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PEN is a widely used triazole fungicide, usually used to control grape white rot. In the process of agricultural use, PEN will be scattered to the soil and water environment, which brings certain environmental safety risks. In this study, we used a 200-μg/L solution of Rac-PEN, (+)-PEN, and (-)-PEN to perform a 28-day exposure test on zebrafish. The results showed that long-term low-dose PEN exposure did not significantly change the growth factor K and the number of spawning of zebrafish. However, the content of four important hormones vitellogenin, 17β-estradiol, testosterone, and 11-ketotestosterone in zebrafish has changed significantly. Furthermore, we measured the expression of hypothalamus-pituitary-gonads-liver (HPGL) axis-related genes, and the results showed that the expressions of related genes in the brain, gonads, and liver all changed significantly. Combining the above results, we can conclude that PEN has obvious endocrine disrupting effect on zebrafish, and has gender-specific endocrine effects. Meanwhile, Rac-PEN and (+)-PEN had stronger effects on the endocrine system of zebrafish than (-)-PEN. [ABSTRACT FROM AUTHOR]

Chiral fungicide prothioconazole has a wide range of antifungal spectrum; however, little research has been conducted to evaluate prothioconazole on an enantiomeric level. Five target pathogens and three common aquatic organisms were tested for the enantioselective bioactivity and toxicity of prothioconazole in this work. The antifungal activity of the enantiomers against wheat phytoalexin, rice blast fungus, exserohilum turcicum, Alternaria triticina, and Fusarium avenaceum was determined, and it was found that (−)‐prothioconazole were 85 to 2768 times more active than (+)‐prothioconazole toward these target organisms. In order to reflect the risk to aquatic ecosystem, the acute toxicity of the enantiomers to Daphnia magna, Chlorella pyrenoidosa, and Lemna minor L. was assessed. It was observed that the toxicity of (−)‐prothioconazole to D. magna was 2.2 times higher than (+)‐prothioconazole, but it was lower to C. pyrenoidosa and L. minor L. The toxicities of (+)‐enantiomer and (−)‐enantiomer to D. magna and C. pyrenoidosa were synergy, indicating that the racemate had higher threat to the organisms. It could be concluded that the effects of prothioconazole on target organisms and the acute toxicity to nontarget species were enantioselective with (−)‐enantiomer possessing higher efficiency and lower toxicity. Such enantiomeric differences should be taken into consideration when assessing the performance of prothioconazole. [ABSTRACT FROM AUTHOR]

Alpha-cypermethrin (α-cypermethrin), an important chiral pyrethroid insecticide, is frequently detected in human samples. Because of the possible human health risks caused by α-cypermethrin, we studied dynamics, residues, and metabolism of α-cypermethrin in five common vegetables (tomato, cucumber, rape, cabbage, and pepper) on enantiomeric levels after foliar spray. α-Cypermethrin was qualified by a HP-5 column and its enantiomers could be separated by gas chromatograph (GC) using a BGB-172 chiral column. The results of degradation showed that α-cypermethrin dissipated rapidly in vegetables with half-lives being only 2.85-8.88 days. Stereoselective degradation was observed on pepper and cucumber while the two metabolites (cis-DCCA and 3-PBA) of α-cypermethrin were not detected during its dissipation in all plants. This is the first evidence of enantioselective degradation of α-cypermethrin in the five common vegetables and the results should be considered in future environmental risk and food safety evaluations. [ABSTRACT FROM AUTHOR]

Abstract The environmental contaminant, especially pesticides, threatened the amphibian population. In this assay, the enantioselective behavior of cyproconazole on Rana nigromaculata was studied. We found LC50 (lethal concentration causing 50% mortality) of 4-enantiomers was nearly twice as 3-enantiomers in 96 h acute toxicity test. Besides, the significant considerable variation of oxidative stress and LDH (lactic dehydrogenase) induced by the four enantiomers indicated that cyproconazole could enantioselectively affect enzymes in tadpoles. Bioaccumulation experiments showed the order of cyproconazole in the tadpoles was 4-enantiomers>3- enantiomers>2- enantiomers>1- enantiomers during the exposure for 28d. In tissue distribution test, cyproconazole was formed and accumulated in order of 4-enantiomers>2-enantiomers>3- enantiomers>1- enantiomers, except that in the gut. During the elimination experiment, cyproconazole was rapidly eliminated by 95% within the only 24 h. These results suggested that the influence of enantioselective behavior should consider when assessing ecological risk of chiral pesticides to amphibians. Graphical abstract Image Highlights • The acute toxicity of cyproconazole against R. nigromaculata was enantioselective. • Oxidative stress and LDH induced by the four enantiomers was enantioselective. • There was enantioselective bioaccumulation in the tadpoles exposed to racemate. • There was enantioselective tissue distribution in the tadpoles exposed to racemate. It improves the understanding of the acute and chronic toxic effects of cyproconazole on amphibious animals at the chiral level. [ABSTRACT FROM AUTHOR]

Research on the enantioselective environmental behavior of chiral pesticides has been a hot spot of environmental chemistry recently. In this study, the acute toxicity and digestion of furalaxyl enantiomers were determined on the aquatic algae Scendesmus obliquus. After exposure for 96 hours, the EC50 values for (S)‐furalaxyl and (R)‐furalaxyl were 13.59 and 15.26 mg/L, respectively. In addition, enantioselectivity was observed from the determined chlorophyll contents and antioxidant enzyme (CAT and SOD) activities of algae cells after exposure to furalaxyl enantiomers for 96 hours. The digestion rate of (S)‐furalaxyl and (R)‐furalaxyl were almost the same in S. obliquus. On the basis of these data, the inactive enantiomers (S)‐ furalaxyl is more toxic than the active one on the non‐target species S. obliquus, indicating that such enantiomeric differences should be taken into consideration in the study of pesticide risk assessment. [ABSTRACT FROM AUTHOR]

In recent years, serious environmental pollution has caused a decrease in the abundance of many species worldwide. Reptiles are the most diverse group of terrestrial vertebrates. There are large amounts of toxicological data available regarding myclobutanil, but the adverse effects of myclobutanil on lizards has not been widely reported. In this study, treatment groups were orally administered a single-dose of myclobutanil (20 mg/kg body weight (bw)). Subsequently, it was found that there were differences in myclobutanil levels between the different tissues and concentrations also changed with degradation time. The tissue concentrations of myclobutanil decreased in the order of: stomach > liver > lung > blood > testis > kidney > heart > brain. Based on our results, the liver and testis were considered to be the main target organs in lizards, indicating that the myclobutanil could induce potential hepatic and reproductive toxicity on lizards. Meanwhile, it was also demonstrated that the toxic effects of myclobutanil was different in different species, and the distribution of different pesticides in lizards were different. [ABSTRACT FROM AUTHOR]

Pesticides are frequently detected in water bodies due to the agricultural application, which may pose impacts on aquatic organisms. The enantioselective bioaccumulation and metabolism of the herbicide lactofen in aquatic floating macrophyte Lemna minor ( L. minor ) were studied and the potential L. minor phytoremediation was investigated. Ultra-high performance liquid chromatography – tandem mass spectrometry (UHPLC-MS-MS) analysis for lactofen and its two known metabolites in L. minor was performed. The initial concentrations of racemic lactofen, R-lactofen and S-lactofen were all 30 μg L −1 in the growth solution. The distribution of lactofen and its metabolites in growth solution and L. minor was determined throughout a 5-d laboratory trial. It was observed that S-lactofen was preferentially taken up and metabolized in L. minor . After rac-lactofen exposure, the accumulation amount of S-lactofen was approximately 3-fold more than that of R-lactofen in L. minor and the metabolism rate of S-lactofen (T 1/2 =0.92 d) was significantly faster than R-lactofen (T 1/2 =1.55 d). L. minor could only slightly accelerate the metabolism and removal of lactofen in the growth solution. As for the metabolites, desethyl lactofen was found to be the major metabolite in L. minor and the growth solution, whereas the metabolite acifluorfene was undetectable. No interconversion of the two enantiomers was observed after individual enantiomer exposure, indicating they were configurationally stable. The findings of this work represented that the accumulation and metabolism of lactofen in L. minor were enantioselective, and L. minor had limited capacity for the removal of lactofen and its metabolite in water. [ABSTRACT FROM AUTHOR]

The enantiomeric separation of the enantiomers of three phenylpyrazole pesticides (fipronil, flufiprole, ethiprole) and two fipronil metabolites (amide-fipronil and acid-fipronil) were investigated by high-performance liquid chromatography (HPLC) with a CHIRALPAK® IB chiral column. The mobile phase was n-hexane or petroleum ether with 2-propanol or ethanol as modifier at a flow rate of 1.0 mL/min. The influences of mobile phase composition and column temperature between 15 and 35°C on the separations were studied. All the analytes except ethiprole obtained complete enantiomeric separation after chromatographic condition optimization. Fipronil, flufiprole, amide-fipronil, and acid-fipronil obtained complete separation with the best resolution factors of 2.40, 3.40, 1.67, and 16.82, respectively, but ethiprole showed no enantioselectivity under the optimized conditions. In general, n-hexane with 2-propanol gave better separations in most cases. The results showed decreasing temperature and content of modifier in the mobile phase resulted in better separation and longer analysis time as well. The thermodynamic parameters calculated according to linear the Van't Hoff equation indicated the chiral separations in the study were enthalpy-driven. Fipronil and its two chiral hydrolyzed metabolites obtained baseline separation simultaneously under optimized conditions. [ABSTRACT FROM AUTHOR]

Enantiomers of chiral compounds often exhibit enantioselective adverse effects and biochemical processes in non-target organisms. In this study, enantioselective metabolism and toxic effects of metalaxyl enantiomers on primary rat hepatocytes were investigated. Stereoselectivity was observed on both degradation of metalaxyl and formation of metabolites. (−)-R-metalaxyl eliminated faster than (+)-S-metalaxyl, while the hydroxylmetalaxyl, demethylmetalaxyl, and didemethylmetalaxyl metabolites derived from 50-μM (+)-S-metalaxyl after 24 h of incubation were approximately 1.57, 1.43, and 1.86 times more than that of (−)-R-metalaxyl, respectively. According to the methyl tetrazolium (MTT) assay, the EC values (24 h) for rac-, (+)-S-, and (−)-R-metalaxyl were 1788.22, 2066.73, and 2263.71 μM, respectively. An accordant enantioselective effect on oxidative stress suggested that the enantioselective cytotoxicity induced by metalaxyl enantiomers may partly contribute to enantioselective oxidative damage and mitochondrial dysfunction. Such results could be of great importance for credible environmental and toxicological risk assessment of metalaxyl. [ABSTRACT FROM AUTHOR]

Understanding of xenobiotic metabolism is necessary for risk assessment as well as toxicological research. In the present study, nanoLC/LTQ-Orbitrap mass based non-targeted metabolomics method coupled with ultra-performance liquid chromatography (UPLC)/triple quadrupole mass based targeted metabolomics method was carried out to investigate the stereoselective metabolism of benalaxyl in mouse hepatic microsomes. As a result, 7 metabolites of benalaxyl were identified, including 5 previously reported and 2 newly identified metabolites in present work. Hydroxylation, oxidation and esterolysis were major biotransformation reactions of benalaxyl in mouse hepatic microsomes. For stereoselective metabolism study, (−)-R-benalaxyl degraded much faster than its antipode with the t 1/2 of 81.24 and 190.38 min for (−)-R- and (+)-S-benalaxyl, respectively. More importantly, stereoselectivity was also observed in the formation of the identified metabolites. In conclusion, the combined use of the mass spectrometry based targeted and non-targeted metabolomics provided a new approach to investigate stereoselective metabolism and identify novel metabolites of chiral pesticides. This study highlights the stereoselective metabolic profile of benalaxyl enantiomers and provides reliable data for benalaxyl toxicological risk assessment in mammal. [ABSTRACT FROM AUTHOR]

Metalaxyl is an important chiral acetanilide fungicide, and the activity almost entirely originates from the R-enantiomer. Racemic metalaxyl has been gradually replaced by the enantiopure R-enantiomer (metalaxyl-M). In this study a chiral residue analysis method for metalaxyl and the metabolite metalaxyl acid was set up based on high-performance tandem mass spectroscopy (HPLC-MS/MS). The degradation and chiral stability of metalaxyl-M in tomato fruits in two geographically distinct regions of China ( Heilongjiang and Hunan Province) were evaluated and the of metalaxyl acid was also investigated. Tomato plants grew under field conditions with a one-time spray application of metalaxyl-M wettable powder. It was found that R-metalaxyl was not chirally stable and the inactive S-metalaxyl was detected in tomato fruits. At day 40, S-metalaxyl derived from R-metalaxyl accounted for 32% and 26% of the total amount of metalaxyl, respectively. The metabolites R-metalaxyl acid and S-metalaxyl acid were both observed in tomato, and the ratio of S-metalaxyl acid to the sum of S- and R-metalaxyl acid was 36% and 28% at day 40, respectively. For both metalaxyl and metalaxyl acid, the half-life of the S-enantiomer was longer than the R-enantiomer. The results indicated that the enantiomeric conversion should be considered in the bioactivity evaluation and environmental pollution assessment. Chirality 28:382-386, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Pyriproxyfen is a chiral insecticide, and over 10 metabolites have been identified in the environment. In this work the separations of the enantiomers of pyriproxyfen and its six chiral metabolites were studied by high-performance (HPLC). Both normal phase and reverse phase were applied using the chiral columns Chiralpak IA, Chiralpak IB, Chiralpak IC, Chiralcel OD, Chiralcel OD-RH, Chiralpak AY-H, Chiralpak AD-H, Chiracel OJ-H, (R,R)-Whelk-O 1, and Lux Cellulose-3. The effects of the chromatographic parameters such as mobile phase composition and temperature on the separations were investigated and the enantiomers were identified with an optical rotation detector. The enantiomers of these targets could obtain complete separations (resolution factor Rs > 1.5) on Chiralpak IA, Chiralpak IB, Chiralcel OD, Chiralpak AY-H, or Chiracel OJ-H under normal conditions. Chiralcel OJ-H showed the best chiral separation results with n-hexane as mobile phase and isopropanol (IPA) as modifier. The simultaneous enantiomeric separation of pyriproxyfen and four chiral metabolites was achieved on Chiralcel OJ-H under optimized condition: n-hexane/isopropanol = 80/20, 15°C, flow rate of 0.8 ml/min, and UV detection at 230 nm. The enantiomers of pyriproxyfen and the metabolites A, C, and D obtained complete separations on Chiralpak IA, Chiralpak IC, and Lux Cellulose-3 under reverse phase using acetonitrile/water as the mobile phase. The factors (k) and selectivity factors (α) decreased with increasing temperature, and the separations were better under low temperature in most cases. The work is of significance for the investigation of the environmental behaviors of pyriproxyfen on an enantiomeric level. Chirality 28:245-252, 2016. © 2016 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

1. The enantiomeric enrichment or degradation of epoxiconazole has been reported in grape, soil, tubifex and mealworm beetle. But, little is known about its enantioselective behaviors in mammals. 2. To further understand differences in the distribution, degradation and excretion of epoxiconazole enantiomers in vivo, male CD-1 mice were selected as the test model to investigate the enantioselective behaviors after a single oral gavage. Mice were sacrificed after 1 h, 3 h, 7 h, 12 h, 24 h, 48 h, 72 h treatment, blood, tissues and excretions were collected for epoxiconazole analysis by LC-MS/MS. 3. On the Lux-Cellulose-1 chiral column, an enrichment of the second eluting (+)-epoxiconazole was generally observed, and feces and urine showed similar EF with major tissues. 4. To elucidate the potential role of intestinal bacterial flora in stereospecific degradation of epoxiconazole, mice fecal flora were culturedin vitroand incubated with epoxiconazole for 48 h. Results showed that (−)-epoxiconazole was preferentially degraded by intestinal bacterial. 5. These results may provide useful information for risk assessment of epoxiconazole on non-target animals. [ABSTRACT FROM AUTHOR]

ABSTRACT The bioactivity against pathogens (Cercospora arachidicola, Fulvia fulva, and Phytophthora infestans) and acute toxicity to Daphnia magna of the fungicide myclobutanil enantiomers were studied. The (+)-enantiomer in an test was about 1.79-1.96 times more active than the (-)-enantiomer. In the toxicity assay, the calculated 24-h LC50 values of the (-)-form, rac-form and (+)-form were 16.88, 13.17, and 11.91 mg/L, and the 48-h LC50 values were 10.15, 9.24, and 5.48 mg/L, respectively, showing that (+)-myclobutanil was more toxic. Meanwhile, the metabolism of myclobutanil enantiomers following a single intravenous (i.v.) administration was investigated in rabbits. Total plasma clearance value (CL) of the (+)-enantiomer was 1.68-fold higher than its antipode. Significant differences in pharmacokinetics parameters between the two enantiomers indicated that the high bioactive (+)-enantiomer was preferentially metabolized and eliminated in plasma. Consistent consequences were found in the tissues (liver, brain, heart, kidney, fat, and muscle), resulting in a relative enrichment of the low-activity (-)-myclobutanil. These systemic assessments of the stereoisomers of myclobutanil cannot be used only to investigate environmental and biological behavior, but also have human health implications because of the long persistence of triazole fungicide and enantiomeric enrichment in mammals and humans. Chirality 26:784-789, 2014. © 2014 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The pharmacokinetic and distribution of the enantiomers of quizalofop-ethyl and its metabolite quizalofop-acid were studied in Sprague-Dawley male rats. The two pairs of enantiomers were determined using a validated chiral high-performance liquid chromatography method. Animals were administered quizalofop-ethyl at 10 mg kg−1 orally and intravenously. It was found high concentration of quizalofop-acid in the blood and tissues by both intragastric and intravenous administration, and quizalofop-ethyl could not be detected through the whole study which indicated a quick metabolism of quizalofop-ethyl to quizalofop-acid in vivo. In almost all the samples, the concentrations of (+)-quizalofop-acid exceeded those of (−)-quizalofop-acid. Quizalofop-acid could still be detected in the samples even at 120 h except in brain due to the function of blood-brain barrier. Based on a rough calculation, about 8.77% and 2.16% of quizalofop-acid were excreted through urine and feces after intragastric administration. The oral bioavailability of (+)-quizalofop-acid and (−)-quizalofop-acid were 72.8% and 83.6%. [ABSTRACT FROM AUTHOR]

ABSTRACT Many pesticides are chiral compounds and stereochemistry is an important factor for any reaction of chiral structures in biological systems. In this study, experiment about bioaccumulation of the two metalaxyl enantiomers in Tubifex (Oligochaeta, Tubificida) was conducted in laboratory aquatic ecosystems. Terrestrial soil spiked with two dose levels of metalaxyl was employed as the artificial bottom substrate. A method of determination of metalaxyl enantiomers in tubifex tissue, soil and overlying water were developed by HPLC. During a 14-day exposure, concentrations of metalaxyl in tubifex increased with the of soil concentration, however, the enantioselective bioaccumulation was only detected at high-dose exposure group, with the preferential accumulation of (-)-(R)-metalaxyl. The bioturbation activity of tubifex decreased water clarity and released soil-associated metalaxyl to overlying water. In those experiments where tubifex was exposed to metalaxyl from soil, pore water and overlying water, each route contributed to the total body burden, and our results indicated the pore water and soil are the primary exposure routes for high-dose exposure concentration treatment. Chirality 26:33-38, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT Research on the environmental behavior of chiral pesticides has been a hot spot of environmental chemistry recently. In this study, the acute toxicity of myclobutanil enantiomers was investigated with the aquatic algae Scendesmus obliquus. After exposure for 96 h, the EC50 values for (−)-myclobutanil, rac-myclobutanil and (+)-myclobutanil were 3.951, 2.760, and 2.128 mg/L, respectively. The photosynthetic pigment (chlorophyll a, chlorophyll b, and carotenoids) and antioxidant enzyme activities catalase (CAT) were determined to evaluate the different when S. obliquus were exposed to 1.5, 5 and 15 mg/L of rac-myclobutanil, (−)-myclobutanil, and (+)-myclobutanil for 96 h, respectively. In addition, the degradation of myclobutanil enantiomers in S. obliquus was also studied. Myclobutanil in the medium inoculated with algae degraded faster than in the uninoculated medium. The degradation of (−)-myclobutanil was faster than that of (+)-myclobutanil at a concentration of 3 mg/L. On the basis of these data, the acute toxicity and of myclobutanil against S. obliquus were concluded to be , and such enantiomeric differences should be taken into consideration in pesticide . Chirality 25:858-864, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT In the present study we investigated the disappearance of hexaconazole in rat liver microsomes system prepared from both genders. High-performance (HPLC) was used for identification and quantification. The degradation of the (+)-hexaconazole was faster than that of the (−)-hexaconazole in racemic hexaconazole and single enantiomer incubation in both sexes. The degradation half-life of the (+)-hexaconazole or (−)-hexaconazole was also gender-related. The metabolism of (+)-hexaconazole and (−)-hexaconazole were faster in male rat hepatic microsomes than that in female, suggesting that at least one of the cytochrome P450s (CYP) in the male rat liver microsomes system responsible for hexaconazole metabolism was male-specific or considerably more active. Kinetic assays showed that the intrinsic clearance in male rat liver microsomes was higher than that in female. All these results strongly suggest that sexual dimorphic metabolism of hexaconazole exists in rats. The inhibition experiments with CYP inhibitors showed that the inhibitory effect of inhibitors was and affected by sex. The results suggest that the metabolism of hexaconazole was determined by the amount of hepatic cytochrome P450 and the expression of individual isoforms of CYPs. Chirality 25:852-857, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT In this contribution, the interactions between diclofop (DC) and human serum albumin (HSA) were explored by steady-state and 3D fluorescence, ultraviolet-visible spectroscopy (UV-vis), and . The binding constants between R-DC and HSA were 0.9213 × 105, 0.9118 × 105, and 0.9009 × 105 L · mol-1 at 293, 303, 313 K, respectively. Moreover, the binding constants of S-DC for HSA were 1.4766 × 105, 1.2899 × 105, and 1.0882 × 105 L · mol-1 at 293, 303, and 313 K individually. Such consequences markedly implied the binding between DC enantiomers and HSA were with higher affinity for S-DC. Steady-state fluorescence study evidenced the formation of DC-HSA complex and there was a single class of binding site on HSA. The thermodynamic parameters (ΔH, ΔS, ΔG) of the reaction clearly indicated that hydrophobic effects and H-bonds contribute to the formation of DC-HSA complex, which was in excellent agreement with molecular simulations. In addition, both site-competitive replacement and suggested that DC enantiomers were located within the binding pocket of Sudlow's site II. Furthermore, the alterations of HSA in the presence of DC enantiomers were verified by UV-vis absorption and 3D fluorescence spectroscopy. This study can provide important insight into the interaction of physiological protein HSA with chiral aryloxyphenoxy propionate herbicides and gives support to the use of HSA for chiral pesticides ecotoxicology and environmental . Chirality 25: 719-725, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

ABSTRACT A rapid, simple, reliable, and environment-friendly method for the residue analysis of the enantiomers of four chiral fungicides including hexaconazole, triadimefon, tebuconazole, and penconazole in water samples was developed by dispersive liquid-liquid microextraction (DLLME) pretreatment followed by chiral high-performance (HPLC)-DAD detection. The enantiomers were separated on a Chiralpak IC column by HPLC applying n-hexane or petroleum ether as mobile phase and ethanol or isopropanol as modifier. The influences of mobile phase composition and temperature on the resolution were investigated and most of the enantiomers could be completely separated in 20 min under optimized conditions. The thermodynamic parameters indicated that the separation was enthalpy-driven. The elution orders were detected by both circular dichroism detector (CD) and optical rotatory dispersion detector (ORD). Parameters affecting the DLLME performance for pretreatment of the chiral fungicides residue in water samples, such as the extraction and dispersive solvents and their volume, were studied and optimized. Under the optimum microextraction condition the enrichment factors were over 121 and the linearities were 30-1500 µg L−1 with the correlation coefficients (R2) over 0.9988 and the recoveries were between 88.7% and 103.7% at the spiking levels of 0.5, 0.25, and 0.05 mg L−1(for each enantiomer) with relative standard deviations varying from 1.38% to 6.70% ( n = 6) The (LODs) ranged from 8.5 to 29.0 µg L−1(S/N = 3). Chirality 25:567-574, 2013. © 2013 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

The stereoselective degradations of racemate metalaxyl (rac-MX) and its single enantiomers in rat and rabbit hepatic microsomes were assayed by a chiral high-performance liquid chromatography method. The t1/2 of (+)-S-MX in rat liver microsomes was between 7–8 min tested by rac-MX and the individual (+)-S-enantiomer, respectively, and that for (−)-R-MX was 15–16 min. In contrast, t1/2 in rabbit liver microsomes was much longer and showed great difference when using racemate and single enantiomer, which was similar to the results of in vivo study. The enantioselectivity in rat hepatic microsomes was more evident and the degradations of MX enantiomers in rat and rabbit hepatic microsomes were Nicotinamide adenine dinucleotide phosphate-dependent. Michaelis constant (Km) and intrinsic metabolic clearance (CLint) of (+)-S-MX were larger than that of (−)-R-MX and there was no chiral inversion from (+)-S-MX to (−)-R-MX or vice versa in both rat and rabbit hepatic microsomes. [ABSTRACT FROM AUTHOR]

A chiral stationary phase (CSP) was prepared by coating cellulose-tris(3, 5-dimethyl-phenylcarbamate) (CDMPC) onto aminopropylated spherical gel, and used this CSP to separate the enantiomers of metalaxyl and metalaxyl intermediate successfully by high performance liquid chromatography (HPLC). The effects of 2-propanol concentration in mobile phase on retention and resolution were investigated, and according to this analytical method the optical purity of metalaxyl and metalaxyl intermediate was established. [ABSTRACT FROM AUTHOR]

(±) - PEN is a chiral fungicide widely used to control powdery mildew in agriculture. Currently, only a few studies have investigated the toxic effects of (±) – penconazole ((±) – PEN) on non-target organisms, and whether (±) - PEN from the enantiomeric level have toxic effects remains unclear. In this study, we systematically evaluated the effects of exposure to (±) – PEN, (+) – PEN and (−) – PEN on liver function in mice. Biochemical and histopathological analyses showed that exposure to (±) – PEN and (−) – PEN led to significant liver damage and inflammation. However, exposure to (+) – PEN treatment did not cause no adverse effects on liver function and inflammation. 1H-NMR-based metabolomics revealed that exposure to (±) – PEN, (+) – PEN and (−) – PEN led to the animals developing liver metabolic disorder that was caused by changes in glycolipid metabolism. Quantitative analysis of genes regulating glycolipid metabolism revealed that expression of gluconeogenesis and glycolytic pathway genes were altered in individuals exposed to (±) – PEN, (+) – PEN and (−) – PEN. We also found that (±) – PEN, (+) – PEN and (−) – PEN have different effects on lipid metabolism of the liver. Exposure to (±) – PEN and (−) – PEN resulted in significant accumulation of lipids by regulating fatty acid synthesis, triglyceride synthesis, and fatty acid β oxidation pathways. In summary, we found different toxicological effects in individuals exposed to (±) – PEN, (+) – PEN and (−) – PEN. The results of this study are important for assessing the potential health risks of (±) – PEN. Image 1 • Exposure to (±) – PEN and its enantiomers caused hepatic glycolipid metabolism disorder of mice. • Both (±) – PEN and (-) – PEN exposures resulted in significant accumulation of lipids. • Gluconeogenesis and glycolytic pathways were significantly interfered with (±) – PEN and its enantiomers exposure. Different toxicological effects on hepatic glycolipid metabolism were produced with (±) – PEN, (+) – PEN and (−) – PEN exposure. [ABSTRACT FROM AUTHOR]

Famoxadone is a chiral fungicide frequently found in the environment and agricultural products. However, the health risks of famoxadone enantiomers are not well understood. This study investigated the stereoselective cytotoxicity and metabolic behavior of famoxadone enantiomers in mammals. Results showed that R -famoxadone was 1.5 times more toxic to HepG2 cells than S -famoxadone. R -famoxadone induced more pronounced ferroptosis compared to S -famoxadone. It caused greater upregulation of genes related to iron transport and lipid peroxidation, and greater downregulation of genes related to peroxide clearance. Furthermore, R -famoxadone induced more severe lipid peroxidation and reactive oxygen species (ROS) accumulation through ACSL4 activation and GPX4 inhibition. Additionally, the bioavailability of R -famoxadone in mice was six times higher than that of S -famoxadone. Liver microsome assays, cytochrome P450 (CYP450) inhibition assays, human recombinant CYP450 assays, and molecular docking suggested that the lower binding affinities of CYP2C8, CYP2C19, and CYP2E1 for R -famoxadone caused its preferential accumulation. Overall, R -famoxadone poses a higher risk than S -famoxadone due to its greater cytotoxicity and persistence. This study provides the first evidence of ferroptosis-induced stereoselective toxicity, offering insights for the comprehensive health risk assessment of chiral famoxadone and valuable references for the application of high-efficiency, low-risk pesticide enantiomers. [Display omitted] • R -famoxadone is 1.5 times more toxic to HepG2 cells than S -famoxadone. • R -famoxadone induces stronger ferroptosis via ACSL4 activation and GPX4 inhibition. • CYP2C8, 2C19 and 2E1 mediate the preferential accumulation of R -famoxadone. [ABSTRACT FROM AUTHOR]

Hexaconazole and epoxiconazole are the worldwidely used fungicides. However, limited information is known about the toxicological effects of their enantiomers on aquatic organisms. In this study, zebrafish were separately exposed to 100 and 1000 μgL−1 hexaconazole and epoxiconazole enantiomers for 21 d 1H NMR-based metabolomics analysis showed that the exposure of low and high dose of hexaconazole enantiomers altered energy metabolism, lipid metabolism and amino acid metabolism of zebrafish, with the different metabolic profiles resulted from the same dose of (+)-hexaconazole and (−)-hexaconazole. Similar to hexaconazole enantiomers, the metabolic profiles, including the changes related to energy metabolism, lipid metabolism and amino acid metabolism, were demonstrated in low and high dose epoxiconazole enantiomers treatment groups. There are differences in the metabolic profiles of zebrafish between exposed to (+)-epoxiconazole and (−)-epoxiconazole of the same dose. The results of histological examination revealed that the exposure of both enantiomers for hexaconazole and epoxiconazole resulted in the similar histopathological changes. The exposure of hexaconazole and epoxiconazole enantiomers at low and high dose resulted the vacuolization and swell in the liver of the female and male zebrafish. Compared to female zebrafish, more liver damage was found in male zebrafish in the hexaconazole enantiomers exposure groups. The reduction of spermatids was observed in hexaconazole and epoxiconazole enantiomers treatment groups of both doses. Hexaconazole enantiomers exposure of low and high dose resulted the increase in the number of mature eggs, while such effect was not observed in epoxiconazole enantiomers exposure groups. Hexaconazole and epoxiconazole enantiomers exposure resulted in no changes in brains of female and male zebrafish. As a result, both triazole-based chiral bactericides, hexaconazole and epoxiconazole, have similar toxicological effects but their mechanisms of action are not exactly the same. The above results will play an important part in making the differences in toxic effects of hexaconazole and epoxiconazole enantiomers clear. What's more, it is an indispensable part for an integrated environmental risk assessment. • The exposure of hexaconazole and epoxiconazole enantiomers altered energy metabolism, lipid metabolism and amino acid metabolism of zebrafish. • The results of histological examination revealed that the exposure of both enantiomers for hexaconazole and epoxiconazole resulted the liver damage and reproductive toxicity. • There is a difference in toxicity mechanism between the two enantiomers of the same pesticide. [ABSTRACT FROM AUTHOR]

Enantioselectivity in ecotoxicity, digestion and uptake of chiral pesticide cyproconazole to Chlorella pyrenoidosa was studied. The 96h-EC 50 values of rac- and the four enantiomers were 9.005, 6.616, 8.311, 4.290 and 9.410 mg/L, respectively. At the concentrations of 8 mg/L and 14 mg/L, the contents of pigments exposed in rac-, enantiomer-2 and 4 were higher than that exposed in enantiomer-1 and 3. The superoxide dismutase (SOD) and catalase (CAT) activity of algae exposed to enantiomer-1 and 3 was higher than that exposed to the rac-, enantiomer-2 and 4 at three levels. In addition, the malondialdehyde (MDA) concentrations in algae disposed with enantiomer-1 and 3 were increased remarkably at three levels. For the digestion experiment, the half-lives of four enantiomers in algae suspension were 28.06, 19.10, 21.13, 15.17 days, respectively. During the uptake experiment, the order of the concentrations of cyproconazole in algae cells was enantiomer-4, 2, 3 and 1. Based on these data, we concluded that ecotoxicity, digestion and uptake of chiral pesticide cyproconazole to C. pyrenoidosa were enantioselective, and such enantiomeric differences must be taken into consideration when assessing the risk of cyproconazole to environment. [ABSTRACT FROM AUTHOR]

An enantioselective chromatographic method to analyze enantiomers of quizalofop-ethyl and its metabolite quizalofop-acid was established using a high-performance liquid chromatography (HPLC) on (R, R) Whelk-O 1 column. The enantioselective degradation kinetics of quizalofop-ethyl and quizalofop-acid in three soils were investigated. Moreover, the interaction with urease and catalase in the soils and the acute toxicity to Eisenia foetida of quizalofop-ethyl were also determined in order to assess their metabolism mechanism and environmental risk. From the results, quizalofop-ethyl was configurationally stable and was hydrolyzed rapidly to quizalofop-acid, which also degraded enantioselectively but slowly, and the inversion of the S-(−)-quizalofop-acid into the R-(+)-quizalofop-acid was observed in Xinxiang soil. In addition, quizalofop-ethyl and quizalofop-acid enantioselectively affected urease activity but not catalase. The acute toxicity assays to earthworm indicated that the racemic quizalofop-ethyl and quizalofop-acid were more toxic than quizalofop-p-ethyl and quizalofop-p-acid respectively, dramatically, the toxicity of the metabolite was much higher than the parent compound. These results revealed the enantioselective degradation of quizalofop-ethyl and quizalofop-acid, and the differences of toxicity among the enantiomers of the parent compound and the metabolite, which should be considered in future environmental risk evaluation. [ABSTRACT FROM AUTHOR]

The stereoselective degradation and transformation of the enantiomers of the herbicide fluazifop-butyl in soil and water were studied to investigate the environmental behavior and chiral stability of the optical pure product. Its main chiral metabolite fluazifop was also monitored. LC/MS/MS with Chiralpak IC chiral column was used to separate the enantiomers of fluazifop-butyl and fluazifop. Validated enantioselective residue analysis methods were established with recoveries ranging from 77.1 to 115.4% and RSDs from 0.85 to 8.9% for the enantiomers. It was found the dissipation of fluazifop-butyl was rapid in the three studied soils (Beijing, Harbin and Anhui soil), and the degradation half-lives of the enantiomers ranged from 0.136 to 2.7 d. Enantioselective degradations were found in two soils. In Beijing soil, R-fluazifop-butyl was preferentially degraded leading to relative enrichment of S-enantiomer, but in Anhui soil, S-fluazifop-butyl dissipated faster. There was no conversion of the R-fluazifop-butyl into S-fluazifop-butyl or vice versa in the soils. The formation of fluazifop in the soils was rapidly accompanied with the fast degradation of fluazifop-butyl, and the enantioselectivity and the transformation of S-fluazifop to R-fluazifop were found. The degradation of fluazifop-butyl in water was also quick, with half-lives of the enantiomers ranging from 0.34 to 2.52 d, and there was no significant enantioselectivity of the degradation of fluazifop-butyl and the formation of fluazifop. The effects of pH on the degradation showed fluazifop-butyl enantiomers degraded faster in alkaline conditions. This study showed an evidence of enantioselective behavior and enantiomerization of the chiral herbicide fluazifop-butyl. [ABSTRACT FROM AUTHOR]

A simple, rapid and effective method was developed based on matrix solid-phase dispersion (MSPD) for the determination of organochlorine pollutants including sixteen organochlorine pesticides (OCPs) and seven polychlorinated biphenyls (PCBs) in oil seeds (peanuts and soybeans). Among the organochlorine pollutants selected, α-HCH, heptachlor, o,p′-DDT, o,p′-DDD, trans-chlordane and cis-chlordane were chiral and their enantiomers were determined by GC–ECD with a chiral column. The MSPD procedure was optimized focusing on the type and amount of dispersion sorbent, co-column sorbent and eluting solvent. Under the optimized condition, good recoveries were obtained in the range of 68.9–103.3% with relative standard deviations (RSD) values below 16.1% in all cases. LODs and LOQs were in range of 0.1–2.0 ng g −1 and 0.4–6.7 ng g −1 respectively. In summary, the method set up was qualified to be used for the determination of the pollutants and the enantiomers in oil seeds. [ABSTRACT FROM AUTHOR]

Enantioselectivity of chiral pesticide enantiomers should be taken into consideration in pesticide application and environmental risk assessment. The phytotoxicity of the enantiomers of napropamide to cucumber, soybean, and the bioactivity to the target weeds Poa annua and Festuca arundinacea have been studied in this work. To the nontarget crops, the influences of napropamide on the root, shoot, fresh weight, chlorophyll, superoxide dismutase (SOD) and catalase (CAT) activities and membrane lipid peroxides have been studied. (−)-Napropamide was more toxic than the racemate and (+)-napropamide to soybean and cucumber in terms of root, shoot and fresh weight. The content of chlorophyll was not affected by napropamide. The impacts on the activities of SOD, CAT and membrane lipid peroxides showed that napropamide could induce the oxidative stress and rac-napropamide caused a stronger oxidative damage to cucumber and soybean than (−)-napropamide and (+)-napropamide. For the target weeds, the influences of napropamide on root, shoot and fresh weight have been studied. (−)-Napropamid was more active to P. annua , while rac-napropamide was more active to F. arundinacea . To reduce environmental pollution and improve the effectiveness of chiral pesticide, single enantiomer should be developed and produced. This work may provide evidence for developing optical pure product. [ABSTRACT FROM AUTHOR]

Little is known about the bioaccumulation and toxicity of hexaconazole (HEX) in spite of the fact that they are indispensable parts for a comprehensive assessment of its environmental behavior and toxic effects in organisms of freshwater ecosystems. In this study, adult zebrafish were used to study the enantioselective bioaccumulation of HEX and its effect endpoints in liver, including oxidative stress and the regulation of apoptosis-related gene expression. Significant enantioselective bioaccumulation was demonstrated when exposed to HEX of 100 and 200 μg L − 1 , finding that the (−)-enantiomer tended to accumulate in zebrafish more easily than (+)-enantiomer. Activities of antioxidant enzymes (SOD, CAT and GPx) and GSH content were all significantly decreased when zebrafish were exposed to 50 and 200 μg L − 1 HEX for 21 d. A series of genes of the apoptosis pathway were examined in groups treated with 50 and 200 μg L − 1 HEX for 21 d using real-time PCR. Significant up-regulation of p53, Puma, Apaf-1, caspase-3 and caspase-9 expression and down-regulation of Bcl-2/Bax expression ratio were proved. The overall results indicated that waterborne HEX was able to produce oxidative stress and induce apoptosis through the involvement of caspases in adult zebrafish. The above information will play a vital role in the integrated environmental risk assessment of HEX and make its toxic mechanism in fish clear. [ABSTRACT FROM AUTHOR]

The benthic fauna is of great importance to assess the environmental fate of contaminations in aquatic ecosystem. In this study, tubificids were exposed to both laboratory-contaminated aqueous phases and spiked sediment to study the bioaccumulation of isocarbophos (ICP). Two types of spiked sediments were used in the spiked sediment experiment. During the exposure period, an enantioselective bioaccumulation was found in spiked water treatment, with concentrations of the (−)-ICP higher than that of the (+)-ICP, but no enantioselectivity was detected in the spiked sediment treatments. However, different bioaccumulation patterns were observed in the two spiked sediment treatments. Results showed that for spiked forest field sediment (FF sediment) incubation, bioaccumulation was governed by the concentrations in soil. Whereas ICP was bioaccumulated dominantly from overlying water in spiked Chagan Lake sediment (CG sediment) test. The dissipation rates were proved different in the two sediments and ICP dissipated much faster in CG sediment than that in FF sediment. Significant difference in ICP’s half-life was also observed between worm-present and worm-free treatments in FF sediment. The detections of concentrations in overlying water indicated that much more ICP diffused to aquatic phase with the present of tubificids. [ABSTRACT FROM AUTHOR]

An efficient and reliable enantioseparation method by high-performance liquid chromatography (HPLC) for the chiral herbicide diclofop-methyl (DM) and its primary metabolite diclofop (DC) was developed and validated, and the biological process of the enantiomers in loach liver microsomes (LLM) in vitro was investigated. The enantiomers of DM and DC were first separated on an immobilized-type stationary phase of Chiralpak IC. The best resolutions were achieved under the chromatographic condition of n -hexane/IPA/TFA 96:4:0.1(v/v/v) at 20 °C with each R s > 2 and the two pairs of enantiomers could be eluted in about 10 min. The extraction recoveries of the analytes from LLM were 79.6–108.9% with RSD ≤ 11.5%. The enzyme kinetics of DM enantiomers were different, with the K m value 320.7 for (S)-DM and 392.1 for (R)-DM. The metabolism experiment in vitro showed DM underwent a rapid phase-I metabolism with or without NADPH, indicating the esterases in liver played a dominant role. No interconversion between the two enantiomers was observed by single-enantiomer incubation. The preferential degradation of (S)-DM was confirmed with the half-time ( t 1/2 ) of (S)-DM 5.27 min and 21.2 min for (R)-DM. DC enantiomer was generated by its corresponding ester form and could not be further degraded during the incubation. It was the first study on biotransformation of DM and DC enantiomers in LLM in vitro . The results may help to evaluate the ecological risks of chiral pesticides. [ABSTRACT FROM AUTHOR]

Research highlights: [•] The acute toxicity to Daphnia magna of hexaconazole enantiomers was enantioselective. [•] (−)-Hexaconazole showed much higher bioactivity to target fungi than its antipode. [•] The degradation was enantioselective in tomato, but not in green pepper. [ABSTRACT FROM AUTHOR]

Abstract: The dissipation behavior of the two enantiomers of malathion was elucidated in five plant species using enantioselective high performance liquid chromatography (HPLC), and the acute toxicity of the individual enantiomers toward earthworms and honeybees was studied. The calculated LC50 values of the R-, S- and rac-malathion to earthworms were 0.3869, 25.17, and 19.19μg/cm2, respectively, while the calculated LC50 values of R-, S- and rac-malathion to bees were 2.15, 36.67, and 7.11μg/mL, respectively. This indicated that the R-enantiomer was more toxic than S-enantiomer. The results of the degradation of racemate in Chinese cabbage and rape showed that the inactive S-(−)-enantiomer degraded faster than the active R-(+)-enantiomer. Inversely, we found a preferential degradation of the R-(+)-enantiomer in sugar beet. However, the degradation of malathion in paddy rice and wheat were nonenantioselectivity. In all plants, malathion was degraded to levels <10% after 5 days, and the calculated t ½ values of the enantiomers ranged from 0.83 to 1.43 days in these five plants. In conclusion, our findings of enantioselectivity in the environmental fate and acute toxicity of the malathion enantiomers may have implications for better environmental and ecological risk assessment for chiral pesticides in general. [Copyright &y& Elsevier]

Abstract: Enantioselective behavior of chiral pesticides in the aquatic environment has been a subject of growing interest. In this study, the enantioselective bioaccumulation of fipronil enantiomers in Tubifex tubifex (Oligochaeta, Tubificida) was detected in both spike–water and spike–soil systems, respectively. For the spike–water treatment, a 9-day exposure experiment was employed and the enantiomer fraction in tubifex tissue was maintained approximately at 0.58 during the experiment. In addition, a 14-day bioaccumulation period was chosen for the spike–soil treatment and a more significant deviation of enantiomer fraction from 0.5 in tubifex tissue was detected, with concentrations of the R-form higher than that of the S-form. Therefore, the bioaccumulation of fipronil was enantioselective in tubifex tissue for the two treatments and the magnitude of enantioselectivity may be influenced by different exposure conditions. For the spike–soil treatment, the concentrations of fipronil in verlying water and soil were also determined. With the presence of tubifex worms, higher concentrations of fipronil in overlying water and lower concentrations in soil were detected than that in the absence of tubifex treatment during the whole 14-day exposure period. This means that tubifex has positive functions in fipronil''s diffusion from soil to overlying water and in the degradation of the soil-associated fipronil. [Copyright &y& Elsevier]

Abstract: This experiment studied the behaviour of diclofop-methyl (DM) and its main metabolite, diclofop (DC), during the pickling process. DM showed obvious enantioselective degradation in the pickled cabbage in the pickling process, with a half-life of 4.95days for (+)-(R)-DM but less than 12h for (−)-(S)-DM. In addition, the stereoselective degradation of DM also led to the enantioselective formation of DC. Therefore, (−)-(S)-DC showed a higher residue level than (+)-(R)-DC in both pickled cabbage and its brine. Rac-DC was added into the cabbage used for pickling to study the behaviour of the enantiomers of DC; no enantioselective degradation was observed either in the pickled cabbage or in the brine. DM and DC were configurationally stable in the process, showing no interconversion of (−)-(S)- to (+)-(R)- enantiomer, or vice versa. This research provides information for evaluating the risk of food safety and environmental pollution at the enantiomer level. [Copyright &y& Elsevier]

Abstract: Alpha-cypermethrin, a synthetic pyrethroid, is highly effective against a wide range of chewing and sucking insects in crops, and it is a racemic mixture of two enantiomers ((+)-1R-cis-αS +(−)-1S-cis-αR). Studies about the toxicity of alpha-cypermethrin to non-target organisms are mainly focused on aquatic organisms, whereas information regarding terrestrial organisms is relatively much less. Very little report about its enantioselective toxicity is known, so the present study tested the enantiomer-specific acute toxicity to earthworm Eisenia fetida. Experiment about bioaccumulation of two enantiomers in soil was conducted, peak-shaped accumulation curves were observed for both enantiomers, and the calculated biota to soil accumulations factor (BSAF) have significant difference between the two enantiomers. It was obvious that earthworm can uptake alpha-cypermethrin enantioselectively, preferentially accumulating (−)-(1S-cis-αR)-enantiomer. Great difference in toxicity to earthworm between two enantiomers was found, and the calculated LC50 values for (+)-(1R-cis-αS)-, (−)-(1S-cis-αR)-, and rac-alpha-cypermethrin were 49.53, 1663.87 and 165.61ng/cm2, respectively. The acute toxicity of alpha-cypermethrin enantiomers was enantioselective. [Copyright &y& Elsevier]

Abstract: Knowledge about the enantioselective bioavailability of chiral pesticides in soil invertebrates facilitates more accurate interpretation of their environmental behaviors. In this study, the acute toxicities of R-metalaxyl and rac-metalaxyl to earthworm (Eisenia foetida) were assayed by filter paper contact test. After 48h of exposure, the calculated LC50 values for R- and rac-metalaxyl were 0.052 and 0.022mgcm−2, respectively, resulting in a two fold difference in toxicity. For uptake experiment, earthworms were exposed in soil at two dose levels (10 and 50mg ). The concentrations of two enantiomers in soil and earthworm were determined by high-performance liquid chromatography based on cellulose tri-(3,5-dimethylphenyl-carbamate) chiral stationary phase. The results showed that metalaxyl was taken up by earthworm rapidly, and the bioaccumulation of metalaxyl in earthworm was enantioselective with preferential accumulation of S-enantiomer. In addition, biota to soil accumulation factor (BSAF) used to express the bioaccumulation of metalaxyl enantiomers was investigated, and significant difference was observed between rac-metalaxyl and R-metalaxyl. [Copyright &y& Elsevier]

Abstract: In this paper, a new chiral stationary phase (CSP) based on Candida antarctica lipase B (CALB) bounding to the surface of macroporous silica gel was developed and its stereoselectivity in enantioseparation and asymmetrical hydrolysis was evaluated. Three CALB-based HPLC columns with different amounts of enzyme immobilized were prepared by employing the immobilization method, namely “in batch”. In this technique two chromatographic supports epoxy silica and aminopropyl silica were considered. This novel CSP was proven capable of hydrolyzing chiral esters asymmetrically as bioreactor and separating several aromatic alcohols and diniconazole enantiomers. [Copyright &y& Elsevier]

Abstract: The stereoselective degradation of the racemic diclofop-methyl and its chiral degradation product, diclofop (the hydrolysate of diclofop-methyl), in cole has been investigated. Both enantiomers of diclofop-methyl and diclofop were extracted by organic solvent and detected by chiral high-performance liquid chromatography–diode array detector (DAD). Cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral column was used for the chiral separation of the four enantiomers applying a mixture of n-hexane and 2-propanol (98:2) concluding 0.1% TFA as mobile phase at a flow rate of 1.0mL/min. The assay method was linear over a range of concentrations (0.5–250mgL−1), and the mean recovery was more than 60% for all the enantiomers. The limit of detection for all the enantiomers was 0.2μgg−1 in plant. Racemic diclofop-methyl was foliar sprayed to cole. Stereoselective behaviour was observed in the diclofop-methyl degradation process. The (S)-diclofop-methyl dissipated faster than (R)-diclofop-methyl. In the case of diclofop, the generation and degradation rates of (S)-enantiomer were higher than (R)-enantiomer in the plant. [Copyright &y& Elsevier]

Abstract: The enantioselective metabolism of racemic fipronil in water hyacinth (Eichhornia crassipes) had been investigated. In this study, the degradation data and the enantiomer fraction (EF) were determined by chiral high-performance liquid chromatography (HPLC) with a column cellulose-tri-(3, 5-dimethylphe-nylcarbamate)-based chiral stationary phase (CDMPC-CSP). During the uptake phase, the EF value of plant sample increased from 0.50 at 1st day to 0.72 at 63rd day, while it was almost unchanged in water. For the depuration phase, the S- and R-enantiomer of fipronil in water hyacinth plants were degraded 92.22% and 82.07% after 17days, respectively. The process of the degradation of the two enantiomers was followed first-order kinetics (R 2 ⩾0.94). Stereoselective behavior was observed in both accumulation and degradation process. In this study, fipronil-sulfone and fipronil-sulfide, the metabolites of fipronil, were detected by GC–MS to show the main metabolic pathway of fipronil in water hyacinth. [Copyright &y& Elsevier]

Abstract: Chiral pesticide enantiomers often show different bioactivity and residual toxicity, but this property is usually ignored when evaluating the environmental risk and public safety. In this study, a convenient and precise chiral method was developed and validated for measuring fipronil enantiomers in Chinese cabbage (Brassica pekinensis) based on a high-performance liquid chromatography (HPLC) using (R,R) Whelk-O 1 column. Then the proposed method was successfully applied to the study of enantioselective degradation of fipronil in Chinese cabbage under field conditions. The results showed that the degradation of the two enantiomers in Chinese cabbage was proved to be enantioselective and followed pseudo first-order kinetics (R 2 ⩾0.98). The (R)-enantiomer degraded faster than the (S)-enantiomer, resulting in the relative enrichment of (S)-enantiomer in residue. The detected metabolites MB46513 (desthio), MB45950 (sulfide) and MB46136 (sulfone) by GC–MS suggested that degradation was mainly contributed by oxidization, reduction and photodegradation. Due to the more insecticide activity and lower mammalian toxicity of S-form, the higher concentration of S-fipronil may result in higher activity in crop protection and lower risk to environment and human beings compared to the recemate. This result should be considered in future environmental risk and food safety evaluation. [Copyright &y& Elsevier]

Abstract: The stereoselective degradation of the racemic diclofop-methyl in Chinese cabbage and several agricultural soils had been investigated. Both the enantiomers were analyzed by organic solvent extraction and validated by chiral high-performance liquid chromatography-diode array detector (DAD). Cellulose-tris-(3,5-dimethylphenylcarbamate)-based chiral column was used for the chiral separation of the two enantiomers applying a mixture of n-hexane and 2-propanol (90:10) as mobile phase at a flow rate of 1.0mL/min. The elution order of the two enantiomers was distinguished by a JASCO 2000 HPLC-circular dichroism (CD) system and the first elution was (−)-enantiomer while the other was (+)-enantiomer. Racemic diclofop-methyl was fortified into 10 types of agricultural soils and foliar applied to Chinese cabbage. The assay method was linear over a range of concentrations (0.5–250mgL−1) and the mean recovery was more than 80% for both enantiomers. The limit of detection for both enantiomers was 0.1μgg−1 in soil and plant samples. The results of the stereoselectivity degradation of diclofop-methyl enantiomers in soil showed that the (−)-enantiomer was dissipated faster than the (+)-enantiomer in two typical soils and this enantioselectivity may be caused by microorganism, but no stereoselectivity was observed in other soils. In Chinese cabbage plant, (+)-enantiomer accumulated and eliminated faster than its antipode. [Copyright &y& Elsevier]

Abstract: A simple chiral high-performance liquid chromatography (HPLC) method with ultraviolet (UV) and circular dichroism (CD) detection was developed and validated for measuring benalaxyl enantiomers using (R,R) Whelk-O 1 column. The effects of mobile phase composition and column temperature on the entioseparation were investigated. A CD detector was used to determine the elution order of the enantiomers. Excellent resolution was easily obtained using n-hexane-polar organic alcohols mobile phase. The chiral recognition mechanism was also discussed. Based on the developed chiral HPLC method, enantioselective analysis methods for this fungicide in environment matrix (soil and water) were developed and validated. Good linearities were obtained over the concentration range of 0.25–25mgL−1 for both enantiomers. Liquid–liquid extraction and solid phase extraction (SPE) were used for the enrichment and cleanup of soil and water samples. Recoveries for the two enantiomers were 79–91% at 0.02, 0.04 and 0.2mgkg−1 levels from soil, and 89–101% at 0.0025, 0.01 and 0.05mgL−1 levels from water. Run-to-run and day-to-day assay precisions were below 10% for both enantiomers at concentrations of 0.5, 1 and 5mgL−1. Individual detection limits of the two enantiomers were both 2ng. Limits of detection (LOD) were 0.004mgkg−1 in soil and 0.001mgL−1 in water. [Copyright &y& Elsevier]

Abstract: Metalaxyl [methyl-N-(2′-methoxyacetyl)-N-(2,6-dimethylphenyl)-d,l- alaninate] is a potent phenylamide fungicide. The (−)-(R)-isomer accounts for most of the fungicidal activity. A possible stereo and/or enantioselective kinetics of metalaxyl in rabbits was investigated by intravenous injection. The concentrations of (−)-(R)- and (+)-(S)-metalaxyl in plasma, liver, and kidney tissue were determined by HPLC with a cellulose–Tris-(3,5-dimethylphenylcarbamate)-based chiral stationary phase and gas chromatography-mass spectroscopy. After intravenous administration of racemic metalaxyl (40mg/kg), the (+)-(S)-enantiomer levels in plasma, liver, and kidney decreased more rapidly than the (−)-(R)-isomer. The area ratio of the (−)-(R)-/(+)-(S)-enantiomer under the concentration–time curve (AUC0→∞) in plasma after drug application was 1.62. The total plasma clearance value of the (+)-(S)-enantiomer was 1.53 and higher than that of the (−)-(R)-enantiomer. The [R]/[S] ratio in plasma was >1 for standard rac-metalaxyl at each time point. The other pharmacokinetic parameters of the enantiomers were also different. The results indicate substantial stereoselectivity in the degradation of metalaxyl enantiomers in rabbits. [Copyright &y& Elsevier]

Imazethapyr (IMZT) is a typical chiral pesticide with two enantiomers with the R -IMZT having the main herbicidal activity. However, the enantioselectivity of the effects of IMZT enantiomers on human and animals is still unclear. In this study, a nuclear magnetic resonance (NMR)-based metabolomics method and determination of oxidative stress were used to evaluate the enantioselectivity of IMZT enantiomers in mice. The results showed that the R -IMZT caused larger disturbances of endogenous metabolites and the S -IMZT had stronger interferences to oxidation defense system. The significantly perturbed metabolic pathways in mice exposed to the R -enantiomer were the valine, leucine and isoleucine biosynthesis pathway as well as the phenylalanine, tyrosine and tryptophan biosynthesis pathway. However, exposure of mice to the S -enantiomer did not significantly affect the metabolic pathways, but exposure led to an increase of catalase (CAT) activity and an increase in malondialdehyde (MDA) content in the liver. These results indicate that we need to conduct a more comprehensive assessment of the health risks of pesticide monomers in the future. In a word, these results provide more evidence for assessing the differences in health risks of IMZT enantiomers to mammals as well as provide more references for the promotion and use of pesticide monomers in the future. Unlabelled Image • The effects of imazethapyr enantiomers on mice were enantioselective. • The R -IMZT more significantly perturbed metabolic homeostasis. • Exposure to the R -IMZT significantly interfered with two metabolic pathways. • The S -IMZT more significantly affected the oxidation defense system. [ABSTRACT FROM AUTHOR]

• R-cis-bifenthrin(R-cis-BF) has higher acute aquatic toxicity than S-cis-bifenthrin. • Cis-bifenthrin influenced behavioral endpoints of tadpoles. • Expression of development-related genes were affected by cis-bifenthrin. • Cis-bifenthrin influenced levels of thyroid hormone. • Stereoselective tissue distribution of cis-bifenthrin occurred in tadpoles. Chirality should be taken into consideration when assessing the effect of synthetic pyrethroids to aquatic environmental safety. In our study, 96 h acute toxicity assay showed that enantiomers of cis-BF had an addictive effect of toxicity on Xenopus laevis and R-cis-bifenthrin(R-cis-BF) had higher acute toxicity than S-cis-BF. In chronic assay, R-cis-BF exerted more toxic effect on behavior and development of tadpoles than S-cis-BF, and there was also enantioselective effect of cis-BF on antioxidant enzyme and LDH activity. Besides, thyroid development was also affected at the gene and hormone level, with varied effects observed with different exposure enantiomers. Moreover, in the enantioselective accumulation and tissue distribution of enantiomer assays, results showed that R-cis-BF had higher affinity to organisms than S-cis-BF. This study provided the evidence that chiral pesticides enantioselectively affected development of amphibians, and also shed light on the understanding of enantioselectivity in both acute and chronic eco-toxicities to improve risk assessment and regulation of chiral pesticides. [ABSTRACT FROM AUTHOR]