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PubMed1982

MS/MS analysis of diesel emissions and fuels treated with NO2.

Correlations between direct-acting mutagens in diesel emissions and the activity of nitroaromatic compounds have been noted, but detection and identification of nitro-compounds in diesel particulates has remained an elusive problem. In the results reported here, MS/MS (tandem mass spectrometry) was found to detect nitroaromatic compounds in fractionated and unfractionated diesel soot extracts. The nitro-compounds detected ranged from two- to four-ring polynuclear aromatic hydrocarbon derivatives and were primarily mono-nitro derivatives. An aromatic fraction from diesel fuel reacted with NO2 resembled diesel exhaust extracts from an engine operating on the same fuel. Therefore, it is possible that nitroaromatic derivatives in diesel exhaust may be in part due to unburned fuel residues reacting with NO chi formed in the combustion process. The utility of MS/MS in comparing complex mixtures from different sources or subfractions thereof is discussed.

Fuel Oils↗

PubMed1999

The detection and comparison of the genotoxic effects of some nitro aromatic compounds by the umu and SOS chromotest systems.

Four nitroarenes were tested in two standard genotoxicity assay systems using three well-known bacterial tester strains. The results were as follows: 4-nitroquinoline l-oxide (4NQO) was positive in Quillardet and Hofnung's SOS chromotest using Escherichia coli strain PQ37 both in the presence and absence of microsomal (S9) supplements and in the Salmonella typhimurium umu tester strains NM2009 and NM3009, which express high levels of O-acetyltransferase (O-AT) and O-AT plus nitroreductase (NR) respectively. m-Nitrocinnamic acid (m-NCA) was weakly positive in strains NM2009 and NM3009, but negative in the SOS chromotest; m-dinitrobenzene (m-DNB) was weakly positive in strain NM2009, intermediate positive in strain NM3009, but negative in the SOS chromotest; 2,4-dinitrotoluene (2,4-DNT) was weakly positive in strain NM3009, but negative in strain NM2009 and in the SOS chromotest. However it still showed a dose-response relationship in strain NM2009. In view of these results, it is suggested that investigators planning to screen miscellaneous nitroarenes for their genotoxicity in the future should consider taking advantage of the increased sensitivity which is conferred on S. typhimurium strains NM2009 and NM3009 by virtue of their capacity to overexpress O-AT or O-AT and NR.

4-Nitroquinoline-1-oxide↗

PubMed1981

Metabolic activation of aromatic amines and azo dyes.

Aromatic amines, amides and nitro compounds are a class of chemicals that produce tumors in a wide variety of tissues in experimental animals, including liver, urinary bladder, forestomach, small intestine, Zymbal's gland, subcutaneous tissue or skin. In man, exposure to some aromatic amines is associated with tumours of the urinary bladder and carcinoma of the renal pelvis. Their biological activity as carcinogens or genotoxic agents is, in all the cases that have been studied in detail, dependent on metabolic activation in vivo, occurring by multiple pathways. Differences in these metabolic pathways may largely account for the differences in tissues and species susceptibilities to cancer induction. Carcinogenicity of aromatic amines or amides is dependent on their oxidation to N-hydroxy derivatives, whilst the carcinogenicity of aromatic nitro compounds is linked to their reduction to hydroxylamines. Further conversion of the N-hydroxylamine or N-hydroxyamide to reactive intermediates can occur in several ways, which include (i) esterification of the N-hydroxy group, (ii) non-enzymic protonation of the nitrogen of the hydroxylamine and (iii) oxidation to a free radical of arylhydroxamic acids. Following generation of such reactive electrophilic intermediates in tissues or cells, macromolecular binding has been observed to nucleic acids and proteins. In many cases, arylamidated and arylaminated products are formed with nucleic acid bases; in the case of the well-studied 2-acetylaminofluorene, nucleophilic atoms of guanine are the predominant site of reaction. Relatively little is known of the structure and biological consequences of DNA adducts formed from other aromatic amines, amides or nitro compounds; more research in these directions is warranted.

1-Naphthylamine↗

PubMed1987

Correlation of nitroaromatic compounds with the mutagenic activity of coal fly ash.

Stack-collected fly-ash particles from a commercial pulverized-coal power plant were extracted with 60/40 w/w benzene-methanol to remove as much of the organic fraction as possible. The extract was sequentially fractionated on a series of high-performance liquid chromatography columns, and the Salmonella bacterial mutagenicity assay using both normal and nitroreductase-deficient strains was used to localize the most mutagenic fractions. Selected fractions were analyzed by a variety of techniques, including gas chromatography with dual-flame ionization and thermionic nitrogen-phosphorus detectors, gas chromatography-mass spectrometry, direct-probe low-resolution or low-voltage mass spectrometry, and high-resolution mass spectrometry. Mutagenicity data indicated that nitroorganic compounds were the primary mutagens in all samples submitted for chemical analysis. A series of homologous alkylated nitrophenanthrenes appear to be important mutagens in one major fraction, while alkylated nitrofluorenones appear to be the dominant mutagens in a second major fraction. No nitro compounds were identified in a third major fraction. In addition to the nitro compounds, substantial amounts of fluorenones were also found, although these are not believed to contribute to the direct-acting mutagenic activity of the samples.

Animals↗

PubMed1977

An in situ fluorimetric method for the detection and quantitative analysis of fenitrothion, its breakdown products and other amine-generating compounds.

A procedure is described for the in situ detection of primary amine-generating pesticides on thin layers of silica gel. The technique is based on the reaction of fluorescamine with primary amines to yield highly fluorescent derivatives. Nitro compounds are first reduced to their corresponding primary amines. Pesticides studied were aminotriazole, fenitrothion, parathion and parathion-methyl. Possible breakdown products of fenitrothion were also included. Detection limits were in the low nanogram range. The method is simple, rapid and very selective and can also distinguish between primary amines and nitro compounds. An example of a typical chromatographic separation is presented and quantitative aspects are discussed.

Amines↗

PubMed1989

Electrochemical characteristics of nitro-heterocyclic compounds of biological interest. III. Nitroso derivative formation.

Upon electrolytic reduction of a range of nitro-aromatic complexes (including imidazoles, benzenoids, furans and pyrazoles) an associated oxidation-reduction process is observed at more positive potentials with respect to nitro group reduction when using repeat scan cyclic voltammetry. This new couple has been identified as the reversible first reduction of the nitroso derivative for chloramphenicol, by the addition of a genuine sample of nitrosochloramphenicol to the electrochemical cell. We have failed to observe formation of the new redox-active species for five 5-nitroimidazoles examined. Possible reaction schemes for nitroso formation under electrolytic reduction conditions and the importance of the nitroso redox couple with respect to the cytotoxic action of the parent drug are discussed. The applicability of nitrosochloramphenicol as a model for the behaviour of nitro-heterocycles in general is shown.

Chloramphenicol↗

PubMed2005

Simultaneous congener-specific determination of selected organochlorine compounds and nitro musks in human whole blood samples by solid-phase extraction and capillary gas chromatography with electron capture detection.

Chlororganic compounds like pesticides or polychlorinated biphenyls (PCB) and nitro musks are environmental contaminants, which remain public health concerns because of their persistence in humans and their toxicological properties. Many of these substances are associated with endocrine dysfunction or with carcinogenicity. Therefore, a simple method using solid-phase extraction followed by capillary gas chromatography with electron capture detection for the simultaneous determination of both organochlorines and nitro musks in human whole blood samples has been developed. Recovery rates of 13 PCB congeners and of 7 pesticides ranged from 67.5% to 100.4% and from 81.1% to 110.5%, respectively. Recoveries of the 5 nitro musks were consistent and ranged from 90.2% to 98.8%. The accuracy for organochlorines and nitro musks varied from 6.3% to 8.6%. Method detection limits ranged from 0.02 microg/L to 0.11 microg/L for the organochlorines and from 0.04 microg/L to 0.08 microg/L for the nitro musks. The method has a high sensitivity with a low detection limit even in slightly contaminated human blood samples. The time and technical effort is small, so the method is feasible for epidemiological studies with regard to the impact of organochlorines and nitro musks on certain diseases.

Chromatography, Gas↗

PubMed1993

[Nitro-musk compounds in breast milk].

Musk xylene, ketone, ambrette, tibetene and moskene are synthetic nitroaromatic compounds. Because of their scent, they are used as substitutes for natural musk. In particular musk xylene and musk ketone are added to cosmetics, washing agents and other products. Acute toxicity of nitro musks has been estimated to be low. Knowledge on the toxicokinetics, chronic toxicity, as well as mutagenic and carcinogenic potential is based so far on only few studies. First evidence for the persistence of these lipophilic compounds in the environment and their potential to accumulate in organisms came from their identification in the aquatic ecosystem. Nitro musks have now been identified in mother's milk. The analysis of 391 samples from Southern Bavaria, Germany, in 1991 and 1992 revealed concentrations of musk xylene ranging from 0.01-1.22 mg/kg fat with a mean content of 0.10 mg/kg fat. This was 2-3 times higher than the mean contents of musk ketone or musk ambrette. Average levels of the nitro musks were in the range of those usually found for various chlorinated compounds like hexachlorocyclohexanes and cis-heptachloroepoxide. Because of their presence in cosmetic products and washing agents dermal absorption could be an important route of uptake of nitro musks in man. Toxicologic relevance of the present findings for humans is still unclear. In order to assess consequences for health, further investigation of effects caused by a continual uptake of small amounts of these substances is necessary.

Adult↗

PubMed1997

Identification of the major hepatic DNA adduct formed by the food mutagen 2-amino-9H-pyrido[2,3-b]indole (A alpha C).

2-Amino-9H-pyrido[2,3-b]indole (A alpha C) is among the most prevalent heterocyclic amines detected in grilled or panfried meat; it was shown to be carcinogenic in mice, to induce preneoplastic foci in rat liver, and to form covalent DNA adducts in vitro and in vivo. The corresponding nitro compound 2-nitro-9H-pyrido[2,3-b]indole (N alpha C) was prepared and shown to be a direct acting mutagen in the Salmonella assay, while the amino compound required external metabolic activation with rat liver homogenate (S9). When A alpha C was incubated with S9 in the presence of calf thymus DNA, one major DNA adduct spot was detected upon 32P-postlabeling analysis. This adduct comigrated on ion-exchange TLC and reversed-phase HPLC with the major adduct detected in primary hepatocytes treated with A alpha C. In DNA isolated from livers of male F344 rats treated with 800 and 160 ppm, the formation of the same major adduct was observed with relative adduct levels of 20.6 +/- 9.6 and 1.4 +/- 1.1 adducts/10(8), respectively, as determined with the butanol extraction variant of the 32P-postlabeling assay. No DNA adducts were detected in liver DNA from rats treated with 32 ppm A alpha C or control animals. The major adduct spot was eluted and hydrolyzed and the modified base characterized by chromatographic and UV spectral comparison with a synthetic standard synthesized from acetylated guanine N3-oxide and A alpha C. Electrospray mass spectrometry and 1H- and 13C-NMR spectroscopy provided further evidence for the major adduct as N2-(guanin-8-yl)-2-amino-9H-pyrido[2,3-b]indole. A alpha C is formed especially in high-temperature preparation of food and may contribute considerably to the human carcinogenic risk that might be imposed by heterocyclic amines.

Animals↗

PubMed1989

[Synthesis and biological activity of isomeric 5- and 6-nitro-1-alkylbenzimidazoles].

Either the alkylation of 5(6)-nitro-benzimidazoles (R = H, CH3) or the nitration of 1-alkyl-benzimidazoles afforded corresponding mixtures of 1-alkyl-5-nitro- and 1-alkyl-6-nitro-benzimidazoles (III, IV, VII, VIII, XI). Fractional crystallization from water was employed for isolation of 6-nitro isomers V, VI and IX from mixtures III, IV and VII. On the other hand, application of this isolation method to mixtures VIII and XI proved unsuccessful. 6-Nitro-compound X and 5-nitro derivatives XIII and XV were obtained by direct syntheses. From calibration curves depicting dependence of absorbance of the mixtures upon their composition, percentage ratios of 5-nitro to 6-nitro isomers in the mixtures were estimated. Usefulness of thin-layer chromatography, and UV and IR spectrometry for identification of 5-nitro and 6-nitro isomers was stated; e. g. 5-nitro isomers have higher epsilon values, while 6-nitro isomers exhibit two vmax values of the benzene ring. Compounds IV, IX and X proved to exert antihelminthic, antibacterial and antiphlogistic activities.

Animals↗

PubMed1991

Quantitative structure-activity relationships for chemical toxicity to environmental bacteria.

Quantitative structure-activity relationships (QSARs) were developed for nonreactive chemical toxicity to each of four groups of bacteria of importance in environmental engineering: aerobic heterotrophs, methanogens, Nitrosomonas, and Microtox. The QSARs were based on chemicals covering a range of structures and including important environmental pollutants (i.e., chlorinated and other substituted benzenes, phenols, and aliphatic hydrocarbons). QSARs were developed for each chemical class and for combinations of chemical classes. Three QSAR methods (groups of chemical describing parameters) were evaluated for their accuracy and ease of use: log P, linear solvation energy relationships (LSER), and molecular connectivity. Successful QSARs were found for each group of bacteria and by each method, with correlation coefficients (adjusted r2) between 0.79 and 0.95. LSER QSARs incorporated the widest range of chemicals with the greatest accuracy. Log P and molecular connectivity QSARs are easier to use because their parameters are readily available. Outliers from the QSARs likely due to reactive toxicity included acryls, low pKa compounds, and aldehydes. Nitro compounds and chlorinated aliphatic hydrocarbons and alcohols showed enhanced toxicity to the methanogens only. Chemicals with low IC50 concentrations (log IC50 mumol/liter less than 1.5) were often outliers for Nitrosomonas. QSARs were validated statistically and with literature data. A suggested method is provided for use of the QSARs.

Bacteria↗

PubMed2002

Quantitative structure-activity relationships for the toxicity of nitrobenzenes to Tetrahymena thermophila.

In this study IGC50 (50% inhibitory growth concentration) values of 26 nitrobenzenes were determined for population growth endpoint of Tetrahymena thermophila. The toxicity order of the observed compounds has been found as follows: dinitro compounds > mono-nitro compounds; dichloronitrobenzenes > monochloronitrobenzenes; and meta-substituted nitrobenzenes > ortho-/para-substituted nitrobenzenes (NT, NPh, NAnis) except for the dinitrobenzenes and nitroanilines (DNB, NAn). Quantitative structure activity relationships (QSARs) were developed using log of the inverse of the IGC50 (logIGC50(-1)) in mole liter as the dependent variable and six molecular descriptors--logP, 1X(V), I, K alpha, sigma sigma- and E(LUMO) as the independent variables. Through multiplicate regression analysis, one best equation was obtained: log IGC50(-1) = 2.93 + 0.830sigma sigma- + 0.350I, n = 26, r = 0.923, r2 = 0.852, s = 0.265, f = 66.4 The equation was used to estimate IGC50 for seven analogues.

Animals↗

PubMed1976

Hypoxia-dependent reduction of 1-(2-nitro-1-imidazolyl)-3-methoxy-2-propanol by Chinese hamster ovary cells and KHT tumor cells in vitro and in vivo.

Incubation of Chinese hamster ovary cells and KHT murine fibrosarcoma tumor cells in the absence of oxygen with 1-[2-14C]nitro-1-imidazolyl)-3-methoxy-2-propanol, one of the most effective radiation sensitizers of hypoxic cells, results in the preferential reduction of 1-[2-14C]nitro-1-imidazolyl)-3-methoxy-2-propanol. The radioactivity associated with the acid-insoluble precipitate from cells incubated in nitrogen is about four times higher than that of cells incubated in air. When aqueous extracts of tissues of a C3H mouse bearing the KHT tumor, after i.p. injection with 1-[2-14C]nitro-1-imidazolyl)-3-methoxy-2-propanol, are analyzed, a reduction product is found in relatively higher yields in the tumor than in normal tissues. The relative radioactivity in the pellet from the tumor homogenate is also high in comparison with those of most normal tissues. These results provide suggestive evidence for a higher degree of hypoxic in the tumor than in most normal tissues. The formation of reduction products and their subsequent binding to macromolecules may explain the preferential toxicity of nitro compounds to mammalian cells under hypoxia conditions. These results suggest that some nitro compounds may be useful for the treatment of tumors having a high fraction of hypoxic cells even in the absence of radiation.

Animals↗

PubMed2003

Synthesis and structure-activity relationships of a new set of 1,2,4-triazolo[4,3-a]quinoxalin-1-one derivatives as adenosine receptor antagonists.

In a previous paper (Colotta V. et al., J. Med. Chem. 2000, 43, 1158), we reported the synthesis and the binding activity of some 4-oxo (A) and 4-amino (B) substituted 1,2,4-triazolo[4,3-a]quinoxalin-1-ones, bearing different substituents on the appended 2-phenyl ring (region 1), some of which were potent and selective A(1) or A(3) antagonists. To further investigate the SAR in this class of antagonists, in the present paper some 2-phenyl-1,2,4-triazolo[4,3-a]quinoxalin-1-one derivatives of both series A and B, bearing simple substituents on the benzofused moiety (region 2), are reported. The binding data at bovine A(1) (bA(1)) and A(2A)(bA(2A)) and at human A(3) (hA(3)) adenosine receptors (ARs) show that in series A (compounds 1, 4-11) the presence of substituents on the benzofused moiety is, in general, not advantageous for anchoring at all three AR subtypes, while within series B (compounds 12-21) it exerts a beneficial effect for both bA(1) and hA(3) AR affinities which span the low nanomolar range. In particular, among the 4-amino derivatives 12-21, the 8-chloro-6-nitro (compound 17) and the 6-nitro (compound 18) substitutions afford, respectively, the highest bA(1) and hA(3) AR affinity. Moreover, compound 18, additionally investigated in binding assays at human A(1) (hA(1)) receptors, shows a 183-fold selectivity for hA(3) versus hA(1) receptors. Finally, the SAR studies provide some new insights about the steric and lipophilic requirements of the hA(3) receptor binding pocket which accommodates the benzofused moiety of our 4-amino-triazoloquinoxalin-1-one derivatives.

Animals↗

PubMed1989

Correlation of kinetic parameters of nitroreductase enzymes with redox properties of nitroaromatic compounds.

The well-established mechanism of regeneration of the parent nitro compound by the reaction of the nitro anion radical with oxygen in aerobic systems is the basis of the correlation of kinetic parameters of purified flavoenzymes with electron affinities of some selected nitroaryl and nitroheterocyclic compounds. We have found that there is a linear relationship between log Vmax/Km and the one-electron reduction potentials of these compounds and that the measured values of redox dependence for these compounds is similar to that determined by other methods. Our results support the proposal of a rate-determining single electron-transfer as the initial step in the reduction of nitro compounds by purified flavoenzymes and are discussed in terms of the Marcus electron transfer theory.

Ferredoxin-NADP Reductase↗

PubMed2001

CYP83B1, a cytochrome P450 at the metabolic branch point in auxin and indole glucosinolate biosynthesis in Arabidopsis.

Auxins are growth regulators involved in virtually all aspects of plant development. However, little is known about how plants synthesize these essential compounds. We propose that the level of indole-3-acetic acid is regulated by the flux of indole-3-acetaldoxime through a cytochrome P450, CYP83B1, to the glucosinolate pathway. A T-DNA insertion in the CYP83B1 gene leads to plants with a phenotype that suggests severe auxin overproduction, whereas CYP83B1 overexpression leads to loss of apical dominance typical of auxin deficit. CYP83B1 N-hydroxylates indole-3-acetaldoxime to the corresponding aci-nitro compound, 1-aci-nitro-2-indolyl-ethane, with a K(m) of 3 microM and a turnover number of 53 min(-1). The aci-nitro compound formed reacts non-enzymatically with thiol compounds to produce an N-alkyl-thiohydroximate adduct, the committed precursor of glucosinolates. Thus, indole-3-acetaldoxime is the metabolic branch point between the primary auxin indole-3-acetic acid and indole glucosinolate biosynthesis in Arabidopsis.

Arabidopsis↗

PubMed1980

Respiratory effects and ascorbate reactions with misonidazole and other recently developed drugs.

A number of nitro compounds behave as electron acceptors with ascorbate in a non-enzyme-catalyzed reaction and with NADPH as electron donor in an enzyme-catalyzed reaction with liver homogenate. In both systems, the oxygen consumption is conveniently monitored by a Clark-type oxygen electrode. The oxygen consumption by S9 homogenate was found to be influenced by the electron affinity of the nitro compound. Detailed studies with misonidazole as the electron acceptor demonstrated that the oxygen consumption was influenced by protein and drug concentrations. Various inhibitors of electron transfer reactions, such as rotenone, antimycin A, and sodium azide, had no effect on misonidazole-stimulated oxygen utilization. However, cyanide was found to be stimulating in this system and this may be due to the inhibition of enzymes such as catalase and superoxide dismutase known to be present in S9. The oxygen consumption by S9 did not appear to be due to a hydroxylating reaction because metyrapone, a known inhibitor of this reactions, had no effect. Methional, a hydroxyl radical scavenger, was inhibitory as was glutathione. Clelands reagent had no effect. Additional studies with thiol-reactive agents suggest that a protein thiol may be important for the enzyme-catalyzed reaction between NADPH, misonidazole, and oxygen.

Animals↗

PubMed2002

(n-Nitrophenyl)acetonitrile, with n = 2, 3 and 4.

The molecular structures of the three title nitro-substituted phenylacetonitriles, C(8)H(6)N(2)O(2), at 123 K show that the molecules are linked together very differently. In the 2- and 4-nitro compounds, there are both O...H and N(cyano)...H interactions, whereas the crystal lattice of the 3-nitro compound is essentially built up by O...H interactions. The O atoms seem to prefer the aromatic H atoms, while the cyano N atoms prefer the methylene H atoms. The phenyl-nitro torsion angles are -19.83 (13), -5.69 (12) and -2.88 (12) degrees, while the phenyl-cyanomethyl torsion angles are -62.27 (12), -147.99 (9) and -16.75 (14) degrees in the 2-, 3- and 4-NO(2)-substituted compounds, respectively.

Journal Article↗