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PubMed1998

Characterization of novel N,N'-disubstituted piperazines as sigma receptor ligands.

sigma Receptors have been the focus of extensive studies because of their potential functional role in several important physiological and biochemical processes. To further evaluate the properties of sigma receptors, especially sigma-1 and sigma-2 subtypes, we have synthesized a series of N,N'-disubstituted piperazine compounds (1-32). The design of these compounds was based upon the early structure-activity relationship (SAR) studies of the minimum structural requirements of a molecule necessary to elicit sigma receptor binding activity. In the N-(3-phenylpropyl)piperazine series, compounds with the ethylenediamine moiety (8-11, 15-17) showed 6-20-fold higher affinity for sigma-1 and 2-40-fold higher affinity for sigma-2 relative to their corresponding amides (1-7). The (m-nitrophenethyl)piperazine 10 exhibits a subnanomolar affinity for the sigma-1 site, whereas the corresponding o-nitro compound 9 shows the highest affinity for the sigma-2 site (Ki = 4.9 nM). Compounds with a free amino terminus were designed as precursors for use as bioconjugated affinity compounds. Some of these compounds displayed high affinity for sigma-1 and moderate affinity for sigma-2 sites and are currently used for the purification and characterization of the receptor subtypes.

Animals↗

PubMed2005

Engineering Pseudomonas fluorescens for biodegradation of 2,4-dinitrotoluene.

Using the genes encoding the 2,4-dinitrotoluene degradation pathway enzymes, the nonpathogenic psychrotolerant rhizobacterium Pseudomonas fluorescens ATCC 17400 was genetically modified for degradation of this priority pollutant. First, a recombinant strain designated MP was constructed by conjugative transfer from Burkholderia sp. strain DNT of the pJS1 megaplasmid, which contains the dnt genes for 2,4-dinitrotoluene degradation. This strain was able to grow on 2,4-dinitrotoluene as the sole source of carbon, nitrogen, and energy at levels equivalent to those of Burkholderia sp. strain DNT. Nevertheless, loss of the 2,4-dinitrotoluene degradative phenotype was observed for strains carrying pJS1. The introduction of dnt genes into the P.fluorescens ATCC 17400 chromosome, using a suicide chromosomal integration Tn5-based delivery plasmid system, generated a degrading strain that was stable for a long time, which was designated RE. This strain was able to use 2,4-dinitrotoluene as a sole nitrogen source and to completely degrade this compound as a cosubstrate. Furthermore, P. fluorescens RE, but not Burkholderia sp. strain DNT, was capable of degrading 2,4-dinitrotoluene at temperatures as low as 10 degrees C. Finally, the presence of P. fluorescens RE in soils containing levels of 2,4-dinitrotoluene lethal to plants significantly decreased the toxic effects of this nitro compound on Arabidopsis thaliana growth. Using synthetic medium culture, P. fluorescens RE was found to be nontoxic for A.thaliana and Nicotiana tabacum, whereas under these conditions Burkholderia sp. strain DNT inhibited A.thaliana seed germination and was lethal to plants. These features reinforce the advantageous environmental robustness of P. fluorescens RE compared with Burkholderia sp. strain DNT.

Biodegradation, Environmental↗

PubMed1997

[Dual-wavelength method for analysis of overlapped high performance liquid chromatographic peaks with multiwavelength diode array detection].

High performance liquid chromatography (HPLC) is one of the analytical techniques most frequently used. Its chief limitation lies in the need to avoid the overlap of chromatographic peaks as much as possible. In this work, a new method for the treatment of HPLC data allowing the resolution of extensively overlapped peaks has been developed. This method uses a diode array spectrophotometer and treats the generated data by dual-wavelength method. Its foundation is based on calculating the peak areas for two given wavelength in order to determine the contribution of each component to the mixed peak. Because the area is the integration of absorption at different wavelength, the wavelength can be chosen from the absorption spectra of the two compounds for eliminating the interference of the other component in the mixture, and the concentration of the corresponding component can be calculated. This method provides a simplification of the calculation process and a reduction of the amount of the data used. The applicability of the method is checked on mixture of two aromatic nitro-compounds. Though the two components almost have the same retention time and their peaks overlapped extensively, the results are satisfactory.

English Abstract↗

PubMedDate not supplied

The metabolism of 3-aminobiphenyl and 3-acetamidobiphenyl in vitro.

The metabolism of 3-aminobiphenyl (3-ABP) and 3-acetamidobiphenyl (3-AABP) has been studied using fortified rat liver microsomal preparations. Metabolites in concentrates of ether extracts from hepatic microsomal preparations were analysed by TLC and GLC. The metabolites were characterised by a comparison of their chromatographic characteristics with synthetic compounds and response to detection reagents. 3-ABP appeared to be hydroxylated predominantly at the 2- and 4-ortho positions and to a minor extent at the 6-position, whereas 3-AABP was converted to 3-acetamido-6-hydroxybiphenyl as the major metabolite. 3-ABP was also converted to the corresponding hydroxylamine, nitroso and nitro compound although the latter may have arisen via a non enzymic process.

Aminobiphenyl Compounds↗

PubMed1990

Toxicity of nitrobenzene compounds towards isolated hepatocytes: dependence on reduction potential.

1. The cytotoxicity of p-substituted nitrobenzenes towards isolated hepatocytes under aerobic or hypoxic conditions has been determined. The nitrobenzene concentration required to cause 50% cytoxicity in 2 h was a function of the one-electron reduction potential of the nitrobenzene, with the more cytotoxic compounds having the strongest electron-withdrawing substituents. 2. The effectiveness of the nitrobenzenes at causing cytotoxicity under aerobic but not hypoxic conditions was markedly increased if hepatocyte catalase was inhibited with azide. 3. Nitrobenzenes at cytotoxic concentrations induced cyanide-resistant respiration in isolated hepatocytes. Their effectiveness correlated with their cytotoxicity. 4. The rate of oxygen activation of these nitrobenzenes by ascorbate was also a function of the one-electron reduction potential. The nitro compounds with the strongest electron-withdrawing substituents were the most rapidly reduced. 5. Most nitrobenzenes were more cytotoxic under aerobic than hypoxic conditions. Ascorbate enhanced hypoxic, but not aerobic, cytotoxicity. 6. It was concluded that the cytotoxicity of different nitrobenzenes is related to their ease of reduction to nitro radical anions and nitrosobenzenes. Aerobic cytotoxicity is probably initiated by redox cycling and oxygen activation by the nitro radical anions whereas hypoxic cytotoxicity is probably initiated by the alkylation of macromolecules by nitrosobenzene metabolites.

Alkylation↗

PubMed2003

Prediction of reactive hazards based on molecular structure.

There is considerable interest in prediction of reactive hazards based on chemical structure. Calorimetric measurements to determine reactivity can be resource consuming, so computational methods to predict reactivity hazards present an attractive option. This paper reviews some of the commonly employed theoretical hazard evaluation techniques, including the oxygen-balance method, ASTM CHETAH, and calculated adiabatic reaction temperature (CART). It also discusses the development of a study table to correlate and predict calorimetric properties of pure compounds. Quantitative structure-property relationships (QSPR) based on quantum mechanical calculations can be employed to correlate calorimetrically measured onset temperatures, T(o), and energies of reaction, -deltaH, with molecular properties. To test the feasibility of this approach, the QSPR technique is used to correlate differential scanning calorimeter (DSC) data, T(o) and -deltaH, with molecular properties for 19 nitro compounds.

Calorimetry↗

PubMed1992

Genotoxicity of 2-amino-3-methylimidazo[4,5-f]quinoline (IQ) and related compounds in Drosophila.

The potent food mutagen and carcinogen 2-amino-3-methylimidazo[4,5- f]quinoline (IQ) and the structurally related heterocyclic aromatic amines 2-aminoimidazo[4,5-f]quinoline (demethyl-IQ) and 2-amino-1-methylimidazo[4,5-f]quinoline (iso-IQ) were assayed for genotoxicity in the wing somatic mutation and recombination test (SMART) as well as in the sex-linked recessive lethal (SLRL) test in Drosophila melanogaster. In addition, 3-methyl-2-nitroimidazo[4,5-f]quinoline (nitro-IQ), 2-nitrofluorene and 1,8-dinitropyrene were also assayed in the wing spot test. IQ was clearly mutagenic in the SLRL test with highest activity in spermatids. Iso-IQ was more active than IQ whereas demethyl-IQ was inactive in this test. The same pattern of results was obtained in the wing SMART: iso-IQ produced greater than 2-fold higher frequencies of spots than IQ and demethyl-IQ was clearly negative. In addition, nitro-IQ exhibited an approximately equal genotoxic activity as IQ. 2-Nitrofluorene and 1,8-dinitropyrene were both inactive in the wing spot test. These data provide good evidence for a correlation of genotoxic effects in germinal and somatic cells, and for the practical advantage of the wing spot test in Drosophila. Moreover, the results show structure-activity relationships among the heterocyclic aromatic amines and nitro compounds similar to those found in Salmonella.

Animals↗

PubMed2001

Nonacid nitration of benzenedicarboxylic and naphthalenecarboxylic acid esters.

When treated with nitrogen dioxide in the presence of ozone and a catalytic amount of iron(III) chloride in inert organic solvent at -10 to +5 degrees C, benzenedicarboxylic acid diesters 1, 4, and 6 underwent smooth nitration to give the corresponding mononitro derivatives 2/3, 5, and 7, respectively, in good yield (kyodai nitration). Naphthalenecarboxylic acid esters 8 and 11 and naphthalene-1,8-dicarboxylic acid diester 16 were similarly nitrated in the absence of catalyst to give the expected nitro compounds 9/10, 12-15, and 17-22, respectively. Different from conventional nitration based on the combined use of concentrated nitric and sulfuric acids, no hydrolytic cleavage of the ester function was observed under these conditions. The isomer distribution has been determined for the nitration of naphthalenecarboxylic acid esters 8, 11, and 16, and spectral data were collected for less common nitro derivatives. A unique changeover of the orientation mode observed in the kyodai nitration of diester 16, from the initial exclusive meta to the final meta/para, has been discussed in terms of the competition between the electrophilic substitution process involving the nitronium ion (NO2+) and the addition-elimination sequence involving the nitrogen trioxide radical (*NO3).

Journal Article↗

PubMed1987

The in vitro/in vivo comparative metabolism of 4-aminobiphenyl using isolated hepatocytes.

The metabolism of 4-aminobiphenyl by isolated hepatocytes from various species was compared with urinary metabolite profiles in the same species. Radioactive compounds in concentrates of ether extracts from hepatocytes or urine following hydrolysis were analysed by TLC and reversed phase HPLC in conjunction with radioactivity monitoring and synthetic standards. The major metabolites from hepatocytes and in urine were 4-acetamidobiphenyl, 3-hydroxy-4-aminobiphenyl 4'-hydroxy-4-aminobiphenyl and 4'-hydroxy-4-acetamidobiphenyl. Oxidation of the amine nitrogen gave hydroxylamino, nitroso and nitro compounds. Minor metabolites were 2'-hydroxy amine and amide, the hydroxamic acid and the oxamic acid. The urinary metabolite profiles correlated well with those from hepatocytes for each species.

Aminobiphenyl Compounds↗

PubMed2000

Chromatographic detection of nitroaromatic and nitramine compounds by electrochemical reduction combined with photoluminescence following electron transfer.

The oxidizing agent tris(bipyridyl)ruthenium(III), or Ru-(bpy)(3)3+, is used as a postcolumn reagent for the detection of nitroaromatic and nitramine explosive compounds. After separation, the explosives are reduced electrochemically to oxidizable products such as hydroxlamines and nitrosamines, and these products react readily with Ru-(bpy)(3)3+ and Ru(bpy)(3)2+. The photoluminescence from the latter is used for detection. A porous carbon electrode was used for on-line analyte reduction following chromatography. Another porous carbon electrode was used to generate the nonluminescent Ru(bpy)(3)3+ from Ru(bpy)(3)3+ on-line at high efficiency. The two streams were combined, and the Ru(bpy)(3)2+ produced by oxidation of the reduced analytes was detected by laser illumination and light detection. Reductive hydrodynamic voltammograms of nitrobenzene, 2,4,6-trinitrotoluene, and hexahydro-1,3,5-trinitro-1,3,5-triazine indicated that a potential of - 1500 mV vs Ag/AgCl was sufficient to achieve a maximum signal from the reduced analytes. HPLC with a water/acetonitrile gradient on a C-18 reversed-phase column was then used to determine these three compounds plus the four additional examples, 1,3,5,7-tetrazocine, 2,4-dinitrotoluene; 2,6-dinitrotoluene, and 4-nitrotoluene. For both hydrodynamic voltammetry and HPLC detection, the photoluminescence following electron-transfer signal was calibrated using the one-electron standards ferrocene and ferrocenecarboxylic acid. Detection limits were in the low-nanomolar range for 20-microL injections of nonpreconcentrated nitro compounds.

Aniline Compounds↗

PubMedDate not supplied

[Use of surviving infectious larvae of Dipetalonema dessetae in study and research on filaricidal substances].

Dipetalonema dessetae in Proechimys oris, the natural final host is a rodent filariasis model used as an in vivo antifilarial screening test. The laboratory vector is Aedes aegypti. Infective larvae L3 isolated from the intermediate host develop and remain healthy for up to 30 days in a biphasic culture medium composed of a cell feeder layer (L 929) and RPMI 1640 supplemented with foetal calf serum. This culture technique has enabled us to screen antifilarial compounds on a new in vitro test. This model has been tested to several pharmacological classes of anthelmintics and effective concentrations 90% are given: diethylcarbamazine 430 mg/l, suramin 490 mg/l, Mel W 3.5 mg/l, mebendazole 78 mg/l, flubendazole 45 mg/l, levamisole 0.55 mg/l, morantel 0.62 mg/l, ivermectin 1.2 mg/l, amoscanate 2.3 mg/l. In vitro test response is remarkable for neurotoxic anthelmintics and nitro-compounds. Furthermore, all compounds considered as reference filaricides are active. For each compound, the in vitro and in vivo results have been compared to appreciate usefulness as well as limits of this in vitro test.

Animals↗

PubMed1982

The effect of caffeine on the cytotoxicity of misonidazole and some other nitroheterocyclic compounds.

Caffeine was found to potentiate the cytotoxic effect of misonidazole (1-(2-nitroimidazol-1-yl)-3-methoxy-2-propanol) towards mammalian cells in vitro. This enhancement of toxicity is shown to occur under both aerobic and hypoxic conditions. Split dose experiments indicate that the general shape of the hypoxic survival curve can be restored by exposure of cells of O2 between doses. Exposure of cells to 2mM caffeine during the split dose experiment has no potentiating effect. Further experiments showed that caffeine affects the expression of misonidazole-induced potentially lethal damage. Other electron-affinic nitro compounds which show greater toxicity to hypoxic compared to aerobic cells, viz. metronidazole and nitrofurantoin, also have their toxicities enhanced by subsequent exposure to caffeine.

Animals↗

PubMed2003

Nitro-functionalized oligothiophenes as a novel type of electroactive molecular material: spectroscopic, electrochemical, and computational study.

A novel series of terthiophenes bearing electron-donor and electron-acceptor groups at the end alpha-positions has been prepared. The analysis of the UV-vis, infrared, and Raman spectra, performed with the aid of density functional theory calculations, shows that the asymmetrically substituted nitro compounds PhT(3)NO(2) and BrT(3)NO(2) behave as push-pull systems and present an intense photoinduced charge transfer in the visible spectrum. The symmetrically substituted dinitro compound NO(2)T(3)NO(2) displays a highly delocalized structure with a low single-double bond length alternation and also displays a low-energy absorption band in the visible region. The novel nitroterthiophenes possess attractive electrochemical properties since they generate stable species both upon oxidation and reduction. Oxidation mainly involves changes in the oligothiophene backbone and leads to the formation of stable cations even for NO(2)T(3)NO(2). Reduction is mainly nitro-centered but also affects the conjugated structure. Radical anions and dianions are formed for PhT(3)NO(2) and BrT(3)NO(2). Dianions, not radical anions, and trianions are obtained for NO(2)T(3)NO(2). Nitro-functionalized terthiophenes are shown to be very promising as electroactive molecular materials since they behave as push-pull systems, present a very intense photoinduced charge transfer in the visible region, and could act as both n- and p-channel conductors in organic electronic transistors.

Journal Article↗

PubMed2005

A new method to evaluate the stability of the covalent compound: by the charges on the common atom or group.

A new method of comparing and analyzing the electrostatic potential (ESP) charges of the common atom or group to evaluate and compare the stabilities of covalent compounds was introduced. That is, covalent compounds will become more stable when the electron acceptors accept adequate electrons and possess adequate negative charges, and the electron donors donate adequate electrons and possess adequate positive charges accordingly. All calculations were performed by density functional theory (DFT) and the general gradient approximation (GGA) method with the Beck-LYP hybrid functional and the DNP basis set in Acceryls' code Dmol3. Calculation results verified the method considering the molecular structure is well applied in the covalent molecule systems of hydrides, oxides, alkyl radicals, and nitro compounds. Furthermore, the method has good operability, for the charges can be easily obtained by simple calculation.

Journal Article↗

PubMed1986

Separation of lipophilic substances in environmental samples with special reference to toxaphene.

A microcolumn of alumina, activated at 250 degrees C over night and deactivated with 2% water in an oven at 150 degrees C, has shown better separation characteristics than similar ones, deactivated at room temperature, for a great number of organochlorine compounds, particularly with respect to multicomponent toxaphene and PCB. The microcolumn is a simple disposable Pasteur pipette. Three fractions are collected: one with PCB and DDE, one with toxaphene components having similar lipophilicity to DDT and the third, toxaphene components similar to DDD in lipophilicity. Two such toxaphene fractions give a better GLC-pattern than only one fraction. DDD and DDT, which interfere with the analysis of toxaphene can be eliminated, after their GLC analysis, from the "Toxaphene fractions" by nitration followed by reduction of the nitro compounds formed to their corresponding amines. Performance of the column using environmental samples showed that it is a useful tool in routine pesticide residue analysis, especially when toxaphene is present.

Aluminum Oxide↗

PubMed2004

Treatment of portal hypertension with NCX-1000, a liver-specific NO donor. A review of its current status.

Portal hypertension, a life threatening complication of liver cirrhosis, results from increased intrahepatic resistance and increased portal blood inflow through a hyperdynamic splanchnic system. The increased intrahepatic vascular tone is the result of an enhanced activity of endogenous vasoconstrictors and a deficiency of nitric oxide (NO) release by sinusoidal endothelial cells. These pathophysiological events provide the rational basis for using NO-based therapies for the treatment of portal hypertension. Clinical studies have demonstrated that nitrate therapy results in a significant reduction of portal pressure as assessed by hepatic venous portal gradient but causes vasodilation in both systemic arterial and venous vascular beds, aggravating the progression of the vasodilatory syndrome of cirrhotic patients. For this reason, the ideal drug for the treatment of portal hypertension should act by decreasing intrahepatic vascular resistance, without worsening the splanchnic/systemic vasodilatation. NCX-1000 is the prototype of a family of NO-releasing derivatives of ursodeoxycholic acid (UDCA). These compounds are releasing selectively, from parenchymal and non-parenchymal hepatic cells, biologically active NO into the liver microcirculation with no detectable effect on systemic circulation. Preclinical studies have shown that long- and short-term administration of NCX-1000 to rodents with chronic liver injury protects against the development of portal hypertension and reduces the intrahepatic hyperreactivity to alpha1-adrenoceptor agonists. The finding of increased liver nitrite/nitrate content in NCX-1000-treated animals together with an increase in cGMP levels in their liver homogenates suggests that this nitro-compound behaves as a liver-selective NO donor. In contrast to conventional NO-donors such as isosorbide mono- and di-nitrate, which are also used for primary and secondary prevention of gastrointestinal bleeding, NCX-1000 has no effect on mean arterial pressure in either normal or cirrhotic animals indicating the absence of adverse systemic effect. In summary, these data suggest that NCX-1000 may provide a novel therapy for the treatment of patients with portal hypertension.

Animals↗

PubMed1994

Bioreductive drugs for cancer therapy: the search for tumor specificity.

The activity of three different classes of bioreductive drug, i.e., heterocyclic nitro compounds, N-oxides and quinones are compared. The major characteristics of RB-6145, tirapazamine and E09 are summarized and future directions for development of new bioreductive drugs are outlined. The concept of potentiating bioreductive drug activity by increasing tumor hypoxia is described and illustrated in particular by the use of photodynamic therapy (PDT) in combination with RSU-1069. Examples of how the therapeutic effectiveness of this approach can be studied by the use of 31P magnetic resonance spectroscopy is described. The effects of manipulation of nitric oxide (NO) levels in tumors by the use of modifiers of NO-synthase activity is illustrated by studies with the inhibitor nitro-L-arginine in experimental tumors. Associated changes in tumor physiology indicate promise for potential applications in therapy. Finally, changes in expression of reductase enzyme levels are considered in the context of the heterogenous nature of the tumor microenvironment.

Animals↗

PubMed1983

Mechanism of nitrate-induced vasodilation and tolerance.

Various NO-forming compounds have in common that along with their mechanically relaxing effect, they increase the concentration of cyclic 3'5'-guanosine monophosphate (cGMP) in vascular smooth muscle. This has been shown for nitroglycerin, NaNO2, nitroprusside-Na, 2'3'-dinitroadenosine-5'-ethylcarboxamide (B-744-99), and more recently for SIN-1, the vasoactive metabolite of molsidomine, and for nicorandil (SG-75). In isolated circular strips of bovine coronary arteries, suspended in a partially depolarizing Tyrode's solution containing 27 mM K+, these drugs produced dose-dependent relaxations which were slightly preceded by concomitant increases in cGMP levels, measured at various moments of drug action by freeze-clamping the strips, and by subsequent determinations of cyclic nucleotide levels by RIA. Levels of cyclic 3',5'-AMP were not significantly changed, except by B-744-99. Inhibition of cGMP hydrolysis by the addition of M & B 22,948 (2-o-propoxyphenyl-8-azapurin-6-one) augmented the nitrate-induced rises in cGMP as well as their relaxing effects on coronary arterial strips. In the presence of the vital stain methylene blue - which was shown in vitro to prevent nitrate-induced activation of guanylate cyclase, the enzyme which forms cGMP from GTP - the relaxant actions as well as the increases in cGMP produced by several of these nitro-compounds in coronary strips were almost abolished. The actions of organic nitrates appear to depend on their previous reduction to NO by a rate-limiting step involving cysteine, whereas those of nitroprusside and SIN-1 are probably independent of cysteine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗