Nitroarenes metabolism

Nitrosoarenes are readily formed by the oxidation of primary N-hydroxy arylamines and several mechanisms appear to be involved. These include 1) the metal-catalyzed oxidation/reduction to nitrosoarenes, azoxyarenes and arylamines (144) 2) the 02-dependent, metal-catalyzed oxidation to nitrosoarenes (145) 3) the 02-dependent, hemoglobin-mediated co-oxidation to nitrosoarenes and methe-moglobin (146) and 4) the 0 2-dependent conversion of N-hydroxy arylamines to nitrosoarenes, nitrosophenols and nitroarenes (147,148). Each of these processes can involve intermediate nitroxide radicals, superoxide anion radicals, hydrogen peroxide and hydroxyl radicals, all of which have been observed in model systems (149,151). Although these radicals are electrophilic and have been suggested to result in DNA damage (151,152), a causal relationship has not yet been established. Nitrosoarenes, on the other hand, are readily formed in in vitro metabolic incubations (2,153) and have been shown to react covalently with lipids (154), proteins (28,155) and GSH (17,156-159). Nitrosoarenes are also readily reduced to N-hydroxy arylamines by ascorbic acid (17,160) and by reduced pyridine nucleotides (9,161). 

Howard, P. C., S. S. Hecht, and F. A. Beland, Eds., Nitroarenes Occurrence, Metabolism, and Biological Impact, Environmental Science Research, Vol. 40, Plenum, New York, 1990. 

In reduced cytochrome P450, the iron(II) is electron-rich by virtue of the porphyrin ring and the endogenous thiolate, and can reduce a variety of organic substrates, including nitroarenes, amine oxides, and halomethanes (75). The metabolism of CC14 or CF3CHClBr ( halothane anesthetic)... 

Various modern products may serve as sources for trace amounts of PAA. The origins, known hazards, release restrictions and environmental fate of PAA derived from azo dyes have been reviewed2. The metabolism of nitroarenes is closely linked to that of aromatic amines, as shown in a simplified way in equation 369. Gloeophyllum trabeum cultures spiked with TNT show formation of nitroaromatic amines such as 2-ami no-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene and 2,4-diamino-6-nitrotoluene. Also, autoxi-dation of the methyl group of TNT or its metabolites may take part in the degradation process, as shown by the presence of Schiff bases and oligomeric and polymeric species detection and determination of the analytes after LLE and concentration were by HPLC-UVD or GC-MS70. 

Next to the limited analytical information available from studies of PAH-metabolism, there is a surprising lack in the current literature of research data on analytical methods for polar PAH-derivatives in environmental samples, e.g. epoxides, phenols, nitroarenes, which may be of great toxicological significance. 

In parallel with molecular nonculture methods, the well-established methods of enrichment culture are more frequently being applied under anaerobic and other nonstandard conditions in an effort to obtain novel microbial types. This approach also suggests that biodegradative capabilities are more widespread in the microbial world than has been appreciated by some. For example, halophiles have been identified which metabolize nitroarenes, and members of the Heliobacterium group are known that catabolize polychlorinated biphenyls (PCBs) and chlorophenols (O Table 15.2). These and other recent observations are expanding the taxonomic range of bacteria that catabolize environmental pollutants. Further experiments are likely to expand this further. 

Corbett, M. D. and B. R. Corbett. 1990. Biochemical studies on the putative nitroso metabolite of chloramphenicol a new model for the cause of aplastic anemia, p. 245-255. In P.C. Howard, S.S. Hecht and F.A. Beland (ed.), Nitroarenes occurrence, metabolism and biological impact. Plenum Press, New York. 

Volume 40 — NITROARENES Occurrence, Metabolism, and Biological Impact... 

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