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PubMed1990

Effects of sulfhydryl-modifying reagents, 3-nitro-2-pyridinesulfenyl compounds, on the coupling between inhibitory receptors and GTP-binding proteins Gi/Go in rat brain membranes.

To gain insight into the coupling mechanism of inhibitory receptors, 5-hydroxytryptamine1A receptors and alpha 2-adrenoceptors, with GTP-binding proteins (G proteins) in the central nervous system, we examined the effects of two 3-nitro-2-pyridinesulfenyl compounds, S-(3-nitro-2-pyridinesulfenyl)-L-cysteine [Cys(Npys)] and N-t-butoxy-carbonyl-S-(3-nitro-2-pyridinesulfenyl)-L-cysteine [Boc-Cys(Npys)], on 1) specific binding of [3H]8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) (5-hydroxytryptamine1A agonist) and [3H]clonidine (alpha 2-agonist) to rat brain membranes, 2) [35S]guanosine 5'-O-(3-thio)triphosphate (GTP gamma S) binding, and 3) pertussis toxin (islet-activating protein) (IAP)-catalyzed ADP-ribosylation of purified Go (an IAP-sensitive G protein present in abundance in the mammalian brain). Treatment with Cys(Npys) led to decreased [3H]8-OH-DPAT and [3H]clonidine binding, similar to the inhibitory effects of IAP and N-ethylmaleimide (NEM) on such binding. However, further treatment of Cys(Npys)-pretreated membranes with dithiothreitol completely abolished the inhibitory effect of Cys(Npys) on the binding of both ligands. On the other hand, treatment with Boc-Cys(Npys) inhibited the effect of several GTP analogs (GTP gamma S, guanylyl-imidodiphosphate, guanylyl)-(beta, gamma-methylene)-diphosphate, and GTP) on [3H]8-OH-DPAT and [3H]clonidine binding. Dithiothreitol and mercaptoethanol treatment of Boc-Cys(Npys)-pretreated membranes did not lead to a recovery of the effect of GTP analogs on agonist binding. Regardless of the presence or absence of GTP gamma S, agonist binding to Boc-Cys(Npys)-pretreated membranes was decreased by further addition of NEM or Cys(Npys). Cys(Npys) blocked [35S]GTP gamma S binding as well as IAP-catalyzed ADP-ribosylation in purified Go. In contrast, Boc-Cys(Npys) partially inhibited ADP-ribosylation and did not affect [35S]GTP gamma S binding. These results suggested that Cys(Npys) modifies the receptor-coupling domain in G proteins, followed by the uncoupling of inhibitory receptors from G proteins, similar to the effects of NEM and IAP. Boc-Cys(Npys), however, seems to stabilize the coupling state between the receptors and G proteins, thus abolishing the GTP gamma S effect.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1994

Metabolic and radiolytic reduction of 4-alkylamino-5-nitroquinoline bioreductive drugs. Relationship to hypoxia-selective cytotoxicity.

The 4-alkylamino-5-nitroquinolines (5NQs) are a new series of bioreductive drugs that exhibit varying degrees of selective toxicity (up to 60-fold) under hypoxic conditions in cell culture. This study tested the hypothesis that differences in hypoxia-selective cytotoxicity in this series reflect differences in the efficiency with which oxygen inhibits metabolic reduction. The products of reduction of six 5NQs were characterized and rates of reduction compared in aerobic and hypoxic AA8 cells. The major stable products of both radiolytic and metabolic reduction under anoxic conditions were the corresponding amines, which were not responsible for the toxicity of the parent nitro compounds. Metabolism of each compound was inhibited completely in aerobic cells, indicating that differences in hypoxia-selective toxicity in this series are not due to variations in efficiency as substrates for oxygen-insensitive nitro reduction. Rates of hypoxic metabolism correlated broadly with hypoxia-selective cytotoxicity; the 5NQ derivatives with high rates of hypoxic metabolism had good hypoxia-selective cytotoxicity, whereas the compounds with low rates of reduction (the 3,6-dimethyl and 8-methylamino compounds; 3,6diMe-5NQ and 8NHMe-5NQ) were non-selective. Low rates of drug-induced oxygen consumption by 3,6-diMe-5NQ and 8NHMe-5NQ in respiration-inhibited cells confirmed that these compounds are poor substrates for enzymatic nitro reduction. While there was an overall correlation between one-electron reduction potential at pH 7 (E1(7)) and rate of metabolic reduction, the relatively high E1(7) of 3,6diMe-5NQ (-367 mV) indicates that rates of reduction, and hypoxic selectivity of cytotoxicity, cannot be predicted from reduction potential alone. 3,6diMe-5NQ and 8NHMe-5NQ are cytotoxic through a non-bioreductive mechanism, the variable contribution of which may underlie the differences in hypoxia-selective cytotoxicity within this series of bioreductive drugs.

Aminoquinolines↗
PubMed2002

Conjugate addition of mixed diorganozinc compounds and functionalized organozinc cuprates to nitroolefins.

[reaction: see text] The copper-catalyzed conjugate addition of symmetrical and mixed diorganozinc compounds as well as functionalized diorganozinc cuprates to nitroolefins leads to synthetically versatile nitro compounds in moderate to good yields. Mixed TMSM-organozinc compounds are suitable reagents for conjugate addition, since the TMSM group is not being transferred. Ipso substitution is observed in the absence of a catalytic amount of copper(I) salt. The nitroalkene moiety in 3-nitroacrylates proved to be the predominant Michael acceptor.

Journal Article↗
PubMed1977

The metabolism of niclosamide and related compounds by Moniezia expansa, Ascaris lumbricoides var suum, and mouse- and sheep-liver enzymes.

1. Niclosamide and related nitro compounds were reduced to the corresponding amines by Moniezia expansa, Ascaris lumbricoides var suum and by enzymes prepared from these species and by mouse and sheep liver homogenates. The reduction of niclosamide by the helminths required as cofactors NADH2 and glutathione, but was inhibited 50% by 2 X 10(-7) M allopurinol. 2. Unlike benzanilide, niclosamide was not hydrolysed by either the helminths, or the mammalian liver preparations. Rates of hydrolysis of compounds related to niclosamide indicate that niclosamide was not hydrolysed because substituents in both benzene rings ortho to the amide bond sterically hinder the hydrolase. 3. Hydrolysis of benzanilide and related compounds was inhibited by anthelmintic organophosphates.

Allopurinol↗
PubMed1995

Biodegradation ranks of priority organic compounds under anaerobic conditions.

The biodegradations of 52 priority organic compounds were evaluated under anaerobic conditions by two tests developed in a preceding paper (Urano et al., 1995). Namely, the biodegradabilities of the compounds were classified into 13 ranks by the method proposed by Urano et al. (1995). Most of the aliphatic alcohols and carboxylic acids were not inhibitory and were biodegraded, but the compounds having ether bonds or branched hydrocarbon groups were biodegraded slowly. Aliphatic aldehyde and amines were not so much inhibitory but were hardly biodegraded. The benzene substitutes having groups of -CH2OH, -CHO, -CH2CH(NH2)COOH, -COOH and -OH were easily biodegraded, but the compounds having groups of -NO2, -NH2 and -SO3H were hardly biodegraded. Most of the nitro compounds were inhibitory in the higher concentration test though they were reduced into amino compounds. Since the biodegradation characteristics of many organic compounds could be classified and discussed appropriately, the suitability of the proposed method is substantiated.

Anaerobiosis↗
PubMed1991

Purine and 1-deazapurine ribonucleosides and deoxyribonucleosides: synthesis and biological activity.

A series of 6-(hydroxylamino)purine and -1-deazapurine nucleosides were synthesized and tested for their antitumor and adenosine deaminase inhibitory activity. All the examined molecules displayed an in vitro activity comparable to that of the reference compounds 6-(hydroxylamino)-9-beta-D-ribofuranosylpurine (HAPR) and ara-A, their ID50 ranging from 0.9 microM to approximately 100 microM. The 6-hydroxylamino derivatives of 1-deazapurine 9, 12, and 17 and also the blocked compound 13 are inhibitors of ADA whereas the purine derivatives 4 and 6 and the nitro compounds 11 and 16 are resistant to the enzyme. 7-(Hydroxylamino)-3-(2-deoxy-beta-D-erythro-pentofuranosyl)-3H-imi dazo[4,5- b]pyridine, the less cytotoxic but the most active ADA inhibitor in the series (Ki = 2.7 x 10(-7)), greatly potentiates the antitumor activity of ara-A in vitro.

Adenosine Deaminase Inhibitors↗
PubMed2001

Relationships between chemical structures and mutagenicity: a preliminary survey for a database of mutagenicity test results of new work place chemicals.

A database of mutagenicity test results of new chemicals has been developed. Based on the amendment of the Industrial Safety and Health Law (ISHL) in 1979, manufacturers and importers in Japan are required to register any new work place chemicals with bacterial mutagenicity test results. At present more than ten thousand substances have been examined. We have surveyed correlations between 44 substructures and mutagenicity in 2,857 ISHL data as well as in 1,207 National Toxicology Program data as a preliminary analysis. The percentages of the mutagenic compounds were calculated. High percentages were found for electrophilic reagents such as epoxides (63%), aromatic nitro compounds (49%) and primary alkyl monohalides (46%). 71% of peroxides was found to be mutagenic. The results suggest that several types of reactions such as nucleophilic substitution reaction, nitrenium cation reaction and radical reaction are included in the process of the mutagenic alterations of DNA.

Databases, Factual↗
PubMed1996

New NO-donors with antithrombotic and vasodilating activities, part 15 nitrolic acids.

Five 1-oximino-1-nitro compounds (nitrolic acids) were prepared and tested for antithrombotic and blood pressure lowering activities. 1-Nitro-ethanone 1-oxime (1, ethylnitrolic acid) 2 h after oral administration to rats inhibited thrombus formation by a laser beam in mesenteric arterioles of rats by 69% and by 46% in venules (60 mg/kg). The blood pressure of SHR rats even at this high dose only was decreased by 10% suggesting that antithrombotic and blood pressure effects can be dissociated. The in vitro decomposition of 1 at 37 degrees C nearly exclusively gave N2O and acetic acid indicating that HNO primarily had been formed.

Animals↗
PubMed1996

Conversion of Allylic Alcohols into Allylic Nitromethyl Compounds via a Palladium-Catalyzed Solvolysis: An Enantioselective Synthesis of an Advanced Carbocyclic Nucleoside Precursor(1).

A two-step reaction sequence to homoallylic nitro compounds from allylic alcohols is presented. Ethoxy carbonylation of the alcohols with ethyl chloroformate provides the corresponding allylic ethyl carbonates in high yields. Exposure of these substrates to catalytic palladium(0) in CH(3)NO(2) initiates a reaction sequence, ionization-decarboxylation-nitromethylation, that culminates with the formation of nitroalkenes. The regio- and stereochemical outcomes of the nitromethyl allylation reaction can be explained by the behavior of the transient pi-allylpalladium complexes. This methodology serves as a centerpiece for the synthesis of an important carbocyclic nucleoside intermediate.

Journal Article↗
PubMed2006

Experimental and density functional theoretical investigations of linkage isomerism in six-coordinate FeNO(6) iron porphyrins with axial nitrosyl and nitro ligands.

A critical component of the biological activity of NO and nitrite involves their coordination to the iron center in heme proteins. Irradiation (330 < lambda < 500 nm) of the nitrosyl-nitro compound (TPP)Fe(NO)(NO(2)) (TPP = tetraphenylporphyrinato dianion) at 11 K results in changes in the IR spectrum associated with both nitro-to-nitrito and nitrosyl-to-isonitrosyl linkage isomerism. Only the nitro-to-nitrito linkage isomer is obtained at 200 K, indicating that the isonitrosyl linkage isomer is less stable than the nitrito linkage isomer. DFT calculations reveal two ground-state conformations of (porphine)Fe(NO)(NO(2)) that differ in the relative axial ligand orientations (i.e., GS parallel and GS perpendicular). In both conformations, the FeNO group is bent (156.4 degrees for GS parallel, 159.8 degrees for GS perpendicular) for this formally {FeNO}(6) compound. Three conformations of the nitrosyl-nitrito isomer (porphine)Fe(NO)(ONO) (MSa parallel, MSa perpendicular, and MSa(L)) and two conformations of the isonitrosyl-nitro isomer (porphine)Fe(ON)(NO(2)) (MSb parallel and MSb perpendicular) are identified, as are three conformations of the double-linkage isomer (porphine)Fe(ON)(ONO) (MSc parallel, MSc perpendicular, MSc(L)). Only 2 of the 10 optimized geometries contain near-linear FeNO (MSa(L)) and FeON (MSc(L)) bonds. The energies of the ground-state and isomeric structures increase in the order GS < MSa < MSb < MSc. Vibrational frequencies for all of the linkage isomers have been calculated, and the theoretical gas-phase absorption spectrum of (porphine)Fe(NO)(NO(2)) has been analyzed to obtain information on the electronic transitions responsible for the linkage isomerization. Comparison of the experimental and theoretical IR spectra does not provide evidence for the existence of a double linkage isomer of (TPP)Fe(NO)(NO(2)).

Crystallography, X-Ray↗
PubMed1990

The biosynthesis of cyanogenic glucosides in higher plants. Identification of three hydroxylation steps in the biosynthesis of dhurrin in Sorghum bicolor (L.) Moench and the involvement of 1-ACI-nitro-2-(p-hydroxyphenyl)ethane as an intermediate.

N-Hydroxytyrosine, (E)- and (Z)-p-hydroxyphenyl-acetaldehyde oxime, p-hydroxyphenylacetonitrile, and p-hydroxymandelonitrile are established intermediates in the biosynthesis of the tyrosine-derived cyanogenic glucoside dhurrin (Halkier, B. A., Olsen, C. E., and Møller, B. L. (1989) J. Biol. Chem. 264, 19487-19494. Simultaneous measurements of oxygen consumption and biosynthetic activity using a microsomal enzyme system isolated from etiolated sorghum seedlings demonstrate a requirement for three oxygen molecules in the conversion of tyrosine to p-hydroxymandelonitrile. Two oxygen molecules are consumed in the conversion of tyrosine to (E)-p-hydroxyphenylacetaldehyde oxime, indicating the existence of a previously undetected hydroxylation step in addition to that resulting in the formation of N-hydroxytyrosine. Radioactively labeled 1-nitro-2-(p-hydroxyphenyl)ethane was chemically synthesized and tested as a possible intermediate. Biosynthetic experiments demonstrate that the microsomal enzyme system metabolizes the nitro compound to the subsequent intermediates in dhurrin synthesis (Km = 0.05 mM; Vmax = 14 nmol/mg of protein/h). Low amounts of 1-nitro-2-(p-hydroxyphenyl)ethane are produced in the microsomal reaction mixtures when tyrosine is used as substrate. These data support the involvement of 1-nitro-2-(p-hydroxyphenyl)ethane or more likely its aci-nitro tautomer as an intermediate between N-hydroxytyrosine and p-hydroxyphenylacetaldehyde oxime. The conversion of (E)-p-hydroxyphenylacetaldehydeoxime to p-hydroxymandelonitrile requires a single oxygen molecule. The oxygen molecule is utilized for hydroxylation of p-hydroxyphenylacetonitrile into p-hydroxymandelonitrile. This indicates that the conversion of p-hydroxyphenylacetaldehyde oxime into p-hydroxyphenylacetonitrile proceeds by a simple dehydration reaction.

Carbon Radioisotopes↗
PubMed1994

Radiosensitizing and cytotoxic properties of DNA targeted phenanthridine-linked nitroheterocycles of varying electron affinities.

2-Nitroimidazoles targeted to DNA via intercalation have previously been shown to be as much as 10-100 times more efficient on a molar basis than the untargeted nitroimidazole, misonidazole, in vitro as hypoxic cell selective radiosensitizers and cytotoxins based on extracellular concentrations. In this work the effect of varying the nitroaromatic group has been examined through the preparation of a DNA-targeted 4-nitroimidazole (4-MeNLP-3), a 5-nitroimidazole (5-NLP-3) and a 5-nitrofuran (FEP-2) linked to phenanthridinium ions. With the previously synthesized 2-nitroimidazoles, this provides a series of DNA targeted compounds of varying electron affinity as well as structure at the nitroaromatic position. The present series of compounds was tested for partition coefficient, DNA binding ability, reduction potentials and in vitro radiosensitizing and cytotoxic abilities. The 4-nitro compound displays good radiosensitizing ability, with an SER of approximately 2, despite its low reduction potential, -551 mV. However, hypoxia selective toxicity is lost at the lower reduction potentials presumably due to redox-independent mechanisms. The results obtained indicate that targeting such compounds to DNA diminishes the dependency of radiosensitizing and cytotoxic properties on reduction potential and may allow significant uncoupling of toxicity from radiosensitizing ability.

Animals↗
PubMed2003

Biodegradation of nitro-explosives.

Environmental contamination by nitro compounds is associated principally with the explosives industry. However, global production and use of explosives is unavoidable. The presently widely used nitro-explosives are TNT (Trinitrotoluene), RDX (Royal Demolition Explosive) and HMX (High Melting Explosive). Nevertheless, the problems of these nitro-explosives are almost parallel due to their similarities of production processes, abundance of nitro-explosives and resembling chemical structures. The nitro-explosives per se as well as their environmental transformation products are toxic, showing symptoms as methaemoglobinaemia, kidney trouble, jaundice etc. Hence their removal/degradation from soil/water is essential. Aerobic and anaerobic degradation of TNT and RDX have been reported, while for HMX anaerobic or anoxic degradation have been described in many studies. A multisystem involvement using plants in remediation is gaining importance. Thus the information about degradation of nitro-explosives is available in jigsaw pieces which needs to be arranged and lacunae filled to get concrete degradative schemes so that environmental pollution from nitro-explosives can be dealt with more successfully at a macroscale. An overview of the reports on nitro-explosives degradation, future outlook and studies done by us are presented in this review.

Biodegradation, Environmental↗
PubMed1988

Methemoglobinemia due to ingestion of N,N-dimethyl-p-toluidine, a component used in the fabrication of artificial fingernails.

An acute cyanotic episode due to methemoglobinemia occurred in a 16-month old girl following the ingestion of N,N-dimethyl-p-toluidine, a commercially available component used in the production of artificial fingernails. The amount of the parent compound ingested was about 6 mg/kg of body weight. Administration of methylene blue was effective in the reversal of the methemoglobinemia. In vitro studies suggest that the activity of the compound was probably due to its biochemical transformation to the toxic metabolite p-methylphenylhydroxylamine. We expand the list of aromatic amino or nitro compounds and their derivatives capable of producing methemoglobinemia and call attention to the hazard of their ingestion.

Accidents, Home↗
PubMed1997

Salivary nitrate, nitrite and N-nitroso compounds in patients with cancer of the upper aerodigestive tract.

N-nitroso compounds are carcinogens that can be ingested directly or synthesized from nitrites and nitrates. The possible role of N-nitroso compounds in the induction of upper aerodigestive tract tumours was considered in a case-control study conducted in the Valle d'Aosta, an Italian region with a high incidence of these neoplasms. Nitrate, nitrite, labile and stable N-nitroso compounds were analysed in the saliva of 36 patients with cancers of the upper aerodigestive tract and 23 healthy individuals. After allowing for tobacco, salivary nitrate, nitrite and N-nitroso compounds were not associated with an increased risk of upper aerodigestive tract cancers. The odds ratio for continuous units of total N-nitros compounds was 0.99 (95% confidence interval 0.9-1.1). Thus, salivary nitrate, nitrite and N-nitroso compounds might not be suitable markers for the assessment of the risk of cancer of the upper aerodigestive tract, although a role for N-nitroso compounds cannot be excluded.

Adult↗
PubMed2000

Syntheses of 1-[(2-hydroxyethoxy)methyl]- and 1-[(1,3-dihydroxy-2-propoxy)methyl]- derivatives of 5-substituted-2,4-difluorobenzene: unnatural acyclo thymidine mimics for evaluation as anticancer and antiviral agents.

A group of 1-[(2-hydroxyethoxy)methyl]- (12) and 1-[(1,3-dihydroxy-2-propoxy)methyl]- (13) derivatives of 2,4-difluorobenzene possessing a variety of C-5 substituents (R = Me, H, I, NO2) were designed with the expectation that they may serve as acyclic 5-substituted-2'-deoxyuridine (thymidine) mimics. Compounds 12 and 13 (R = Me, H, I) were inactive as anticancer agents (CC50 = 10(-3) to 10(-4) M range), whereas the 5-nitro compounds (12d, 13d) exhibited weak-to-moderate cytotoxicity (CC50 = 10(-5) to 10(-6) M range) against a variety of cancer cell lines. All compounds prepared (12a-d, 13a-d) were inactive as antiviral agents in a broad-spectrum antiviral screen that also included the human immunodeficiency virus (HIV-1 and HIV-2) and herpes simplex virus (HSV-1 and HSV-2).

Animals↗
PubMed2004

Electronic spectra, solvatochromic behavior and acid-base properties of some azo cinnoline compounds.

The electronic spectra of three azo cinnoline derivatives have been studied in pure and mixed organic solvents of different characteristics as well as the effect of concentration of the compounds in the different solvents. The different bands observed have been assigned to the proper electronic transition. The longer wavelength band displayed by the para nitro cinnoline derivative in dimethylformamide (DMF) solution is assigned to an intermolecular CT transition. The solvated H-bonding complexes formed between DMF and the para nitro derivative were investigated. DeltaG and K(f) values of these complexes have been determined. The acidity constants of the para nitro compound were determined from the spectra in aquous-methanolic solution of varying pH values. The effect of temperature on the longer wavelength visible band of p-NO(2) has been investigated.

Acids↗