separation, Herbicidal Activity, and Degradation in Soil

Chlorbufam is a photosynthesis inhibitor chiral herbicide with a pair of enantiomers, which is rarely a concern. In this work, the optically pure enantiomers of chlorbufam were first synthesized and characterized, and the enantioselective herbicidal activity and mechanism were studied. Chlorbufam enantiomers showed significant differences in bioactivity against Echinochloa crus-galli and Abutilon theophrasti, and R-(+)-chlorbufam was identified as the most active against the targeted organisms with higher bioactivity of 3.95 and 1.71 times than S-(-)-chlorbufam. Chlorbufam enantiomers exerted herbicidal activity by inhibiting photosynthesis according to the results of the determination of photosynthetic pigment contents and molecular docking. Additionally, a novel HPLC-MS/MS method was successfully developed and validated for the detection of chlorbufam enantiomers and further applied for the enantioselective degradation study in soil. As a result, chlorbufam was satisfactory enantioseparated with a resolution of 2.37 on a Chiralpak IH column using the mobile phase of acetonitrile and water (60:40, v/v). Good linearity for chlorbufam enantiomers was obtained with correlation coefficients ≥0.9990, and the recovery ranged from 74.1 to 119% with relative standard deviations ≤10.9% at three spiked levels. The degradation behaviors of chlorbufam enantiomers were significantly different, and S-(-)-chlorbufam was preferentially degraded. The findings encouraged the application of enantiopure R-(+)-chlorbufam herbicide to reduce dosage rates, decrease environmental risks, and protect human health.

Enantioselective Assessment of Etoxazole Enantiomers in Earthworms (Eisenia fetida): Bioaccumulation, Degradation, Transcriptome, and Oxidative Stress

This study systemically investigated the enantioselective bioaccumulation and degradation of etoxazole (ETZ) in earthworms along with the transcriptome and oxidative stress responses to ETZ enantiomer exposure. Based on the M-shaped bioaccumulation trends for ETZ enantiomers, R-ETZ was found to be preferentially bioaccumulated in earthworms. Sublethal toxicity analysis showed that S-ETZ induced greater changes in protein content, malondialdehyde content, detoxifying metabolic enzyme activity, and oxidative stress in earthworms, compared to those induced by R-ETZ. Integrated biomarker response analysis suggested that S-ETZ induced higher sublethal toxicity in earthworms than R-ETZ. Finally, transcriptomic analysis indicated that 845 and 314 genes were differentially expressed after R-ETZ and S-ETZ exposure, respectively, when compared to the nonexposed control group. Enrichment analysis indicated that these differentially expressed genes were primarily enriched in the digestion and absorption of proteins, lysosome, peroxisome, and peroxisome proliferator-activated receptor signaling pathways. These results suggest that earthworms exhibit distinct enantioselective responses to S-ETZ and R-ETZ. This study elucidates the enantioselective bioaccumulation, degradation, transcriptome, and oxidative stress characteristics of ETZ enantiomers in earthworms at the enantiomer level, offering a theoretical foundation to improve the risk assessment of ETZ in the soil-earthworm microsomes.

Stereoselective toxicity: Investigating the adverse effects of benzovindiflupyr on Xenopus laevis tadpoles

The novel chiral fungicide benzovindiflupyr exerts adverse effects on aquatic organisms; however, its toxic mechanism and stereoselectivity remain largely unknown. The current study aimed to investigate the enantioselective ecotoxicity mechanism of benzovindiflupyr in Xenopus laevis tadpoles using a 28-day exposure experiment. Results of the acute toxicity assessment indicated that (1S,4R)- and (1R,4S)-benzovindiflupyr exhibited high toxicity, with (1S,4R)- demonstrating approximately 75 times greater toxicity than (1R,4S)-. Compared to the latter, (1S,4R)-benzovindiflupyr significantly affected the growth, movement behavior, and oxidative stress of X. laevis tadpoles. The integration of metabolomics and transcriptomics data revealed that (1S,4R)-benzovindiflupyr disrupted the glycine, serine, and threonine metabolic pathways by modulating the activities of key enzymes. This dysregulation resulted in aberrant carbohydrate utilization, antioxidant pathways, and structural protein synthesis and degradation. Molecular docking confirmed that (1S,4R)-benzovindiflupyr exhibited superior docking activity with key enzymes, potentially contributing to its stereoselective toxicity. This study offers novel molecular perspectives on the enantioselective ecotoxicity mechanism of benzovindiflupyr toward aquatic organisms and highlights potential target proteins implicated in metabolic disorders.

Enantioseparation, Absolute Configuration, and Enantioselective Bioactivity Mechanism of the Chiral Fungicide Nuarimol

In this study, the nuarimol enantiomers were successfully baseline separated with Rs 1.70 by ultraperformance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The absolute configurations of the nuarimol enantiomers were confirmed as R-(+)-nuarimol and S-(-)-nuarimol. The enantioselective bioactivity assay indicated that R-(+)-nuarimol exhibited greater potency against seven phytopathogenic fungi, with values approximately 1.4-3.5 and 4.5-51.4 times higher than those of rac-nuarimol and S-(-)-nuarimol. The active contribution value of R-enantiomer was 82-98%, showing that R-(+)-nuarimol played a crucial role in bioactivity. Meanwhile, R-(+)-nuarimol exhibited stronger effects in increasing the cell membrane permeability, compromising the cell membrane integrity, and inhibiting ergosterol biosynthesis. Molecular docking analysis showed that R-(+)-nuarimol possessed a stronger binding affinity to sterol 14-α demethylase (CYP51) than S-(-)-nuarimol, with docking energies of -7.42 and -7.36 kcal/mol. This study contributes essential data for screening a high-activity enantiomer of nuarimol and provide guidance for reducing used dosage and increasing the efficiency of nuarimolAQ.

Adsorption-desorption and leaching behavior of benzovindiflupyr in different soil types

Benzovindiflupyr is a succinate dehydrogenase inhibitor fungicide that targets mitochondrial function for disease control. In this study, we investigated the adsorption-desorption and leaching behavior of benzovindiflupyr in eight soil types using the batch equilibrium method and the soil column leaching method. A Freundlich model (r2 > 0.9959) was used to better characterize the adsorption-desorption process in eight soil types, with adsorption coefficients (KF-ads) ranging from 2.303 to 17.886. KF-ads was significantly and positively correlated (p < 0.05) with the organic carbon content. High temperatures and increased initial pH of aqueous solutions led to a decrease in benzovindiflupyr adsorption in the soil. The adsorption was also influenced by factors such as ionic strength, humic acid, surfactant type, microplastic type, and particle size and concentration. Moreover, benzovindiflupyr exhibited low leachability in all four soils selected, but different leaching solutions affected the risk of benzovindiflupyr migration to groundwater. Overall, this study provides insights into the adsorption characteristics of benzovindiflupyr in different soils and provides key information for environmental risk assessment.

Study on the enantioselective behaviors, activity, toxicity and mechanism of novel SDHI fungicide benzovindiflupyr to reduce the environmental risks

Benzovindiflupyr (BEN) has emerged as one of the fastest-growing SDHI fungicides in recent years, but it is considered "very highly toxic" to aquatic fish, invertebrates and crustaceans (EC50 or LC50, 0.0035-0.056 mg/L, acute toxicity). The comprehensive study on bioactivity, toxicity, and degradation behaviors of BEN at the enantiomeric level would facilitate the development of a high-efficiency and low-risk application method. The bioactivities of 1S, 4R-(-)-BEN against five target pathogens (Alternaria alternata, Phoma multirostrata, Selerotium rolfsii, Magnaporthe oryzae, and Rhizoctonia solani) (EC50, 0.00562-0.329 mg/L, high-efficiency) were 6.7-1029 times higher than 1R, 4S-(+)-BEN, demonstrating significant enantioselectivity. For Danio rerio, 1S, 4R-(-)-BEN (LC50, 0.0360 mg/L, "very highly toxic") exhibited higher toxicity than 1 R, 4S-(+)-BEN, but the toxic interaction was concentration addition (TUrac, 0.94), indicating an enhanced toxicity in the presence of 1R, 4S-(+)-BEN. Molecular docking was employed to offer insights at the molecular level and elucidate the factors influencing enantioselectivity. The stronger binding affinity of 1S, 4R-(-)-BEN with SDH was in line with the quantitative experimental findings. The degradation of two BEN enantiomers in four different fruits followed the first-order degradation kinetics equation, and displayed enantioselectivity. The preferential degradation of 1R, 4S-(+)-BEN was found in pears and grapes, while varying enantioselectivity was found at different stages in tomatoes and watermelons. The residual concentrations of BEN in grapes were higher than the EU's MRL, which in the other three fruits were below the MRLs during the sampling. In conclusion, 1S, 4R-(-)-BEN proved to be the more effective monomer. Utilizing the pure monomer could not only reduce the dosage of racemate by about 44-59 %, but also mitigate the risk of introducing inefficient monomer into the environment (especially for fish).

Stereoselective study on chiral fungicide metconazole in four kinds of fruits: Absolute configuration, SFC-MS/MS enantioseparation, degradation and risk assessment

Metconazole is a novel chiral fungicide with two chiral carbon atoms, but the research on its stereoselective behavior is limited. Therefore, the stereoselective behaviors of metconazole in four fruits, including grape, peach, pear and jujube, were summarized in this study. After determining the absolute configuration of metconazole stereoisomers, a chiral separation method through supercritical fluid chromatography/tandem triple quadrupole mass spectrometry was first developed, which combined an improved QuEChERS method obtained the recoveries of 71.6-113 % with RSD ≤ 19.8 %. The LOD and LOQ were 4.30-95.9 and 10.5-143.2 ng/kg, respectively. Different stereoselective and diastereoselective behaviors were observed in four fruits. Dietary risk assessments of rac-metconazole were performed in populations with different ages and genders. Both acute (RQa, 0.0124-0.140 %) and chronic (HQ, 0.0234-0.0794 %) intake risks were acceptable. The results of this study would contribute to more complete risk assessments of metconazole and provide data for chiral studies.

Design and Enantioselective Synthesis of Chiral Pyranone Fused Indole Derivatives with Antibacterial Activities against Xanthomonas oryzae pv oryzae for Protection of Rice

A new class of chiral pyranone fused indole derivatives were prepared by means of N-heterocyclic carbene (NHC) organocatalysis and demonstrated notable antibacterial activity against Xanthomonas oryzae pv oryzae (Xoo). Bioassays showed that compounds (3S,4R)-5b, (3S,4R)-5d, and (3S,4R)-5l exhibited promising in vitro efficacy against Xoo, with EC50 values of 9.05, 9.71, and 5.84 mg/L, respectively, which were superior to that of the positive controls with commercial antibacterial agents, bismerthiazol (BT, EC50 = 27.8 mg/L) and thiodiazole copper (TC, EC50 = 70.1 mg/L). Furthermore, single enantiomer (3S,4R)-5l was identified as an optimal structure displaying 55.3% and 52.0% curative and protective activities against Xoo in vivo tests at a concentration of 200 mg/L, which slightly surpassed the positive control with TC (curative and protective activities of 47.2% and 48.8%, respectively). Mechanistic studies through molecular docking analysis revealed preliminary insights into the distinct anti-Xoo activity of the two single enantiomers (3S,4R)-5l and (3R,4S)-5l, wherein the (3S,4R)-configured stereoisomer could form a more stable interaction with XooDHPS (dihydropteroate synthase). These findings underscore the significant anti-Xoo potential of these chiral pyranone fused indole derivatives, and shall inspire further exploration as promising lead structures for a novel class of bactericides to combat bacterial infections and other plant diseases.

Stereoselective, Diastereoselective Dissipation and Risk Assessment of Chiral Metconazole in Soybean, Peanut, Cabbage, Celery, Tomato, and Soil

The stereoselective behaviors and dietary risks of metconazole (MZE) in soil and five vegetables were investigated. The results showed that there was species-specific stereoselective and diastereoselective dissipation, and the half-lives ranged from 0.69 to 8.17 days. cis-(+)-1S,5R-MZE was preferentially dissipated in soybean pods, cabbages, celeries, and tomatoes, which was contrary to soybean plants and soil. trans-(+)-1R,5R-MZE was preferentially dissipated in peanut plants, peanut shells, celeries, and tomatoes, while trans-(-)-1S,5S-MZE was preferentially dissipated in soybean plants. cis-MZE was preferentially dissipated in the test vegetables and soil, except celery. The stereoisomeric excess changes were higher than 10%, indicating that the stereoselectivity and diastereoselectivity should be considered in the risk assessment of MZE in soybean plants, pods, and peanut plants. The acute and chronic dietary intake risks of rac-MZE for different groups of people were acceptable. The preferentially dissipated and high activity cis-(+)-1S,5R-MZE with lower toxicity might be suitable for application as monocase.