Comprehensive study of pydiflumetofen in Danio rerio: Enantioselective insight into the toxic mechanism and fate

Elucidating enantioselective fate and sensitive biomarkers in zebrafish of chiral pesticide fenpropidin: Insights into metabolic pathways and hazard assessment

Fenpropidin (FPD), a widely utilized chiral fungicide, has been detected in aquatic environments. This study systematically evaluated the bioaccumulation, depuration, biotransformation, and sensitive biomarkers of FPD enantiomers in zebrafish to assess their environmental risks. Compared with S-FPD, R-FPD demonstrated a higher rate of enrichment and an increased level of bioaccumulation. The half-lives of R-FPD and S-FPD were 0.49 ± 0.01 and 0.91 ± 0.02 days at 0.05 mg/L and 1.65 ± 0.01 and 1.85 ± 0.03 days at 0.5 mg/L. Nontarget metabolism analysis identified nine metabolites, primarily formed through hydroxylation, oxidation, dehydration, glutathione conjugation, and glucuronidation pathways. Some metabolites exhibited high toxicity, underscoring the necessity for continuous monitoring of their toxicological effects and environmental fate in risk assessments. The toxicity of S-FPD in zebrafish was 1.21 times greater than that of R-FPD. Furthermore, this study identified sensitive markers for the enantiomers at both protein and transcriptional levels using an integrated biomarker response approach. S-FPD exhibited increased sensitivity to apoptosis and metabolic gene expression, while R-FPD showed greater sensitivity to antioxidant kinase activity. These findings facilitate timely monitoring of environmental pollution caused by FPD enantiomers. This study provides critical insights for assessing potential risks associated with pesticide exposure to human health.

Assessing the stereoselective bioactivity and biotoxicity of penthiopyrad in soil environment for efficacy improvement and hazard reduction

Penthiopyrad, a chiral pesticide, has been widely used in agricultural production. However, systematic evaluation of stereoselective bioactivity and biotoxicity of penthiopyrad in soil environment is insufficient. In this study, the stereoselective bioactivity of penthiopyrad against three soil-borne disease pathogens and its stereoselective biotoxicity to soil non-target organisms were investigated. The present results showed that the bioactivities of S-penthiopyrad were 546, 76 and 1.1-fold higher than those of R-penthiopyrad due to their different interaction modes with SDH in different target pathogens. S-penthiopyrad was more persistent in the soil environment and had stronger bioaccumulation than R-penthiopyrad. The accumulation of penthiopyrad in earthworms induced the response of detoxification system, resulting in the significant increases in the activity of detoxifying enzymes, such as GST, CarE, and CYP450. Additionally, both S-penthiopyrad and R-penthiopyrad induced cell apoptosis, intestinal damage and differentially expressed genes in earthworms, especially S-penthiopyrad. Furthermore, S-penthiopyrad has stronger binding capacity with COL6A and ACE proteins, while R-penthiopyrad has stronger binding capacity with CYP450 family proteins, which may be the main reason for the differences in biotoxicity between PEN enantiomers. Considering the differences in bioactivity and biotoxicity of penthiopyrad enantiomers, as well as the modes of action of pesticides on target and non-target organisms, S-penthiopyrad has greater potential for future development.

Comprehensive study of chiral herbicide flusulfinam uptake, translocation, degradation, and subcellular distribution in rice (Oryza sativa L.)

The biological behavior of flusulfinam, a potential commercial chiral herbicide for rice, has not been well explored. Herein, the uptake of chiral flusulfinam by rice and its transport, degradation, and subcellular distribution in rice (Oryza sativa L.) were investigated. The enantiomeric fraction (EF) in roots was 0.54 during 0 d to 7 d in hydroponic laboratory conditions. The bioconcentration factor of flusulfinam enantiomers was 2.1, suggesting an absence of observed enantioselectivity in the absorption process. Notably, the EF in the shoots decreased to 0.35 on the 7th day. The translocation factors of R- and S-flusulfinam were 0.12 and 0.27, respectively, indicating a preferential transfer of the S-flusulfinam from the root to the shoot. Flusulfinam was identified in the root after spraying. The translocation factors of R- and S-flusulfinam were consistently similar, signifying the capacity for downward movement without enantioselectivity. Interestingly, the degradation half-lives of R- and S-flusulfinam in the total plant were 5.50 and 5.06 d (p < 0.05), respectively, supporting the preferential degradation of S-flusulfinam throughout the total plant. Flusulfinam primarily entered the roots via the apoplastic pathway and was subsequently transported within the plant through aquaporins and ion channels. The subcellular distribution experiment revealed the predominant accumulation of flusulfinam enantiomers in soluble components (84%) with no enantioselectivity in these processes. There was upregulation lipid transfer protein-2 and carboxylesterases15 genes, which could explain the preferential transport and degradation of S-flusulfinam. This study is important in assessing the environmental risk associated with flusulfinam and ensuring food safety.

Systemic evaluation of novel acaricide hexythiazox for bioactivity improvement and risk reduction at the enantiomer level

Traditional risk assessments of chiral pesticides mainly depend on racemic form, which is often incomprehensive. This study conducted systemic investigations on the bioactivity, toxicity, and ecotoxicological effects of hexythiazox (HTZ) at the enantiomer level. The elution order and absolute configuration of HTZ enantiomers were determined. (4R, 5R)-(+)-HTZ exhibited 708 and 1719 times higher bioactivity against Tetranychus cinnabarinus and Tetranychus urticae eggs than (4S, 5S)-(-)-HTZ, respectively. Molecular docking indicated greater interactions between (4R, 5R)-(+)-HTZ and chitin synthase leading to higher bioactivity of (4R, 5R)-(+)-HTZ. However, (4S, 5S)-(-)-HTZ induced greater changes in protein and malondialdehyde content, and antioxidant and detoxification enzyme activities than (4R, 5R)-(+)-HTZ in earthworms. Furthermore, integrated biomarker response results indicated (4S, 5S)-(-)-HTZ exhibited higher toxic effects on earthworms than (4R, 5R)-(+)-HTZ. Finally, significant differentially expressed genes (DEGs) were observed in earthworms after exposure to (4R, 5R)-(+)-HTZ and (4S, 5S)-(-)-HTZ, respectively. These DEGs were mainly enriched in glycolysis/gluconeogenesis and purine metabolism pathways in earthworms. Additionally, six metabolism pathways were also enriched, including pyruvate metabolism, fatty acid biosynthesis, oxidative phosphorylation, citric acid cycle, fatty acid degradation, and ATP-binding cassette transporters. These findings suggest that earthworms exhibited enantiomer-specific responses to (4R, 5R)-(+)-HTZ and (4S, 5S)-(-)-HTZ. This study provides systemic insight into the toxicity mechanism of HTZ at the enantiomer level and the potential to develop (4R, 5R)-(+)-HTZ as a high-efficiency and low-risk pesticide.

Enantioselective fate and risk assessment of chiral fungicide pydiflumetofen in rice-fish and wheat farming systems

Fungicides have been widely used for reducing the losses caused by plant diseases. Rice and wheat are the most basic food crops, and the potential risks after applying fungicides are worthy of attention. Especially rice-fish farming system is an ecological symbiosis system that is beneficial to both environmental and ecological protection. However, the application of pesticides will stress the ecosystem, and the pesticide residues in rice and fish would be transmitted along the food chain, which is harmful to human health. Here, the enantioselective behaviors of chiral pydiflumetofen in rice-fish and wheat farming systems were clarified. In the rice-fish farming system, pydiflumetofen enantiomers were preferentially attached to the plants, entering the paddy water and settling into the paddy soil, and then accumulating and dissipating in the fish. With the growth of rice, it was transported to rice fruits. The wheat farming system was similar. Enantioselective dissipation occurred in carp (Cyprinus carpio), brown rice and wheat soil, and S-(+)-pydiflumetofen was preferentially dissipated. In other words, R-(-)-pydiflumetofen showed higher concentrations, especially in carp, which meant R-(-)-pydiflumetofen was more easily accumulated in the environment, and posed a greater potential risk to the farming system. The pydiflumetofen residues in brown rice and wheat were lower than MRLs from the EFSA (0.02 mg/kg) and eCFR (0.3 mg/kg), respectively. What deserves attention is that the MRL of pydiflumetofen in fish is not clear. Meanwhile, pydiflumetofen in paddy soil and wheat soil had a persistent residual effect, and the risks could not be ignored. Combined with the previous research, developing S-(+)-pydiflumetofen products will help to reduce the dosage and reduce the risks to environment and people. This study evaluated the environmental fate and risk of chiral pydiflumetofen from the perspective of farming system, and would provide data support for its rational use and risk assessment.

Comprehensive evaluation of chiral sedaxane with four stereoisomers for risk reduction: Bioactivity, toxicity, and stereoselective dissipation in crop planting systems

A comprehensive evaluation of chiral pesticide at the stereoisomeric level is an effective strategy to improve efficiency and reduce risk on foods. For chiral sedaxane with four stereoisomers, there were 517-1013 fold differences in bioactivity for three kinds of phytopathogens and 3.73 fold differences in toxicity against model organism (Danio rerio) between the best (trans-1R2S-sedaxane) and worst stereoisomer (cis-1S2S-sedaxane). Trans-1R2S-sedaxane had the strongest affinity with the active site than other stereoisomers, which might contribute to the highest bioactivity. Trans-sedaxane was 28.2-331 fold more effective than cis-sedaxane. The dissipation half-lives of sedaxane stereoisomers ranged from 3.28 to 30.7 d in the test crops and soils. Trans-1S2R-sedaxane and cis-1S2S-sedaxane were preferentially dissipated in corn plants, while the preferential dissipation of trans-1R2S-sedaxane was found in wheat plants, potato plants and corn soil. The preferential dissipation of trans-sedaxane in corn plants, wheat plants, potato plants and corn soil would be environmentally friendly.

Stereoselectivity of paclobutrazol enantiomers to oxidative stress in wheat

Chiral pesticides have the special chiral structures, so enantioselective biological effects are usually observed in living organisms. Current study used paclobutrazol as a case study and explored the enantioselective degradation and oxidative stress effect on wheat. The results demonstrated that the degradation of R-paclobutrazol was faster than S-paclobutrazol significantly and improved the content of MDA and O2 - in wheat plants, which proved that the R-paclobutrazol induced oxidative damage in wheat, showing selective biological effects, and S-paclobutrazol was friendly to wheat. This study provided a theoretical basis for the selective activity of chiral pesticides and the development of chiral pesticide monomers.