- HPLC-based bioactivity profiling of plant extracts: A kinetic assay for the identification of monoamine oxidase-A inhibitors using human recombinant monoamine oxidase-A
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An assay for the HPLC-based search for monoamine oxidase-A (MAO-A) inhibitors in plant extracts was established. It combines human recombinant MAO-A, expressed as GST-fusion protein in yeast, with a kinetic measurement of the conversion of kynuramine to 4-hydroxyquinoline. Substrate selectivity and kinetic parameters of the GST-fusion protein were comparable to the wild-type enzyme. The applicability of the assay to HPLC-based activity profiling was tested with plant extracts spiked with small amounts of known MAO inhibitors.
- Dittmann, Kathrin,Riese, Ulrike,Hamburger, Matthias
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- 1-methyl-2-undecyl-4(1H)-quinolone as an irreversible and selective inhibitor of type B monoamine oxidase.
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The inhibitory compound of monoamine oxidase (MAO) activity was isolated from the CH(2)Cl(2) fraction of the fructus of Evodia rutaecarpa and identified as 1-methyl-2-undecyl-4(1H)-quinolone (1). Compound 1 showed a selective inhibition of type B MAO (MAO-B) activity with the IC(50) value of 15.3 microM using a substrate kynuramine, but did not inhibit type A MAO (MAO-A) activity. The kinetic analysis using Lineweaver-Burk plots indicated that compound 1 competitively inhibited MAO-B activity with the K(i) value of 9.91 microM. The inhibition of MAO-B by compound 1 was found to be irreversible by dialysis of the incubation mixture. These results suggest that compound 1 is a potent irreversible inhibitor of MAO-B, and may regulate catecholamine content in the neurons.
- Lee, Myung Koo,Hwang, Bang Yeon,Lee, Seon A,Oh, Gab Jin,Choi, Woo Hoi,Hong, Seong Su,Lee, Kyong Soon,Ro, Jai Seup
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- In vitro monoamine oxidase inhibition potential of alpha-methyltryptamine analog new psychoactive substances for assessing possible toxic risks
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Tryptamines have emerged as new psychoactive substances (NPS), which are distributed and consumed recreationally without preclinical studies or safety tests. Within the alpha-methylated tryptamines, some of the psychoactive effects of the prototypical alpha-methyltryptamine (AMT) have been described decades ago and a contributing factor of its acute toxicity appears to involve the inhibition of monoamine oxidase (MAO). However, detailed information about analogs is scarce. Therefore, thirteen AMT analogs were investigated for their potential to inhibit MAO. An in vitro assay analyzed using hydrophilic interaction liquid chromatography–high resolution-tandem mass spectrometry was developed and validated. The AMT analogs were incubated with recombinant human MAO-A or B and kynuramine, a non-selective MAO substrate to determine the IC50values. The known MAO-A inhibitors 5-(2-aminopropyl)indole (5-IT), harmine, harmaline, yohimbine, and the MAO-B inhibitor selegiline were tested for comparison. AMT and all analogs showed MAO-A inhibition properties with IC50values between 0.049 and 166?μM, whereas four analogs inhibited also MAO-B with IC50values between 82 and 376?μM. 7-Me-AMT provided the lowest IC50value against MAO-A comparable to harmine and harmaline and was identified as a competitive MAO-A inhibitor. Furthermore, AMT, 7-Me-AMT, and nine further analogs inhibited MAO activity in human hepatic S9 fraction used as model for the human liver which expresses both isoforms. The obtained results suggested that MAO inhibition induced by alpha-methylated tryptamines might be clinically relevant concerning possible serotonergic and adrenergic effects and interactions with drugs (of abuse) particularly acting as monoamine reuptake inhibitors. However, as in vitro assays have only limited conclusiveness, further studies are needed.
- Wagmann, Lea,Brandt, Simon D.,Kavanagh, Pierce V.,Maurer, Hans H.,Meyer, Markus R.
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- Copper-Catalyzed Chemoselective Cyclization Reaction of 2-Isocyanoacetophenone: Synthesis of 4-Hydroxyquinoline Compounds
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A copper-catalyzed intramolecular cyclization reaction of 2-isocyanoacetophenone derivatives to afford 4-hydroxyquinolines chemoselectively is described. The transformation proceeds through enol tautomerism and a subsequent C-C bond formation. Compared to previous methods, this study provides a new protocol for the construction of 4-hydroxyquinoline compounds from functionalized isocyanides under mild conditions.
- Yuan, Qing,Rao, Weidong,Wang, Shun-Yi,Ji, Shun-Jun
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p. 1279 - 1284
(2020/01/22)
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- Combining 1,3-Ditriazolylbenzene and Quinoline to Discover a New G-Quadruplex-Interactive Small Molecule Active against Cancer Stem-Like Cells
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Quadruplex nucleic acids are promising targets for cancer therapy. In this study we used a fragment-based approach to create new flexible G-quadruplex (G4) DNA-interactive small molecules with good calculated oral drug-like properties, based on quinoline
- Mendes, Eduarda,Cadoni, Enrico,Carneiro, Filipa,Afonso, Marta B.,Brito, Hugo,Lavrado, Jo?o,dos Santos, Daniel J. V. A.,Vítor, Jorge B.,Neidle, Stephen,Rodrigues, Cecília M. P.,Paulo, Alexandra
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supporting information
p. 1325 - 1328
(2019/06/21)
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- Photoreductive Removal of O-Benzyl Groups from Oxyarene N-Heterocycles Assisted by O-Pyridine-pyridone Tautomerism
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Facile photoreductive protocols have been developed to remove benzyl O-protective groups from oxyarene N-heterocycles at positions capable for 2-/4-O-pyridine-2-/4-pyridone tautomerism. Blue light irradiation, a [Ru] or [Ir] photocatalyst, and ascorbic acid in a water-acetonitrile solution debenzylates a variety of aryl N-heterocycles cleanly and selectively. Ascorbic acid has two functions in the reaction. On the one hand, it protonates the N-heterocycles that reduces their reduction potentials notably and on the other hand it acts as a sacrificial reductant. Reduction potentials and free energy barriers calculated at the CPCM-B3LYP/6-31+G? level can predict the reactivities of the studied substrates.
- Todorov, Aleksandar R.,Wirtanen, Tom,Helaja, Juho
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p. 13756 - 13767
(2017/12/26)
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- UVA photoinduced yeast protein modifications by methylene blue and naproxen
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UVA photosensitization by methylene blue (MB) or by naproxen (NAP) towards cell proteins in yeast Saccharomyces cerevisiae was investigated in order to compare this system with two simpler models, such as free Trp in solution and as a component of bovine and human serum albumin. The process was studied by monitoring protein tryptophan (Trp) residue integrity. The sensitized photodegradation of proteins resulted in different degrees of Trp damage with different Trp (photo)-products. Indeed, many of these Trp derivatives are diagnostic for the photosensitization mechanism and some of them were obtained from cells by UVA photosensitization for the first time in this work. The analysis of quantum yields of photoproduct distribution allowed us to weigh up the type I/II contribution on a UVA photosensitization mechanism. The UVA mediated generation of these Trp derivatives is consistent with the occurrence of singlet oxygen formation (almost dominant in MB), and photoionization (significant in NAP) within the protein matrix. The results obtained in the case of this more complex system (cell) are in agreement with the two simpler models recently studied in our lab. The quantum yields of Trp photoinduced degradation, as well as of its photoproducts formation, decrease with increasing the complexity of the investigated target. The Royal Society of Chemistry and Owner Societies 2013.
- Bracchitta, Giuseppina,Catalfo, Alfio,De Guidi, Guido
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p. 967 - 973
(2013/09/12)
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- Highly efficient thermal cyclization reactions of alkylidene esters in continuous flow to give aromatic/heteroaromatic derivatives
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Intramolecular thermal cyclization and benzannulation reactions of the Gould-Jacobs and Conrad-Limpach types were performed in a designed continuous flow reactor system at temperatures in the range of 300-360°C and under high pressure conditions (100-160 bar) with very short residence times (0.45-4.5 min) in tetrahydrofuran as a low-boiling point solvent. Substituted heteroaromatic compounds including pyridopyrimidinones and hydroxyquinolines were synthesized in moderate to high yields. Application of the reaction conditions also allows the synthesis of naphthol and biphenyl derivatives. The procedure involves an easy work-up and the non-batchwise preparative synthesis method is suitable for automation.
- Lengyel, László,Nagy, Tibor Zs.,Sipos, Gellért,Jones, Richard,Dormán, Gy?rgy,ürge, László,Darvas, Ferenc
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p. 738 - 743
(2012/03/08)
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- Inhibition of monoamine oxidase by 8-benzyloxycaffeine analogues
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Based on recent reports that several (E)-8-styrylcaffeinyl analogues are potent reversible inhibitors of monoamine oxidase B (MAO-B), a series of 8-benzyloxycaffeinyl analogues were synthesized and evaluated as inhibitors of baboon liver MAO-B and recombinant human MAO-A and -B. The 8-benzyloxycaffeinyl analogues were found to inhibit reversibly both MAO isoforms with enzyme-inhibitor dissociation constants (Ki values) ranging from 0.14 to 1.30 μM for the inhibition of human MAO-A, and 0.023-0.59 μM for the inhibition of human MAO-B. The most potent MAO-A inhibitor was 8-(3-methylbenzyloxy)caffeine while 8-(3-bromobenzyloxy)caffeine was the most potent MAO-B inhibitor. The analogues inhibited human and baboon MAO-B with similar potencies. A quantitative structure-activity relationship (QSAR) study indicated that the MAO-B inhibition potencies of the 8-benzyloxycaffeinyl analogues are dependent on the Hansch lipophilicity (π) and Hammett electronic (σ) constants of the substituents at C-3 of the benzyloxy ring. Electron-withdrawing substituents with a high degree of lipophilicity enhance inhibition potency. These results are discussed with reference to possible binding orientations of the inhibitors within the active site cavities of MAO-A and -B.
- Strydom, Belinda,Malan, Sarel F.,Castagnoli Jr., Neal,Bergh, Jacobus J.,Petzer, Jacobus P.
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experimental part
p. 1018 - 1028
(2010/04/26)
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- Assembly of 4-aminoquinolines via palladium catalysis: A mild and convenient alternative to SNAr methodology
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4-Aminoquinolines, classically prepared via SNAr chemistry from an amine and 4-haloquinoline, are important scaffolds in medicinal chemistry. Interest in these compounds prompted us to explore palladium catalysis as an alternative to the existing methods for their preparation. Initial results followed by an iterative screening paradigm confirmed Pd(OAc)2/ DPEphos/K3PO4 as a mild and convenient alternative for the formation of the C-N bond in 4-aminoquinolines. A description of the screen and the scope of this methodology are discussed herein.
- Margolis, Brandon J.,Long, Kimberly A.,Laird, Dana L. T.,Ruble, J. Craig,Pulley, Shon R.
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p. 2232 - 2235
(2007/10/03)
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- Mild cleavage of aryl mesylates: Methanesulfonate as potent protecting group for phenols
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A mild protocol for the chemoselective deprotection of aryl methanesulfonates is described. The transformation can be conducted on highly functionalized substrates and renders the methanesulfonate a useful, previously underutilized protecting group for phenols.
- Ritter, Tobias,Stanek, Kyrill,Larrosa, Igor,Carreira, Erick M.
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p. 1513 - 1514
(2007/10/03)
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- Preparation of 4-hydroxyquinolines
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Process for the preparation of 4-hydroxyquinolines of the general formula: STR1 in which R represents a hydrogen atom, or one, two or three substituents, which may be the same or different, selected from halogen atoms, alkyl radicals containing 1 to 4 carbon atoms, alkoxy radicals containing 1 to 4 carbon atoms, and the trifluoromethyl radical, the substituent(s) being in the 2-, 3-, 5-, 6-, 7- or 8-position, by the oxidation, by means of oxygen or air, in the presence of a catalyst based on platinum or ruthenium, or alloys thereof, of a 1,2,3,4-tetrahydroquinolin-4-one of the general formula: STR2 in which R is as defined above.
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- Studies on Ketene and Its Derivatives. CXIII. Reaction of Dichloroketene with Aromatic Amine N-Oxides
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Reaction of dichloroketene with pyridine 1-oxide (1) gave four products, namely, 2-dichloromethylpyridine (2), 4-dichloromethylpyridine (3), 3,3,7-trichloro-6-dichloroacetyl-2-oxo-2,3,3a,6,7,7a-hexahydrofuropyridine (4), and 3,3-dichloro-6-dichloroacetyl-7-hydroxy-2-oxo-2,3,3a,6,7,7a-hexahydrofuropyridine (5).Reaction of dichloroketene with 1, followed by treatment with abs. methanol gave 3, methyl 2,2-dichloro-2-(2-pyridyl)acetate (6), and methyl 2,2-dichloro-2-(4-pyridyl)acetate (7).Similar reaction of dichloroketene with methylpyridine 1-oxides gave the corresponding 2-dichloro and 4-dichloro methylpyridines.On the other hand, reaction of dichloroketene with 2,6-dimethylpyridine 1-oxide (18), followed by treatment with abs. methanol gave 4-dichloromethyl-2,6-dimethylpyridine (19) and bis(2,6-dimethyl-4-pyridyl)dichloromethane (21).Dichloroketene also reacted with quinoline 1-oxide (24) and isoquinoline 2-oxide (29) to give the corresponding dichloromethyl derivatives (25 and 26, and 30, respectively).Keywords --- aromatic amine N-oxide; dichloroketene; dichloromethylpyridine; dichloromethylquinoline; dichloromethylisoquinoline
- Katagiri, Nobuya,Niwa, Ryuji,Furuya, Yoichi,Kato, Tetsuzo
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p. 1833 - 1841
(2007/10/02)
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- Theoretical Description of Solvent Effects. V. The Medium Influence on the Lactim-Lactam Tautomerism of Hydroxyazines
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Der Loesungsmitteleffekt auf die Tautomeriegleichgewichte der Titelverbindungen wird mit Hilfe klassischer und quantenchemischer Versionen der Solvatonen- und der Reaktionsfeldtheorie berechnet.In Uebereinstimmung mit dem Experiment ergeben alle getesteten Verfahren eine Gleichgewichtsverschiebung zugunsten der Lactamform.Zur quantitativen Beschreibung dieses Effektes ist jedoch das Reaktionsfeldmodell besser geeignet.
- Krebs, C.,Foerster, W.,Weiss, C.,Hofmann, H.-J.
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p. 369 - 378
(2007/10/02)
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