Enantioselective environmental behavior and cytotoxicity of chiral acaricide cyflumetofen

Exploring the effects of the acaricide cyflumetofen on the vital organs of the honey bee Apis mellifera (Hymenoptera: Apidae) workers

Bees are important for maintaining ecosystems, pollinating crops and producing marketable products. In recent years, a decline in bee populations has been reported, with multifactorial causes, including the intensification of pesticide use in agriculture. Among pesticides, cyflumetofen is an insecticide and acaricide used in apple, coffee and citrus crops, whose main pollinator is the honey bee Apis mellifera. Therefore, this bee is a potential target of cyflumetofen during foraging. This study evaluated the histopathological and cytological damage in the midgut, hypopharyngeal glands and fat body of A. mellifera workers exposed to LC50 of cyflumetofen. The midgut epithelium of exposed bees presented cytoplasmic vacuolization, release of vesicles and cell fragments, which indicate autophagy, increased production of digestive enzymes and cell death, respectively. The cytological analysis of the midgut revealed the dilation of the basal labyrinth and the presence of spherocrystals in the digestive cells. The hypopharyngeal glands produced greater amounts of secretion in treated bees, whereas no changes were observed in the fat body. The results indicate that acute exposure to cyflumetofen negatively affect A. mellifera, causing damage to the midgut and changes in the hypopharyngeal glands, which may compromise the survival and foraging of this pollinator.

Absorption, distribution, metabolism, and elimination of epoxiconazole enantiomers in lizards (Eremias argus)

Epoxiconazole (EPX) is a world widely used chiral triazole fungicide in the agriculture field. The excessive application of this triazole may cause damage to lizards. However, limited information is known about the toxicokinetics of EPX on lizards. Our study aimed to investigate the enantioselective absorption, distribution, metabolism, and elimination (ADME) of EPX in lizards following low and high dose exposure (10 and 100 mg kg-1 bodyweitht (bw)). The results demonstrated that (+)-EPX was easier absorbed than (-)-EPX in lizard plasma. Both (+)-EPX and (-)-EPX were detected in the liver, gonad, kidney, skin, brain, and intestine, with (+)-EPX preferentially distributed in these tissues. The elimination of (-)-EPX was faster than that of (+)-EPX in lizard liver and kidney in the high dose groups. Chiral conversion was found between EPX enantiomers in lizard skin. Simultaneously, five metabolites including M2, M4, M10, M18 and M19 were detected in lizard liver and kidney after EPX enantiomers exposure. The relative concentrations of M2, M4, and M10 were higher in the liver and kidney of (-)-EPX groups than those produced from (+)-EPX groups. The metabolic enzymes CYP3A4 and SULT1A1 primarily mediated enantioselective metabolism of EPX. The conclusions drawn from this study significantly enhance our understanding of the enantioselective behaviors of chiral triazole fungicides in reptiles, offering essential guidance for assessing the risks associated with different enantiomers of triazole fungicides.

Fate characteristics and risk quantification of cyflumetofen from tomato cultivation to processing based on large-scale applications

Elucidating the fate characteristics of cyflumetofen and its main metabolite 2-TFMBA in tomato from cultivation to processing is crucial for safeguarding the environment and humans from hazardous effects. Cyflumetofen and 2-TFMBA could exist stably in tomato matrices for at least 343 days under frozen and dark conditions according to UHPLC-MS/MS, with a limit of quantitation of 0.001 mg/kg and retention time within 2.12 min. The occurrence, dissipation, and concentration variation of cyflumetofen were reflected by original depositions of 0.02-0.44 mg/kg, half-lives of 1.7-7.2 days, and terminal magnitudes of 0.005-0.30 mg/kg, respectively, with various influencing factors, e.g., climate conditions and tomato cultivars. Additionally, 13.5-59.3% of cyflumetofen was metabolized to 2-TFMBA, showing significant toxicological effects ranging from cultivation to processing. When the concentration decreased by 0.06 mg/kg, cyflumetofen was effectively removed by peeling, while washing was the recommended method for removing 2-TFMBA with a processing factor of 0.70. The comparative dietary risks of sum cyflumetofen were assessed for all life cycle populations using deterministic and probabilistic models. The risk quotients decreased to 1.3-4.8 times during the preparation of home canning tomato paste. Despite the low exposure risk, the potential health hazards of sum cyflumetofen should be considered, given its ubiquity and cumulative effects.

Enantioselective effects of chiral prothioconazole and its metabolites: Oxidative stress in HepG2 cells and lysozyme activity

Chiral pesticides may exhibit enantioselectivity in terms of bioconcentration, environmental fate, and reproductive toxicity. Here, chiral prothioconazole and its metabolites were selected to thoroughly investigate their enantioselective toxicity and mechanisms at the molecular and cellular levels. Multispectral techniques revealed that the interaction between chiral PTC/PTCD and lysozyme resulted in the formation of a complex, leading to a change in the conformation of lysozyme. Meanwhile, the effect of different conformations of PTC/PTCD on the conformation of lysozyme differed, and its metabolites were able to exert a greater effect on lysozyme compared to prothioconazole. Moreover, the S-configuration of PTCD interacted most strongly with lysozyme. This conclusion was further verified by DFT calculations and molecular docking as well. Furthermore, the oxidative stress indicators within HepG2 cells were also affected by chiral prothioconazole and its metabolites. Specifically, S-PTCD induced more substantial perturbation of the normal oxidative stress processes in HepG2 cells, and the magnitude of the perturbation varied significantly among different configurations (P > 0.05). Overall, chiral prothioconazole and its metabolites exhibit enantioselective effects on lysozyme conformation and oxidative stress processes in HepG2 cells. This work provides a scientific basis for a more comprehensive risk assessment of the environmental behaviors and effects caused by chiral pesticides, as well as for the screening of highly efficient and less biotoxic enantiomeric monomers.

Synergistic effects on oxidative stress, apoptosis and necrosis resulting from combined toxicity of three commonly used pesticides on HepG2 cells

The widespread use of pesticides performs a vital role in safeguarding crop yields and quality, providing the opportunity for multiple pesticides to co-exist, which poses a significant potential risk to human health. To assess the toxic effects caused by exposures to individual pesticides (chlorpyrifos, carbofuran and acetamiprid), binary combinations and ternary combinations, individual and combined exposure models were developed using HepG2 cells and the types of combined effects of pesticide mixtures were assessed using concentration addition (CA), independent action (IA) and combination index (CI) models, respectively, and the expression of biomarkers related to oxidative stress, apoptosis and cell necrosis was further examined. Our results showed that both individual pesticides and mixtures exerted toxic effects on HepG2 cells. The CI model indicated that the toxic effects of pesticide mixtures exhibited synergistic effects. The results of the lactate dehydrogenase (LDH) release and apoptosis assay revealed that the pesticide mixture increased the release of LDH and apoptosis levels. Moreover, our results also showed that individual pesticides and mixtures disrupted redox homeostasis and that pesticide mixtures produced more intense oxidative stress effects. In conclusion, we have illustrated the enhanced combined toxicity of pesticide mixtures by in-vitro experiments, which provides a theoretical basis and scientific basis for further toxicological studies.

Systematic assessment of cyflumetofen toxicity in soil-earthworm (Eisenia fetida) microcosms

Cyflumetofen was widely applied in agriculture with its excellent acaricidal effect. However, the impact of cyflumetofen on the soil non-target organism earthworm (Eisenia fetida) is unclear. This study aimed to elucidate the bioaccumulation of cyflumetofen in soil-earthworm systems and the ecotoxicity of earthworms. The highest concentration of cyflumetofen enriched by earthworms was found on the 7th day. Long-term exposure of earthworms to the cyflumetofen (10 mg/kg) could suppress protein content and increases Malondialdehyde content leading to severe peroxidation. Transcriptome sequencing analysis demonstrated that catalase and superoxide-dismutase activities were significantly activated while genes involved in related signaling pathways were significantly upregulated. In terms of detoxification metabolic pathways, high concentrations of cyflumetofen stimulated the number of Differentially-Expressed-Genes involved in the detoxification pathway of the metabolism of glutathione. Identification of three detoxification genes (LOC100376457, LOC114329378, and JGIBGZA-33J12) had synergistic detoxification. Additionally, cyflumetofen promoted disease-related signaling pathways leading to higher disease risk, affecting the transmembrane capacity and cell membrane composition, ultimately causing cytotoxicity. Superoxide-Dismutase in oxidative stress enzyme activity contributed more to detoxification. Carboxylesterase and glutathione-S-transferase activation play a major detoxification role in high-concentration treatment. Altogether, these results contribute to a better understanding of toxicity and defense mechanisms involved in long-term cyflumetofen exposure in earthworms.

Enantioselective activity and toxicity of chiral acaricide cyflumetofen toward target and non-target organisms

Cyflumetofen (CYF), a novel chiral acaricide, exert enantiomer-specific effects on target organisms by binding to glutathione S-transferase. However, there is limited knowledge regarding the response of non-target organisms to CYF, including enantioselective toxicity. In this study, we investigated the effects of racemic CYF (rac-CYF) and its two enantiomers (+)-CYF and (-)-CYF on MCF-7 cells and non-target (honeybees) and target (bee mites and red spider mites) organisms. The results showed that similar to estradiol, 1 μM (+)-CYF promoted the proliferation and disturbed the redox homeostasis of MCF-7 cells, whereas at high concentrations (≥100 μM) it exerted a negative effect on cell viability that was substantially stronger than that of (-)-CYF or rac-CYF. (-)-CYF and rac-CYF at 1 μM concentration did not significantly affect cell proliferation, but caused cell damage at high concentrations (≥100 μM). Analysis of acute CYF toxicity against non-target and target organisms revealed that for honeybees, all CYF samples had high lethal dose (LD₅₀) values, indicating low toxicity. In contrast, for bee mites and red spider mites, LD₅₀ values were low, whereas those of (+)-CYF were the lowest, suggesting higher toxicity of (+)-CYF than that of the other CYF samples. Proteomics profiling revealed potential CYF-targeted proteins in honeybees related to energy metabolism, stress responses, and protein synthesis. Upregulation of estrogen-induced FAM102A protein analog indicated that CYF might exert estrogenic effects by dysregulating estradiol production and altering estrogen-dependent protein expression in bees. Our findings suggest that CYF functions as an endocrine disruptor in non-target organisms in an enantiomer-specific manner, indicating the necessity for general ecological risk assessment for chiral pesticides.

Systematic Stereoselectivity Evaluations of Tetramethrin Enantiomers: Stereoselective Cytotoxicity, Metabolism, and Environmental Fate in Earthworms, Soils, Vegetables, and Fruits

Tetramethrin is a widely applied type I chiral pyrethroid insecticide that exists as a mixture of four isomers. In the present study, its stereoselective cytotoxicity, bioaccumulation, degradation, and metabolism were investigated for the first time at the enantiomeric level in detail by using a sensitive chiral high-performance liquid chromatography-tandem mass spectroscopy (HPLC-MS/MS) method. Results showed that among rac-tetramethrin and its four enantiomers, the trans (+)-1R,3R-tetramethrin had the strongest inhibition effect on the PC12 cells. In the earthworm exposure trial, the concentration of trans (-)-1S,3S-tetramethrin was 0.94-8.92 times in earthworms (cultivated in natural soil) and 1.67-5.01 times (cultivated in artificial soil) higher than trans (+)-1R,3R-tetramethrin, respectively. In the greenhouse experiment, the trans (+)-1R,3R-tetramethrin and cis (+)-1R,3S-tetramethrin were preferentially degraded. Furthermore, for rat liver microsome in vitro incubation, the maximum metabolism rate of cis (-)-1S,3R-tetramethrin was 1.50 times higher than its antipodes. Altogether, the aim of this study was to provide a scientific and reasonable reference for the possibility of developing a single enantiomer to replace the application of rac-tetramethrin, which could possess better bioactivity and lower ecotoxicity, and thus permit more reliable and accurate environmental monitoring and risk assessment.

Evaluation of hepatotoxicity and nephrotoxicity induced by Fenpyroximate in subchronic-orally exposed Wistar rats

Backgrounds. Fenpyroximate (FEN) is an acaricide that inhibits the complex I of the mitochondrial respiratory chain. The aim of this work was to explore the hepatotoxic and nephrotoxic effects of FEN on Wistar rats. Methods. The study involved five groups: a control group and four groups treated with FEN at 1, 2, 4, and 8 mg/Kg bw for 28 consecutive days. Histological examination and biochemical analysis of hepatic and renal biomarkers were performed. The malondialdehyde (MDA), protein carbonyl levels, and antioxidant enzymes activities were measured. Comet assay was conducted to explore FEN genotoxicity. Results. FEN induced a disturbance of the hepatic and renal functions as evidenced by an increase in AST, ALT, ALP, creatinine, and uric acid levels and histopathological modifications in the two examined tissues. FEN increased hepatic and renal lipid peroxidation and protein oxidation. The activities of liver and kidney SOD, CAT, GPX, and GST are increased significantly in FEN-treated rats at doses of 2 and 4 mg/kg bw. However, with the dose of 8 mg/kg bw of FEN, these activities are decreased. Moreover, FEN increased DNA damage in a dose-dependent manner. Conclusion. FEN was hepatotoxic and nephrotoxic very likely through induction of oxidative stress.

Chiral separation of new chiral insecticide pyraquinil isomers and establishment of analytical methods in vegetables

以全新手性杀虫剂唑虫酯为研究对象,通过筛选手性色谱柱和优化流动相比例,建立了唑虫酯及其氧化代谢物异构体的拆分方法,在此基础上开发利用高效液相色谱-串联质谱(HPLC-MS/MS)同时测定小白菜和蕹菜中唑虫酯及其氧化产物手性异构体的分析方法。以纤维素-三(3,5-二氯苯基氨基甲酸酯)共价键合手性柱(Chiral INC)(250 mm×4.6 mm, 5 μm)为分析柱,乙腈和2 mmol/L甲酸铵水溶液作为流动相进行梯度洗脱分离,在多反应监测负离子模式下进行检测,唑虫酯4个异构体分离度分别为1.63、2.83和1.74,唑虫酯氧化产物异构体分离度为5.82。通过衍生化的方法进一步确定出峰顺序为RS-唑虫酯、SS-唑虫酯、RR-唑虫酯、SR-唑虫酯、S-唑虫酯氧化产物和R-唑虫酯氧化产物。唑虫酯和其氧化产物的手性异构体分别在1.25~1250 μg/L和2.5~2500 μg/L范围内具有良好的线性关系,相关系数(R²)大于0.99。在蕹菜和小白菜样品中同时添加唑虫酯和唑虫酯氧化产物消旋体进行添加回收试验,添加水平为1、20、400 μg/kg(即唑虫酯异构体为0.25、5、100 μg/kg;唑虫酯氧化代谢产物异构体为0.5、10、200 μg/kg),回收率为72.6%~110.6%,相对标准偏差(RSD)均在9.4%以下,其中日内重复性的RSD在0.5%~9.4%之间;日间重复性的RSD在1.0%~8.6%之间,表明该方法具有良好的回收率和精密度。该研究可为唑虫酯这一新型手性农药的环境行为研究及后续质量控制、药效评价等提供相应的分析技术,为新农药开发应用提供有力的技术支撑。

Systemic Stereoselectivity Study of Fenobucarb: Environmental Behaviors in Greenhouse Vegetables, Fruits, Earthworms, and Soils and Its Cytotoxicity

Fenobucarb (2-sec-butylphenyl methylcarbamate, BPMC) is a potent carbamate pesticide with high insecticidal activity. In this study, the enantioselective accumulation of BPMC in earthworms (Eisenia foetida) and dissipation in cabbage, Chinese cabbage, strawberry, and soils were investigated. The samples were prepared using the QuEChERS method and analyzed using fast and sensitive chiral high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS) analysis. The stereoselective accumulation of BPMC enantiomers revealed that S-(+)-BPMC was preferentially accumulated in earthworms rather than its antipode. However, the dissipation studies showed that S-(+)-BPMC degraded faster than the R-(-)-isomer in cabbage, Chinese cabbage, strawberry, and soils. Furthermore, the cytotoxic effect of BPMC enantiomers toward PC12 and N9 neuronal, A549 lung cancer, and MRC5 lung fibroblast cell lines was evaluated using an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Compared with R-(-)- and rac-isomers, S-(+)-BPMC exhibited lower cytotoxicity in neuronal cells and a weaker proliferating effect on lung cancer and lung fibroblast cells. Altogether, the findings suggest the use of the pure S-(+)-enantiomer in agricultural management rather than the use of the racemate or the R-(-)-isomer, which might reduce the environmental risk.

Enantioselective effects of cyflumetofen on microbial community and related nitrogen cycle gene function in acid-soil

Cyflumetofen (CYF) is a novel chiral acaricide widely used in commercial crops to control mites. The environmental risks exposed by CYF in the soil, especially at the enantiomer level, remain unclear. We found that the (+)-CYF enantiomer was preferentially degraded in acid-soil, resulting in (-)-CYF enrichment. 16S rRNA and qPCR analysis indicated that decreased bacterial abundance by 12.79-61.80% and 2.52-52.48% in (-)-CYF treatment and (+)-CYF treatment, respectively. Diversity was also decreased with (-)-CYF treatment. Interestingly, several beneficial bacteria, for instance, Alphaproteobacteria (class), Sphingomonadaceae (family), and Arthrobacter (specise) were more enriched following (-)-CYF. The abundance of N₂-fixing bacteria showed a sustained reduction with time, and the decrease was 3.24-72.94% with (-)-CYF and 25.37-73.11% with (+)-CYF treatment. Compared with the (+)-CYF treatment could positively promote nitrification, while the treatment (-)-CYF significantly reduced the abundance of amoA gene; namely it significantly negatively affected the nitrification in the nitrogen cycle. Through our further research, we found that Actinobacteria, Alphaproteobacteria, Lysobacter; Sphingomonas, Patescibacteria, Saccharimonadia, and Saccharimonadales showed synergistic effects with the nitrogen cycling-related genes nifH and amoA. These results contribute to a comprehensive environmental risk assessment of CYF in acid-soil at the enantiomer level.

Analysis of the Physicochemical Properties of Acaricides Based on Lipinski's Rule of Five

This study aimed to explore the similarity between the physical and chemical properties of different acaricides, determine whether Lipinski's Rule of Five (RO5) used in the design of drug molecules is suitable for screening acaricides, and provide methods for selection of new acaricides. We evaluated and predicted the molecular properties of >180 acaricides using Molinspiration. We calculated physicochemical property parameters, such as log p, molecular weight (MW), and number of hydrogen bond donors (HBDs), hydrogen bond acceptors (HBAs), and rotatable bonds (Rot B). We then conducted qualitative and quantitative analyses of the physicochemical properties of acaricides. The MW of all acaricides ranged from 141 to 663, with an average value of 337.8. The number of HBDs ranged from 0 to 5, with an average value of 0.46. The number of HBAs ranged from 0 to 9, with an average value of 4.07. The log p ranged from -0.79 to 8.74, with an average value of 4.61. The number of Rot B ranged from 0 to 14, with an average value of 5.62. Except for the microbial and plant-derived acaricides, the molecular properties of the remaining acaricides are in accordance with the Lipinski's RO5. Therefore, the Lipinski's RO5 can provide a basis for screening new acaricide drugs.

Enantioselectivity and allelopathy both have effects on the inhibition of napropamide on Echinochloa crus-galli

Napropamide is a chiral acetamide herbicide commonly applied to control Echinochloa crus-galli in maize. The inhibition effect may be enantioselective for Echinochloa crus-galli and maize. It may also be affected by the potential allelopathy at field condition. To investigate this, we have examined the inhibition effect of napropamide on Echinochloa crus-galli mono-cultured or co-cultured with maize at field conditions. Our results on morphology, physiology, chlorophyll content and chlorophyll fluorescence suggest that R-napropamide has stronger inhibitory effect than Rac-napropamide and S-napropamide on Echinochloa crus-galli, while none of them affects maize. We found that both glutathione-S-transferase (GST) genes and oxidative enzymes (superoxide dismutase, malondialdehyde) played roles in the inhibition. Accumulations of napropamide in Echinochloa crus-galli were more prominent in roots than in shoots, and no enantioselectivity was found in medium dissipation. We have observed relative allelopathy when applying napropamide to Echinochloa crus-galli co-cultured with maize. The results warrant further field studies on the enantioselectivity and allelopathy of herbicides.

Enantioselective metabolism of four chiral triazole fungicides in rat liver microsomes

Triazole fungicides with one or two chiral centers are widely used worldwide. The liver microsomes plays a major role in the metabolism and systemic elimination of chiral pesticides after exposure. In this present work, enantioselective metabolism of four representative chiral triazole fungicides (prothioconazole, flutriafol, triticonazole, and epoxiconazole) in rat liver microsomes (RLM) was investigated using LC-MS/MS. Baseline separation of the four chiral fungicides and prothioconazole-desthio was achieved on Lux-cellulose-1. The results demonstrated that the R-enantiomers of flutriafol and triticonazole were preferentially metabolized with half-life ranged from 17.33 min to 99.00 min. The R,S-epoxiconazole accumulated with a half-life of 173.25 min. There was no stereoselectivity for prothioconazole. However, remarkable stereoselective metabolism was observed for prothioconazole-desthio. The results of enzyme kinetic revealed different affinities between the enantiomers and metabolic enzymes. In addition, homologous modeling and molecular docking results indicated that enantioselectivity were partially to enantiospecific binding affinities with CYP enzymes. This study highlights a new quantitative approach for stereoselective metabolism of chiral agrochemicals and provides more accurate data on risk assessment of triazole fungicides.

Enantioselectivity in biotransformation and bioaccumulation processes of typical chiral contaminants

Chirality is a critical topic in the medicinal and agrochemical fields. One quarter of all agrochemicals was chiral in 1996, and this proportion has increased remarkably with the introduction of new compounds over time. Despite scientists have made great efforts to probe the enantiomeric selectivity of chiral chemicals in the environment since early 1990s, the different behaviours of individual enantiomers in biologically mediated processes are still unclear. In the present review, we highlight state-of-the-knowledge on the stereoselective biotransformation and accumulation of chiral contaminants in organisms ranging from invertebrates to humans. Chiral insecticides, fungicides, and herbicides, polychlorinated biphenyls (PCBs), pharmaceuticals, flame retardants hexabromocyclododecane (HBCD), and perfluorooctane sulfonate (PFOS) are all included in the target compounds. Key findings included: a) Changes in the enantiomeric fractions in vitro and in vivo models revealed that enantioselectivity commonly occurs in biotransformation and bioaccumulation. b) Emerging contaminants have become more important in the field of enantioselectivity together with their metabolites in biological transformation process. c) Chiral signatures have also been regarded as powerful tools for tracking pollution sources when the contribution of precursor is unknown. Future studies are needed in order to understand not only preliminary enrichment results but also detailed molecular mechanisms in diverse models to comprehensively understand the behaviours of chiral compounds.

Stereoselective bioactivity, acute toxicity and dissipation in typical paddy soils of the chiral fungicide propiconazole

Propiconazole is a widely used systemic agricultural triazole fungicide with two chiral centers. In the present study, systemic assessments of propiconazole stereoisomers are reported for the first time, including absolute configuration, stereoselective bioactivity toward pathogens (Ustilaginoidea virens, Magnaporthe oryzae, Fusarium moniliforme, Thanatephorus cucumeris, and Rhizoctonia solani), and stereoselective acute toxicity toward aquatic organisms (Scenedesmus obliquus, and Daphnia magna). Moreover, the stereoselective dissipation of propiconazole in three types of paddy soil under laboratory-controlled conditions (aerobic, anaerobic and sterile) was investigated. The degree of bioactivity and acute toxicity of the propiconazole stereoisomers differed depending on the type of target pathogens and non-target organisms. There were 2.43-23.47 and 1.48-2.13 fold differences between the best and worst stereoisomer in bioactivity and toxicity, respectively. Under aerobic conditions, (2S,4S)-propiconazole and (2S,4R)-propiconazole were preferentially degraded in the three types of soils. However, no significant stereoselectivity was observed under anaerobic and sterile conditions. Propiconazole was configurationally stable throughout the study. In comprehensive consideration of bioactivity, toxicity and environmental behavior, using stereoisomer mixture rather than pure stereoisomer may help to control more species of disease in practical application, and the stereoselectivity should be taken into consideration in risk assessment.

Enantioselective degradation and transformation of the chiral fungicide prothioconazole and its chiral metabolite in soils

Prothioconazole is a widely used chiral triazole fungicide. In this work, the enantioselective degradation and transformation of prothioconazole and its chiral metabolite prothioconazole-desthio in five kinds of soils were investigated under native and sterile conditions using reversed phase liquid chromatography tandem mass spectrometry with a Lux-cellulose-1 column. The results showed that an enantioselective degradation was observed with R-prothioconazole preferentially degraded in the five soils and enantiomeric fraction values that ranged from 0.32 to 0.41 under native conditions. Furthermore, the major metabolite prothioconazole-desthio was formed rapidly during prothioconazole dissipation. The prothioconazole-desthio enantiomers were degraded slowly, and there was a slight enantioselectivity with enantiomeric fraction values that ranged from 0.45 to 0.51 in the Nanjing and Jilin soils. Under sterile conditions, prothioconazole and its metabolite enantiomers were more slowly degraded with no enantioselectivity. The result of the incubation experiment with single enantiomers verified that R- and S-prothioconazole were transformed to R- and S-prothioconazole-desthio, respectively. No enantiomerization for prothioconazole and its chiral metabolite was observed. In addition, the excellent correlation between organic matter content and degradation rate indicated that organic matter could promote the degradation of prothioconazole and its metabolite enantiomers. The data in this study provide the experimental evidence of the stereoselective degradation and metabolism of both prothioconazole and its chiral metabolite in the environment.

A microRNA-1 gene, tci-miR-1-3p, is involved in cyflumetofen resistance by targeting a glutathione S-transferase gene, TCGSTM4, in Tetranychus cinnabarinus

microRNA-1 (miR-1) is a well-studied conservative microRNA (miRNA) involved in immune responses in mammals and insects. However, little is known about its role in pesticide resistance in arthropods. In this study, we found that a microRNA belong to miR-1 family (tci-miR-1-3p) was significantly down-regulated in a cyflumetofen-resistant strain (CYR) of Tetranychus cinnabarinus compared with its homologous susceptible strain (SS), indicating an involvement of miR-1 in cyflumetofen resistance in mites. One glutathione S-transferase (GST) gene (TCGSTM4, a mu class GST gene), a candidate target gene of tci-miR-1-3p, was found to be significantly down-regulated when tci-miR-1-3p was over-expressed. The specific interaction between tci-miR-1-3p and the target sequence in the 3' untranslated region of TCGSTM4 was confirmed. A decrease or increase in tci-miR-1-3p abundance through feeding miRNA inhibitors or mimics significantly increased or decreased TCGSTM4 expressions at the mRNA and protein levels, respectively. In addition, an over-expression of tci-miR-1-3p resulted in a decrease in the tolerance of T. cinnabarinus to cyflumetofen in both SS and CYR strains, and vice versa. After decreasing TCGSTM4 transcription via RNA interference, T. cinnabarinus became more sensitive to cyflumetofen in both resistant and susceptible mites, and the change in mortality was greater in CYR than that in SS. Moreover, the recombinant TCGSTM4 could significantly decompose cyflumetofen, indicating that TCGSTM4 is a functional gene responsible for cyflumetofen resistance in mites.

Residue and Dietary Risk Assessment of Chiral Cyflumetofen in Apple

Ultra-performance convergence chromatography is an environmentally-friendly analytical method that uses dramatically reduced amounts of organic solvents. In addition, a robust and highly sensitive chiral separation method was developed for the novel chiral acaricide cyflumetofen by using ultra-performance convergence chromatography coupled with tandem mass spectrometry, which shows that stereoisomer recoveries determined for various apple parts ranged from 78.3% to 119.9%, with the relative standard deviations being lower than 14.0%. The half-lives of (−)-cyflumetofen and (+)-cyflumetofen obtained under 5-fold applied dosage equal to 22.13 and 22.23 days, respectively. For 1.5-fold applied dosage, the respective values were determined as 22.42 and 23.64 days, i.e., the degradation of (−)-cyflumetofen was insignificantly favored over that of its enantiomer. Importantly, cyflumetofen was unevenly distributed in apples, with its relative contents in apple peel, peduncle, and pomace equal to 50%, 22%, and 16%, respectively. The proposed method can be used to efficiently separate and quantify chiral pesticide with advantages of a shorter analysis time, greater sensitivity, and better environmental compatibility. Additionally, the consumption of apples with residue of cyflumetofen did not pose a health risk to the population if the cyflumetofen applied under satisfactory agricultural practices after the long-term dietary risk assessment.

Influence of lactic acid bacteria on stereoselective degradation of theta-cypermethrin

The purpose of this study was to investigate the influence of four kinds of Lactic acid bacteria (LAB) on stereoselective degradation of theta-cypermethrin (CYP), including Lactobacillus plantarum, Lactobacillus casei, Lactobacillus delbrueckii, and Streptococcus thermophilus. An effective analytical method for (±)-theta-CYP in medium was developed by high-performance liquid chromatography with cellulose tris-(3,5-dimethylphenylcarbamate) chiral stationary phase. theta-Cypermethrin was spiked to LAB medium with different inoculation rates and sampled at 0, 2, 8, 24, 36, 48, 72, 120, 168, and 240 hours. The results showed that LAB influenced the half-lives and enantiomer fractions of theta-CYP enantiomers, which lead a closer degradation rate between the 2 stereoisomers, and no obvious difference was found among 4 LABs. Besides, the stereoselective degradation of theta-CYP was closely related to pH. The lower the pH (pH of 3, 5, 7, and 9), the lower the enantiomer fraction (from 4.88 to 6.69). At pH of 3, 7, and 9, significant differences of half-lives between enantiomers were observed. (-)-theta-Cypermethrin decreased faster than (+)-theta-CYP under pH of 3, while opposite results were indicated under pH of 7 and 9. Moreover, the acidic condition contributed to the higher chiral configuration stability of (±)-theta-CYP. (+)-Enantiomer was influenced by pH in a greater degree than (-)-enantiomer.

Stereoselective Analysis and Degradation of Pyrisoxazole in Cabbage, Pakchoi, and Pepper by Liquid Chromatography Tandem Mass Spectrometry

Pyrisoxazole is a chiral fungicide with high sterilizing activity to the plant pathogenic bacteria and thus can be used for protecting the vegetables from gray mold, powdery mildew, and brown rot. The present work aimed to explore its stereoselective degradation in cabbage, pakchoi, and pepper samples. The enantioseparation and analysis on chiral column Lux Cellulose-3 based on liquid chromatography tandem mass spectrometry was developed coupled to the QuEChERS method. The recoveries of the stereoisomers in various vegetables ranged from 72.6 to 124% with RSD lower than 5.0%. Enantioselective dissipation of pyrisoxazole in vegetables displayed that (-)-A-pyrisoxazole was preferentially degraded versus (+)-A-pyrisoxazole in all the vegetables. (+)-B-pyrisoxazole was preferentially degraded in cabbage, while there was no obvious enantioselectivity in pakchoi and pepper. Meanwhile, stereoselectivity analysis demonstrated that (±)-A-pyrisoxazole was degraded faster than (±)-B-pyrisoxazole in pakchoi and pepper, while there was no stereoselective degradation in cabbages.

Insecticide pyrethroids in liver of striped dolphin from the Mediterranean Sea

Pyrethroid pesticides were analysed in liver of striped dolphin (Stenella coeruleoalba) from the Alboran Sea (south of Spain, Mediterranean Sea). The occurrence and bioaccumulation of pyrethroid insecticides in marine mammal tissues from the northern hemisphere had never been determined before. Pyrethroids were detected in 87% of the specimens with a mean total concentration of 300 ng g^-1 lw ± 932 (range 2.7-5200 ng g^-1 lw). Permethrin and tetramethrin were the main contributors to the pyrethroid profiles, with enantiospecific accumulation for the first and isomer specific accumulation for the latter. Bioaccumulation of pyrethroids was unlike that of persistent organic pollutants (POPs), as pyrethroid concentrations were not correlated to the maturity stage of the specimens. Concentrations slightly increased from calves to juveniles, whereas juveniles presented similar concentrations to adults. Metabolization of pyrethroids after achieving sexual maturity might account for this pattern.