Isomerization of chiral pesticides in the environment

Katagi, Toshiyuki

doi:10.1584/jpestics.d11-036

Cited by 30 publications

(27 citation statements)

References 122 publications

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“…A steady‐state enantiomeric composition was not achieved within 40 days. The proposed mechanism for the conversion was that the chiral carbon of metalaxyl activated by either the adjacent functional group C = O or an enzyme action may be deprotonated to a carbanion and then protonated concomitantly with enantiomerization or racemization …”

Section: Resultsmentioning

confidence: 99%

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Enantioselective Degradation and Chiral Stability of Metalaxyl‐M in Tomato Fruits

et al. 2016

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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 liquid chromatography tandem mass spectroscopy (HPLC-MS/MS). The enantioselective 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 enantioselectivity 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.

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Section: Resultsmentioning

confidence: 99%

“…There is an increasing interest to evaluate the enantioselective behavior of chiral pesticides in the environment, because certain enantiomers are often preferentially degraded over the others . R‐triadimefon dissipated faster than the S‐form in soils, while S‐fenoxaprop‐ethyl degraded faster than the R‐enantiomer .…”

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confidence: 99%

Enantioselective Degradation and Chiral Stability of Metalaxyl‐M in Tomato Fruits

et al. 2016

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“…Such discrepancies in enantioselective degradation may arise from the variety of microbial populations, which are dependent on sampling locations and experimental conditions such as the moisture content and aerobicity of sediments. [31][32][33] Although no cis-trans isomerization has occurred at the cyclopropyl moiety, the epimerization at the α-cyanobenzyl carbon via abiotic base-catalyzed reaction probably proceeded along with degradation processes 33) in the tested water-sediment system at pH >8. These factors, acting in a complicated manner, may cause the different enantioselectivity in the degradation of 1.…”

Section: Discussionmentioning

confidence: 95%

Behavior of cyphenothrin in aquatic environment

et al. 2017

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The behavior of cyphenothrin (1) [(RS)-α-cyano-3-phenoxybenzyl (1RS)-cis-trans-2,2-dimethyl-3-(2-methylprop-1-enyl)cyclopropanecarboxylate] in an aquatic environment was investigated by using the 14 C-labeled trans and cis isomers. In parallel with the rapid partition from water phase to bottom sediment, 1 was degraded with the first-order half-lives of 2.0 (trans-1) and 7.3 days (cis-1) in the water-sediment system under dark conditions. 1 underwent extensive microbial degradation via ester cleavage to form 3-phenoxybenzoic acid, finally forming bound residues and mineralizing to CO 2 . Aqueous photolysis significantly accelerated the degradation of 1 with a half-life of <1 day, mainly via photo-induced oxidation at the 2-methylprop-1-enyl group and ester cleavage without cis-trans isomerization. These results strongly suggest that 1 is unlikely to persist in the actual aquatic environment due to its rapid photolysis and extensive microbial degradation.

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“…21 In this study, this kinetic was calculated by Sigmaplot 12.5. Enantiomeric fractions (EF), as given by Harner et al, 22 were used to express the differences between enantiomers, that is,…”

Section: ■ Materials and Methodsmentioning

confidence: 99%

Enantioselective Dissipation of Acephate and Its Metabolite, Methamidophos, during Tea Cultivation, Manufacturing, and Infusion

Pan

Chen

Wang

et al. 2015

J. Agric. Food Chem.

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The enantioselective dissipation of acephate and its metabolite, methamidophos, was investigated during tea cultivation, manufacturing, and infusion, using QuEChERS sample preparation technique and gas chromatography coupled with a BGB-176 chiral column. Results showed that (+)-acephate and (-)-acephate dissipated following first-order kinetics in fresh tea leaves with half-lives of 1.8 and 1.9 days, respectively. Acephate was degraded into a more toxic metabolite, methamidophos. Preferential dissipation and translocation of (+)-acephate may exist in tea shoots, and (-)-methamidophos was degraded more rapidly than (+)-methamidophos. During tea manufacturing, drying and spreading (or withering) played important roles in the dissipation of acephate enantiomers. The enantiometic fractions of acephate changed from 0.495-0.496 to 0.479-0.486 (P ≤ 0.0081), whereas those of methamidophos changed from 0.576-0.630 to 0.568-0.645 (P ≤ 0.0366 except for green tea manufacturing on day 1), from fresh tea leaves to made tea. In addition, high transfer rates (>80%) and significant enantioselectivity (P ≤ 0.0042) of both acephate and its metabolite occurred during tea brewing.

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Isomerization of chiral pesticides in the environment

Cited by 30 publications

References 122 publications

Enantioselective Degradation and Chiral Stability of Metalaxyl‐M in Tomato Fruits

Enantioselective Degradation and Chiral Stability of Metalaxyl‐M in Tomato Fruits

Behavior of cyphenothrin in aquatic environment

Enantioselective Dissipation of Acephate and Its Metabolite, Methamidophos, during Tea Cultivation, Manufacturing, and Infusion

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