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PubMed2000

Analysis of metal complex azo dyes by high-performance liquid chromatography/electrospray ionization mass spectrometry and multistage mass spectrometry

Five metal complex azo compounds were analyzed using negative-ion electrospray ionization mass spectrometry (ESI-MS). Mass spectra of all compounds yield intense peaks corresponding to [M - H](-) ions without any fragmentation, where M denotes the neutral compound with a proton as the counterion. Under collision induced dissociation (CID) conditions, structurally important fragment ions were studied using the ion trap analyzer with a multistage mass spectrometry (MS(n) facility. Synthesized compounds with (15)N atoms in the azo group facilitated the fragmentation pattern recognition. A reversed-phase high-performance liquid chromatography (HPLC) method using 5 mM ammonium acetate in 70% aqueous acetonitrile as mobile phase was developed making possible the separation of all complex compounds tested. The lower detection limits of the ESI-MS method are in the range 10-20 ng of each compound. The HPLC/ESI-MS method makes possible the monitoring of ligand exchange in aqueous solutions of metal complex azo dyes, and also investigation of the stabilities of the complexes in solution. Copyright 2000 John Wiley & Sons, Ltd.

Journal Article↗
PubMed2005

Efficient preparation of nitrosoarenes for the synthesis of azobenzenes.

[reaction: see text] Reaction conditions are described for the oxidation of anilines furnishing nitrosoarenes and the synthesis of unsymmetrically substituted azobenzenes. In a comparative study, the catalytic oxidation of methyl 4-aminobenzoate by hydrogen peroxide was investigated, and SeO(2) proved to be superior or equal to methyl trioxorhenium (MTO) and Na(2)WO(4), respectively. Nevertheless, the application of the inexpensive, environmentally friendly, Oxone in a biphasic system proved to be more efficient, and a variety of useful nitrosoarenes for the synthesis of azo compounds were prepared in high yield and purity on a large scale.

Azo Compounds↗
PubMed1982

In vitro metabolism of o-aminoazotoluene and mutagenesis of Salmonella by the metabolites.

Incubation of hepatocarcinogenic aminoazo dye, o-aminoazotoluene (OAT) with rat liver microsomes together with NADPH and NADH yielded N-hydroxy-OAT (I), 4'-hydroxy-OAT (II) and a smaller amount of 2'-hydroxymethyl-3-methyl-4-aminoazobenzene (III). As an artifact 4,4'-bis(o-tolylazo)-2,2' -dimethylazoxybenzene (IV) was also detected in a small quantity. The mutagenicities of these metabolites were assayed by using Salmonella typhimurium TA98 and TA100 together with S-9 prepared from the livers of rats treated with polychlorinated biphenyl mixture (PCB). OAT and III were strongly mutagenic, but only when S-9 was present. In contrast, I was a strong mutagen regardless of the presence or absence of S-9. II and IV were non-mutagenic. The yields of I, II and III from OAT were pronouncedly reduced by addition of cytochrome P-450 inhibitors, especially by a cytochrome P-448 inhibitor 7,8-benzoflavone. Mutagenesis by OAT was also inhibited by addition of 7,8-benzoflavone. Activation of OAT for mutagenesis was enhanced by pretreatment of the donor rats with PCB or 3-methyl-cholanthrene and to a much lesser extent by phenobarbital. These findings suggest that N-hydroxylation of OAT mainly proceeds via catalysis by cytochrome P-448 and that this process is an obligatory step for the activation of OAT. Synthetic methods for the preparation of new azo compounds such as I, IV and 2',3-dimethyl-4-nitrosoazobenzene are described.

Animals↗
PubMed1998

2,2'-Azobis (4-methoxy-2,4-dimethylvaleronitrile), a new lipid-soluble azo initiator: application to oxidations of lipids and low-density lipoprotein in solution and in aqueous dispersions.

Both hydrophilic and hydrophobic azo radical initiators are useful for in vitro studies on lipid peroxidation and its inhibition by antioxidants. In the present study, a new lipophilic azo compound, 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile) (MeO-AMVN), was introduced and its action as an initiator of lipid peroxidation was examined. MeO-AMVN decomposed about 15 times as fast as 2,2'-azobis(2,4-dimethylvaleronitrile) (AMVN), a widely used lipophilic azo initiator, and MeO-AMVN-initiated free radical-mediated peroxidations of lipids in organic solution and in micelles, membranes, and low-density lipoprotein in aqueous dispersions with much smaller concentration than AMVN. The rate of chain initiation by MeO-AMVN varied significantly with the medium and decreased with increasing viscosity of the medium. The advantage and cautions for using MeO-AMVN as a lipophilic radical source have been discussed and it has been concluded that MeO-AMVN, when properly used, is a useful radical initiator of lipid peroxidations especially in micelles, membranes, and lipoproteins.

Acetonitriles↗
PubMed1999

The protective role of plasmalogens in iron-induced lipid peroxidation.

The role of plasmalogens in iron-induced lipid peroxidation was investigated in two liposomal systems. The first consisted of total brain phospholipids with and without plasmalogens, and the second of phosphatidylethanolamine/phosphatidylcholine liposomes with either diacyl- or alkenylacyl-phosphatidylethanolamine. By measuring thiobarbituric acid reactive substances, oxygen consumption, fatty acids and aldehydes, we show that plasmalogens effectively protect polyunsaturated fatty acids from oxidative damage, and that the vinyl ether function of plasmalogens is consumed simultaneously. Furthermore, the lack of lag phase, the increased antioxidant efficiency with time, and the experiments with lipid- and water-soluble azo compounds, indicate that plasmalogens probably interfere with the propagation rather than the initiation of lipid peroxidation, and that the antioxidative effect cannot be related to iron chelation.

Azo Compounds↗
PubMed1983

Arsonate-specific murine T cell clones. I. Genetic control and antigen specificity.

The antigen-induced proliferative response of lymph node cells (LNC) from mice sensitized to the monofunctional antigen L-tyrosine-p-azobenzenearsonate (ABA-Tyr) was used to monitor genetic control. All strains tested mounted significant responses, but those that were H-2(b) at both the I-A and I-E loci [B10., B6., B10.A(18R), A.BY, and C3H.SW] gave consistently weaker responses than other haplotypes. The F(1) progeny of matings between high and low responder phenotype parents (DBA/2 and B6, respectively) were high responders, establishing the dominance of the responder trait. Proliferative responses of LNC to ABA-Tyr were blocked by the appropriate anti-Ia monoclonal reagents. For example, B10.A(4R) LNCI (I-A(k), I-E(b)) were blocked by anti-I-A(k), whereas B10.A(3R) LNC (I-A(b), I-E(k)) were blocked by anti-I-E(k). Long-term cultures of T cell lines specifically reactive to ABA-Tyr were established from LNC of A/J mice immunized with ABA-Tyr and were cloned by limiting dilution. The proliferative responses to ABA-Tyr of 14 out of 15 clones tested were I-A restricted on the basis of activation by antigen-presenting cells from appropriate recombinant strains and the blocking activity of the monoclonal anti-Ia antibodies. The response of the other clone was I-E restricted. The fine antigen specificity of the clones was studied using structural analogs of the homologous antigen to induce proliferation. The clones could be divided into three types with respect to responsiveness to ABA-histidine (ABA-His). One group responded about equally well to ABA-His and ABA-Tyr. A second set responded less strongly to ABA-His than to ABA-Tyr, while the third showed no response above background to ABA- His. In all instances, the ABA-His-responding clones discriminated exquisitely between the 2-azo and 4-azo histidine isomers, responding only to the 4-azo compound. These T cell clones provide extremely useful tools for studies of T cell specificity, antigen recognition and lymphoid cell interaction systems.

Animals↗
PubMed1984

32P-postlabeling test for covalent DNA binding of chemicals in vivo: application to a variety of aromatic carcinogens and methylating agents.

Carcinogen--DNA adducts were detected and determined by 32P-postlabeling assay after exposure of mouse or rat tissues in vivo to a total of 28 compounds comprising 7 arylamines and derivatives, 3 azo compounds, 2 nitroaromatics, 12 polycyclic aromatic hydrocarbons, and 4 methylating agents. DNA was isolated from mouse skin, mouse liver, and rat liver after treatment with the individual carcinogens, then digested enzymatically to deoxyribonucleoside 3'-monophosphates, which were converted to 5'-32P-labeled deoxyribonucleoside 3',5'-bisphosphates by T4 polynucleotide kinase-catalyzed [32P]phosphate transfer from [gamma-32P]ATP. The nucleotides were resolved by anion-exchange t.l.c. on polyethyleneimine-cellulose and detected by autoradiography. The determination of low levels of DNA binding of the aromatic carcinogens entailed the removal of normal nucleotides prior to the resolution of adduct nucleotides. For this purpose, an alternative procedure employing reversed-phase t.l.c. was devised which offered advantages for the detection of quantitatively minor adducts. The procedures described enabled the detection of 1 aromatic DNA adduct in approximately 10(8) normal nucleotides, while the limit of detection of methylated adducts was 1 adduct in approximately 6 X 10(5) nucleotides. The results show that a great number of carcinogen-DNA adducts of diverse structure are substrates for 32P-labeling by polynucleotide kinase-catalyzed phosphorylation. Because covalent DNA adduct formation in vivo appears to be an essential property of the majority of chemical carcinogens, 32P-postlabeling analysis of carcinogen--DNA adducts in mammalian tissues may serve as a test for the screening of chemicals for potential carcinogenicity.

Alkylating Agents↗
PubMed2005

Total hydroxyoctadecadienoic acid as a marker for lipid peroxidation in vivo.

An improved method for the measurement of lipid peroxidation in vivo has been recently developed, where total hydroxyoctadecadienoic acid (HODE) and 7-hydroxycholesterol (FCOH) were determined by GC/MS analysis from physiological samples after reduction with sodium borohydride and saponification by potassium hydroxide. In this method, both free and ester forms of hydroperoxides and ketones as well as hydroxides of linoleic acid and cholesterol are measured as HODE and FCOH, respectively. The ratio of stereo-isomer, (Z, E)-HODE/(E, E)-HODE, could be also measured. In the present study, in order to examine the effect of continuous, slow flux of free radicals in vivo, a water-soluble radical generator was administered to rats and mice and the amounts of HODE and 8-isoprostane in plasma and liver were measured. It was found that the administration of free radical-generating azo compound increased the level of HODE and decreased the (Z, E)-HODE/(E, E)-HODE ratio in both plasma and liver. The level of HODE was much higher than 8-isoprostane.

Amidines↗
PubMed1992

D and C Red No. 9: genotoxic or non-genotoxic carcinogen?

The azo-compound, D and C Red No. 9 was assayed for genotoxicity in vivo using the rat micronucleus test and the rat ex vivo liver UDS assay. Uniformly negative results were obtained in both assays, even though large oral doses were used (2 g/kg). These results suggest that the tumorigenic effects of this compound in rats are mediated through non-genotoxic rather than a genotoxic mechanism. Further experiments using additional end-points such as 32P-post-labelling would further substantiate this conclusion.

Administration, Oral↗
PubMed1994

Inhibition of lipoperoxidation of linoleic acid by five antioxidants of different lipophilicity.

The efficacy of oxidation inhibition of five natural and synthetic antioxidants (BHT, BHA, nordihydroguaiaretic acid (NDGA), quercetin and rutin) was studied in O/W emulsions. Linoleic acid was used as a reference molecule; the reaction was initiated by an azo-compound. The kAH characterizing the reaction of the antioxidant with the peroxyl radical decreases in the following order: kAH(BHA) > kAH(BHT) > kAH(NDGA) > kAH(quercetin) > kAH(rutin).

Antioxidants↗
PubMed1988

Structure-activity relationship studies on the mutagenicity of some azo dyes in the Salmonella/microsome assay.

Analogs of Direct Black 19 and Direct Black 38 were synthesized and tested in the Salmonella/microsome assay. Those dyes which gave positive responses in strains TA98 and TA1538 would be expected to be metabolized to p-phenylenediamine by the liver microsomal enzymes (S9). Pure p-phenylenediamine is non-mutagenic in this assay but becomes mutagenic after it is oxidized. Thus the positive response of our synthetic azo compounds are most likely due to the formation of oxidized p-phenylenediamine. Modification of the moieties that can be metabolized to p-phenylenediamine by sulfonation, carboxylation or copper complexation eliminated the mutagenic responses.

Animals↗
PubMed1994

Evaluation of the genotoxicity of 4-diethylamino-4'-nitroazobenzene and seven analogues.

A series of eight nitroaromatic azo compounds based on 4-diethylamino-4'-nitroazobenzene has been examined for genotoxic activity in a collaborative study conducted under the auspices of the Ecological and Toxicological Association of Dyes and Organic Pigments Manufacturers (ETAD). The evaluation has been conducted in two parts, firstly an examination in vitro to assess any intrinsic genotoxic activity of the compound. The chemicals were examined in the Salmonella assay in a standard plate incorporation protocol in both the presence and absence of S9 and in a minimum of the four tester strains recommended in the OECD guideline for this assay, i.e. TA1535, TA1537, TA98 and TA100. All of the compounds were mutagenic in one or more of the Salmonella tester strains, and all were positive in TA98 with S9. A considerable range of potency was seen in this assay. The chemicals were further examined in vitro for mammalian cell gene mutation at either the HGPRT or TK locus in a standard (CHO, V79 or L5178Y) cell system. Only one of the chemicals was mutagenic and only with S9. This chemical also showed the most potent response in the Salmonella assay. The second part of the study was an examination in vivo to see whether any genotoxic activity was expressed in the whole animal. The in vivo rat liver DNA repair (unscheduled DNA synthesis; UDS) assay was chosen as being the most likely to be sensitive to aromatic nitroazo compounds. All of the materials were negative when tested alongside a structurally related positive control. The chemicals were also examined in the mouse bone marrow micronucleus assay in order to provide a second in vivo assessment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2003

Cloning and characterization of the gene coding for the aerobic azoreductase from Pigmentiphaga kullae K24.

The gene coding for an aerobic azoreductase was cloned from Pigmentiphaga kullae K24, which is able to grow with the carboxylated azo compound 1-(4'-carboxyphenylazo)-4-naphthol (carboxy-Orange I) as sole source of carbon and energy. The gene encoded a protein with a molecular weight of 20,557 Da, with a conserved putative NAD(P)H-binding site in the amino-terminal region. The deduced amino acid sequence showed no further significant sequence homologies to previously studied aerobic azoreductases. The azoreductase was heterologously expressed in Escherichia coli and shown to convert the sulfonated azo dye Orange I and furthermore Magneson II [4-(4-nitrophenylazo)-1-naphthol].

Aerobiosis↗
PubMed1987

Mode of action of antiprotozoan agents. Electron transfer and oxy radicals.

Cyclic voltammetry data were obtained for most of the main classes of antiprotozoan agents, specifically, nitroheterocycles, quinones, metal complexes and derivatives, iminium-type ions, and azo compounds. The reductions were generally reversible in the range of -0.3 to -0.9 V. Catalytic production of oxidative pressure from redox cycling involving oxygen is believed to be an important mode of action by the medicinal agents. Literature data contribute support.

Antiprotozoal Agents↗
PubMed1993

Screening of azo dyes for mutagenicity with Ames/Salmonella assay.

Azo dyes, the largest portion of manufactured dyestuffs, are primarily used as colouring substances in food, textiles, and the plastic industry. It has been estimated that 128 tonnes per annum of dyes are released into the environment worldwide [Anliker, 1977]. Certain azo compounds are known to be mutagenic in bacterial tests [Yahagi et al., 1975; Venitt and Bushell, 1976; Brown et al., 1978]. Watersoluble dyes are biotransformed by intestinal micro-organisms in the gastro intestinal tract, and the toxicity, mutagenicity, and carcinogenicity of these dyes in the gut or liver may be attributed to their metabolites. Since it is desirable to have a genotoxic evaluation of a chemical being released into the environment in order to check their indiscriminate use, a project has been initiated to determine the mutagenicity of the azo dyes being used commercially. The present report deals with the results of 13 dyes tested in Salmonella typhimurium with and without metabolic activation.

Azo Compounds↗
PubMed2002

Molecular cloning and characterization of the gene coding for the aerobic azoreductase from Xenophilus azovorans KF46F.

The gene coding for an aerobic azoreductase was cloned from Xenophilus azovorans KF46F (formerly Pseudomonas sp. strain KF46F), which was previously shown to grow with the carboxylated azo compound 1-(4'-carboxyphenylazo)-2-naphthol (carboxy-Orange II) as the sole source of carbon and energy. The deduced amino acid sequence encoded a protein with a molecular weight of 30,278 and showed no significant homology to amino acid sequences currently deposited at the relevant data bases. A presumed NAD(P)H-binding site was identified in the amino-terminal region of the azoreductase. The enzyme was heterologously expressed in Escherichia coli and the azoreductase activities of resting cells and cell extracts were compared. The results suggested that whole cells of the recombinant E. coli strains were unable to take up sulfonated azo dyes and therefore did not show in vivo azoreductase activity. The turnover of several industrially relevant azo dyes by cell extracts from the recombinant E. coli strain was demonstrated.

Aerobiosis↗
PubMed2005

New azo dyes as colored isoelectric point markers for isoelectric focusing in acidic pH region.

Newly prepared azo compounds and several commercially available indicators were investigated for their applicability as colored isoelectric point (pI) markers for isoelectric focusing (IEF) in the acidic range below pH 5. The majority of compounds described here can serve as primary standards since their pI values were determined by UV-VIS spectrophotometry independently IEF and direct measurement with a pH electrode. Subjected to gel IEF they show narrow and well-observable zones of different colors. Finally, our work resulted in suggestion of a color ladder composed of pI markers covering the pH range from 1.5 to 4.7.

Azo Compounds↗