952 resultados para Degradation of azo dye


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Prepared for U.S. Environmental Protection Agency, Office of Research and Development, Environmental Research Laboratory, Athens, Ga., under grant no. R800371.

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Mode of access: Internet.

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Technical report 6520. AD 627 210.

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Echinacea preparations are widely used herbal remedies for the prevention and treatment of colds. In this study we have investigated the metabolism by human liver microsomes of the alkylamide components from an Echinacea preparation as well as that of pure synthetic alkylamides. No significant degradation of alkylamides was evident in cytosolic fractions. Time and NADPH-dependent degradation of alkylamides was observed in microsomal fractions suggesting they are metabolised by cytochrome P450 (P450) enzymes in human liver. There was a difference in the susceptibility of 2-ene and 2,4-diene pure synthetic alkylamides to microsomal degradation with (2E)-N-isobutylundeca-2-ene-8,10-diynamide (1) metabolised to only a tenth the extent of (2E,4E,8Z,IOZ)-N-isobutyldodeca-2,4,8,10-tetracnamide (3) under identical incubation conditions. Markedly less degradation of 3 was evident in the mixture of alkylamides present in an ethanolic Echinacea extract, suggesting that metabolism by liver P450s was dependent both on their chemistry and the combination present in the incubation. Co-incubation of 1 with 3 at equimolar concentrations resulted in a significant decrease in the metabolism of 3 by liver microsomes. This inhibition by 1, which has a terminal alkyne moiety, was found to be time- and concentration-dependent, and due to a mechanism-based inactivation of the P450s. Alkylamide metabolites were detected and found to be the predicted epoxidation, hydroxylation and dealkylation products. These findings suggest that Echinacea may effect the P450-mediated metabolism of other concurrently ingested pharmaceuticals. (c) 2005 Elsevier Ireland Ltd. All rights reserved.

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The thermal degradation of high density polyethylene has been modelled by the random breakage of polymer bonds, using a set of population balance equations. A model was proposed in which the population balances were lumped into representative sizes so that the experimentally determined molecular weight distribution of the original polymer could be used as the initial condition. This model was then compared to two different cases of the unlumped population balance which assumed unimolecular initial distributions of 100 and 500 monomer units, respectively. The model that utilised the experimentally determined molecular weight distribution was found to best describe the experimental data. The model fits suggested a second mechanism in addition to random breakage at slow reaction rates. (c) 2005 Elsevier Ltd. All rights reserved.

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