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At least 433 records · Page 24Linked to original sources

PubMed1983

Functional differences between peroxidase compound I and the cytochrome P-450 reactive oxygen intermediate.

A series of seven hemeproteins, cytochromes P-450LM2, P-450LM4, and P-420LM2, horseradish peroxidase, chloroperoxidase, catalase, and metmyoglobin, as well as hemin were tested for their ability to catalyze a set of five oxidative reactions. These reactions were a typical peroxidative reaction (oxidation of pyrogallol to purpurogallin) and three characteristic P-450 reactions (aliphatic hydroxylation, aromatic hydroxylation, and olefinic epoxidation). In addition, the ability to decarboxylate a peroxyacid was measured. All hemeproteins were able to carry out peroxidation, but three (horseradish peroxidase, chloroperoxidase, and catalase) were much better catalysts than the others. Only the P-450 enzymes were competent catalysts for the hydroxylation and epoxidation reactions. Furthermore, the decarboxylation reaction was strictly limited to the P-450 enzymes, establishing it as a new, unique P-450 activity. Since the decarboxylation of peroxyacids is diagnostic of peroxide homolysis, these results indicate a fundamentally different manner of processing of peroxides by cytochrome P-450 than by the peroxidases. Thus, the possibility of close similarity of reactive oxygen intermediates in the two series is called into question.

Benzene↗

PubMed1977

Synthesis of auxins from tryptophan and tryptophan-precursors by fungi isolated from mycorrhizae of pine (Pinus silvestris L.).

Fungi isolated from mycorrhizae of pine required tryptophan for auxin synthesis. More auxins were found in culture grown with pyrogallol than in those without this compound. The fungi studied produced also auxins from other than tryptophan compounds. Indole employed with serine was more suitable for the production of auxins than indole or anthranilic acid used separately. The active compounds showing auxin activity were located on the chromatograms at Rf 0.2--0.4 and 0.3--0.5 with the solvent system isopropanol, ammonia, water (10:1:1 v/v).

Culture Media↗

PubMed1981

[Changes in segmental reflexes upon stimulation of the locus coeruleus of the brain stem and potentiation of catecholamine action].

Rhythmic stimulation of locus coeruleus was accompanied by a depressed inhibitory action of flexor reflex afferents and recurrent inhibition on extensor motoneurons in anaesthetized and decerebellized cats. Such stimulation had no essential effect on the direct inhibition of extensor and flexor motoneurons, on the excitatory action of flexor reflex afferents and recurrent inhibition on the flexor motoneurons. The injection of pyrogallol caused similar effect but it was greatly diminished by cold blockage or transsection of the spinal cord. The experiments with partial cuts of the spinal cord to consider the effects as a result of activation of coerulo-spinal pathway which descend in the ventral quadrant of the spinal cord.

Animals↗

PubMedDate not supplied

Bioassay and pharmacological characterization of the nitrergic neurotransmitter.

Based on organ bath experiments illustrating nitric oxide (NO) or an NO-releasing substance as mediator of the nonadrenergic noncholinergic (NANC) nerve-induced relaxations in the canine ileocolonic junction and rat gastric fundus, a bioassay superfusion technique was developed to detect and characterize the inhibitory NANC neurotransmitter. Evidence is provided that NANC nerve stimulation results in the release of a vasorelaxant factor with pharmacological properties similar to NO: its release is blocked by inhibition of the NO biosynthesis and tetrodotoxin, but enhanced by L-arginine. Its half-life is comparable to that of NO, and its biological activity is enhanced by superoxide dismutase, but abolished by hemoglobin. In addition, the nitrergic transferable factor is similarly affected as authentic NO by pyrogallol, hydroquione, hydroxocobalamin and L-cysteine. Nitrosothiols, like S-nitroso-L-cysteine, S-nitrosoglutathione and S-nitroso-N-acetyl-D,L- penicillamine, on the other hand, have a different pharmacological profile compared to NO and the nitrergic factor, indicating that NO, and not a nitrosothiol, is released from inhibitory NANC nerves in the canine ileocolonic junction. This nerve-induced release is Ca(2+)-dependent and prejunctionally regulated by K+ channels and alpha 2-adrenoceptors: blockade of K+ channels enhances the release, whereas alpha 2-adrenoceptor activation reduces the release of the nitrergic factor, possibly by activating K+ channels.

Animals↗

PubMed1995

Informations on the active site of palmito polyphenol oxidase.

pH studies of palmito polyphenol oxidase are carried out with either 4-methylcatechol or pyrogallol as substrates. The pH profile is independent of the nature of the substrates tested. The symmetrical behaviour and the very slight differences between the values obtained suggest the existence of only one site on the molecule for o-diphenol substrates.

Antioxidants↗

PubMed1994

Measuring urinary protein with the new BioRad reagent kit: evaluation and comparison with five other methods.

Total urinary protein was measured by five methods: BioRad Total Protein Test (TPT), pyrogallol red, benzethonium chloride, sulfosalicylic acid, trichloroacetic acid, and the results compared to those obtained by a method combining preparative ultrafiltration and the biuret reaction. TPT was linear to 1.5 g protein/l, the detection limit 0.0135 g/l, and it was 3-5 times more sensitive than the other methods. Within-day precision (CV) was 4.3%, (0.60 g/l), the day-to-day precision was 4.5%. The protein contents of 35 selected urine samples assigned to one of five groups according to their electrophoretic pattern were assayed by the five methods. No method accurately measured physiological proteinuria, but the values for light chain (Bence Jones), glomerular, tubular and overload proteinurias measured by TPT did not differ significantly from the biuret value. The other methods differed significantly for at least three groups. Alpha 1 acid glycoprotein slightly inhibited TPT, but peptones, amino acids, antibiotics or normal urine constituents had little or no effect. The TPT method has been automated (Kone Progress); normal 24-h urinary protein excretion was 36 mg/day (range 12-114), the protein creatinine ratio was 34 mg/g (12-106 mg/g).

Autoanalysis↗

PubMedDate not supplied

Gas chromatographic determination of total fat extracted from food samples using hydrolysis in the presence of antioxidant.

A method for the quantitative measurement of total fat in foodstuffs is described. Fat is extracted by hydrolysis and inter-esterified to fatty acid methyl esters for gas chromatographic analysis. Total fat and fatty acid patterns are calculated to comply with the regulations for food label declaration under the Nutrition Labeling and Education Act of 1990. Quantitative recovery of fat from soy oil is obtained in the presence of the antioxidant pyrogallol. Extraction and measurements of fat from a variety of food samples (e.g., cereal, baked goods, dairy, and fish) are also reported, and fat levels ranged from 0.8 to 95% (w/w). Coefficients of variation of < or = 5% demonstrate the efficiency of the method.

Chromatography, Gas↗

PubMed1993

Possible superoxide radical-induced alteration of vascular reactivity in aortas from streptozotocin-treated rats.

We investigated the possible involvement of the superoxide (.O2-) radical in alterations of vascular reactivity and phosphoinositide (PI) turnover in aortas from streptozotocin (STZ)-induced diabetic (4 week) rats. STZ treatment increased the maximal contractile response of the aorta to norepinephrine (NE), phenylephrine (PE) and high K+, whereas the sensitivity remained unaltered. Ca(++)-induced contractions in the presence of maximally effective concentrations of PE and K+ were also augmented after STZ treatment. The increased maximal response was associated with both decreased endothelium-dependent relaxation and increased NE-induced PI turnover. Pyrogallol (PYR), a potent .O2- generating agent, did not affect basal tone or PI turnover but, depending on concentrations, it significantly increased or decreased both the contractile response to PE and NE-induced PI turnover in control aorta. In contrast, PYR decreased NE-induced PI turnover in diabetic aorta. The malondialdehyde content of liver, serum and aorta, and of .O2- from aorta of diabetic rats, were increased significantly. Copper catalyzed oxidation of ascorbic acid resulted in contraction followed by relaxation, depending upon the ascorbic acid concentration in both control and diabetic aorta. Pretreatment with superoxide dismutase (300 U/ml) prevented the PYR-induced potentiation of the PE contraction, but not of NE+PYR-induced PI turnover in control aorta and decreased further NE+PYR-induced PI turnover in diabetic aorta. The present findings indicate that .O2- may be responsible, at least in part, for the impaired endothelial integrity, enhanced alpha adrenergic receptor-mediated PI turnover and augmented contractility, possibly through modification of calcium channels in STZ-induced short-term (4 week) diabetic rat aorta.

Animals↗

PubMed1995

Rumen involvement in sheep tannic acid metabolism.

Tannic acid (TA) metabolism was studied in sheep after p.o., intra-abomasal and i.p. administration. TA and its phenolic metabolites in ruminal fluid, abomasal fluid, plasma and urine were determined using high-performance liquid chromatography at various intervals post-dosing. After po administration, gallic acid (GA) and pyrogallol (PYR) were present in ruminal fluid and plasma, and GA, PYR and 4-O-methyl gallic acid (40MGA) were found in urine. The concentration of GA in ruminal fluid and urine gradually decreased after dosing, while PYR concentration continued to rise. By contrast, after intra-abomasal dosing, GA and ellagic acid (EA) as well as TA were found in abomasal fluid, GA, 40MGA, EA and TA were present in plasma, and GA, 40MGA and PYR were in urine. The latter 3 metabolites were also detected in the urine after ip administration of TA. The plasma concentration of TA after intra-abomasal administration was significantly correlated with liver necrosis, and PYR concentration in ruminal fluid following po administration was significantly correlated to blood methemoglobin level. It was concluded that the methemoglobinemia seen in sheep given TA po is caused by high levels of the phenolic metabolite PYR, which is produced in the rumen. Liver and kidney necrosis, seen in sheep given TA directly into the abomasum, appears caused by unmetabolized TA rather than by metabolites.

Abomasum↗

PubMed1996

Effects of nitric oxide on detrusor relaxation.

PURPOSE: Recently we (1994) reported the photo-induced adequate nitric oxide (PIANO) system, in which an NO- or NO2-carrying molecule which has been photoactivated to release NO, could be exploited to investigate the role of NO in various smooth muscle functions. This study was designed to characterize the effect of nitric oxide (NO) exploiting PIANO on rat detrusor relaxation by isometric tension recording and measuring changes in cGMP content. MATERIALS AND METHODS: Exposure to ultraviolet light was used (1 to 60 seconds) to evoke PIANO in the presence of streptozotocin, an NO-carrier, and N omega-nitro-L-arginine (L-NOARG), an NO2-carrier. During relaxation the cyclic guanosine monophosphate (cGMP) content was measured by radioimmunoassay. RESULTS: Rat detrusor strips were reversibly relaxed upon NO generation via PIANO. Pyrogallol, an O2 generator, significantly (p < 0.01) diminished PIANO-mediated relaxation. During PIANO-mediated relaxation, the tissue level of cyclic GMP significantly (p < 0.05) increased over that of the control. Furthermore, methylene blue, a guanylate cyclase inhibitor, significantly (p < 0.01) inhibited both the relaxation and the increase of cGMP. CONCLUSION: We concluded that rat detrusor muscle was capable of responding to NO, and these findings might lead to a treatment for bladder instability and detrusor hyperreflexia, by the use of intravesical instillation of NO donors.

Animals↗

PubMed1998

Microtiter plate assay for superoxide dismutase using MTT reduction by superoxide.

A simple microtiter plate based colorimetric assay for superoxide dismutase is described. The method, involves generation of superoxide by pyrogallol autoxidation and the inhibition of superoxide dependent reduction of the tetrazolium dye MTT [3-(4,5-dimethyl-thiazol-2-yl) 2,5-diphenyl tetrazolium bromide] to its formazan, measured at 570 nm. The reaction was terminated by the addition of dimethyl sulfoxide (DMSO) which also helps to solubilize the formazan formed and the colour evolved was stable for many hours. The method was compared with other known methods to measure the activity of purified erythrocyte Cu,ZnSOD and superoxide dismutase activity from various rat tissues. This procedure involves inexpensive reagents, allows a rapid and sensitive measurement of SOD activity and the microtiter plate assay is suitable for use with large number of samples.

Animals↗

PubMed1996

Negative ion electrospray mass spectrometry of polyphenols, catecholamines and their oxidation products.

Polyphenols, catecholamines and their oxidation products have a variety of physiological effects and are key components of insect cuticle and other biological structures. Three dihydroxybenzene isomers were easily differentiated using negative ion electrospray mass spectrometry (ESMS) or tandem mass spectrometry (MS/MS). Ions at m/z 107-109 were diagnostic for more complex polyphenols and catecholamines with a dihydroxybenzene moiety. The product ion spectra of other compounds including 3,4-dihydroxyphenylacetic acid, 3,4-dihydroxyphenylalanine (DOPA) and N-acetyldopamine (NADA) had product ions at m/z 121-123 corresponding to methylene homologues of dioxygenated benzene. Oxidation of DOPA using tyrosinase, Ag2O or NaIO4 could be followed using ESMS and several proposed intermediates proceeding from DOPA through a quinone methide intermediate, 5,6-dihydroxyindole and dihydroxyindole quinone were confirmed using negative ion ESMS/MS. Spectra of the NaIO4 oxidation products of 1,2,3-trihydroxybenzene (pyrogallol) were consistent with tetrahydroxybenzene, two non-cyclic tetraoxygenated derivatives and a bicyclic polymerization product, purpurogallin. ESMS can be used to analyse complex polyphenolic conjugates commonly encountered in biological specimens.

Catecholamines↗

PubMedDate not supplied

A new screening method to detect water-soluble antioxidants: acetaminophen (Tylenol) and other phenols react as antioxidants and destroy peroxynitrite-based luminol-dependent chemiluminescence.

This study is based on a simple chemical interaction of peroxynitrite (O = N-O-O-) and luminol, which produces blue light upon oxidation. Since peroxynitrite has a half-life of about 1 s, a drug known as linsidomine (SIN-1) is used as a peroxynitrite generator. Peroxynitrite can oxidize lipids, proteins and nucleic acids. Upon the stimulation of inflammation and/or infection, macrophages and neutrophils can be induced to produce large amounts of peroxynitrite, which can oxidize phenols and sulphhydryl-containing compounds. Therefore, phenols and sulphhydryls eliminate peroxynitrite. This is an example of the Yin-Yang hypothesis e.g. oxidation-reduction. Acetaminophen (Tylenol) can inhibit fever and some types of pain without being a particularly effective anti-inflammatory. Since it is a phenol, it could act as a nitration target for peroxynitrite. Then peroxynitrite, the possible cause of pain and elevated temperature, might be destroyed in the reaction. Acetaminophen is a phenolic compound which produces a clear inhibitory dose-response curve with peroxynitrite in its range of clinical effectiveness. Whether acetaminophen actually works as we suggest is to be proven. Three different types of reaction could decrease the amount of peroxynitrite: (a) interference with base-catalysed opening of the SIN-1 molecule; (b) destruction of one or both substances needed to form it--superoxide and/or nitric oxide; when the SIN-1 degrades to superoxide and nitric oxide, the former may be destroyed by superoxide dismutase (SOD); (c) peroxynitrite may react directly with phenols (mono-, di-, tri- and tetraphenols), possibly by nitration. Nordihydroguaiaretic acid and 2-hydroxyestradiol (catechol estrogen) are potent inhibitors of luminol light emission. Epineprine, isoproterenol, pyrogallol, catechol and ascorbic acid (a classic antioxidant) are all inhibitors of luminol chemiluminescence. Isoproterenol, norepinephrine/and epinephrine first inhibit light but overall stimulate the light production. Initially, SIN-1 degrades to produce peroxynitrite, which reacts with luminol to produce blue light. If any of three catecholamines are present with the reaction that produces light, there is an initial inhibition of light production, and then a marked stimulation. A possible reason for this is that these catechols are oxidized and the metabolized phenol stimulates the production of light from luminol. Also, during oxidation of catecholamines superoxide is sometimes formed, which could stimulate production of peroxynitrite. This simple screening system is introduced to find useful antioxidants against peroxynitrite.

Acetaminophen↗

PubMedDate not supplied

Chemiluminescent detection of catecholamines by generation of hydrogen peroxide with imidazole.

A novel detection method for catecholamines using imidazole was investigated using a chemiluminescence coupled flow injection system. Imidazole catalysed decomposition of catecholamines to generate hydrogen peroxide, then the hydrogen peroxide was detected by chemiluminescence. The optimal condition for generation of hydrogen peroxide from a catecholamine was to incubate the catecholamines (53 pmol) in an imidazole solution (50 mmol/L, pH 9.0, 1.0 mL) at 60 degrees C for 30 min. Peroxide-was detected by peroxyoxalate chemiluminescence, and the rank order of the light emission intensities was as follows; dopamine (100%) >epinephrine (78%) >L-DOPA (62%) >norepinephrine (58%) >deoxyepinephrine (51%) >isoproterenol (43%) >dihydroxybenzylamine (25%). The light intensities of the reaction mixtures (corresponding to 1.06 pmol catecholamines) varied depending on the chemiluminescence (CL) detection reaction, and the rank order of the light intensity was as follows; luminol CL catalysed with horseradish peroxidase (HRP) (371%) >peroxyoxalate chemiluminescence (100%) >luminol CL catalysed with ferrycyanide (62%) >lucigenin CL (15%) >pyrogallol CL (0.8%) >purpurogallin CL (0.4%) >luminol CL (0.3%). The luminol CL reaction catalysed by HRP is recommended for the detection of peroxide in this method for catecholamines.

Catecholamines↗

PubMedDate not supplied

Detection of substances with alcoholic or phenolic hydroxyl groups by generation of hydrogen peroxide with imidazole and peroxyoxalate chemiluminescence.

On-line detection of substances with an alcoholic or phenolic hydroxyl group using imidazole and peroxyoxalate chemiluminescence was investigated qualitatively using a flow-injection method. The substances tested included six polyphenols, five monophenols and six sugars. After incubation at 80 degrees C with an imidazole buffer (pH 9.5) the substances were detected by peroxyoxalate chemiluminescence. The polyphenols tested (e.g., pyrogallol, purpurogallin, and dopamine) showed the strongest light emission. The sugars with hydroxyl groups (e.g., fructose and lactose) and the monophenols (e.g., phenol, serotonin, and beta-estradiol) produced only a weak light emission. Imidazole served two roles, it catalysed the reaction with the hydroxyl compound and initiated peroxyoxalate chemiluminescence on-line. A novel reactor formed by packing glass beads into a flow cell (Teflon) of a chemiluminometer improved the sensitivity of light detection.

Alcohols↗

PubMed2000

Tea catechins and related polyphenols as anti-cancer agents.

Epigallocatechin gallate (EGCg) and theaflavins, a major constituent of green tea infusion and the constituents of black tea, respectively, were found to inhibit matrix metalloproteinases (MMPs) which are intimately associated with tumor invasion and metastasis. EGCg and related polyphenols exhibited apoptosis-inducing activity for several cancer cell lines including human stomach and colon cancer cells. Comparison of the activity of these compounds revealed the importance of the number and the steric disposition of hydroxyl groups. A pyrogallol-type structure in a molecule is a minimum requirement for apoptosis induction of catechin compounds and that in the B ring has an important role in the activity. These data would provide useful information for designing anti-cancer agents on the basis of anti-inhibitory activity for MMPs and/or apoptosis-inducing activity.

Anticarcinogenic Agents↗

PubMed2003

Oxidation of 4-bromophenol by the recombinant fused protein cellulose-binding domain-horseradish peroxidase immobilized on cellulose.

A fused protein consisting of cellulose-binding domain (CBD) and horseradish peroxidase (HRP) was constructed and expressed in Escherichia coli. Refolded recombinant CBD-HRP (95% recovery yield) was bound to microcrystalline cellulose and applied for the oxidation of a model toxic phenol, 4-bromophenol (BP). Oxidation of BP by CBD-HRP resulted in the formation of dimers to pentamers as evidenced by mass spectrometry analysis. When immobilized, the vast majority of the oxidation products adsorbed to the cellulose matrix. CBD-HRP (0.75 pyrogallol units) bound to 0.1 g cellulose was packed in a column, connected to an HPLC pump and monitoring system, and column performance and capacity were studied under various operating conditions. When performance was studied as a function of BP loading rate at a constant H(2)O(2) loading rate of 1500 nmol/min, V(app) (max) and K(m) (app) were calculated to be 5.29 +/- 0.46 micromol mL min and 644.9 +/- 114.3 microM, respectively. Immobilized CBD-HRP exhibited enhanced stability to H(2)O(2) and oxidized considerably more BP than free CBD-HRP. Inclusion of gelatin, which suppresses product-dependent inactivation, further increased the amount of BP oxidation. These findings may have potential impact in terms of enzyme supply in high-rate treatment of wastewater contaminated with toxic phenols, since the susceptibility of peroxidases to both H(2)O(2) - and product-dependent inactivation demands continuous supply of fresh enzyme.

Cellulase↗

PubMed2003

Waste-free and facile solid-state protection of diamines, anthranilic acid, diols, and polyols with phenylboronic acid.

Phenylboronic acid (2) reacts quantitatively by ball-milling in the solid state with o-phenylendiamine, 1,8-diaminonaphthalene, anthranilic acid, pyrocatechol, pyrogallol, pinacol, bicyclic cis-diols, mannitol, and inositol to form the five- or six-membered cyclic phenylboronic amides or esters. Catalysts or other auxiliaries are strictly excluded as they are not required and would have to be removed after the reactions. These varied model reactions provide pure protected products without the necessity of further purifying workup and the potential for protection chemistry is demonstrated. Some of the reactions can also be quantitatively performed if stoichiometric mixtures of the reactants are co-ground or co-milled and heated to appropriate temperatures either below the eutectics or above the melting points. The temperatures are much higher in the latter case. Similar reactions in solution suffer from less than 100 % yield of the mostly sensitive compounds that are difficult to purify and thus create much waste. The hydrolysis (deprotection) conditions of the products are rather mild in most cases. Therefore, this particularly easy access to heteroboroles, heteroborolanes, heteroborinones, heteroborines, and heteroborinines is highly valuable for their more frequent use in protective syntheses.

Journal Article↗