- In situ insights into the nanoscale deposition of 5,6-dihydroxyindole-based coatings and the implications on the underwater adhesion mechanism of polydopamine coatings
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The biomimetic coating polydopamine (PDA) has emerged as a promising coating material for various applications. However, the mechanism of PDA deposition onto surfaces is not fully understood, and the coating components of PDA and its relation to the putative intermediate 5,6-dihydroxyindole (DHI) are still controversial. This investigation discloses the deposition mechanisms of dopamine (DA)-based coatings and DHI-based coatings onto silicon surfaces by monitoring the nanoscale deposition of both coatings in situ using high-precision ellipsometry. We posit that the rapid and instantaneous nano-deposition of PDA coatings onto silicon surface in the initial stages critically involves the oxidation of DHI and/or its related oligomers. Our studies also show that the slow conversion of DA to DHI in PDA solution and the coupling between DA and DHI-derived precursors could be crucial for subsequent PDA coating growth. These findings elucidate the critical role of DHI, acting as an 'initiator' and a 'cross linker', in the PDA coating formation. Overall, our study provides important information on the early stage nano-deposition behavior in the construction of PDA coatings and DHI-based coatings.
- Lyu, Qinghua,Song, Hongyan,Yakovlev, Nikolai L.,Tan, Wui Siew,Chai, Christina L. L.
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- Short-lived quinonoid species from 5,6-dihydroxyindole dimers en route to eumelanin polymers: Integrated chemical, pulse radiolytic, and quantum mechanical investigation
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The transient species formed by oxidation of three dimers of 5,6-dihydroxyindole (1), a major building block of the natural biopolymer eumelanin, have been investigated. Pulse radiolytic oxidation of 5,5′,6,6′-tetrahydroxy-2,4′-biindolyl (3) and 5,5′,6,6′-tetrahydroxy-2,7′-biindolyl (4) led to semiquinones absorbing around 450 nm, which decayed with second-order kinetics (2k = 2.8 × 109 and 1.4 × 109 M-1 s -1, respectively) to give the corresponding quinones (500-550 nm). 5,5′,6, 6′-Tetrahydroxy-2,2′-biindolyl (2), on the other hand, furnished a semiquinone (λmax = 480 nm) which disproportionated at a comparable rate (2k = 3 × 109 M -1 s-1) to give a relatively stable quinone (λmax = 570 nm). A quantum mechanical investigation of o-quinone, quinonimine, and quinone methide structures of 2-4 suggested that oxidized 2-4 exist mainly as 2-substituted extended quinone methide tautomers. Finally, an oxidation product of 3 was isolated for the first time and was formulated as the hydroxylated derivative 5 arising conceivably by the addition of water to the quinone methide intermediate predicted by theoretical analysis. Overall, these results suggest that the oxidation chemistry of biindolyls 2-4 differs significantly from that of the parent 1, whereby caution must be exercised before concepts that apply strictly to the mode of coupling of 1 are extended to higher oligomers.
- Pezzella, Alessandro,Panzella, Lucia,Crescenzi, Orlando,Napolitano, Alessandra,Navaratman, Suppiah,Edge, Ruth,Land, Edward J.,Barone, Vincenzo,D'Ischia, Marco
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- MECHANISM OF THE REARRANGEMENT OF DOPACHROME TO 5,6-DIHYDROXYINDOLE
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Kinetic and isotopic labelling studies provide for the first time evidence that at physiological pH the rearrangement of dopachrome (1) to 5,6-dihydroxyindole (2) involves abstraction of the proton at position 3 and formation of the intermediate quinone-methide 4.
- Costantini, C.,Crescenzi, O.,Prota, G.
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- Effect of aluminum (III) on the conversion of dopachrome in the melanin synthesis pathway
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The effect of aluminum ions on the kinetics and mode of the conversion of dopachrome (DC) in acidic environment has been studied using UV-Vis spectrophotometric and cyclic voltammetric methods. The DC conversion step is an important reaction in melanogenesis. Aluminum ions catalyze greatly the decarboxylative transformation of DC to give 5,6-dihydroxyindole (DHI) rather than 5,6-dihydroxyindole-2-carboxylic acid (DHICA) at pH 5.5, which enhance the ratio of formation DHI/DHICA in melanin synthesis pathway. The kinetics of DC conversion catalyzed by aluminum ions is dependent on the concentration of DC and aluminum ions. These results provide evidence that aluminum ions could play a role in the synthesis of melanin pathway in acidic condition through catalyzing the DC decarboxylative transformation to yield DHI and influence the melanin structure and properties.
- Di, Junwei,Bi, Shuping
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- Effect of stacking and redox state on optical absorption spectra of melanins-comparison of theoretical and experimental results
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In this work the effect of aggregation and oxidation on the optical absorption of eumelanin oligomeric sheets is investigated by applying quantum mechanics and atomistic simulation studies to a simplified eumelanin structural model that includes 1 -3 sheets of hexameric oligomer sheets. The oligomeric hypothesis is supported by AFM characterizations of synthetic eumelanins, formed by auto-oxidation or electrochemical oxidation of dihydroxyindole (DHI). Comparison of calculated absorption spectra to experimental spectra demonstrates a red shift in absorption with oxidation and stacking of the eumelanin and validates the theoretical results.
- Stark, Klaus B.,Gallas, James M.,Zajac, Gerry W.,Golab, Joseph T.,Gidanian, Shirley,McIntire, Theresa,Farmer, Patrick J.
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- Ultra-low temperature oxidation of 5,6-dihydroxyindole: A novel approach to study synthetic melanogenesis
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The detailed structure of melanin remains elusive due to the complexity and insolubility of the pigment. Herein we describe a novel oxidation of 5,6-dihydroxyindole (DHI) as a means to characterize soluble intermediates formed prior to oligomerization. The approach entails the use of a biomimetic copper-peroxo oxidant, at ultra-low temperature (-78°C). DHI oxidized by [LCuII(O2)CuIIL]B(C6F 5)4 (L = 2,6,10-trimethyl-2,6,10-triazaundecane) under argon produces the one electron oxidation product, semiquinone radical, which is spectroscopically observed at -78°C. MS analysis of the reaction mixture reveals the DHI dimer as well as other extensively oxidized DHI units.
- Hatcher, Lanying Q.,Simon, John D.
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- Detection of melanochromes by MALDI-TOF mass spectrometry
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Melanin formation from dopamine, DOPA, DHI, or DHICA, was analyzed by means of matrix-assisted laser desorption mass spectrometry. Oligomers of dihydroxyindoles, i.e. melanochromes, up to DP11 were detected. Increments of 16 mass units provide evidence for the presence of trihydroxyindole units. The results indicate that polymerization of dihydroxyindoles towards melanins occurs by sequential coupling of monomers with concomitant oxygenation.
- Kroesche, Christoph,Peter, Martin G.
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- Evidence for the intermediacy of quinone-methides in the rearrangement of aminochromes to 5,6-dihydroxyindoles
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Oxidation of α-methyldopa methyl ester leads to the aminochrome 4, which, at neutral pH, spontaneously rearranges to give a relatively stable quinone-methide identified as 5. This provides the first evidence for the postulated intermediacy of quinone-methides in the conversion of aminochromes to 5,6-dihydroxyindoles.
- Crescenzi,Costantini,Prota
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- Chemical, pulse radiolysis and density functional studies of a new, labile 5,6-indolequinone and its semiquinone
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The chemical and spectroscopic characterization of 5,6-indolequinones and their semiquinones, key transient intermediates in the oxidative conversion of 5,6-dihydroxyindoles to eumelanin biopolymers, is a most challenging task. In the present paper, we report the characterization of a novel, relatively long-lived 5,6-indolequinone along with its semiquinone using an integrated chemical, pulse radiolytic, and computational approach. The quinone was obtained by oxidation of 5,6-dihydroxy-3-iodoindole (1a) with o-chloranil in cold ethyl acetate or aqueous buffer: it displayed electronic absorption bands around 400 and 600 nm, was reduced to 1a with Na2S2O4, and reacted with o-phenylenediamine to give small amounts of 3-iodo-1H-pyrrolo[2,3- b]phenazine (2). The semiquinone exhibited absorption maxima at 380 nm (sh) and 520 nm and was detected as the initial species produced by pulse radiolytic oxidation of 1a at pH 7.0. DFT investigations indicated the 6-phenoxyl radical and the N-protonated radical anion as the most stable tautomers for the neutral and anion forms of the semiquinone, respectively. Calculated absorption spectra in water gave bands at 350 (sh) and 500 nm for the neutral form and at 310 and 360 (sh) nm for the anion. Disproportionation of the semiquinone with fast second-order kinetics (2k = 1.1 × 1010 M-1 s -1) gave a chromophore with absorption bands resembling those of chemically generated 1a quinone. Computational analysis predicted 1a quinone to exist in vacuo as the quinone-methide tautomer, displaying low energy transitions at 380 and 710 nm, and in water as the o-quinone, with calculated absorption bands around 400 and 820 nm. A strong participation of a p orbital on the iodine atom in the 360-380 nm electronic transitions of the o-quinone and quinone-methide was highlighted. The satisfactory agreement between computational and experimental electronic absorption data would suggest partitioning of 1a quinone between the o-quinone and quinone-methide tautomers depending on the medium.
- Pezzella, Alessandro,Crescenzi, Orlando,Natangelo, Anna,Panzella, Lucia,Napolitano, Alessandra,Navaratnam, Suppiah,Edge, Ruth,Land, Edward J.,Barone, Vincenzo,D'Ischia, Marco
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- Method for preparing 5, 6-dihydroxyindole by using modified ordered mesoporous carbon supported metal catalyst
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The invention belongs to the technical field of organic synthesis, and discloses a method for preparing 5, 6-dihydroxyindole by using a modified ordered mesoporous carbon supported metal catalyst. According to the invention, phenolic resin is taken as a carbon source, polyether F127 is taken as a soft template, an ordered mesoporous carbon loaded metal material is prepared as a catalyst, and high catalytic activity and good stability are shown in the reaction of 3, 4-dimethoxyaniline and ethylene glycol. The catalyst prepared by the method has remarkable effects of avoiding agglomeration and stripping of active components, improving the reaction catalytic activity and prolonging the service life. The raw materials are easy to obtain, the cost is low, the product is white powder, the product purity reaches 98.3%, the ethylene glycol conversion rate in the reaction is close to 60%, the selectivity of the 5, 6-dimethoxy indole reaches 85% or above, and the final yield of the 5, 6-dihydroxy indole can reach 81% or above.
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Paragraph 0032; 0039-0041; 0048-0049
(2021/05/01)
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- PRODUCTION METHOD FOR DIHYDROXYINDOLES
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A method for producing dihydroxyindoles includes: a step 1 of obtaining an aqueous first solution including dihydroxyindoles obtained by causing at least a material selected from the group consisting of 3-(3,4-dihydroxyphenyl)alanine and a derivative of 3-(3,4-dihydroxyphenyl)alanine to react with an oxidizing agent; and a step 2 of obtaining an oleaginous second solution in which the dihydroxyindoles are extracted in an extraction solvent by mixing the first solution obtained in the step 1 with the extraction solvent. Before the first solution obtained in the step 1 is mixed with the extraction solvent in the step 2, a water-insoluble by-product is removed from the first solution.
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Paragraph 0120-0127
(2020/09/09)
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- Method for efficiently preparing 5,6-dihydroxyindole (by machine translation)
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The preparation method 5,6 - of the compound,dihydroxyindole comprises the following steps :(1): dissolving 3,4 - dialkoxybenzylethylamine and a catalyst in an organic solvent, in an organic solvent, carrying out reflux reaction, in the heated stirring state ;(2) and then further purifying to obtain (1)-hydroxyindole solid powder, which is suitable for industrial production, and has a high, product purity, stability, and easy long-term storage after the operation steps, are short ;(3) reaction steps, through an oxidation reaction, and then further purifying the intermediate compound I, and then purifying the compound I by the oxidizing agent, and then purifying the intermediate compound. I by using a, reducing agent, and then, purifying the intermediate compound I by the, oxidation reaction step 5,6 - and further, purifying the obtained dopamine white solid, powder . by oxidation reaction . The method comprises the following steps. (by machine translation)
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Paragraph 0031; 0038-0039; 0040; 0047-0048
(2020/04/29)
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- Regulatory Activities of Dopamine and Its Derivatives towards Metal-Free and Metal-Induced Amyloid-β Aggregation, Oxidative Stress, and Inflammation in Alzheimer's Disease
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A catecholamine neurotransmitter, dopamine (DA), is suggested to be linked to the pathology of dementia; however, the involvement of DA and its structural analogues in the pathogenesis of Alzheimer's disease (AD), the most common form of dementia, composed of multiple pathogenic factors has not been clear. Herein, we report that DA and its rationally designed structural derivatives (1-6) based on DA's oxidative transformation are able to modulate multiple pathological elements found in AD [i.e., metal ions, metal-free amyloid-β (Aβ), metal-bound Aβ (metal-Aβ), and reactive oxygen species (ROS)], with demonstration of detailed molecular-level mechanisms. Our multidisciplinary studies validate that the protective effects of DA and its derivatives on Aβ aggregation and Aβ-mediated toxicity are induced by their oxidative transformation with concomitant ROS generation under aerobic conditions. In particular, DA and the derivatives (i.e., 3 and 4) show their noticeable anti-amyloidogenic ability towards metal-free Aβ and/or metal-Aβ, verified to occur via their oxidative transformation that facilitates Aβ oxidation. Moreover, in primary pan-microglial marker (CD11b)-positive cells, the major producers of inflammatory mediators in the brain, DA and its derivatives significantly diminish inflammation and oxidative stress triggered by lipopolysaccharides and Aβ through the reduced induction of inflammatory mediators as well as upregulated expression of heme oxygenase-1, the enzyme responsible for production of antioxidants. Collectively, we illuminate how DA and its derivatives can prevent multiple pathological features found in AD with identification of molecular-level mechanisms. The overall studies could advance our understanding regarding distinct roles of neurotransmitters in AD and identify key interactions for alleviation of AD pathology.
- Nam, Eunju,Derrick, Jeffrey S.,Lee, Seunghee,Kang, Juhye,Han, Jiyeon,Lee, Shin Jung C.,Chung, Su Wol,Lim, Mi Hee
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- pH stability and antioxidant power of CycloDOPA and its derivatives
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CycloDOPA (leukodopachrome), a well known metabolite of tyrosine, is a precursor of melanine in mammalian organisms and of the pigment betalain in plants. However, the isolation of cycloDOPA from natural sources has not been widely reported. In the present work, the stabilities of cycloDOPA and cycloDOPA methyl ester at various pH levels were studied. Both compounds were stable under acidic conditions. By contrast, both compounds were unstable when the pH was shifted from neutral to basic to form indole derivatives as major products. Based on the pH stability, cycloDOPA and its derivatives were subjected to the DPPH radical scavenging assay for the first time.
- Nakagawa, Shiori,Tachrim, Zetryana Puteri,Kurokawa, Natsumi,Ohashi, Fumina,Sakihama, Yasuko,Suzuki, Takeyuki,Hashidoko, Yasuyuki,Hashimoto, Makoto
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supporting information
(2018/09/06)
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- The influence of hydroquinone on tyrosinase kinetics
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In vitro studies, using combined spectrophotometry and oximetry together with hplc/ms examination of the products of tyrosinase action demonstrate that hydroquinone is not a primary substrate for the enzyme but is vicariously oxidised by a redox exchange mechanism in the presence of either catechol, l-3,4-dihydroxyphenylalanine or 4-ethylphenol. Secondary addition products formed in the presence of hydroquinone are shown to stimulate, rather than inhibit, the kinetics of substrate oxidation.
- Stratford, Michael R.L.,Ramsden, Christopher A.,Riley, Patrick A.
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experimental part
p. 4364 - 4370
(2012/08/28)
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- Fast deprotection of phenoxy benzyl ethers in transfer hydrogenation assisted by microwave
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Phenoxy benzyl ethers are easily and quickly deprotected in the presence of ammonium formate and microencapsulated Pd(0)EnCat with the assistance of microwave irradiation. This procedure can be applied in the presence of other functional groups as well. The described protocol is particularly convenient for the preparation in a parallel and automatic fashion of libraries of compounds possessing a phenol type moiety.
- Quai, Monica,Repetto, Claudio,Barbaglia, Walter,Cereda, Enzo
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p. 1241 - 1245
(2007/10/03)
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- HAIR DYE COMPOSITION
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An air-oxidative type hair dye composition containing a melanin precursor prepared by a process including (A) an oxidation step for converting, into the melanin precursor, a tyrosine or derivative thereof used as a starting substance with an enzyme or cell that is derived from a fungus selected from the group consisting of fungi belonging to the genera Aspergillus, Neurospora, Rhizomucor, Trichoderma, and Penicillium and that exhibits a catechol oxidase activity.
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Page/Page column 12
(2008/06/13)
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- Indolocarbazole anticancer agents and methods of using same
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The present invention relates to anti-tumor compounds, compositions and methods. In particular, the invention relates to indolocarbazole analogues of the following general formulas that inhibit topoisomerase I activity. 1
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- Indolocarbazole anticancer agents and methods of using them
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The present invention relates to anti-tumor compounds, compositions and methods. In particular, the invention relates to indolocarbazole analogues of the following general formulas that inhibit topoisomerase I activity. 1
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- Process for the preparation of substituted indoles
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A process for the preparation of 5,6-disubstituted indoles in which a 4-5-disubstituted-2,β-nitrostyrene is subjected to a reductive cyclization in the presence of a water soluble dithionite salt.
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- Expedient synthesis of 5,6-dihydroxyindole and derivatives via an improved Zn(II)-assisted 2,β-dinitrostyrene approach
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A facile 3-step synthesis of 5,6-dihydroxyindole (4a) is reported, featuring the Zn(II)-controlled regioselective nitration of 3,4- dihydroxynitrostyrene (2) with tetranitromethane at pH 8.0, and the reductive cyclization of the resulting 4,5-dihydroxy-2,β-dinitrostyrene (3a) with Na2S2O4/Zn(II) at pH 4. The latter procedure was successfully extended to the conversion of the 2,β-dinitrostyrenes 3b and 3c to 5,6-dibenzyloxyindole (4b) and 5,6-diacetoxyindole (4c) in good-to-high yields.
- Novellino, Luisa,D'Ischia, Marco,Prota, Giuseppe
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p. 793 - 796
(2007/10/03)
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- Nitrite- and peroxide-dependent oxidation pathways of dopamine: 6- nitrodopamine and 6-hydroxydopamine formation as potential contributory mechanisms of oxidative stress- and nitric oxide-induced neurotoxicity in neuronal degeneration
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In the presence of nitrite ions (NO2-) in phosphate buffer (pH 7.4) and at 37 °C, dopamine was oxidized by a variety of hydrogen peroxide (H2O2)-dependent enzymatic and chemical systems to give, in addition to black melanin-like pigments via 5,6-dihydroxyindoles, small amounts of the potent neurotoxin 6-hydroxydopamine (1) and of 6-nitrodopamine (2), a putative reaction product of dopamine with NO-derived species. Treatment of 0.5 or 1 mM dopamine with horseradish peroxidase (HRP) or lactoperoxidase (LPO) in the presence of 1 or 2 mM H2O2 with NO2- at a concentration of 0.5-10 mM resulted in the formation of 1 and 2 in up to 8 and 2 μM yields, respectively, depending on the substrate concentration and the NO2-: H2O2 ratio. Nitration and hydroxylation of 0.1 mM dopamine was observed with 1 mM NO2- using HRP and the D-glucose/glucose oxidase system to generate H2O2 in situ. In the presence of NO2, Fe2+-, or Fe2+/EDTA-promoted oxidations of dopamine with H2O2 also led to the formation of 1 and 2, the apparent product ratios varying with peroxide concentration and the partitioning of the metal between EDTA and catecholamine chelates. In the presence of NO2-, Fe2+-promoted autoxidation of dopamine gave 2 but no detectable 1. When injected into the brains of laboratory rats, 2 caused sporadic behavioral changes, indicating that it could elicit a neurotoxic response, albeit to a lower extent than 1. Model experiments using tyrosinase as an oxidizing system and mechanistic considerations suggested that formation of 2 does not involve reactive nitrogen radicals but results mainly from nucleophilic attack of NO2- to dopamine quinone. Generation of 1, on the other hand, may be derives from different H2O2-dependent pathways. Collectively, these results outline a complex interplay of NO2-- and peroxide-dependent oxidation pathways of dopamine, which may contribute to impair dopaminergic neurotransmission and induce cytotoxic processes in neurodegenerative disorders.
- Palumbo, Anna,Napolitano, Alessandra,Barone, Paolo,D'Ischia, Marco
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p. 1213 - 1222
(2007/10/03)
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- Process for the preparation of indole compounds
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The present invention relates to a novel process for the preparation of a monohydroxyindole or dihydroxyindole compound by a single step of placing in contact, in a solvent medium, at least one hydrolase with at least one indole compound bearing one or two radicals connected by an ester function to the benzene ring.
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- Process for the preparation of indole compounds from N-protected indolines
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The present invention relates to a novel process for the preparation of indole compounds of the formula II: STR1 from N-protected indolines of the formula I. STR2
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- Synthesis of indoles by dehydrogenation of indolines
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STR1 By dehydrating indolines or their salts, the corresponding indoles having formula (I) are obtained. In the formula, R1 and R3 represent independently from each other hydrogen or alkyl groups with 1 to 4 C atoms, R2 stands for hydrogen, a methyl or a carboxyl group, R4 and R5 represent independently from each other hydrogen, amino groups, hydroxy groups, alkyl groups with 1 to 4 C atoms or alkoxy groups with 1 to 4 C atoms, or, in case R4 and R5 are bound to adjacent C atoms, both residues may also represent together an alkylene dioxy group with 1 to 4 C atoms. This process allows high yields of very pure indoles to be produced.
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- Process for the preparation of 5,6-dihydroxyindole and intermediate compounds
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Process for the preparation of 5,6-dihydroxyindole, wherein the compound of formula: STR1 in which R' denotes a hydrogen atom or an optionally substituted benzyl radical, is subjected either to the action of hydrogen under pressure or to a hydrogen transfer operation, in a solvent medium and in the presence of a hydrogenation catalyst.
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- Method for dyeing keratinous fibres using a monohydroxyindole or dihydroxyindole and a non-oxidizing aromatic carbonyl derivative and dyeing agent
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The present invention relates to a method for dyeing keratinous fibers, characterized in that the following are applied to the fibers: a) a composition (A) containing, in a medium appropriate for dyeing, at least one monohydroxyindole or dihydroxyindole, this application being preceded or followed by the application of b) a composition (B) containing, in a medium appropriate for dyeing, at least one aromatic carbonyl derivative chosen from hydroxyacetophenones, hydroxybenzophenones, 2-hydroxy-1,4-benzoquinones, hydroxy-1,4-naphthoquinones,amino-1,4-naphthoquinones,hydroxy-9,10-anthraquinones and amino-9,10-anthraquinones. It also relates to the dyeing agents for carrying it out.
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- Product based on inorganic or organic lamellar particles, containing a melanotic pigment, process for preparing it and its use in cosmetics
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The invention relates to a product in powder form consisting of organic or inorganic particles having a lamellar structure, having a size of less than 50 microns and containing at least one synthetic melanotic pigment formed in situ by oxidation of an indole compound, and to its use for the protection of the human epidermis, in make-up products and for dyeing hair.
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- Process for the preparation of 5,6-diacetoxyindole
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An indole of the formula STR1 wherein R5 and R6 are acetoxy or hydrogen, at least one of R5 and R6 being acetoxy, is prepared, in good yield, in a one pot synthesis, without extraction, recrystallization or isolation of intermediate reaction product; A compound of the formula STR2 wherein R1 and R2 are benzyloxy or hydrogen, provided that at least one of R1 and R2 is benzyloxy, is subjected to reductive cyclization followed by acetylation of the resultant reaction product.
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- THE ALLEGED STABILITY OF DOPA-MELANINS REVISITED
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In neutral aqueous buffer at 25 deg C, enzymatic dopa-melanin is shown to undergo self-oxidation with a marked increase in the content of carboxyl groups, due probably to peroxidative cleavage of quinonoid units.
- Crescenzi, Orlando,d'Ischia, Marco,Napolitano, Alessandra,Prota, Giuseppe
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p. 241 - 242
(2007/10/02)
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- A New Oxidation Pathway of the Neurotoxin 6-Aminodopamine. Isolation and Characterisation of a Dimer with a Tetrahydroiminoethanophenoxazine Ring System.
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Oxidation of the neurotoxin 6-aminodopamine (1) is known to proceed through the o-quinone 3, which undergoes intramolecular cyclisation to give 5,6-dihydroxyindole (6).In a re-examination of the reaction, we have found that at concentrations of 1 higher than 5 * 10-3 M a quite different course prevails, leading to the formation of the novel 7-amino-8-(2-aminoethyl)-3-hydroxy-2-oxo-2,3,4,10-tetrahydroiminoethanophenoxazine (7).Product 7 was formed by aerobic, chemical (persulphate, periodate) or enzymatic (tyrosinase, peroxidase/H2O2) oxidation of 1.On acetylation, 7 afforded the tetraacetate 8.Oxidation of the model compound 5-amino-4-methylcatechol (9) proceeded similarly as that of 1, to give the tetrahydrophenoxazinedione 11.
- Napolitano, Alessandra,d'Ischia, Marco,Costantini, Claudio,Prota, Giuseppe
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p. 8515 - 8522
(2007/10/02)
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- Process for dyeing keratinous fibres with a hydroxyindole in combination with a quinone derivative; and novel 1,4-benzoquinones
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Process for dyeing keratinous fibres, comprising the step of applying to these fibres at least one composition A containing, in a medium appropriate for dyeing, at least one mono- or di-hydroxyindole the application of the composition A being preceded or followed by the application of a composition B containing, in a medium appropriate for dyeing, at least one quinone derivative chosen from ortho- or para-benzoquinones, monoimines or diimines of ortho- or para-benzoquinones, 1,2- or 1,4-naphthoquinones, sulphonimides of ortho- or para-benzoquinones, α, ω-alkylene-bis-1,4-benzoquinones, or 1,2- or 1,4-naphthoquinone-monoimines or -diimines; the mono- or di-hydroxyindoles and the quinone derivatives being chosen such that the oxidation-reduction potential difference ΔE between the oxidation-reduction potential Ei of the mono- or di-hydroxyindoles, determined at pH 7 in a phosphate medium on a vitreous carbon electrode by voltametry, and the oxidation-reduction potential Eq of the quinone derivative determined at pH 7 in a phosphate medium by polarography on a mercury electrode and relative to a saturated calomel electrode is such that
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- Dyeing process employing indole dyes and oxidation dye precursors and dyeing agents employed
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A process for dyeing keratinous fibers comprises a two-step operation in which in the first step the fibers are contacted with an indole dye in a medium suitable for dyeing the fibers, the medium being free from any oxidation catalyst and oxidation catalyst. Thereafter, in the second step the fibers are contacted with a para type oxidation dye precursor in a medium which is also suitable for dyeing the fibers and is free from any oxidation catalyst and oxidation agent. A multi-compartment kit housing the indole dye and para type oxidation dye precursor is also provided.
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- The participation of Singlet Oxygen in Dye-Sensitized Photooxidation Reaction of Catecholamines
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The photooxidation of catecholamines (adrenaline, noradrenaline and dopamine) sensitized by methylene blue (MB), rose bengal (RB) and fluoresceine (FL) proceed via aminochromes and an indolic pathway.In D2O rate constants of sensitized photooxidation are increased for about 2,7 times over rates in water. 1,3-diphenylisobenzofuran (DPBF), 1,4-diazobicyclooctane (DABCO) and azide anion were more effective inhibitors of the reaction in D2O than in H2O.Superoxide dismutase markedly decreases the rates of photooxidation in H2O and in D2O.Isotope effects and 1O2-quenchers sensitivities indicate that singlet oxygen participates on photooxidation processes of catecholamines.
- Kruk, I.
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p. 607 - 613
(2007/10/02)
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- Process for preparing 5,6-dihydroxyindole
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5,6-Dihydroxyindole is prepared by the catalytic reductive cyclization of 4,5-dihydroxy-2,β-dinitrostyrene in a single step using hydrogen with a palladium, platinum or rhodium catalyst in a polar hydroxylic reaction system. No reaction byproducts or only a single reaction byproduct are produced. The 4,5-dihydroxy-2,β-dinitrostyrene intermediate can be prepared by the chemoselective debenzylation of 4,5-dibenzyloxy-2,β-dinitrostyrene using trifluoroacetic acid. 5,6-Dihydroxyindole is a useful component in hair dye formulations and as an intermediate in the synthesis of melanin.
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- A RE-EXAMINATION OF THE ZINC-CATALYSED REARRANGEMENT OF DOPACHROME USING IMMOBILISED TYROSINASE
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The effect of zinc ions on the rearrangement of dopachrome, 1, has been reinvestigated using an improved technique to obtain the aminochrome which involves aereal oxidation of dopa with mushroom tyrosinase immobilesed on activated sepharose.Zinc-catalysed rearragement of dopachrome thus obtained was found to give 5,6-dihydroxyindole-2-carboxylic acid, 3, mainly, rather than 5,6-dihydroxyindole, 2, as previously reported.Interestingly, the rate of rearrangement and the formation ratio 3/2 are strongly dependent on the amount of metal added, decreasing as zinc concentration is lowered from 10percent to 0.1percent.The relevance of these in vitro experiments is discussed in relation to the role of metallic cations in the biosynthesis of eumelanins.
- Napolitano, Alessandra,Chioccara, Francesco,Prota, Giuseppe
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p. 357 - 360
(2007/10/02)
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- SYNTHESIS OF 5,6-DIHYDROXYINDOLE: A NOVEL REDUCTIVE CYCLIZATION OF (E)-4,5-DIHYDROXY-2,β-DINITROSTYRENE
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A unique catalytic reductive cyclization of (E)-4,5-dihydroxy-2,β-dinitrostyrene (1) to 5,6-dihydroxyindole (2) is reported.Compound 1 is obtained either by one-step CF3CO2H deprotection of 4,5-dibenzyloxy-2,β-dinitristyrene (7), or by an improved two-step demethylenation of 6-nitropiperonal (5), followed by condensation with CH3NO2.
- Murphy, Bryan P.,Banks, Harold D.
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p. 321 - 330
(2007/10/02)
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- Synthesis of 5,6-carbonyldioxyindole, a melanogenic cyclic carbonate ester of 5,6-dihydroxyindole
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5,6-Carbonyldioxyindole (4), a melanogenic derivative of 5,6-dihydroxyindole (1), was synthesized by a procedure starting with 3,4-methylenedioxycinnamic acid. Compound 4 is a stable crystalline solid which is readily hydrolyzed to 1, a key intermediate on the biosynthetic pathway from tyrosine to melanin.
- Lutz,McNamara,Olinger,et al.
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p. 1183 - 1188
(2007/10/02)
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- Melanin Formation and Break Down of Indole under Udenfriend Condition
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Indol under biomimetic hydroxylation using Udenfriend reaction gives rise to malamin and other products.The results pose a question whether indole could be an alternative substrate for biomelanin.
- Roy, Shyamali,Chakraborty, A. K.,Chakraborty, D. P.
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p. 992 - 993
(2007/10/02)
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