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PubMed1988

Disposition of 5-aminosalicylic acid by 5-aminosalicylic acid-delivering compounds.

Time-related urinary excretion and faecal excretion of 5-ASA and acetyl-5-ASA were measured in eight healthy volunteers after a single oral dose of the azo compounds sulphasalazine and olsalazine, the slow release compounds Pentasa, Asacol and Salofalk, and plain 5-ASA. After ingestion of both azo compounds and slow-release compounds, urinary excretion of 5-ASA was markedly delayed and reduced, and faecal excretion was enhanced. At all points of time, there was a significant, but not very marked difference in urinary excretion of 5-ASA after ingestion of the azo compounds and the slow-release compounds, in favour of the azo compounds. A significantly larger proportion of the ingested 5-ASA, moreover, was excreted in faeces after the intake of azo compounds as compared with slow-release compounds.

Adult↗
PubMed1995

Paracetamol inhibits copper ion-induced, azo compound-initiated, and mononuclear cell-mediated oxidative modification of LDL.

The effects of paracetamol and sodium salicylate on the susceptibility of LDL to oxidative modification were studied. LDL was subjected to Cu(2+)-, azo compound-, or peripheral blood mononuclear cell-initiated oxidation in the absence and presence of paracetamol and salicylate. Paracetamol (100 mumol/L; 25 micrograms LDL/mL) reduced the rate of formation of conjugated dienes and the amount of conjugated dienes formed during Cu(2+)-induced oxidation by 67% and 58%, respectively. Paracetamol (400 mumol/L; 100 micrograms LDL/mL) reduced the generation of lipid peroxides during Cu(2+)-induced oxidation by 43% (P < .05), the relative electrophoretic mobility in agarose gels by 16% (P < .05), and the amount of oxidized LDL taken up by J774 macrophages by 22% (P < .05). Paracetamol (100 mumol/L; 100 micrograms LDL/mL) reduced the 2,2'-azobis-(2-amidinopropane hydrochloride)-initiated lipid peroxidation by 70% (P < .05) and the relative electrophoretic mobility by 34% (P < .05). Paracetamol (100 mumol/L; 100 micrograms LDL/mL) reduced the amount of lipid peroxides generated in LDL during mononuclear cell-mediated oxidation by 69% (P < .01) and the relative electrophoretic mobility by 38% (P < .01). In comparison, 10 mumol/L alpha-tocopherol reduced the amount of lipid peroxides formed during cellular LDL oxidation and the relative electrophoretic mobility by 52% and 65%, respectively (P < .05). In the absence of paracetamol, SOD and catalase inhibited the modification of LDL (P < .05), suggesting that superoxide anions and hydrogen peroxide might be involved in the cell-mediated modification pathway. In the presence of paracetamol, SOD showed no additional inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetaminophen↗
PubMed1988

Disposition of 5-aminosalicylic acid by 5-aminosalicylic acid-delivering compounds.

The disposition of 5-aminosalicylic acid (5-ASA) from 5-ASA-delivering drugs was studied in eight healthy volunteers. Time-related urinary excretion and faecal excretion of 5-ASA and acetyl-5-ASA were measured after a single oral dose of the azo compounds sulphasalazine and olsalazine, of the slow-release compounds Pentasa, Asacol, and Salofalk, and of plain 5-ASA. Plain 5-ASA was rapidly excreted into urine and had a low faecal recovery, indicating fast absorption proximally in the intestine and little availability to the colon. After ingestion of both azo compounds and slow-release compounds, urinary excretion of 5-ASA was markedly delayed and reduced, and faecal excretion was enhanced. At all points of time there was a significant but not very marked difference in urinary excretion of 5-ASA after ingestion of the azo compounds and the slow-release compounds, in favour of the azo compounds. A significantly larger proportion of the ingested 5-ASA, moreover, was excreted in faeces after intake of azo compounds as compared with slow-release compounds.

Adult↗
PubMed2006

Palladium-catalyzed synthesis of aryl ketones by coupling of aryl bromides with an acyl anion equivalent.

Palladium-catalyzed couplings of aryl bromides with N-tert-butylhydrazones as acyl anion equivalents to form aryl ketones are reported. The coupling process occurs at the C-position of hydrazones to form N-tert-butyl azo compounds. Isomerization of these azo compounds to the corresponding hydrazones, followed by hydrolysis, gave the desired mixed alkyl aryl ketones. The selectivity of C- versus N-arylation was strongly influenced by the substituent on nitrogen. Arylation at carbon occurred with N-tert-butylhydrazones, whereas N-arylation occurred with N-arylhydrazones. The arylation of hydrazones containing primary and secondary alkyl groups, as well as aryl groups, gave the desired ketones in good yields after hydrolysis. Functional groups on the aromatic ring, such as alkoxy, cyano, trifluoromethyl, carboalkoxy, carbamoyl, and keto groups, were tolerated. This reaction likely occurs by C-C bond-forming reductive elimination from an intermediate containing an eta1-diazaallyl ligand.

Anions↗
PubMed1991

Conjugation of N-acylated amino sugars to protein by reductive alkylation using sodium cyanoborohydride: application to an azo derivative of alpha-amanitin.

Reductive alkylation mediated by cyanoborohydride is an attractive approach to the conjugation of small molecules, such as drugs, to proteins. This reaction is specific for protein amino groups and can be conducted under mild conditions with little risk of protein polymerization. However, the lability of the aldehyde function that is needed in such reactions presents a difficulty. We have investigated the use of derivatives of D-galactosamine and D-glucosamine in reductive alkylation, since these sugars contain aldehyde groups that are inherently protected and that may be readily linked to other molecules through their amino groups. The amino groups of these sugars were acylated with N-4-nitro-benzoylglycylglycine. Studies of the reductive coupling of the resultant adducts to bovine serum albumin revealed that conjugation to albumin is strongly dependent on cyanoborohydride, is much faster in the presence of borate, and shows a marked increase in rate between pH 7.0 and 9.0. In the presence of borate, the glucosamine derivative coupled much more rapidly than did the galactosamine derivative. The aryl nitro group of the glucosamine adduct was selectively reduced to an amine, diazotized, and reacted with alpha-amanitin to form an azo compound. This azo derivative was reductively coupled to form conjugates that inhibit calf thymus RNA polymerase II.

Alkylation↗
PubMed1968

Pesticide transformations: production of chloroazobenzenes from chloroanilines.

Aniline and 11 different chloroanilines were added to soil. No azo compound was formed from aniline, but all monochloro-and some dichloroanilines were transformed to their corresponding dichloro-and tetrachloroazobenzenes. Other dichloroanilines and the trichloroanilines were stable in soil. Peroxidase catalyzed the formation of azo compounds by some chloroanilines. Correspondence in the range of substrates used and products formed in the two systems suggests a peroxidatic mechanism for the synthesis of azo compounds residues in soil.

Aniline Compounds↗
PubMedDate not supplied

Determination of nickel in biological samples spectrophotometrically involving complexation reaction with some thiazolylazo compounds.

Three new heterocyclic azo compounds, 5(2-benzothiazolylazo)2,2 biphenyldiol (I), 5-(2-benzothiazolylazo)-8-hydroxyquinolene (II) and 4-(2-benzothiazo-lylazo)3-hydroxy-2-naphthoic acid (III) were synthesized. The formation constant of the reagents in 30% (v/v) ethanol and reactions with various metal ions were studied. These reagents (I-III) reacts with nickel ion to form (2:1) colored complex with an absorption band at 604, 635 and 643 nm. The apparent stability constants and the optimum conditions for complete color development were investigated. Beer's law is obeyed over the concentration ranges of 0.05-3.50, 0.05-4.00 and 0.05-3.10 micrograms ml-1. For more accurate analyses, Ringbom optimum concentration ranges were found to be 0.20-3.25, 0.20-3.80 and 0.20-2.90 micrograms ml-1 using reagents I, II and III, respectively. The apparent molar absorptivity and Sandell sensitivity were also calculated. The interference of various foreign ions on the determination of nickel was investigated. The proposed method has been successfully applied to the determination of nickel substrates in various biological samples.

Animals↗
PubMed2005

Degenerate two-photon absorption spectra in azoaromatic compounds.

A systematic study of the degenerate two-photon absorption (2PA) spectra of seven azoaromatic compounds in dimethyl sulfoxide solution is reported, which employed the Z-scan technique with femtosecond laser pulses from the bottom of the azo compound absorption bands up to 1100 nm. The 2PA peaks for pseudostilbene-type azo compounds (Disperse Orange (DO) 3, Disperse Red (DR) 13, DR1, DR19, and DR19-Cl) were observed at twice the peak wavelength of the linear absorption. However, such peaks were not observed for other azo compounds (PAMINO and DIAMINO) because of the symmetry of these molecules. A resonance enhancement of the 2PA cross-section was observed for all compounds. The 2PA peak and the nonlinear resonance enhancement behavior could be adjusted with a model based on perturbation theory. Such knowledge can be a guideline to the understanding of the 2PA process in azoaromatic compounds.

Azo Compounds↗
PubMed1991

Lipid hydroperoxide involvement in copper-dependent and independent oxidation of low density lipoproteins.

The involvement of lipid hydroperoxides in the oxidation of human low density lipoproteins (LDL) induced by Cu++ or azoperoxyl radicals was studied. Concurrent or pretreatment of LDL with the synthetic peroxidase Ebselen and its cofactor glutathione totally prevented Cu+(+)-dependent oxidation, as measured by the formation of thiobarbituric acid reactive substances and LDL mobility on agarose gels. LDL could be oxidized in the absence of metals with peroxy radicals generated via homolysis of azo compounds. With the azo initiator, 2,2'-azobis-2-amidinopropane hydrochloride, Ebselen plus glutathione prevented lipid oxidation when present during oxidation. However, if LDL were first pretreated with Ebselen plus glutathione and these reagents removed before oxidation, they did not prevent oxidation. Analysis by high-performance liquid chromatography of lipids extracted from Cu+(+)- or azoperoxyl radical-modified lipoproteins indicated that the major lipid oxidation products were derived from linoleate and that Ebselen-glutathione addition reduced linoleate hydroperoxides. Oxidation of LDL by human monocyte-derived macrophages was also prevented by coincubation with Ebselen-glutathione or the antioxidant, probucol. These results demonstrate that initiation of Cu+(+)-dependent oxidation absolutely requires the presence of trace amounts of lipid hydroperoxides in the lipoprotein and that hydroperoxides play a major role in the propagation reactions even in the absence of added transition metals.

Azo Compounds↗
PubMed1996

Effect of homocysteine on copper ion-catalyzed, azo compound-initiated, and mononuclear cell-mediated oxidative modification of low density lipoprotein.

Homocysteine is an independent risk factor for cardiovascular diseases. The mechanisms by which elevated plasma concentrations of homocysteine are related to the pathogenesis of atherosclerosis are not fully understood. To examine whether homocysteine is implicated in atherogenesis through the modification of low density lipoprotein (LDL), the effect of homocysteine on the oxidation of LDL was studied by three different oxidation systems. Thus, LDL was subjected to Cu(2+)-catalyzed, azo compound-initiated, and peripheral blood mononuclear cell-mediated oxidative modification. The extent of modification was assessed by measuring the formation of conjugated dienes, lipid peroxides, thiobarbituric acid-reactive substances, and the relative electrophoretic mobility. Homocysteine at a normal plasma concentration (6 microM) showed no effect, whereas a concentration corresponding to moderate hyperhomocysteinemia (25 microM) or to concentrations seen in homocystinuria patients (100, 250, and 500 microM) protected LDL from modification of the lipid as well as of the protein moiety. One exception was observed: when the oxidation was initiated by copper ions, homocysteine at concentrations 6 and 25 microM stimulated the lipid peroxidation of LDL to a small, but statistically significant extent. High concentrations of homocysteine showed antioxidative properties as long as the thiol groups were intact, thereby delaying the onset of the oxidation. The 1,1-diphenyl-2-picrylhydracyl radical test demonstrated that homocysteine at concentrations > or = 50 microM possessed marked free radical scavenging capacity. Finally, LDL isolated from two patients with homozygous homocystinuria showed similar extent of Cu(2+)-catalyzed oxidation as LDL from a group of healthy control subjects. Taken together, our data suggest that low concentrations of homocysteine in the presence of copper ions may enhance the lipid peroxidation of LDL, whereas high concentrations of homocysteine may protect LDL against oxidative modification in the lipid as well as in the protein moiety. Thus, homocysteine-induced atherosclerosis may be explained by mechanisms other than oxidative modification of low density lipoprotein.

Adolescent↗
PubMed2003

Oxygen-insensitive nitroreductases NfsA and NfsB of Escherichia coli function under anaerobic conditions as lawsone-dependent Azo reductases.

Quinones can function as redox mediators in the unspecific anaerobic reduction of azo compounds by various bacterial species. These quinones are enzymatically reduced by the bacteria and the resulting hydroquinones then reduce in a purely chemical redox reaction the azo compounds outside of the cells. Recently, it has been demonstrated that the addition of lawsone (2-hydroxy-1,4-naphthoquinone) to anaerobically incubated cells of Escherichia coli resulted in a pronounced increase in the reduction rates of different sulfonated and polymeric azo compounds. In the present study it was attempted to identify the enzyme system(s) responsible for the reduction of lawsone by E. coli and thus for the lawsone-dependent anaerobic azo reductase activity. An NADH-dependent lawsone reductase activity was found in the cytosolic fraction of the cells. The enzyme was purified by column chromatography and the amino-terminal amino acid sequence of the protein was determined. The sequence obtained was identical to the sequence of an oxygen-insensitive nitroreductase (NfsB) described earlier from this organism. Subsequent biochemical tests with the purified lawsone reductase activity confirmed that the lawsone reductase activity detected was identical with NfsB. In addition it was proven that also a second oxygen-insensitive nitroreductase of E. coli (NfsA) is able to reduce lawsone and thus to function under adequate conditions as quinone-dependent azo reductase.

Amino Acid Sequence↗
PubMed1988

Two sites of azo reduction in the monooxygenase system.

The mechanism of the azo reduction of sulfonazo III and amaranth by the rat hepatic monooxygenase system was studied. Air strongly inhibited (greater than 95%) the enzymatic reduction of both azo compounds; a 100% CO atmosphere inhibited amaranth reduction (greater than 90%) but only slightly inhibited sulfonazo III reduction (13%). The addition of 50 microM sulfonazo III to microsomal incubations stimulated oxygen consumption, NADPH oxidation, and adrenochrome formation, whereas 100 microM amaranth did not. The reduction potentials of these two azo compounds were also very different (amaranth, E = -0.620 V; sulfonazo III, E = -0.265 V versus normal hydrogen electrode). The organic mercurial mersalyl converted cytochrome P-450 to cytochrome P-420 (68%) and markedly decreased NADPH-cytochrome P-450(c) reductase activity (97%) in microsomal preparations, presumably by inactivating or destroying functional sulfhydryl groups important for the catalytic activity of these enzymes. GSH was used to restore, and NADP+ to protect, the activities of the monooxygenase components from the effects of mersalyl. The data indicate that inactivation of NADPH-cytochrome P-450(c) reductase inhibits sulfonazo III and amaranth reduction, whereas inactivation of cytochrome P-450 inhibits only amaranth reduction. Furthermore, the reduction of sulfonazo III by purified microsomal NADPH-cytochrome P-450(c) reductase was significantly faster than the rate of reduction of amaranth. These studies demonstrate that two distinct sites of azo reduction exist in the monooxygenase system and that not all azo compounds are reduced by cytochrome P-450.

Amaranth Dye↗
PubMed2004

Tautomeric structures, electronic spectra, acid-base properties of some 7-aryl-2,5-diamino-3(4-hydroxyphenyazo)pyrazolo[1,5-a]pyrimidine-6-carbonitriles, and effect of their copper(II) complex solutions on some bacteria and fungi.

Infrared and electronic spectra were used to investigate the tautomerism of some azo compounds, in both the solid and solution states. It was found that the compounds exist in azo<==>hydrazone tautomeric equilibrium in solid and in solutions. The different bands displayed in the electronic spectra of the compounds in various organic solvents are assigned to the suitable electronic transitions. The solvatochromic behavior of the compounds was investigated by studying their visible spectra in pure and mixed organic solvents. DeltaG and formation constant, Kf, values of the molecular complexes formed in solution have been determined. Effect of concentration of the compounds in DMF and EtOH solutions has been investigated. The basicity and acidity constants of the different compounds were determined from the spectra of these compounds in aqueous-ethanolic solutions of varying pH values. Some complexes of copper(II) with these compounds in solution were tested as for their antibacterial and antifungal activity.

Anti-Bacterial Agents↗
PubMed1992

Disposition of mesalazine from mesalazine-delivering drugs in patients with inflammatory bowel disease, with and without diarrhoea.

The disposition of mesalazine from the azo compounds sulphasalazine and olsalazine (Dipentum) and from the slow-release mesalazine drugs Pentasa, Asacol, and Salofalk was studied in 20 patients with inflammatory bowel disease. Ten of them had diarrhoea, and 10 had normal stools. On the last 2 days of a 7-day maintenance treatment with each of the study drugs urine and faeces were collected for determination of mesalazine, acetyl-mesalazine, and unsplit azo compound. In patients with and without diarrhoea the urinary and the faecal excretion of acetyl-mesalazine was lowest during treatment with olsalazine. The proportion of acetyl-mesalazine in faeces was highest during treatment with Pentasa in both groups. The presence of diarrhoea was associated with a decrease in the proportion of acetyl-mesalazine in faeces during treatment with all drugs, not significant only for Pentasa. The proportion of unsplit azo compound in faeces increased in the case of diarrhoea to almost 50%. It is concluded that in patients with inflammatory bowel disease diarrhoea substantially influences the disposition from all these drugs except Pentasa.

Adult↗
PubMed1990

Biomonitoring of aromatic amines. III: Hemoglobin binding of benzidine and some benzidine congeners.

Covalent binding of benzidine and some congeners to hemoglobin was studied in female Wistar rats after oral administration. Hemoglobin adducts were hydrolyzed under alkaline conditions, and the arylamines extracted and analysed by HPLC with electrochemical detector. With benzidine, three cleavage products were observed, the major component being monoacetylbenzidine. This indicates that 4-nitroso-4'-N-acetylaminobiphenyl is the major reactive metabolite in erythrocytes. In addition benzidine and 4-aminobiphenyl were identified. The latter indicates a hitherto unknown metabolic pathway of benzidine. With 3,3'-dichlorobenzidine-dihydrochloride, 3,3'-dimethoxybenzidine and 3,3'-dimethylbenzidine two cleavage products were observed, the parent diamines being present in excess to or in amounts comparable to the monoacetyl derivative. With 3,3',5,5'-tetramethylbenzidine a hemoglobin adduct could not be found. When the azo dye direct red 28 was administered to the animals, the three cleavage products typical for benzidine were found, indicating that benzidine became bioavailable after reductive cleavage of the azo compound. In this case the fraction of 4-aminobiphenyl was greater than after benzidine. It is proposed to use the analysis of hemoglobin adducts in human blood to control the exposure of individuals to these carcinogenic chemicals in the course of biochemical effect monitoring.

Administration, Oral↗
PubMed1963

THE CATABOLISM OF PROTEIN ANTIGENS IN THE NEWBORN AND MATURING RABBIT.

The rate of degradation, organ deposition, and blood clearance of SBSA, SRSA, and IRSA has been measured in the newborn, 6-, and 30-day-old rabbits. When the animals were injected with a weight-graded dose of the 3 proteins, differences in their catabolism in the newborns were demonstrable as compared to the 6-, and 30-day-old animals. The capacity to degrade the azo compounds was shown to be incompletely developed at birth. At 6 days of age, however, the rabbits catabolized these proteins much at the same rate as the 30-day-old animals. Addition of the benzenesulfonate moiety determined the rate of degradation organ deposition and excretion rather than the carrier protein when the azo compounds were injected. The biosynthetically labeled S(25) rabbit serum albumin (IRSA) was catabolized at a slower rate than the azoproteins in all age groups. Very little difference in the metabolism and organ deposition of the IRSA was shown to exist between the newborn and maturing animals. A dosage schedule, therefore, designed to test the immunological capacity of developing animals may not be valid when calculated upon body weight. The low level of activity of enzyme systems present at birth which degrade anti-genic material may serve as an explanation as to why this period of development is so vulnerable to the induction of tolerance rather than immunity when compared to the adult.

Animals↗
PubMedDate not supplied

Substrates for microsomal azoreductase. Hammett substituent effects, NMR studies, and response to inhibitors.

In previous studies on azoreduction by microsomal cytochrome P-450, we identified two classes of substrates structurally related to 4-dimethylaminoazobenzene. Both require polar electron-donating groups for binding to enzyme and are differentiated by their structure, their redox potentials, their rates of chemical and enzymic reduction, and the influence on their metabolism of inducing agents, CO and O2. Azo compounds whose reductions are insensitive to CO and O2 (I-substrates) contain electron-donating substituents on either ring. Azo compounds whose reductions are O2- and CO-sensitive (S-substrates) also contain electron-withdrawing groups on the opposite (prime) ring. For all dyes, NMR studies revealed minor differences in the chemical shifts of the protons attached to the phenyl ring substituted with electron-donating substituents (ring A). This is consistent with the narrow range of pKa's (basicity) and KM values for all substrates. However, there are significant differences in the chemical shifts of the aromatic protons of the prime ring (ring B). The difference in chemical shifts is most pronounced for aromatic protons adjacent to the prime ring substituents, showing a clear distinction between I and S substrates. Furthermore, the Hammett sigma substituent constants on the prime ring clearly distinguish between the two classes of dyes. I- and S-substrates have negative and positive sigma Hammett values, respectively. This implies that the mechanism of microsomal azoreduction is critically dependent on the charge and redox potentials of the dyes and is exclusively determined by the nature of the substituents on the prime ring.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗