Authors: John Mumbo Dieter Lenoir Bernhard Henkelmann KarlWerner Schramm
Publish Date: 2013/06/12
Volume: 20, Issue: 12, Pages: 8996-9005
Abstract
3Chlorocarbazole 36dichlorocarbazole dibromocarbazole and 1368tetrabromocarbazole are emerging environmental contaminants which have been detected recently in water sediment and soil samples However their sources and occurrence have not been explained Here we report an enzymatic synthesis of bromo and chlorocarbazoles by chloroperoxidase from Caldariomyces fumago in water Density functional theory DFT method was used to predict the most stable products Carbazole and chloroperoxidase were assayed in vitro in the presence of hydrogen peroxide bromide and chloride ions in different substrate ratio treatments against constant and varying enzyme concentrations Halogenated carbazoles formed were identified by highresolution gas chromatography coupled to mass spectrometry In all treatments bromination and chlorination took place but the composition and concentration of compounds formed varied from one treatment to another Mono di tri and tetrasubstituted bromo and chlorocarbazoles which include the reported environmental contaminants were synthesized 3Substituted and 36substituted congeners were relatively higher in concentration Enzyme concentration did not favor preferential formation of any of the compounds synthesized However their synthesis was influenced by halide concentration Congeners with bromine and chlorine at position of C3 C36 C136 and C1368 were calculated as the stable intermediate sigma complexes by DFT method Regioselectivity in halogenation is discussed and hypothesis of the likely stable products in the environment explained This study provides evidence that bromo and chlorocarbazoles reported previously can be formed enzymatically in the environment demonstrating the need to consider aromatic pollutants transformation and their potential toxicity enhancements in the management of water pollution and contaminated sites
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