Nitro-PAHs

Natural 1580 Matrix Materials Organics in shale oll 5 (3 dlnitro and 1 nitro) PAH s + 4 oxygen-... 

Understanding particulate emissions, their formation and control, is another key issue in meeting the new particulate emission Hmits set by the new EURO emission standards. The particulate emissions formed in diesel engines have a mass median diameter of 0.05-1.0 gm. Particle consists of carbon with various HCs adsorbed on it including polyaromatic hydrocarbon (PAH) as well as nitro-PAH compounds. 

Diesel Particulate Extract PAHs (8) PAH (23) Nitro-PAHs (18)... 

A large number of reagents are available for the preparation of nitro PAHs. These include fuming nitric acid in acetic acid (20) or acetic anhydride (13), sodium nitrate in trifluoroacetic acid (21) or trifluoroacetic acid and acetic anhydride (17), dinitrogen tetroxide in carbon tetrachloride (22), sodium nitrate in trimethyl phosphate and phosphorus pentoxide (23), and nitronium tetrafluoroborate in anhydrous acetonitrile (24). Alternative approaches must be used to synthesize nitro PAHs substituted at positions other than the most reactive carbon. For instance,... 

A wide variety of nitro PAHs have been isolated from different environmental sources including airborne particulates (27-34), coal fly ash (35-37), diesel emission particulates (38-41) and carbon black photocopier toners (42-43). Their presence has also been suggested in the smoke from nitrate-fortified cigarettes (44). The structures of the most commonly detected nitro PAHs are shown in Figure 1 and in each instance it is the kinetically-favored isomer that is found. 

Figure 1. Structures of commonly detected nitro PAHs.

Nitro PAHs have been shown to exhibit a large variety of biological activities. Included in these are the induction of mutations in bacterial (Table I) and eukaryotic cells (9,17,54-57), the neoplastic transformation of cultured mammalian cells (58-59), and the induction of DNA strand breaks (60), DNA repair (61-62), sister chromatid exchanges (63-64), and chromosomal aberrations (65-66). Nitro PAHs have also been demonstrated to bind cellular DNA in bacteria (67-73) and mammalian cells (74-77), to inhibit preferentially the growth of repair-deficient bacteria (78), to have recombinogenic activity in yeast (66,79-80) and to induce tumors in experimental animals (Table II). 

Mutagenicity. The mutagenicity of nitro PAHs has been studied most extensively in the Ames Salmonella typhimurium reversion assay ( 5). The mutagenicities of representative nitro PAHs in this assay are shown in Table I. Some of the more important features regarding their mutagenicity can be summarized as follows ... 

Tumorigenicity. A number of nitro PAHs have been shown to be... 

Table I. Mutagenicity of Representative Nitro PAHs in Salmonella typhimurium strains TA98 and TA100 (revertants per nmole)...

Salmonella typhimurium. Although most nitro PAHs are direct-acting mutagens in Salmonella typhimurium, these compounds must be metabolized to bind covalently to DNA (71,92,112). S. typhimurium contains a family of nitroreductases which are capable of reducing nitro PAHs, and strains which are deficient in these enzymes generally show decreased sensitivity toward nitro PAH-induced mutations (27,92,113-114). These observations suggest that reduced metabolic intermediates may be the critical reactive electrophiles. 

Compared to the extensive data that have been obtained on the mutagenicity of nitro PAHs in S. typhimurium, relatively little is known about the metabolism of these compounds in this organism. Messier et al. (67) reported that incubation of 1-nitropyrene with S. typhimurium TA98 yielded 1-aminopyrene and 1-acetylaminopyrene as major and minor metabolites, respectively. The reduction of 1-nitropyrene was slow and was accompanied by a slow formation of DNA adducts. When incubations were conducted with the nitroreductase-deficient strain, TA100 F50, both the extent of 1-amino-pyrene formation and DNA binding decreased. Howard ej al. (71,115) also found reduction of 1-nitropyrene to 1-aminopyrene in strains TA98, TA1538 and ATCC 14028. 

Certain nitro PAHs appear to require metabolism of their N-hydroxy arylamine derivatives in order to induce mutations. For example, while 2-nitrofluorene showed decreased mutagenicity in the nitroreductase-deficient mutant, TA98NR, and in strain TA98/1,8-DNP, its presumed ultimate mutagenic derivative, N-hydroxy-2-aminofluorene was inactive in only strain TA98/1,8-DNP (117). Observations such as these led McCoy t al. (117) to... 

Other bacteria. Intestinal bacteria may play a critical role in the metabolic activation of certain nitroaromatic compounds in animals (119) and several reports have appeared on the metabolism of nitro PAHs by rat and human intestinal contents and microflora (120-123). Kinouchi et al. (120) found that 1-nitropyrene was reduced to 1-aminopyrene when incubated with human feces or anaerobic bacteria. More recently, Kinouchi and Ohnishi (121) isolated four nitroreductases from one of these anaerobic bacteria (Bacteroides fragilis). Each nitroreductase was capable of converting 1-nitropyrene into 1-aminopyrene, and one form catalyzed the formation of a reactive intermediate capable of binding DNA. Howard ej al. (116) confirmed the reduction of 1-nitropyrene to 1-aminopyrene by both mixed and purified cultures of intestinal bacteria. Two additional metabolites were also detected, one of which appeared to be 1-hydroxypyrene. Recently, similar experiments have demonstrated the rapid reduction of 6-nitro-BaP to 6-amino-BaP (123). 

The In vitro metabolic reduction of nitro PAHs was first reported in 1967 (124). Since then a number of similar investigations have been conducted however, most of these studies have been performed under only anaerobic conditions. The oxidative metabolism of nitro PAHs has been examined only recently, but as considered in the following sections, both reductive and oxidative metabolic pathways may be important in the metabolic activation of nitro PAHs. 

Nitropyrene. 1-Nitropyrene is the principal nitro PAH found in diesel exhaust (40) and, therefore, has been the subject of intense study. Nachtman and Wei (133) found that under anaerobic conditions, 1-nitropyrene was reduced by hepatic S9, cytosol or microsomes to principally 1-aminopyrene. Only limited reduction occurred in the absence of cofactors, while maximum metabolism was observed in the presence of both FMN and NADPH. Although the microsomal fraction had the greatest specific activity toward 1-nitropyrene metabolism, the cytosol had 30 times the total activity. 

Yu, G., Xu, X. (1993) Investigation of aqueous solubility of nitro-PAH by dynamic coupled-column HPLC. Chemosphere 24,1699-1993. 

Among the natively fluorescent compounds determined by the POCL reaction are PAHs in different matrices such as coal tar [100] and biomass emissions [101], and amino-PAHs in shale oil, coal oil, and coal gasifier tar [102], Nitro-PAHs have no fluorescent properties, but have been reduced online (either pre-or postcolumn) to the corresponding amino-PAHs [103], The two fluorescent drugs dipyridamole and benzydamine have been determined in rat plasma by... 

The development of tandem MS techniques has undisputably contributed significantly to the basic understanding of fundamental aspects of nitro compounds. Further possible analytical applications have benefited from an advanced use of ion chemistry. In particular, the MS studies on nitroarenes (nitro-PAHs), which are known to be highly mutagenic, should be emphasized as fast and reliable analytical strategies. 

The effect of solvent polarity on the injection conditions for the determination of nitro-PAH by capillary GC with splitless injection was investigated LOD was 129 pg of 2-methyl- 1-nitronaphthalene (228), at SNR 2, RSD 1.8-6.7% when measuring by peak area using FID474. 

Nitro-PAH were determined by capillary GC-MC, after reduction to amines and conversion to pentafluoropropionamides. This made it possible to prove the presence of 229a, 230 and 3-nitrofluoranthene (231a) in most samples of airborne particular matter taken in Upper Silesia482. 

Nitro-PAH were determined in air particulate matter by RP-HPLC with reductive electrochemical detection sensitivity of 3-0.3 ng injected483. 

Nitro-PAH, Combustion processes, atmospheric Mutagenic and carcinogenic... 

The major route of formation of these nitro compounds is via the reaction of VOCs with the NO arising from hot flue gases, such as automobile exhaust gases and gas streams used for drying food stuffs, etc. In these combustion systems the aliphatics can react with nitro compounds or arenes to produce nitro-PAH and nitroarenes. Some of the NO produced are thus converted into C-nitroso compounds. The interactions and reaction chemistry of these compounds is complex and difficult to interpret. 

The NH2O formed in the series of chain reactions is anticipated to be a short-lived intermediate which could interact with polyaromatic hydrocarbons (PAH) in atmosphere to give nitroarenes or nitro-PAH. 

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