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PubMed2003

Copper(II)-mediated autoxidation of tert-butylresorcinols.

Although copper(II)-mediated oxidation of phenols results in oxidative coupling rather than in oxygenation, it was recently reported that naturally occurring 5-alkylresorcinols undergo oxygenation in the presence of copper(II). To explore the generality of this reaction, the copper(II)-mediated autoxidation of 4-tert-butylresorcinol and 4,6-di-tert-butylresorcinol was investigated and was found to result in direct oxygenation at open activated positions and, at the tert-butyl-substituted positions, in oxygenation with competing loss of (as isobutylene) and 1,2-rearrangement of the tert-butyl group. 5-tert-Butyl-2-hydroxy-1,4-benzoquinone is the major product from both starting materials, and the final product mixture reflects, in part, coupling of metastable initially formed electrophilic and nucleophilic side products. Mechanisms that are consistent with the observed products and control reactions are proposed. The key step appears to be equilibration of a copper(II)-resorcinolate with a charge-transfer radical form that reacts regioselectively with O(2) as prescribed by resonance.

Alkanes↗
PubMed1994

Tyrosinase inhibitors from Anacardium occidentale fruits.

Anacardic acids, 2-methylcardols, and cardols isolated from various parts of the cashew [Anacardium occidentale] (Anacardiaceae) fruit have been found to exhibit tyrosinase inhibitory activity. Kinetic studies with the two principal active compounds, 6-[8(Z),11(Z),14-pentadecatrienyl]salicylic acid and 5-[8(Z),11(Z),14-pentadecatrienyl]resorcinol, have indicated that both of these phenolic compounds exhibit characteristic competitive inhibition of the oxidation of L-3,4-dihydroxyphenylalanine (L-DOPA) by mushroom tyrosinase.

Anacardic Acids↗
PubMed2005

Estrogen receptor ligands. 12. Synthesis of the major metabolites of an ERalpha-selective, dihydrobenzoxathiin antagonist for osteoporosis.

[reaction: see text] During the course of drug metabolism studies, a major metabolite of compound 1 was detected in rhesus monkeys and assigned structure 4. The intriguing biotransformation of 1 leading to 4 was confirmed by a 19-step total synthesis starting from resorcinol (11), the key feature of which was the construction of the oxygen bridge utilizing a phenolic oxidation and trapping sequence. In addition, the synthesis of a related metabolite (5) is described.

Animals↗
PubMed1997

Glycosphingolipid expression in human skeletal and heart muscle assessed by immunostaining thin-layer chromatography.

In this study the comparative TLC immunostaining investigation of neutral GSLs and gangliosides from human skeletal and heart muscle is described. A panel of specific polyclonal and monoclonal antibodies as well as the GM1-specific choleragenoid were used for the overlay assays, combined with preceding neuraminidase treatment of gangliosides on TLC plates. This approach proved homologies but also quantitative and qualitative differences in the expression of ganglio-, globo- and neolacto-series neutral GSLs and gangliosides in these two types of striated muscle tissue within the same species. The main neutral GSL in skeletal muscle was LacCer, followed by GbOse3Cer, GbOse4Cer, nLcOse4Cer and monohexosylceramide, whereas in heart muscle GbOse3Cer and GbOse4Cer were the predominant neutral GSLs beside small quantities of LacCer, nLcOse4Cer and monohexosylceramide. No ganglio-series neutral GSLs and no Forssman GSL were found in either muscle tissue. GM3(Neu5Ac) was the major ganglioside, comprising almost 70% in skeletal and about 50% in cardiac muscle total gangliosides. GM2 was found in skeletal muscle only, while GD3 and GM1b-type gangliosides (GM1b and GD1 alpha) were undetectable in both tissues. GM1a-core gangliosides (GM1, GD1a, GD1b and GT1b) showed somewhat quantitative differences in each muscle; lactosamine-containing IV3Neu5Ac-nLcOse4Cer was detected in both specimens. Neutral GSLs were identified in TLC runs corresponding to e.g. 0.1 g muscle wet weight (GbOse3Cer, GbOse4Cer), and gangliosides GM3 and GM2 were elucidated in runs which corresponded to 0.2 g muscle tissue. Only 0.02 g and 0.004 g wet weight aliquots were necessary for unequivocal identification of neolacto-type and GM1-core gangliosides, respectively. Muscle is known for the lowest GSL concentration from all vertebrate tissues studied so far. Using the overlay technique, reliable GSL composition could be revealed, even from small muscle probes on a sub-orcinol and sub-resorcinol detection level.

Adult↗
PubMed2003

Non-enzymatic interaction of reaction products and substrates in peroxidase catalysis.

A quantitative approach for estimation of the non-enzymatic interaction between ammonium 2,2;-azino-bis(3-ethylbenzthiazoline-6-sulfonate) (ABTS) oxidation product and a poorly oxidized substrate was developed using a system including tobacco peroxidase, a mediator substrate (ABTS), and a second substrate. The approach is based on the establishment of a pseudo-steady-state concentration of the ABTS oxidation product in the course of co-oxidation with a poor substrate. A mathematical description of the experimental curve shape has been proposed to linearize the kinetic data and estimate the rate constant for such non-enzymatic interaction. The rate constants calculated from the steady-state kinetics for the non-enzymatic interaction of ABTS oxidation product with phenol and resorcinol were 360 +/- 40 and 770 +/- 60 M(-1).sec(-1), respectively. The values obtained have the same order of magnitude as the rate constant for ABTS oxidation product interaction with veratryl alcohol, calculated from electrochemical measurements (170 M(-1).sec(-1)) by Donal Leech's group. However, the kinetic curves for co-oxidation of ABTS and veratryl alcohol catalyzed by tobacco peroxidase exhibit a pronounced lag-period, which either points to the high rate of the non-enzymatic interaction between ABTS oxidation product and veratryl alcohol and thus, contradicts the electrochemical calculations, or indicates an enzymatic nature of the co-oxidation phenomenon in this particular case.

Alcohols↗
PubMed2000

Simultaneous determination of dihydroxybenzenes, aminophenols and phenylenediamines in hair dyes by high-performance liquid chromatography on hypercross-linked polystyrene.

The retention of polar organic molecules such as dihydroxybenzenes, aminophenols and phenylenediamines on a 250 x 4.6 mm id column packed with 5 microns hypercross-linked polystyrene Chromalite 5HGN (Purolite) was studied. The influence of separation parameters such as concentration of acetonitrile, buffer (citrate, phosphate) concentration, ionic strength and pH of the eluent on their retention was investigated. Under optimum conditions [acetonitrile-0.3 mol l-1 ammonium phosphate, pH 5.15 (30:70 v/v)], eight substances generally used as dye intermediates in hair colouring compositions could be separated within 20 min. An HPLC method with spectrophotometric detection is proposed for the simultaneous determination of pyrocatechol, resorcinol, hydroquinone, o-, m- and p-aminophenols and p-phenylenediamine in commercial haircolour products. The detection limits of these compounds are in the range 0.05-0.16 microgram ml-1. The suitability of the method is demonstrated by the analysis of three different permanent hair dyes.

Aminophenols↗
PubMed2001

Microchip separations of transition metal ions via LED absorbance detection of their PAR complexes.

Micellar electrokinetic chromatography was utilized in the electrophoretic separation of seven transition metal ions, colorimetrically complexed by 4-(2-pyridylazo)resorcinol (PAR) on a glass capillary electrophoresis microchip. Detection of the PAR metal chelates was demonstrated using a green light emitting diode (540 nm) and a miniature photomultiplier tube. Parameters investigated included the effect of buffer type, pH and surfactant concentration (sodium dodecyl sulfate, SDS) on the separation efficiency. The optimally determined background electrolyte contained 10 mM ammonium phosphate buffer (pH 7.5), 1 mM PAR to prevent kinetic lability problems and 75 mM SDS for enhanced resolution. The separation of seven transition metal ions, Co2+, V3+, Ni2+, Cu2+, Fe2+, Mn2+ and Cd2+, was achievable in under 65 s, with the resolution of each metal ion in excess of 1.60. Detection limits obtained ranged from 400 ppb for Ni2+ to 1.2 ppm for Mn2+.

Chromatography, Micellar Electrokinetic Capillary↗
PubMed1973

Inhibition of the biosynthesis of sterols by phenyl and phenolic compounds in rat liver.

The presence of mitochondria increased the incorporation of [2-(14)C]mevalonate into sterols in a cell-free system from rat liver. Various phenyl and phenolic compounds inhibited the incorporation of mevalonate when added in vitro. p-Hydroxycinnamate, a metabolite of tyrosine, was the most powerful inhibitor among the compounds tested. Catechol, resorcinol and quinol were inhibitory at high concentrations. Organic acids lacking an aromatic ring were not inhibitory. Two hypocholesterolaemic drugs, Clofibrate (alpha-p-chlorophenoxyisobutyrate) and Clofenapate [alpha,4-(p-chlorophenyl)phenoxyisobutyrate], which are known to affect some step before the formation of mevalonate in the biosynthesis of cholesterol in vivo, showed inhibition at a step beyond the formation of mevalonate in vitro. The presence of the aromatic ring and the carboxyl group in a molecule appears to be necessary for the inhibition.

Adenosine Triphosphate↗
PubMed1997

Inhibition of rabbit muscle aldolase by phosphorylated aromatic compounds.

The interactions of the phosphorylated derivatives of hydroquinone (HQN-P2), resorcinol (RSN-P2), 4-hydroxybenzaldehyde (HBA-P) and 2, 4-dihydroxybenzaldehyde (DHBA-P; phosphate group at position 4) with fructose bisphosphate aldolase were analysed by enzyme kinetics, UV/visible difference spectroscopy and site-directed mutagenesis. Enzyme activity was competitively inhibited in the presence of HQN-P2, RSN-P2 and HBA-P, whereas DHBA-P exhibited slow-binding inhibition. Inhibition by DHBA-P involved active-site Schiff-base formation and required a phenol group ortho to the aldehyde moiety. Rates of enzyme inactivation and of Schiff-base formation by DHBA-P were identical, and corresponded to 3.2-3.5 DHBA-P molecules covalently bound per aldolase tetramer at maximal inactivation. Site-directed mutagenesis of the active-site lysine residues at positions 107, 146 and 229 was found to be consistent with Schiff-base formation between DHBA-P and Lys-146, and this was promoted by Lys-229. Mutation of Glu-187, located vicinally between Lys-146 and Lys-229 in the active site, perturbed the rate of Schiff-base formation, suggesting a functional role for Glu-187 in Schiff-base formation and stabilization. The decreased cleavage activity of the active-site mutants towards fructose 1, 6-bisphosphate is consistent with a proton-transfer mechanism involving Lys-229, Glu-187 and Lys-146.

Aminocaproates↗
PubMed2003

Rice seedling whole exudates and extracted alkylresorcinols induce stress-response in Escherichia coli biosensors.

A set of Escherichia coli sensor strains was used to evaluate the stress exerted on surrounding bacteria by germinating rice seed exudates. These biosensor strains contain Vibrio fischeri luxCDABE genes fused to the promoters of different genes involved in bacterial responses to environmental stresses. They provided clear evidence for a stress exerted by rice exudates, as shown by the induction of the universal stress protein gene uspA as well as genes of the heat shock regulon, grpE, lon and dnaK. The oxidative stress gene katG, and the post-transcriptional ompF regulator encoded by micF were also activated. The lack of derepression of recA, uvrA and alkA indicated that damage to the DNA was not induced in the E. coli strains tested. Interestingly, resorcinolic lipids extracted from rice root seedlings induced the same promoters as whole exudates, suggesting that these compounds may contribute to the stress exerted by seedling exudates. The results obtained with E. coli biosensors thus indicate that, in vivo, exudates may also exert a selective pressure on root-colonizing bacteria.

Bacterial Proteins↗
PubMed2002

Oxidation and nitrosation in the nitrogen monoxide/superoxide system.

Based on the previous report of McCord and co-workers (Crow, J. P., Beckman, J. S., and McCord, J. M. (1995) Biochemistry 34, 3544-3552), the zinc dithiolate active site of alcohol dehydrogenase (ADH) has been studied as a target for cellular oxidants. In the nitrogen monoxide ((*NO)/superoxide (O(2)) system, an equimolar generation of both radicals under peroxynitrite (PN) formation led to rapid inactivation of ADH activity, whereas hydrogen peroxide and ( small middle dot)NO alone reacted too slowly to be of physiological significance. 3-Morpholino sydnonimine inactivated the enzyme with an IC(50) value of 250 nm; the corresponding values for PN, hydrogen peroxide, and (*NO) were 500 nm, 50 microm, and 200 microm. When superoxide was generated at low fluxes by xanthine oxidase, it was quite effective in ADH inactivation (IC(50) (XO) approximately 1 milliunit/ml). All inactivations were accompanied by zinc release and disulfide formation, although no strict correlation was observed. From the two zinc thiolate centers, only the zinc Cys(2)His center released the metal by oxidants. The zinc Cys(4) center was also oxidized, but no second zinc atom could be found with 4-(2-pyridylazo)resorcinol (PAR) as a chelating agent except under denaturing conditions. Surprisingly, the oxidative actions of PN were abolished by a 2-3-fold excess of (*)NO under generation of a nitrosating species, probably dinitrogen trioxide. We conclude that in cellular systems, low fluxes of (*)NO and O(2) generate peroxynitrite at levels effective for zinc thiolate oxidations, facilitated by the nucleophilic nature of the complexed thiolate group. With an excess of (*)NO, the PN actions are blocked, which may explain the antioxidant properties of (*)NO and the mechanism of cellular S-nitrosations.

Animals↗
PubMed2003

Rapid stimulation of free glucuronate formation by non-glucuronidable xenobiotics in isolated rat hepatocytes.

Vitamin C synthesis in rat liver is enhanced by several xenobiotics, including aminopyrine and chloretone. The effect of these agents has been linked to induction of enzymes potentially involved in the formation of glucuronate, a precursor of vitamin C. Using isolated rat hepatocytes as a model, we show that a series of agents (aminopyrine, antipyrine, chloretone, clotrimazole, metyrapone, proadifen, and barbital) induced in a few minutes an up to 15-fold increase in the formation of glucuronate, which was best observed in the presence of sorbinil, an inhibitor of glucuronate reductase. They also caused an approximately 2-fold decrease in the concentration of UDP-glucuronate but little if any change in the concentration of UDP-glucose. Depletion of UDP-glucuronate with resorcinol or d-galactosamine markedly decreased the formation of glucuronate both in the presence and in the absence of aminopyrine, confirming the precursor-product relationship between UDP-glucuronate and free glucuronate. Most of the agents did not induce the formation of detectable amounts of glucuronides, indicating that the formation of glucuronate is not due to a glucuronidation-deglucuronidation cycle. With the exception of barbital (which inhibits glucuronate reductase), all of the above mentioned agents also caused an increase in the concentration of ascorbic acid. They had little effect on glutathione concentration, and their effect on glucuronate and vitamin C formation was not mimicked by glutathione-depleting agents such as diamide and buthionine sulfoximine. It is concluded that the stimulation of vitamin C synthesis exerted by some xenobiotics is mediated through a rapid increase in the conversion of UDP-glucuronate to glucuronate, which does not apparently involve a glucuronidation-deglucuronidation cycle.

Aminopyrine↗
PubMed1982

The origin of urinary aromatic compounds excreted by ruminants. 3. The metabolism of phenolic compounds to simple phenols.

Dietary phenolic cinnamic acids are hydrogenated in the side-chain, demethylated and dehydroxylated in the rumen and are responsible for the large urinary output of benzoic acid by ruminants. 2. Decarboxylation of phenolic acids to simple phenols is another reaction of the intestinal microflora and experiments were made to determine the extent of this reaction in the rumen of sheep. 3. In five experiments phenolic compounds, quinic acid or casein were infused into the rumen or abomasum of sheep and increments in urinary outputs of phenolic acids and phenols determined by thin-layer and gas-liquid chromatography. 4. Production of phenols was almost exclusively confined to reactions in the rumen. 5. Rumen administration of phenolic benzoic or phenylacetic acids which contained a 4-hydroxy substituent yielded large increments in urinary phenol outputs. Other phenolic benzoic and phenylacetic acids were not decarboxylated. Rumen decarboxylation of 4-hydroxy-3-phenylpropionic acid did not occur and decarboxylation of 4-hydroxycinnamic acids was slight. 6. Nearly half the tyrosine content of rumen-administered casein was excreted as p-cresol, a decarboxylation product of 4-hydroxyphenylacetic acid, p-Cresol was the principal phenol found in sheep urine. 7. Catechol and phenol were consistently found in sheep urine samples and p-ethylphenol, resorcinol, quinol, 4-methylcatechol, orcinol and pyrogallol were also found when suitable precursors were infused to the rumen. 8. It is concluded that p-cresol is a rumen metabolite of tyrosine. The other phenols found are microbial metabolites of phenolic precursors which are either widely distributed in plants such as 4-hydroxybenzoic, protocatechuic and vanillic acids or of more limited distribution such as the orcinol glycosides of some Ericaceous plants.

Animals↗
PubMed1976

Respiratory function and symptoms: an environmental-epidemiological study of rubber workers exposed to a phenolformaldehyde type resin.

Rubber workers exposed to a hexamethylenetetramine-resorcinol (HR) adhesive system reported an excess of acute symptoms and significant reductions in expiratory flow rates at low lung volumes. Smokers exhibited greater reductions in flow rates than nonsmokers. The greatest reductions in ventilatory capacity were associated with HR exposure. There was a moderate association of reduced flow rates with respirable particulate in the HR exposed workers only.

Acute Disease↗
PubMed2006

Determination of 2,4,6-triiodoresorcinol and other side reaction products and intermediates in the colour additive FD&C Red No. 3 (erythrosine) using high-performance liquid chromatography.

An HPLC method was developed for the quantitative determination of 2,4,6-triiodoresorcinol (I3R), 2-(2',4'-dihydroxy-3',5'-diiodobenzoyl)benzoic acid, resorcinol, phthalic acid, and sodium iodide in the colour additive FD&C Red No. 3 (erythrosine) (R3). Due to the fast decomposition of I3R in aqueous solutions, the dye portions analysed were dissolved in methanol and the determinations were performed in the freshly-made solutions. The HPLC method is rapid (50 min total analysis cycle, approximately 16 min to detect I3R and the other intermediates), simple to implement, and generates only small amounts of solvent waste. It was found to be applicable for use in routine batch-certification as shown by the analysis of test portions from 24 lots of R3 submitted for US-certification by domestic and foreign manufacturers during the past three years.

Benzoates↗
PubMed1992

Antithyroid effects of coal-derived pollutants.

Endemic goiter in iodide-sufficient areas of the United States and Colombia has been linked to watersheds rich in coal and shale, which several reports suggest are the source of water-borne goitrogens. In this report the potential antithyroid activities of aqueous coal and shale extracts and of compounds identified in aqueous effluents from coal conversion processes were assayed in thyroid peroxidase (TPO) and thyroid slice systems. Aqueous extracts of coal and black shale were potent inhibitors of TPO or 125I organification by thyroid slices. The most abundant water-soluble compounds derived from coal are dihydroxy-phenols, thiocyanate, disulfides, and hydroxypyridines. The dihydroxyphenols resorcinol, 2-methylresorcinol, and 5-methylresorcinol (orcinol) were 26.7, 22.5, and 7.2 times more potent, respectively, than the antithyroid drug 6-propylthiouracil (PTU). Other dihydroxyphenols and thiocyanate were less potent but comparable in activity to PTU. All dihydroxypyridines and 3-hydroxypyridine produced inhibitory effects comparable to PTU. None of the disulfides inhibited TPO. The antiperoxidase effects of combinations of two dihydroxyphenols or one dihydroxyphenol and SCN were additive, whereas the effects of a combination of four dihydroxyphenols at threshold inhibitory concentrations were synergistic, resulting in net effects equivalent to or greater than the sum of the individual effects. Thus, antithyroid effects may be greatly amplified by exposure to multiple coal-derived goitrogens and could be many times that produced by any one of the contributing pollutants. These results demonstrate that potent water-borne goitrogens are derived from coal and shale and that their contamination of water supplies could pose a serious threat of thyroid disorders.

Animals↗
PubMed1991

Effects of catechol and its analogs on pancreatic carcinogenesis initiated by N-nitrosobis(2-oxopropyl)amine in Syrian hamsters.

The modifying effects of the phenolic antioxidant catechol (CC) and its analogs hydroquinone (HQ) and resorcinol (RN) on pancreatic carcinogenesis were evaluated in 146 female Syrian golden hamsters. Groups of animals received either saline or 70 mg/kg body wt N-nitrosobis(2-oxopropyl)amine (BOP) s.c. injections, twice with a 2 week interval, followed by basal diet or diet containing 1.5% of CC, HQ or RN, and 0.75% CC from week 4. All hamsters were killed at week 20 and histopathologically examined for development of pancreatic, liver and gall bladder lesions. The total numbers of pancreatic lesions comprising carcinomas, atypical ductal hyperplasias and ductal hyperplasias per hamster were significantly decreased in animals receiving BOP followed by CC, HQ and RN when compared to those in hamsters given BOP followed by basal diet. Incidence values for atypical ductal hyperplasias were also significantly decreased by the RN or 0.75% CC treatments. The results thus suggest that pancreatic carcinogenesis initiated by BOP in Syrian hamsters can be inhibited by treatments with phenolic antioxidants such as CC, HQ and RN for a relatively short experimental period.

Animals↗