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At least 19 recordsLinked to original sources
PubMed2005

[New drinking water reference values for monocyclic nitro compounds].

Nitro compounds are important industrial chemicals with a broad range of applications. During their commercial production or practical use and through leaching from military waste sites they may be released into the environment and thus lead to a contamination of drinking water resources. In the last 15-20 years, the wider public first became aware of nitro compounds as contaminants in groundwater and drinking water resources that originated from manufacturing and processing of secondary explosives during World War II. In 1980, the former Bundesgesundheitsamt (BGA; Federal Health Office) had based its first risk assessment of monocyclic nitro compounds in drinking water on the known carcinogenicity of some aromatic amines in the working environment. On this basis, the BGA recommended for metabolites of aromatic nitro compounds a guide value of 0.1 mug/l for the sum of aromatic amines. From the beginning to the middle of the 1990s, the BGA established a more specific health-related assessment for the individual compounds, but not on the basis of tolerable or acceptable body doses but of dimensionless risk assessment scores ranking their combined toxic and carcinogenic potential on a scale from 1 to 100. In this contribution, we derived new health-based drinking water guide values for 19 nitro(aromatic) compounds and nitramines, including hexogen, octogen, and tetryl as well as the O-nitro compound PETN. All compounds under consideration have been detected within the last 15 years in Germany at contaminated sites close to or directly in groundwater resources for drinking water. For toxicological evaluation and derivation of guideline values for the nitro compounds of interest, the tolerable daily intake (TDI) approach was used for chemicals exhibiting a threshold for toxic effects. This was done by using established tolerable body doses for humans based on an identified NOAEL/LOAEL for the most sensitive toxic endpoint. In the case of non-threshold chemical substances, suitable estimates of excess lifetime cancer risk have been applied.

Databases, Factual↗
PubMed2005

On the [2,3] sigmatropic rearrangement of allylic nitro compounds.

Allylic nitro compounds undergo relatively clean [2,3] sigmatropic rearrangement upon heating in refluxing 1,2-dichlorobenzene in the presence of DABCO to give the corresponding allylic alcohols via the intermediate allylic nitrite. [reaction: see text]

Journal Article↗
PubMed2006

Allylic nitro compounds as nitrite donors.

Allylic nitro compounds were synthesized and evaluated as organic sources of nitrite and nitric oxide. Unactivated allylic nitro compounds do not spontaneously release nitrite and nucleophile promoted nitrite release is slow. However, 2-(nitromethyl)-cyclohex-1-ene-3-one spontaneously dissociates in buffer (pH = 7.4) to release nitrite with a kobs = 1.6 x 10(-5) s(-1). In the presence of L-cysteine, this compound rapidly yields nitrite and reacts with hemoglobin similarly to sodium nitrite. Structural modifications and the nature and amount of nucleophile modulate the rate of nitrite release. In the presence of L-cysteine and ascorbic acid, this compound forms nitric oxide. Together, these results reveal a new structural architecture for the tunable liberation of nitrite and nitric oxide from organic compounds.

Molecular Structure↗
PubMed1987

[Mutagenicity of aliphatic and aromatic nitro compounds. Industrial materials and related compounds].

Mutagenicity of 102 aliphatic and aromatic nitro compounds, industrial materials and related chemicals were tested by pre-incubation method using Salmonella typhimurium TA100 and TA98 strains with and without S9 mix. Escherichia coli WP2uvrA/pKM101 was also used in the mutagenicity assay of aliphatic nitro compounds. Four chemicals out of 8 aliphatic nitro compounds tested were mutagenic to TA100, TA98 and/or WP2 strains. Sixty-one out of 94 nitrobenzene derivatives were mutagenic to TA100 and/or TA98 strains. Thirty-seven chemicals among the 65 mutagens showed higher mutagenic activity than 1,000 rev./mg. The following 15 chemicals showed higher activity than 10,000 rev./mg: tetranitromethane, chloropicrin, 1,3,5-trinitrobenzene, 2,4-dinitrochlorobenzene, 2,3-dinitrophenol, 2,6-dinitroaniline, 3,5-dinitroaniline, 2-bromo-4,6-dinitroaniline, 2,4-dinitrofluorobenzene, p-nitrobenzylchloride, 3,5-dinitrobenzylchloride, p-nitrophenylhydrazine, 2,4-dinitrophenylhydrazine, 2,4-dinitrophenylthiocyanate and nitramine. Nitrobenzene was not mutagenic, but mono-substituted nitrobenzenes having-CH2Cl, -COCl, -NO2, -NH-NH2, -COOH, -OCH3, -NH2, -Br, -OH, -NH-NH2HCl, -OP(OC2H5)2S or -CHO group showed mutagenic. Introduction of-Cl, -CH3, -C2H5 or -SO3H group to nitrobenzene did not contribute to mutagenicity. Mutagenicity of dinitrobenzene was enhanced by the introduction of -F, -SCN, -NH2, -Cl, -CH2Cl, -NO2, -NH-NH2 or -COCl group, and suppressed by the introduction of -COOH or -CH3 group. Twenty-three out of 45 chemicals for which "exposure limits" are established from the stand point of industrial hygiene in many countries in the world, were mutagenic to TA100, TA98 and/or WP2 strains. Furthermore, 42 out of 57 chemicals for which "exposure limits" are not established were also mutagenic. The following three carcinogens, that is, 2-nitropropane, 2,4-dinitrotoluene and 2,6-dinitrotoluene, were all mutagenic, but their mutagenic activity was weak. Many chemicals were found to have a stronger mutagenic activity and a chemical structure similar to carcinogenic dinitrotoluenes. This fact suggests the necessity of conducting carcinogenic assay of these chemicals.

Industry↗
PubMed1979

Evidence for cyclic GMP-mediated relaxant effects of nitro-compounds in coronary smooth muscle.

The effects of the four nitro-compounds nitroglycerin, nitroprusside-Na, NaNO2 and B 744-99 were studied simultaneously on length and on cGMP-levels in isolated circular strips of bovine coronary arteries. 1. All 4 nitro-compounds concentration dependently relaxed the strips in close association with pronounced increases in cGMP-levels which preceded the mechanical responses. 2. The relaxant effects of all 4 nitro-compounds were significantly potentiated by the predominant inhibitor of cGMP-hydrolysis M & B 22,948, which also potentiated the increase in cGMP-levels of the two nitro-compounds in which it was studied (nitroglycerin and nitroprusside-Na). 3. Non-substituted cGMP and -- much stronger -- its 8 bromo-derivative also relaxed the strips and these effects were likewise potentiated by M & B 22,948. 4. When the log increase in cGMP produced by the 4 nitro-compounds were plotted against percent relaxation (probit scale) a linear and highly significant positive correlation was obtained. 5. The results provide evidence that the increases in cGMP caused by the 4 nitro-compounds studied are responsible for the smooth muscle relaxing actions of these drugs.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMedDate not supplied

Interaction of aromatic nitro compounds with reduced hepatic microsomal cytochrome P-450.

Aromatic nitro compounds interact with sodium dithionite-reduced microsomes to generate difference spectra characterized by a maximum at 400 nm and minima at 440 and 528 nm. Spectral binding constants of approximately 1 mM were calculated for ferrohemochromes in which nitrobenzene, p-nitrobenzoate, 2-nitrofluorene, and 2-nitronaphthalene served as ligands. Nitro binding affinity was increased approximately 3-fold by pretreatment of animals with phenobarbital (KS congruent to 0.3 mM). The interaction of nitro compounds with reduced microsomes from 3-methylcholanthrene-pretreated animals, however, failed to give discernable difference spectra. There is apparent mutual inhibition of binding of carbon monoxide, metyrapone, and nitro compounds with reduced cytochrome P-450, since addition of metyrapone or carbon monoxide to reference and sample cuvettes does not alter qualitative aspects of the nitro binding spectra, but only its magnitude. From the relative KS values, it is concluded that metyrapone and carbon monoxide interact with reduced cytochrome P-450 more tenaciously than nitro compounds.

Aerobiosis↗
PubMed1975

[Chemotherapeutic effects of nitro compounds. 1. Nitroanilines].

More than 200 nitro compounds, most of them nitroaniline derivatives substituted with one or more radicals having a basic reaction, were prepared and investigated as to their therapeutic activity against bacteria, fungi, protozoa, helminths, viruses and tumors. Several mono-nitrobenzenes with a radical having a basic reaction showed weak in-vitro activity against gram-positive bacteria and against Crocker's sarcoma 180; they also showed systemic activity against nematodes (Aspiculuris tetraptera) and viruses. The majority of therapeutically active compounds with pronounced in-vivo activity against Trichomonas fetus, Entamoeba histolytica, Schistosoma mansoni, cestodes, nematodes (Ancylostoma caninum), viruses (influenza, MHV, SAV and EMC) and various types of carcinoma (Ehrlich's carcinoma, leukemia 1210, Crocker's sarcoma 180) were dinitrobenzene derivatives with one radical having a basic reaction and electropositive groups or unreactive or reactive chlorine atom, and di-nitrobenzene with two equal or two different radicals having a basic reaction. Compound No. 70 revealed a marked in-vitro activity against fungi (Trichophyton; Microsporum, Candida albicans). Other nitro compounds such as bis-mono- and bis-dinitrobenzene derivatives likewise showed a systemic action against E. histolytica, viruses and, in particular, carcinoma (Crocker's sarcoma 180, Ridgway's osteosarcoma). Oxygen and sulfur analogue compounds as well as compounds produced by reduction also possessed a distinct activity against E. histolytica and viruses. On the basis of the present results particularly the dinitrobenzenes substituted with two radicals having a basic reaction include a number which have in common that a structure/activity relationship is recognizable in respect of E. histolytica, Schistosoma mansoni and different types of viruses. The activity against viruses in this class of compounds is probably due to an increased interferon production in the host animal. Whether the mechanism of action is the same against E. histolytica or Schistosoma mansoni has not been determined so far. A tumorigenic effect was observed mainly in those di-nitrobenzenes which are classed as alkylating compounds. Because of the small chemotherapeutic index the trials were not continued with the most effective compounds mentioned.

Aniline Compounds↗
PubMed1976

Effect of aromatic nitro compounds on oxidative metabolism by cytochrome P-450 dependent enzymes.

The effect of aromatic nitro compounds on the oxidative metabolism of representative type I (hexobarbital and aminopyrene) and type II (aniline and zoxazolamine) substrates by cytochrome P-450 dependent liver enzymes was studied. Nitro compounds (nitrobenzene, p-nitrobenzoate, 2-nitrofluorene, and 2-nitronaphthalene) inhibited the oxidation of type II substrates by rabbit liver microsomal enzymes; however, they had no effect on the metabolism of the type I compounds. Inhibition of type II metabolism was characterized graphically as S,I-hyperbolic non-competitive. The influence of aromatic nitro compounds on the interaction of type I and type II substrates with oxidized and reduced cytochrome P-450 was studied by difference spectroscopy. From Lineweaver-Burke plots, nitro compounds were shown to competitively interact with type II compounds for cytochrome p-450 binding sites. Nitro compounds completely prevented the appearance of a type I binding spectrum with either hexobarbital or aminopyrene even when the modifier was present at concentrations less than 10(-8)M. Aromatic nitro compounds appear to therefore inhibit the metabolism of the type II substrates through a mixed mechanism of interaction with the microsomal drug-metabolizing enzymes.

Aminopyrine↗
PubMed2002

Percutaneous absorption of explosives and related compounds: an empirical model of bioavailability of organic nitro compounds from soil.

The percutaneous absorption potentials of (14)C-labeled 2,4,6-trinitrotoluene (TNT), trinitrobenzene, 2,4-dinitrotoluene (2,4-DNT), 2,6-dinitrotoluene (2,6-DNT), 2-amino-4,6-dinitrotoluene, 4-amino-2,6-dinitrotoluene, 2,4-diamino-6-nitrotoluene, 2,6-diamino-4-nitrotoluene, N-methyl-N,2,4,6-tetranitrobenzamine, hexahydro-1,3,5-trinitro-1,3,5-triazine, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine, and 2,2-thiobis(ethanol) were determined from two soil types, Yolo having 1.9% carbon and Tinker having 9.5% carbon. TNT skin absorption from another low-carbon soil (Umatilla) was also determined. Approximately 10 microg/cm(2) of radiolabeled compound was applied in 5 microl of acetone or 10 mg/cm(2) of soil to excised pigskin mounted in skin penetration-evaporation chambers. Absorption from acetone served as a control. Radiolabel recovered from the dermis and tissue culture media (receptor fluid) was summed to determine the percentage of absorption from the soils. For each compound, percentage absorptions of radiolabel were highest from acetone solution and lowest from Tinker soil, with the results from Yolo soil being intermediate. Skin absorptions of TNT from Yolo and Umatilla soils were similar. For TNT in all vehicles, the penetration rate of radiolabel into the receptor fluid was highest during the 1- to 2-h interval after dosing. HPLC analysis of TNT radiolabel in receptor fluid at maximum flux indicated extensive conversion to monoamino derivatives and other metabolites. For 2,4-DNT and 2,6-DNT applications in Yolo soil, percentage absorptions approached those obtained from acetone applications. After 2,4-DNT and 2,6-DNT applications (acetone and soils), HPLC analysis of radiolabel in receptor fluid during the period of maximum flux revealed no significant metabolites. Skin absorption of the nitro compounds from soils was found to correlate with the compound's water solubility and vapor pressure. These findings formed the basis of an empirical model to predict skin bioavailability.

Animals↗
PubMed1989

Mutagenicity of nitro compounds in Salmonella typhimurium in the presence of flavin mononucleotide in a preincubation assay.

A series of nitro compounds (18 aromatic and one aliphatic) was evaluated using a modification of the standard Salmonella typhimurium mutagenicity assay. A preincubation protocol was used with flavin mononucleotide (FMN) incorporated into the assay mixture to facilitate nitro reduction. Several aromatic nitro compounds (m-nitroaniline, p-nitroaniline, 2,6-dinitrotoluene, 2,4-dinitrotoluene,2,3-dinitrotoluene,1,8-dinitronaphthalene), which were negative or only weakly mutagenic when tested in the standard plate incorporation assay, showed FMN-dependent mutagenic responses with this procedure. For some nitro compounds, the addition of FMN was not needed for the detection of mutagenicity in the modified protocol. Not all nitro compounds were positive using the preincubation procedure with FMN. The lack of mutagenicity, however, does not appear to be the result of the inability of the modified method to reduce nitro compounds, since it was found that reduction does occur under the assay conditions for the two nonmutagens evaluated for nitro reduction (nitrobenzene and p-nitrophenol). It is suggested that the modified protocol may be useful for evaluating the mutagenicity of many nitro compounds.

Aniline Compounds↗
PubMed1981

Mode of reactions between xanthine oxidase and aromatic nitro compounds.

The electron transfer mechanism in the reduction of aromatic nitro compounds by xanthine oxidase was investigated using methyl p-nitrobenzoate and p-nitroacetophenone as substrates. Methyl p-nitrobenzene was reduced by both one-electron and more than two-electron transfer mechanisms in the enzyme-electron donor system. When NADH was used as an electron donor, the ratio of one-electron flux to the total electron flux (the summation of one-electron and more than two-electron fluxes) was dependent on pH of the medium, but not on the concentration of the nitro compounds. The reverse was the case when the electron donor was xanthine. Additional experiments showed that methyl p-nitrobenzoate or p-nitroacetophenone was reduced to the corresponding hydroxylamino compounds and amino compounds by xanthine oxidase supplemented with xanthine or NADH. In these cases, the pattern of formation of the reduction products was dependent on the enzyme activity. The present study strongly suggested that the reduction of aromatic nitro compounds by xanthine oxidase proceeds through the four-electron and six-electron transfer mechanisms as well as the one-electron transfer mechanism.

Acetophenones↗
PubMed1983

On the reduction of aliphatic and aromatic nitro compounds by Clostridia, the role of ferredoxin and its stabilization.

Crude extracts of a variety of Clostridium species reduce aromatic and aliphatic nitro compounds in the presence of hydrogen gas. Using different Clostridia, the uptake of hydrogen by p-nitrobenzoate is about 5--10 times faster than by 2-nitroethanol. Structurally rather different aliphatic nitro compounds show rates which differ by less than a factor of 3. Hydrogenase from Clostridium kluyveri and ferredoxins from Clostridium spec. La 1 and spinach have been purified. The combinations of the hydrogenase and each one of the ferredoxins catalyse the hydrogen uptake by nitro compounds. Clostridial flavodoxin also transfer electrons onto nitro compounds. Nitroaryl and nitroalkyl compounds behave differently with ferredoxin. The first reduction step (1-electron transfer) of p-nitrobenzoate leads to the nitro radical anion which can be detected by EPR measurements. Nitro alkanes seem to form a rather unstable radical which decomposes partially to form nitrite. Furthermore, 2-(N-hydroxyimino)- and 2-(N-hydroxyamino)ethanol, a nitrogen radical of 2-(N-hydroxyamino)ethanol as well as glycol and 1,4-butanediol were detected as intermediates and side products during the reduction of 2-nitro-ethanol to 2-aminoethanol. While the hydrogenase from Clostridium kluyveri seems not to be affected by any reduction intermediate, the ferredoxin from Clostridium spec. La 1 is inactivated by nitrite in a few minutes. Ferrous and sulfide ions in concentrations substoichiometric to that of nitrite stabilize and even reactivate the ferredoxin in the presence of 2-mercaptoethanol. A mechanism for the reduction of aliphatic nitro compounds catalysed by hydrogenase and ferredoxin is proposed.

Clostridium↗
PubMed1984

Direct vasodilators with unknown modes of action: the nitro-compounds and hydralazine.

Several aspects of the mode of action of direct vasodilators are discussed. Nitro-compounds probably act via an intracellular formation of S-nitrosothiols, which stimulate cellular guanylate cyclase. Doubts, however, arise with regard to a generalization of this concept, e.g., methylene blue, an inhibitor of guanylate cyclase, interferes potently with the vasorelaxant action of nitroglycerin, but not with that of nitroprusside and sodium nitrite in KCl-stimulated rabbit aorta. Nitro-compounds do not interfere with transmembrane calcium movements. Hyperpolarization of the vascular smooth-muscle membrane, although reported to occur with nitroprusside, does not seem to be a common feature of the nitro-compounds. On the other hand, all nitro-compounds tested interfered with the noradrenaline-induced increase in 36-Cl steady-state exchange in rabbit aorta, and this effect could be mimicked by 8-Br-cGMP. Chemically skinned vascular smooth muscle was relaxed by pure cGMP-dependent protein kinase, but this effect requires confirmation. The action of hydralazine is augmented in chemically sympathectomized arteries and blocked by purines, such as adenosine, pointing to modulating role of purine-like compounds released from sympathetic nerve endings. The direct vasodilator action of hydralazine consists of a predominantly inhibitory effect on pharmacomechanical coupling. Membrane hyperpolarization with hydralazine has been reported. In addition to having direct effects on vascular smooth muscle, hydralazine can interfere with transmitter release by a prejunctional mechanism, and part of its vasorelaxant action seems to depend on the integrity of the endothelium in vascular smooth muscle.

Animals↗