- Metabolism of carbosulfan II. Human interindividual variability in its in vitro hepatic biotransformation and the identification of the cytochrome P450 isoforms involved
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This study aims to characterize interindividual variability and individual CYP enzymes involved in the in vitro metabolism of the carbamate insecticide carbosulfan. Microsomes from ten human livers (HLM) were used to characterize the interindividual variability in carbosulfan activation. Altogether eight phase I metabolites were analyzed by LC-MS. The primary metabolic pathways were detoxification by the initial oxidation of sulfur to carbosulfan sulfinamide ('sulfur oxidation pathway') and activation via cleavage of the nitrogen sulfur bond (N-S) to give carbofuran and dibutylamine ('carbofuran pathway'). Differences between maximum and minimum carbosulfan activation values with HLM indicated nearly 5.9-, 7.0, and 6.6-fold variability in the km, Vmax and CLint values, respectively. CYP3A5 and CYP2B6 had the greatest efficiency to form carbosulfan sulfinamide, while CYP3A4 and CYP3A5 were the most efficient in the generation of the carbofuran metabolic pathway. Based on average abundances of CYP enzymes in human liver, CYP3A4 contributed to 98% of carbosulfan activation, while CYP3A4 and CYP2B6 contributed 57 and 37% to detoxification, respectively. Significant correlations between carbosulfan activation and CYP marker activities were seen with CYP3A4 (omeprazole sulfoxidation), CYP2C19 (omeprazole 5-hydroxylation) and CYP3A4 (midazolam 1′-hydroxylation), displaying r2=0.96, 0.87 and 0.82, respectively. Activation and detoxification pathways were inhibited by ketoconazole, a specific CYP3A4 inhibitor, by 90-97% and 47-94%, respectively. Carbosulfan inhibited relatively potently CYP3A4 and moderately CYP1A1/2 and CYP2C19 in pooled HLM. These results suggest that the carbosulfan activation pathway is more important than the detoxification pathway, and that carbosulfan activation is predominantly catalyzed in humans by CYP3A4.
- Abass, Khaled,Reponen, Petri,Mattila, Sampo,Pelkonen, Olavi
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experimental part
p. 163 - 173
(2011/10/19)
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- Competitive degradation and detoxification of carbamate insecticides by membrane anodic fenton treatment
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The competitive degradation of six carbamate insecticides by membrane anodic Fenton treatment (AFT), a new Fenton treatment technology, was carried out in this study. The carbamates studied were dioxacarb, carbaryl, fenobucarb, promecarb, bendiocarb, and carbofuran. The results indicate that AFT can effectively degrade these insecticides in both single component and multicomponent systems. The carbamates compete for hydroxyl radicals, and their kinetics obey the previously developed AFT kinetic model quite well. Hydroxyl radical reaction rate constants were obtained, and they decrease in the following order: dioxacarb ≈ carbaryl > fenobucarb > promecarb > bendiocarb > carbofuran. The AFT is shown to have higher treatment efficiency at higher temperature. Degradation products of the carbamates were determined by gas chromatography/mass spectrometry, and it appears that degradation can be initiated by hydroxyl radical attack at different sites in the molecule, depending on the individual structure of the compound. Substituted phenols are the commonly seen degradation products. The AFT treatment can efficiently remove the chemical oxygen demand of the carbamate mixture, significantly increasing the biodegradability. Earthworm studies show that the AFT is also an effective detoxification process.
- Wang, Qiquan,Lemley, Ann T.
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p. 5382 - 5390
(2007/10/03)
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- Heterocyclic dioxethane substrates, process for their preparation and their use
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PCT No. PCT/EP96/04506 Sec. 371 Date Apr. 20, 1998 Sec. 102(e) Date Apr. 20, 1998 PCT Filed Oct. 17, 1996 PCT Pub. No. WO97/14696 PCT Pub. Date Apr. 24, 1997Compounds of the general formula Ia and Ib are described in which R1 and R2 are the same or differ
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- Chemical models of cytochrome P450 catalyzed insecticide metabolism. Application to the oxidative metabolism of carbamate insecticides
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Cytochrome P450 (CP450) catalyzed oxidative metabolism of carbofuran (1), carbaryl (2), and pirimicarb (3) has been modeled using biomimetic oxidations catalyzed by iron(III) tetraarylporphyrins. Oxidation products of 1 were identified by comparison of HPLC retention times measured under standardized conditions for metabolites synthesized and characterized by 1H and 13C NMR spectroscopy. Comparison of product distributions to in vivo metabolic profiles revealed that the H2O2/meso- tetrakis(pentafluorophenyl)porphyrin iron(III) chloride [Fe(TF20PP)] system mimics the action of insect CP450s against carbofuran. The effectiveness of this system was further demonstrated by the biomimetic oxidation of other carbamate insecticides (2 and 3) monitored by HPLC/electrospray MS. The predictive power of this biomimetic model was compared to that of knowledgebased expert systems. Although similar models were recently applied in pharmaceutical research, the usefulness of this approach has first been demonstrated for the prediction of metabolic profiles of agrochemicals.
- Keserue, Gyoergy M.,Balogh, Gyoergy,Czudor, Iren,Karancsi, Tamas,Feher, Andras,Bertok, Bela
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p. 762 - 769
(2007/10/03)
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