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PubMed1992

Structure-activity relationship of genotoxic polycyclic aromatic nitro compounds: further evidence for the importance of hydrophobicity and molecular orbital energies in genetic toxicity.

A quantitative structure-activity relationship (QSAR) has been formulated for 15 polycyclic aromatic nitro compounds acting on E. coli PQ37. Upon damage of DNA by these substances beta-galactosidase is induced and can be easily assayed colorimetrically, hence, this is a short-term test for mutagenicity. The QSAR (log SOSIP = 1.07 log P - 1.57 epsilon LUMO - 6.41) is strikingly similar to that found earlier with nitroaromatics acting in the Ames test (TA100) and differs significantly for that found using TA98 organisms. The QSAR brings out in a unique manner the underlying similarity in the two test systems.

Mutagenicity Tests↗
PubMed2002

Simultaneous determination of various aromatic amines and metabolites of aromatic nitro compounds in urine for low level exposure using gas chromatography-mass spectrometry.

A newly developed method permits the simultaneous quantitative determination of various aromatic amines (or metabolites of aromatic nitro compounds, respectively) in human urine in one analytical run. Applying this method it is possible to determine aniline, toluidines, 4-isopropylaniline, o-anisidine, 3- and 4-chloroaniline, 4-bromoaniline, aminonitrotoluenes, aminodinitrotoluenes, 3,5- and 3,4-dichloroaniline, alpha- and beta-naphtylamine and 4-aminodiphenyl. After separation from the urinary matrix by a simple liquid-liquid extraction at pH 6.2-6.4 the analytes are converted into their pentafluoropropionic acid amides. Separation and quantitative analysis is carried out by capillary gas chromatography and mass-selective detection in the single ion monitoring mode. The limits of detection were within the range from 0.05 microg/l (4-aminobiphenyl, o-anisidine, 3,5-dichloroaniline) to 2 microg/l urine (4-amino-2,6-dinitrotoluene). The relative standard deviation of the within-series imprecision (determined at spiked concentrations of 2.0 microg/l and 10 microg/l) was between 2.9 and 13.6% depending on analyte and concentration. The relative recovery rates were in the range of 70-121%. The analytes that do not contain a nitro function showed better performance regarding the analytical reliability criteria. In order to determine the suitability of this new method for biological monitoring we analysed 20 12-h urine samples of persons without known exposure to aromatic amines, nitroaromatics or precursors in a pilot study. In these samples various aromatic amines could be clearly identified. The general population renally excretes aniline (median: 3.5 microg/l; 95th percentile: 7.9 microg/l), o- (0.12 microg/l; 2.7 microg/l), m- (0.17 microg/l; 2.2 microg/l) and p-toluidine (0.11 microg/l; 0.43 microg/l), and o-anisidine (0.22 microg/l; 0.68 microg/l). Additionally, we found that the persons investigated also excrete 3- (<0.05 microg/l; 0.55 microg/l) and 4-chloroaniline (0.11 microg/l; 0.57 microg/l) as well as 3,5-dichloroaniline (0.18 microg/l; 1.5 microg/l). 3,4-Dichloroaniline was found in some specimens (20%) in concentrations near the limit of detection (<0.05 microg/l; 0.12 microg/l). We did not detect alpha- or beta-naphtylamine, 4-aminobiphenyl or metabolites of explosives in the samples.

Amines↗
PubMed2005

Reductive monoalkylation of aromatic and aliphatic nitro compounds and the corresponding amines with nitriles.

[reaction: see text] A simple, selective, rapid, and efficient procedure for the synthesis of secondary amines from the reductive alkylation of either aliphatic or aromatic nitro compounds and the corresponding amines is reported. Ammonium formate is used as the hydrogen source and Pd/C as the hydrogen transfer catalyst. The reaction is carried out at room temperature. The rate differences for the preferential formation of secondary over tertiary products are due to both steric and electronic factors.

Alkylation↗
PubMed1986

Glutathione-reactive nitro compounds as radiosensitizers: mechanistic and therapeutic implications.

The "extra" radiosensitization seen with GSH-reactive nitro compounds is too large to be accounted for by GSH-depletion acting independently--there must be competition. The GS-conjugate leaks out of cells slowly and is trapped at high concentrations. Its properties, such as concentration trapped and reduction potential, must be considered. Limited therapeutic exploitation of the glutathione conjugate trapping and concomitant GSH depletion may be possible if intratumor injection is permitted.

Animals↗
PubMed1975

Determination of nanogram amounts of primary aromatic amines and nitro compounds in blood and plasma.

A rapid and highly sensitive method, based on the direct fluorimetric scanning of thin-layer chromatograms, is described for the quantitative determination of flunitrazepam and its main metabolites in human blood or plasma. This method is generally applicable to aromatic nitro compounds that are reducible with tin(II) chloride. In particular, it is possible to determine primary amines in nanogram amounts. Fluorescamine is used as a regent to produce fluorescent derivatives. The method is suitable for pharmacokinetic studies of flunitrazepam and its main metabolites in human blood and plasma.

Amines↗
PubMedDate not supplied

[Mechanisms of NO-dependent relaxation in smooth muscles of the rat aorta with nitro compounds].

The membrane potential and smooth muscle tension in rat aorta were studied by the method of sucrose gap junction. It was found that sodium nitroprusside and nitroglycerin produced a dose-dependent membrane repolarization and smooth muscle cell relaxation in rat aorta preliminarily contracted and depolarized by hyperpotassium (40 mM) or phenylephrine solutions. The relaxation effect of sodium nitroprusside was more pronounced on the phenylephrine background. The effect of nitroglycerin showed a different kinetics in time and led to the tolerance development. The effects of both nitro compounds were inhibited by pretreatment with Methylene Blue or potassium channel blockers. It is suggested that nitro vasodilators are involved in the NO-dependent processes in smooth muscle cells of aorta through cGMP-mediated activation of the potassium conductivity and by changing the efficiency of operation of the protein kinase C branch of the Ca2+ signal system.

Animals↗
PubMed1995

Reaction of hydroxyl radicals with alkyl phosphates and the oxidation of phosphatoalkyl radicals by nitro compounds.

The rate constants for reactions of hydroxyl radicals with a number of alkyl phosphates have been determined by competition with KSCN. Hydroxyl radicals react with alkyl phosphates preferentially by H-abstraction at the alpha-position of the phosphate functions. The resulting alpha-phosphatoalkyl radicals are not very efficient one-electron reducing agents towards nitro compounds. They react with tetranitromethane (TNM) by addition to form adduct intermediates with absorption maxima at about 300 nm. The rate constants for decay of these TNM adducts to produce the nitroform anion (NF-) and the corresponding alpha-phosphato-alcohols have been determined by optical and/or conductance detection. The stability of these TNM adducts varies considerably with the chain length (methyl > ethyl > isopropyl) and number (trialkyl > dialkyl > monoalkyl) of the alkyl substituents. Additional formation of proton during or after the decay of the TNM adducts has been tentatively attributed to the hydrolysis of the alpha-phosphato-alcohols. Alpha-Phosphatoalkyl radicals derived from trimethyl, triethyl, triisopropyl, and diethyl phosphates react with p-nitroacetophenone (PNAP) very slowly (k < 5 x 10(7) dm3mol-1S-1) possibly forming adducts. One-electron reduction of PNAP by these radicals to PNAP.- was not observed under pulse radiolysis conditions. The rate constants for the reactions of .OH with glycerol 1-phosphate and glycerol 2-phosphate have been redetermined by competition with KSCN. Using the radical scavengers N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) and TNM, the percentage of .OH attack at each carbon atom was obtained. Contrary to the simple alkyl phosphates described above, the alpha-position to the phosphate function is the least favoured (10-15% in glycerol 1-phosphate and 6% in glycerol 2-phosphate). These so-formed alpha-phosphatoalkyl radicals react with TNM also by forming adducts. The beta-phosphatoalkyl radicals in both cases eliminate inorganic phosphate on formation (k > 10(6)S-1). The gamma-phosphatoalkyl radical from glycerol 1-phosphate undergoes base-catalysed water elimination (kobs = 1.8 x 10(5)S-1 at pH 10.6) to give an oxidizing radical. Products in the gamma-radiolysis of N2O-saturated solutions of glycerol 1-phosphate and glycerol 2-phosphate have been identified and their yields determined. The mechanisms for their formation are discussed.

Alkanes↗
PubMed1983

Studies on bacterial nitroreductases. Enzymes involved in reduction of aromatic nitro compounds in Escherichia coli.

Enzymes involved in reduction of methyl p-nitrobenzoate in Escherichia coli B/r were oxygen-insensitive and precipitated between 30 and 60% ammonium sulfate saturation from cell-free extracts of the strain. The reductases were resolved by DEAE-cellulose column chromatography into three enzymes, NADH-linked, NAD(P)H-linked and NADPH-linked ones. These enzymes were flavoprotein which could be inactivated by dialysis against 1 M potassium bromide and could be reactivated by FMN. The NADH-linked and NAD(P)H-linked reductases were sensitive to dicumarol and exhibited menadione reductase activities. Aromatic nitro compounds with electron-withdrawing p-substituents were easily reduced by the NAD(P)H-linked reductase.

Cell-Free System↗
PubMed1989

Actions of a newly synthesized nitro-compound, E-4701, on rabbit vascular smooth muscles.

The effects of a newly synthesized water soluble and light resistant nitro-compound, E-4701, on the electrical and mechanical properties of smooth muscle cells of rabbit mesenteric and coronary arteries were investigated. In the endothelium-denuded rabbit mesenteric artery, E-4701 relaxed the tissue pre-contracted by noradrenaline (IC50 = 40 microM) to a greater extent than that contracted by high K, but to a lesser extent than that contracted by acetylcholine (ACh) or high K in endothelium-denuded rabbit coronary artery (the IC50 was 20 nM or 60 nM, respectively). Nitroglycerin showed much the same relaxing action on the above tissue (IC50 for the ACh- or K-induced contraction was 20 nM or 65 nM, respectively). Relaxing actions of E-4701 or nitroglycerin were prevented by 10 microM methylene blue. In muscle cells of the porcine coronary artery, E-4701 or nitroglycerin inhibited the Ca-transient provoked by ACh, as examined using fura-2. Both drugs had no effect on the Ca-induced contraction in skinned muscle strips. ACh produced a transient hyperpolarization with subsequent depolarization, but in the endothelium-denuded tissues. ACh only depolarized the membrane. E-4701 inhibited the ACh-induced depolarization, but nitroglycerin did not. We concluded from our observations that E-4701 has the typical characteristics of a nitrocompound with an inhibitory action on the agonist-induced membrane depolarization.

Acetylcholine↗
PubMed1990

A novel pathway to the ultimate mutagens of aromatic amino and nitro compounds.

Photolysis of arylazides in aqueous media was recently found to generate presumed nitrenium ions, species which are generally considered as the ultimate mutagens/carcinogens derived from arylamines and nitroarenes. The primary photolysis products of arylazides, the arylnitrenes, can possibly react as electrophiles themselves, or they can be protonated and thus form the electrophilic nitrenium ions. Numerous arylazides and aryldiazides can be photoactivated to short-lived mutagens detectable in Salmonella typhimurium TA98. Structure-activity comparisons between arylazides and the matching arylamines and nitroarenes show correlations; e.g., phenyl azide and methyl-substituted phenyl azides are not mutagenic or only weakly mutagenic like aniline, nitrobenzene, and their methyl homologues, whereas 4-azidodiphenyl, 2-azidofluorene, 1-azidopyrene, azido-IQ, and azido-isoIQ are increasingly mutagenic in that order, like the matching amino and nitro compounds. It is hypothesized on the basis of these data that the nitrene/nitrenium ion is the reactive intermediate common to the three mutagenic pathways and that the reaction of the nitrene/nitrenium ion with DNA is rate limiting for the overall mutagenic process in Salmonella. The photochemical generation from arylazides of the reactive species, the nitrene/nitrenium ions, opens new perspectives for the understanding of the genotoxic activity of arylamines and nitroarenes in general and, specifically, of the food mutagens/carcinogens of the IQ type.

Amines↗
PubMed1991

Effects of a new nitro compound on the systemic circulatory system in dogs.

The present study was undertaken to evaluate the effects of a newly synthesized nitro compound (E-4701) on the systemic circulatory system with special reference to venous return and vascular compliance. Dogs were anesthetized with sodium pentobarbital. After opening the chest, cannulae were inserted into the superior and inferior vena cavae and into the right atrial appendage. The venous flow from the caval veins was redirected to a blood reservoir with an outlet at a constant height. The blood was pumped into the right atrium at a constant flow rate. E-4701 had a hypotensive effect, and also caused a decrease in reservoir blood volume; i.e., a decrease in venous return. Venous return via the superior vena cava was increased, whereas return via the inferior vena cava was decreased. Similar effects on the systemic circulatory system were observed with nitroprusside. The lowest dose of nitroprusside that caused a significant reduction in blood pressure was the same dose as that which caused a decrease in reservoir blood volume. However, a low dose of E-4701 caused a significant reduction in reservoir blood volume without affecting the systemic blood pressure. Arterial and venous compliances were increased by both E-4701 and nitroprusside. Nitroglycerin and isosorbide dinitrate increased venous compliance, but did not affect arterial compliance. The results suggest that E-4701 caused an almost equipotent reduction in blood pressure and venous return by dilating the arterial and venous vascular beds. The capacitance vessels may be more sensitive to E-4701 than the resistance vessels.

Animals↗
PubMed2003

From azides to nitro compounds in a few seconds using HOF.CH3CN.

HOF.CH3CN, a very efficient oxygen-transfer agent, was reacted with various azides to form the corresponding nitro compounds in excellent yields and in very short reaction times. The respective nitroso derivatives were found to be intermediates in this reaction. When the azides were reacted with MCPBA or DMDO, no reaction took place, and the starting materials were fully recovered.

Journal Article↗