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PubMed1980

Comparative properties of the catechol estrogens, I: methylation by catechol-O-methyltransferase and binding to cytosol estrogen receptors.

Five catechol estrogens and two 2-methoxyestrogens were compared for their relative affinity of binding to hypothalamic, pituitary, and uterine cytosol estrogen receptors; and for the kinetics of the catechols' methylation by hepatic catechol-0-methyltransferase. All of the catechol estrogens tested have similar Km's for 0-methylation (9-14 muM). Estrogen receptor affinities, however, differ widely. In hypothalamus, for example, where estradiol-17 beta has a Kd of 0.039 +/- 0.008 nanomolar, 4-hydroxyestradiol also binds tightly (0.12 +/- 0.02 nM), 2-hydroxyestradiol and 4-hydroxyestrone with intermediate affinity (0.26 +/- 0.06 and 0.28 +/- 0.07 nM, respectively), and 2-hydroxyestrone and 2-hydroxyestriol much less well (1.68 +/- 0.79 and 1.27 +/- 0.26 nM, respectively). The binding of the 2-methoxyestrogens is extremely weak. These receptor affinities roughly parallel the potencies of these compounds in altering gonadotropin secretion.

2-Methoxyestradiol↗
PubMed1993

Activity of mushroom tyrosinase on catechol and on a catechol estrogen in an organic solvent.

A suspension of tyrosinase-coated glass beads in butanol effectively oxidizes catechol substrate. The enzyme is not soluble in the organic solvent and activity can be stopped by removal of the solid state enzyme after low-speed centrifugation or decantation. The product was assayed by HPLC and by its reactivity towards Besthorn's reagent, which gave a reaction typical for o-quinones. Addition of water to the extent of 0.5 to 4% raised the rate of substrate utilization but the accumulation of quinone first increased and then began to decrease. It is suggested that the product in dry butanol is prevented from reacting further by lack of water, which is necessary to promote secondary reactions causing free radical formation and leading ultimately to polymerization to melanin. Successive washes of the solid state enzyme with butanol increased enzyme activity, indicating presence of a butanol extractable inhibitor in the tyrosinase preparation. The enzyme on glass beads in butanol suspension was stabilized by the presence of substrate. 2-Hydroxyestradiol acted as an inhibitor of the tyrosinase-catalyzed oxidation of catechol. The data obtained can be interpreted to mean that the oxidation of the estrogen in the presence of tyrosinase, as previously reported, may be dependent upon the enzyme-catalyzed oxidation of catechol. The oxidation product of catechol, the o-quinone, is likely to function as oxidant towards 2-hydroxyestradiol.

Basidiomycota↗
PubMed1989

Influences of estradiol and of catechol and non-catechol estrogens on the output of prostaglandins in uteri from spayed rats.

The effects of 17-beta estradiol and of some catechol and non-catechol-estrogens on the synthesis and output of prostaglandins (PGs) E and F by uteri from ovariectomized rats, were explored. Uteri from castrated animals released twice as much PGE than PGF. When uterine tissue was obtained from spayed rats injected prior to sacrifice with a low dose of 17-beta estradiol (0.5 + 1.0 microgram, on two consecutive days), the output of PGE diminished significantly. With a higher dose of the hormone (0.5 + 50.0 micrograms) the depressive influence on the synthesis and release of PGE was even more marked, whereas the output of PGF rose significantly. Low or high doses of estrone or of estriol failed to affect the release of either one of the PGs determined. On the other hand, 2-0H-estradiol at a low dose had no action but at a higher one inhibited the release of PGE without influencing PGF. Neither low nor high doses of 2-0H estriol or of 2-0H estrone affected the synthesis and release of uterine PGs. It was also observed that all the compounds tested evoked a significant uterotrophic action. It appears plausible that some catechol metabolites of 17-beta estradiol, but not other catechol-estrogens, could be involved in the mechanism of action of 17-beta estradiol modulating the production of PGs by the rat uterus.

Animals↗
PubMed2000

Gas chromatographic-mass spectrometric procedures for determination of the catechol-O-methyltransferase (COMT) activity and for detection of unstable catecholic metabolites in human and rat liver preparations after COMT catalyzed in statu nascendi derivatization using S-adenosylmethionine.

A procedure is presented for determination of the catechol-O-methyltransferase (COMT) activity in liver cytosolic preparations using 3,4-dihydroxyphenethylamine as substrate and by quantifying the product 3-methoxy-4-hydroxyphenethylamine (3-MHP). For quantification of 3-MHP in liver cytosolic preparations a gas chromatographic-mass spectrometric procedure after liquid-liquid extraction and acetylation was established and validated. The intra- and inter-day accuracy and precision were better than 15% and 20%, respectively. Extraction efficiency and selectivity were also sufficient. For in statu nascendi derivatization of unstable catecholic metabolites in liver microsome preparations, cytosolic preparations with COMT activities of at least 1 nmol product/min/mg protein were used after addition of S-adenosylmethionine. Such catecholic metabolites, which are claimed to be responsible for toxic effects in vivo, e.g., neurotoxicity or carcinogenesis, must not be overlooked in in vitro metabolism studies. Using this trick, gas chromatography-mass spectrometry (GC-MS) was suitable for the determination of catecholic metabolites in human and rat liver preparations after the same sample preparation as for 3-MHP quantification. The applicability was exemplified for the antidepressant paroxetine.

Animals↗
PubMed1992

Pharmacokinetics of catechol cephalosporins. The effect of incorporating substituents into the catechol moiety on pharmacokinetics in a marmoset model.

Two series of cephalosporins A and B have been synthesized, bearing at C-3' catechols substituted with various electron withdrawing groups (Y) and differing links (X), and were evaluated for their in vitro antibacterial activity and their pharmacokinetics in marmosets. Compounds in series A, bearing an isobutyric oxime substituent, proved to be highly active against Gram-negative organisms and were especially noteworthy for showing long elimination phase (beta) half-lives in marmosets. It was established that introduction of electron withdrawing substituents greatly increased the beta half-lives of compounds (5, X = NHCO, Y = H, t1/2 = 1.25 h, AUC = 27 mg/h per L; 11, X = NHCO, Y = 5-Cl, t1/2 = 4.5 h, AUC = 638 mg/h per L) and that the nature of the link also influenced t1/2, the highest values being obtained when X = NHCO and OCO. Acidities (pKa values) of the substituted catechols were measured, and relationships between the acidities and half-lives were evaluated. Thus it was established that the more acidic catechols gave the longest half-lives (12, X = NHCO, Y = 2,5-Cl2, t1/2 = 8.2 h, AUC = 461 mg/h per L). Further elaboration of the catechol to bicyclic systems maintained good pharmacokinetics when the pKa was sufficiently acidic.

Animals↗
PubMed1992

Synergism exerted by 4-methyl catechol, catechol, and their respective quinones on the rate of DL-DOPA oxidation by mushroom tyrosinase.

4-Methyl catechol and catechol, at concentrations ranging from 0.03 to 9 mM and 0.066 to 20 mM, respectively, have a synergistic effect on the rate of DL-DOPA oxidation by mushroom tyrosinase to material absorbing at 475 nm. The synergism results from the ability of 4-methyl catechol-o-quinone (4-methyl-o-benzoquinone) and of catechol-o-quinone (o-benzoquinone) to oxidize DL-DOPA non-enzymatically to dopaquinone, with the later being immediately converted to dopachrome (lambda max = 475 nm).

Basidiomycota↗
PubMed2004

New route to the mixed valence semiquinone-catecholate based mononuclear FeIII and catecholate based dinuclear MnIII complexes: first experimental evidence of valence tautomerism in an iron complex.

The semiquinone-catecholate based mixed valence complex, [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] x DMF (1), and catecholate based (H2bispictn)[Mn2III(Cl4Cat)4(DMF)2] (2) (bispicen = N,N'-bis(2-pyridylmethyl)-1,2-ethanediamine, bispictn = N,N'-bis(2-pyridylmethyl)-1,3-propanediamine, Cl4Cat = tetrachlorocatecholate dianion, and Cl4SQ = tetrachlorosemiquinone radical anion) were synthesized directly utilizing a facile route. Both the complexes have been characterized by single crystal X-ray diffraction study. The electronic structures have been elucidated by UV-vis-NIR absorption spectroscopy, cyclic voltammetry, EPR, and magnetic properties. The structural as well as spectroscopic features support the mixed valence tetrachlorosemiquinone-tetrachlorocatecholate charge distribution in 1. The ligand based mixed valence state was further confirmed by the presence of an intervalence charge transfer (IVCT) band in the 1900 nm region both in solution and in the solid. The intramolecular electron transfer, a phenomenon known as valence tautomerism (VT), has been followed by electronic absorption spectroscopy. For 1, the isomeric form [FeIII(bispicen)(Cl4Cat)(Cl4SQ)] is favored at low temperature, while at an elevated temperature, the [FeII(bispicen)(Cl4SQ)2] redox isomer dominates. Infrared as well as UV-vis-NIR spectral characterization for 2 suggest that the MnIII(Cat)2- moiety is admixed with its mixed valence semiquinone-catecholate isomer MnII(SQ)(Cat)-, and the electronic absorption spectrum is dominated by the mixed charged species. The origin of the intervalence charge transfer band in the 1900 nm range is associated with the mixed valence form, MnII(Cl4Cat)(Cl4SQ)-. The observation of VT in complex 1 is the first example where a mixed valence semiquinone-catecholate iron(III) complex undergoes intramolecular electron transfer similar to manganese and cobalt complexes.

Journal Article↗
PubMed2000

Aminopyridine iron catecholate complexes as models for intradiol catechol dioxygenases. Synthesis, structure, reactivity, and spectroscopic studies.

Four new Fe(III) catecholate complexes, [(bispicMe2en)FeIII(DBC)]+, [(bispicCl2Me2en)FeIII(DBC)]+, [(trispicMeen)FeIII(DBC)]+, and [(BQPA)FeIII(DBC)]+, which all contain aminopyridine ligands, were synthesized. The structure of [(bispicMe2en)FeIII(DBC)]+ was determined by X-ray diffraction. It crystallizes in the triclinic space group P1 with a = 10.666(3) A, b = 13.467(5) A, c = 17.685(2) A, alpha = 93.46(2) degrees, beta = 93.68(2) degrees, gamma = 109.0(3) degrees, V = 2387.4 A3, and Z = 2. All of these complexes were found to be active toward oxidation of catechol by O2 in DMF at 20 degrees C to afford intradiol cleavage products. The catechol was quantitatively oxidized, mainly (90%) into 3,5-di-tert-butyl-5-(carboxymethyl)-2-furanone. Reaction rates were measured, and for the first three (topologically similar) complexes, a correlation of the second-order kinetic constants k with the optical parameters of the two LMCT O(DBC)-->Fe(III) bands was found. In particular, k increases with the epsilon max of the charge-transfer bands. The k value of the complex [(BQPA)FeIII(DBC)]+, containing a tripodal ligand, is smaller than expected on the basis of these correlations. This discrepancy could be related to steric hindrance induced by the BQPA ligand. However, the much lower activity of the bispicen-Fe(III)-type complexes compared to that of the [(TPA)FeIII(DBC)]+ complex synthesized by Jang et al. (J. Am. Chem. Soc. 1991, 113, 9200-9204), despite similar epsilon max values, shows that a knowledge of optical and NMR parameters values is not sufficient to explain the dioxygenase activity rate. In their study of protocatechuate 3,4-dioxygenase, Orville et al. (Biochemistry 1997, 36, 10052-10066) suggested that asymmetric chelation of the catecholate to Fe(III) is of great importance in the efficiency of the intradiol dioxygenase reaction. Indeed, a comparison of the X-ray structures of [(TPA)FeIII(DBC)]+ and [(bispicMe2en)FeIII(DBC)]+ shows that the Fe(III)-O bonds differ by 0.019 A in the former and are identical in the latter. Asymmetry could also play a role in the model complexes. An alternative explanation is the possible existence of a low-spin state for [(TPA)FeIII(DBC)]+, as recently identified in [(TPA)FeIII(cat)]+ by Simaan et al.

Journal Article↗
PubMed1984

Synthesis of bridged catechol-homocysteine derivatives as potential inhibitors of catechol O-methyltransferase.

Catechol derivatives, covalently joined to homocysteine by sulfide or sulfonium linkages, were synthesized as potential catechol O-methyltransferase multisubstrate inhibitors which might bridge the enzymatic binding sites for the catechol substrate and the amino acid portion of the methyl donor S-adenosylmethionine. These compounds were found to be less effective inhibitors than the product inhibitor S-adenosylhomocysteine.

Animals↗
PubMed1990

Cir and Fiu proteins in the outer membrane of Escherichia coli catalyze transport of monomeric catechols: study with beta-lactam antibiotics containing catechol and analogous groups.

Recently, beta-lactam agents containing iron-chelating moieties, such as E0702, which contains catechol, and pirazmonam and U-78,608, which contain 3-hydroxypyridone, have been developed. By determining the susceptibility to these agents of Escherichia coli mutants lacking various iron-repressible outer membrane proteins, we showed that two of these proteins with hitherto unknown functions, Fiu and Cir, were apparently involved in the transport of monomeric catechol and its analogs. These results confirm the conclusion of Curtis and co-workers, which was obtained by using a different set of catechol-containing antibiotics (N. A. C. Curtis, R. L. Eisenstadt, S. J. East, R. J. Cornford, L. A. Walker, and A. J. White, Antimicrob. Agents Chemother. 32:1879-1886, 1988). E0702 was shown to enhance the uptake of radioactive ferric iron into wild-type cells but not into cir fiu double mutants. By combining the influx of E0702 with its hydrolysis by a periplasmic beta-lactamase, we showed that the wild-type cells transported unliganded E0702 at a rate comparable to or even higher than the rate of transport of the E0702-Fe3+ complex. We postulate that the main function of Cir and Fiu may be to recapture the hydrolytic products of enterobactin, such as 2,3-dihydroxybenzoic acid and 2,3-dihydroxybenzoylserine.

Anti-Bacterial Agents↗
PubMed1981

Immunohistochemical localization of catechol-O-methyltransferase in circumventricular organs of the rat: potential variations in the blood-brain barrier to native catechols.

Catechol-O-methyltransferase (COMT) was localized in the organum vasculosum of the lamina terminals, subfornical organ, subcommissural organ and area postrema of rat brain using an indirect immunofluorescence technique. COMT immunofluorescence was apparent in neuroglia within the organum vasculosum and was most intense in the ependyma between this structure and the optic recess of the third ventricle. In both the subfornical organ and the area postrema, COMT was localized in a neuroglial network, but was noticeably absent in the ependymal layer. COMT immunofluorescence in the ependyma of the subcommissural organ was continuous with the more intense immunofluorescence of the cuboidal ependyma of the third ventricle. Each of the circumventricular organs studied, with the exception of the subcommissural organ, lies outside the blood-brain barrier. However, the unique pattern of COMT immunofluorescence in the area postrema and the subfornical organ suggests that these two structures, of all circumventricular organs, are most likely to permit the entry of peripherally circulating catechols to the cerebrospinal fluid.

Animals↗
PubMed1988

Inhibition of catechol-O-methyltransferase activity by two novel disubstituted catechols in the rat.

Catechol-O-methyltransferase (COMT) has an important role in the extraneuronal inactivation of catecholamine neurotransmitters and drugs with a catechol structure. Two novel COMT inhibitors, OR-462 and OR-486, were highly effective (IC50 = 18 and 12 nM, respectively) and selective in inhibiting COMT activity in vitro. Tyrosine hydroxylase was not inhibited until micromolar concentrations of these compounds were used: the IC50 values for OR-462 and OR-486 were 10 and 14 microM, respectively. The IC50 values for dopamine-beta-hydroxylase, dopa-decarboxylase and monoamine oxidase forms A and B were greater than 50 microM. In studies ex vivo oral OR-462 inhibited mainly the COMT activity in the duodenum while OR-486 inhibited COMT activity in the liver and red blood cells as well. Oral OR-462 did not penetrate into the brain in doses up to 30 mg/kg while the same dose of OR-486 had some effect on striatal COMT activity. When tested in combination with levodopa-carbidopa, orally administered OR-462 and OR-486 were more effective in reducing the formation of 3-O-methyldopa from levodopa than was the levodopa-carbidopa treatment alone. These results indicate that OR-462 and OR-486 are effective and long-lasting inhibitors of COMT activity.

Animals↗
PubMed1985

Semiquinone anion radicals of catechol(amine)s, catechol estrogens, and their metal ion complexes.

The characterization and identification of semiquinone radicals from catechol(amine)s and catechol estrogens by electron spin resonance spectroscopy is addressed. The use of diamagnetic metal ions, especially Mg2+ and Zn2+ ions, to detect transient semiquinone radicals in biological systems and to monitor their reactions, is discussed. A brief account of the identification and reactions of quinones is also presented.

Animals↗
PubMed1977

Identification of urinary catechol and methylated catechol metabolites of phenytoin in humans, monkeys, and dogs by GLC and GLC-mass spectrometry.

A catechol metabolite, 5-(3,4-dihydroxyphenyl)-5-phenylhydantoin, and a methylated catechol metabolite, 5-(3-methoxy-4-hydroxyphenyl)-5-phenylhydantoin, were identified as urinary metabolites in humans, monkeys, and dogs following the administration of phenytoin. These metabolites were separated from each other and from other known metabolites of phenytoin as n-butyl derivatives by GLC and positively identified by combined GLC-mass spectrometry.

Animals↗
PubMed1981

Localization of catechol-O-methyltransferase in the leptomeninges, choroid plexus and ciliary epithelium: implications for the separation of central and peripheral catechols.

Catechol-O-methyltransferase (COMT) was localized in cells of the pia-arachnoid, and in epithelial cells of the choroid plexus, using an indirect immunofluorescence technique. The specific activity of COMT derived from these tissues was determined by radioenzymatic assay, and in the case of the choroid plexus was found to be 9-fold greater than that measured in whole rat brain. The level of COMT specific activity in pia-arachnoid was twice as high as that in whole brain. Indirect immunofluorescence studies also revealed an intensity of COMT immunofluorescence in the ciliary epithelium at the blood-aqueous barrier in the rat eye, similar to that visualized in the epithelium of the choroid plexus at the blood-cerebrospinal fluid barrier. The localization of COMT in the leptomeninges, choroid plexus, and ciliary epithelium is consistent with a role for this enzyme in the separation of catechol compounds synthesized in the central nervous system, from those of peripheral origin. Thus, catecholamines derived from the peripheral sympathetic system may be prevented from entering the brain parenchyma, which is innervated by the functionally distinct central catecholaminergic systems.

Animals↗
PubMed1990

CGP 28014, a new inhibitor of cerebral catechol-O-methylation with a non-catechol structure.

CGP 28014 (N-(2-pyridone-6-yl)-N',N'-di-n-propylformamidine) or its methanesulfonate salt CGP 28014 A was suspected to be a catechol-O-methyl-transferase (COMT) inhibitor because it was found to reduce the levels of homovanillic acid (HVA) and to increase those of 3,4-dihydroxyphenylacetic acid (DOPAC) in the rat striatum, after oral or intraperitoneal administration. These effects were maintained after repeated administration. The compound was only weakly active as a COMT inhibitor in vitro. However, its effect on striatal HVA and DOPAC was not prevented by pretreatment with the inhibitor of microsomal drug metabolizing enzymes in the liver, proadifen, indicating that, if CGP 28014 acts as a prodrug, its conversion to the active compound is not by oxidative metabolism in the liver. Also, there was no evidence that conversion to 2-amino-6-hydroxypyridine could explain its effects. The in vivo effect of CGP 28014 was substantiated in two additional in vivo test systems. Thus, it inhibited the accumulation of 3-methoxytyramine in the rat striatum after MAO inhibition by clorgyline, and the formation of O-methyl-DOPA from exogenously administered DOPA. It proved to be equipotent or nearly so with tropolone, and also showed a similar duration of action. Similar to tropolone, it increased S-adenosylmethionine levels in the striatum. Pyrogallol, on the other hand, decreased them, because being a substrate of COMT, it consumes methyl groups. This suggests that CGP 28014 does not inhibit COMT because it is a substrate of the enzyme.(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dihydroxyphenylacetic Acid↗