- CHROMATOGRAPHIC AND SPECTROSCOPIC INVESTIGATION OF THE PRODUCTS OF OXIDATION OF TYROSINE WITH OZONE.
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It has been shown that ozone in low concentrations readily oxidizes aromatic amino acids both in solution and when constituents of proteins resulting in the formation of a whole series of oxidation products. Since the oxidation products are physiologically active it was of interest to study them further. In the present work the main molecular products obtained by oxidation of tyrosine with ozone are established, and possible mechanisms of their formation discussed.
- Ignatenko,Cherenkevich,Komyak
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- Electrochemistry of Chemisorbed Molecules. 4.The Effect of Chirality on the Orientation and Electrochemical Oxidation of l - and dl-DOPA
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The influence of chirality on the orientation and electrochemical oxidation of l- and dl-DOPA chemisorbed on Pt electrodes has been studied.Measurements were made in 1 M HClO4 with thin-layer electrochemical methods.In the flat orientation, Γ (the packing
- Chila, Victor K. F.,Sorilaga, Manuel P.,Hubbard, Arthur T.,Anderson, Stanley E.
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- Biochemical characterization of two differentially expressed polyphenol oxidases from hybrid poplar
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Two polyphenol oxidase isoforms with distinct expression patterns were identified in hybrid poplar (Populus trichocarpax P. deltoides). PPO-1, corresponding to the previously cloned PtdPPO (Constabel et al., Plant Physiol. 124: 285-295) was primarily leaf
- Wang, Jiehua,Constabel, C. Peter
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- Genetically encoded dihydroxyphenylalanine coupled with tyrosinase for strain promoted labeling
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Protein modifications through genetic code engineering have a remarkable impact on macromolecule engineering, protein translocation, protein–protein interaction, and cell biology. We used the newly developed molecular biology approach, genetic code engineering, for fine-tuning of proteins for biological availability. Here, we have introduced 3, 4-dihydroxy-L-phenylalanine in recombinant proteins by selective pressure incorporation method for protein-based cell labeling applications. The congener proteins treated with tyrosinase convert 3, 4-dihydroxy-L-phenylalanine to dopaquinone for strain-promoted click chemistry. Initially, the single-step Strain-Promoted Oxidation-Controlled Cyclooctyne-1,2-quinone Cycloaddition was studied using tyrosinase catalyzed congener protein and optimized the temporally controlled conjugation with (1R,8S,9s)-Bicyclo[6.1.0]non-4-yn-9-ylmethanol. Then, the feasibility of tyrosinase-treated congener annexin A5 with easily reactive quinone functional moiety was conjugated with fluorescent tag dibenzocyclooctyne-PEG4-TAMRA for labeling of apoptotic cells. Thus, the congener proteins-based products demonstrate selective cell labeling and apoptosis detection in EA.hy926 cells even after the protein modifications. Hence, genetic code engineering can be coupled with click chemistry to develop various protein-based fluorescent labels.
- George, Augustine,Indhu, Mohan,Ashokraj, Sundarapandian,Shanmugam, Ganesh,Ganesan, Ponesakki,Kamini, Numbi Ramudu,Ayyadurai, Niraikulam
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supporting information
(2021/11/08)
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- SKIN-WHITENING COSMETIC COMPOSITION COMPRISING LACTOBACILLUS RHAMNOSUS LM1011 HAVING IMMUNOSTIMULATING ACTIVITY
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The present invention relates to a cosmetic composition for skin whitening comprising novel Lactobacillus rhamnosus LM1011 as an active ingredient. More specifically, the present invention provides a cosmetic composition for skin whitening, comprising novel Lactobacillus rhamnosus LM1011 as an active ingredient, and reducing melanin production by regulating tyrosinase activity.(AA) L-tyrosine 4-hydroxy-1-phenylalanine(BB) Tyrosinase(CC) L-dopa 1-3,4-dihydroxyphenylalanine(DD) Dehydroascorbic acid(EE) Ascorbic acid(FF) Tyrosinase(GG) Dopaquinone(HH) MelaninCOPYRIGHT KIPO 2020
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Paragraph 0009
(2020/05/13)
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- Inhibitory effects and molecular mechanism on mushroom tyrosinase by condensed tannins isolation from the fruit of Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow
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The structure of extracted condensed tannin (CT) from the fruit of Sour jujube (Ziziphus jujuba Mill. var. spinosa (Bunge) Hu ex H. F. Chow) and the molecular mechanisms by which CT inhibits the activity of mushroom tyrosinase were investigated. The structure of CT was characterized by high performance liquid chromatography electrospray ionization mass spectrometry, and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The kinetic assays were used to detect inhibition effect, type and mechanism. UV scanning, fluorescence quenching, copper interacting, o-quinone interaction and molecular docking assays were also used to reveal the molecular mechanisms by which CT inhibit tyrosinase. The results showed the structural units of CT containing afzelechin/epiafzelechin, catechin/epicatechin, and gallocatechin/epigallocatechin. Kinetic analysis showed that CT inhibits both the monophenolase and diphenolase activities of tyrosinase and exhibits reversible, mixed type mechanism. The fruit CT interacts primarily with the copper ions and specific amino acid residue (Asn191, Thr203, Ala202, Ser206, Met201, His194, His54, Glu182 and Ile42) in the active site of tyrosinase to disturb oxidation of substrates by tyrosinase. These results suggested the sour jujube fruit is a potential natural source of tyrosinase inhibitors, and has a potential to be used in food preservation, whitening cosmetics.
- Liu, Lu-Lu,Ren, Yuan-Jing,Song, Wei,Wei, Shu-Dong,Yang, Hai-Bo
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p. 1813 - 1821
(2020/11/03)
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- Coumaric acid derivatives as tyrosinase inhibitors: Efficacy studies through in silico, in vitro and ex vivo approaches
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p-Coumaric acid is a known inhibitor of tyrosinase, an enzyme involved in the initial steps of the melanin synthesis in human and other species. However, its low lipophilicity impairs its penetration through skin and efficacy as antimelanogenic agent indeed. Accordingly, this paper reports the assessment of several coumaric acid derivatives as tyrosinase inhibitors and antimelanogenic agents in in vitro, in silico and ex vivo assays. The compounds were designed with modifications in the aromatic and acid moieties of p-coumaric acid, being the coumarate esters the most promising derivatives. The compounds showed higher tyrosinase inhibitory activity (pIC50 3.7–4.2) than the parent acid, being compounds 1d, 1e and 1f the most potent inhibitors. Docking analysis showed that these esters are competitive inhibitors per se, and act independently of a redox mechanism as suggested by DPPH assays. Moreover, the esters showed efficacy in reducing the melanin deposition in human skin fragments at 0.1% concentration, especially compound 1e. In summary, there is an important equilibria between tyrosinase affinity and lipophilicity that must be considered to get effective antimelanogenic agents with adequate permeability in the skin.
- Fernandes, Jo?o Paulo S.,Ferrarini, Márcio,Mercaldi, Vitória Gallo,Nazato, Lucas Idacir Sbrugnera,Padovani, Giovana,Sufi, Bianca da Silva,Varela, Marina Themoteo
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- In vitro tyrosinase, acetylcholinesterase, and HSA evaluation of dioxidovanadium (V) complexes: An experimental and theoretical approach
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The present study reports the biological evaluation of vanadium(V) complexes (1–3) against three different proteins: tyrosinase, acetylcholinesterase (AChE), and human serum albumin (HSA), which were studied by spectroscopic techniques and molecular docki
- Chaves, Otávio Augusto,de Oliveira, Márcia Cristina Campos,de Salles, Cristiane Martins Cardoso,Martins, Francisco Mainardi,Iglesias, Bernardo Almeida,Back, Davi Fernando
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- Determining mushroom tyrosinase inhibition by imidazolium ionic liquids: A spectroscopic and molecular docking study
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The inhibition effects of imidazolium ionic liquids (ILs) on the enzyme kinetics of mushroom tyrosinase is reported. A simple UV-VIS spectrophotometric assay was used to measure the reaction kinetics of the reaction between mushroom tyrosinase and L-dopa.
- Heitz, Mark P.,Rupp, Jason W.
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p. 1971 - 1981
(2017/10/23)
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- Synthesis and biological evaluation of N-aryl-2-phenyl-hydrazinecarbothioamides: Experimental and theoretical analysis on tyrosinase inhibition and interaction with HSA
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A series of N-aryl-2-phenyl-hydrazinecarbothioamides have been investigated as possible inhibitors of tyrosinase, an enzyme involved in the development of melanomas. The hydrazinecarbothioamides 1–6 were synthesized from the reaction between phenylhydrazine and isothiocyanates, for which three different methods have been employed, namely stirring at room temperature, by microwave irradiation or by mechanochemical grinding. Quantitative yields were obtained for the later technique. Compound 4 showed the best value for tyrosinase inhibition (IC50 = 22.6 μM), which occurs through an uncompetitive mechanism. Molecular docking results suggested that 4 can interact via T-stacking with the substrate L-DOPA and via hydrogen bonding and hydrophobic forces with the amino acid residues Ala-79, His-243, Val-247, Phe-263, Val-282, and Glu-321. The interaction between human serum albumin (HSA) and compound 4 occurs through a ground state association and does not perturb the secondary structure of the albumin as well as the microenvironment around Tyr and Trp residues. The binding is spontaneous, moderate and occurs mainly in the Sudlow's site I. Molecular docking results suggested hydrogen bonding, hydrophobic and electrostatic interactions as the main binding forces between the compound 4 and the amino acid residues Lys-198, Trp-214, Glu-449, Leu-452, and Leu-480.
- Sousa-Pereira, Danilo,Chaves, Otávio Augusto,dos Reis, Camilla Moretto,de Oliveira, Márcia C.C.,Sant'Anna, Carlos Maurício R.,Netto-Ferreira, José Carlos,Echevarria, Aurea
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- Biological interactions of fluorinated chalcones: Stimulation of tyrosinase activity and binding to bovine serum albumin
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The evaluation of tyrosinase activity of CH, CH3F, CH4F, CH23F, CH25F, CH35F and CH2356F as well as of the interactions of CH and fluorinated chalcones CH3F, CH4F and CH2356F with bovine serum albumin (BSA) in a PBS buffer solution (pH?=?7.4), at 288?K, 2
- Chaves, Otávio Augusto,de Barros, Leonardo Santos,de Oliveira, Márcia C.C.,Sant'Anna, Carlos Mauricio R.,Ferreira, Aurélio B.B.,da Silva, Francisco Assis,Cesarin-Sobrinho, Dari,Netto-Ferreira, José Carlos
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- Synergic effect of graphene quantum dots and room temperature ionic liquid for the fabrication of highly sensitive voltammetric sensor for levodopa determination in the presence of serotonin
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Levodopa, one of the prescribed medications in Parkinson disease, is electrochemically determined here. A room temperature ionic liquid/graphene quantum dots (GQDs) modified carbon paste electrode (RTIL-GQDs/CPE) was used for the electrochemical determina
- Sanati, Afsaneh L.,Faridbod, Farnoush,Ganjali, Mohammad Reza
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p. 316 - 320
(2017/06/19)
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- Design and synthesis of novel hydroxypyridinone derivatives as potential tyrosinase inhibitors
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Two groups of novel hydroxypyridinone derivatives 6(a-e) and 12(a-c), were designed as potential tyrosinase inhibitors, and synthesized using kojic acid as a starting material. The tyrosinase inhibitory activity of these two groups was demonstrated to be potent, especially compounds 6e and 12a, whose IC50 values for monophenolase activity were 1.95 μM and 2.79 μM, respectively. Both of these values are lower than that of kojic acid (IC50 = 12.50 μM). Compounds 6e and 12a were investigated for the inhibitory effect on diphenolase activity. The results showed that the inhibitory mechanism of these two compounds was reversible and that the inhibitory type was a competitive-uncompetitive mixed-type. The values of IC50 of 6e and 12a on the diphenolase activity of tyrosinase were determined to be 8.97 μM and 26.20 μM, respectively. The inhibitory constants (KI and KIS) of 6e were determined as 17.17 μM and 22.09 μM, respectively; and the KI and KIS values of 12a were 34.41 μM and 79.02 μM, respectively. Compound 6e showed a greater ability to reduce copper and a stronger copper chelating ability than kojic acid.
- Zhao, De-Yin,Zhang, Ming-Xia,Dong, Xiao-Wu,Hu, Yong-Zhou,Dai, Xiao-Yan,Wei, Xiaoyi,Hider, Robert C.,Zhang, Jin-Chao,Zhou, Tao
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p. 3103 - 3108
(2016/06/13)
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- Synthesis and effects of oxadiazole derivatives on tyrosinase activity and human SK-MEL-28 malignant melanoma cells
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Melanin is a form of pigment that gives colour to human skin, hair and eyes. Whilst it protects against skin damage from the sun, accumulation of excessive amounts of epidermal melanin can lead to various dermatological disorders. This study aimed to evaluate the effects of three selected oxadiazoles on the o-diphenolase mushroom tyrosinase activity and their cytotoxic effects on SK-MEL-28 malignant melanoma cells. The results showed that compounds 1, 2 and 3 exhibited significant inhibition on the diphenolase activity of mushroom tyrosinase with IC50 values of 40.46 μM, 27.42 μM and 32.51 μM, respectively. Further kinetic studies revealed that compounds 1 (Ki = 3.8 μM) and 3 (Ki = 3.9 μM) exhibited a mixed-type inhibition while compound 2 (Ki = 0.7 μM) displayed a competitive-type inhibition as suggested by the Lineweaver-Burk plots. Molecular docking and dynamics simulations were also performed to understand the binding behaviour of compound 2 in the active site of tyrosinase. Finally, all three compounds displayed relatively low cytotoxicity to SK-MEL-28 cells up to 100 μM treatment via MTT assay.
- Fasihi Mohd Aluwi, Mohd Fadhlizil,Rullah, Kamal,Huan, Tan Huan,Meng, Chan Kok,Jie, Tan Si,Wei, Leong Sze,Mansor, Ahmad Hasnan,Yamin, Bohari M.,Wai, Lam Kok
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p. 72177 - 72184
(2016/08/09)
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- Highly sensitive voltammetric sensor based on NiO nanoparticle room temperature ionic liquid modified carbon paste electrode for levodopa analysis
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This paper describes the development of 1-methyl-3-butylimidazolium chloride ionic liquid-NiO nanoparticle modified carbon paste electrode (MBICl/NiO/NPs/CPE) for the voltammetric determination of levodopa (l-DOPA) in real samples. We describe the synthes
- Fouladgar, Masoud,Karimi-Maleh, Hassan,Gupta, Vinod Kumar
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- Reactivity of dinuclear copper(II) complexes towards melanoma cells: Correlation with its stability, tyrosinase mimicking and nuclease activity
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In this work, the influence of two new dinuclear copper(II) complexes in the viability of melanoma cells (B16F10 and TM1MNG3) was investigated, with the aim of verifying possible correlations between their cytotoxicity and their structure. One of the comp
- Nunes, Cléia Justino,Borges, Beatriz Essenfelder,Nakao, Lia Sumie,Peyroux, Eugénie,Hardré, Renaud,Faure, Bruno,Réglier, Marius,Giorgi, Michel,Prieto, Marcela Bach,Oliveira, Carla Columbano,Da Costa Ferreira, Ana M.
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- Mimicking hemoproteins: A new synthetic metalloenzyme based on a Fe(III)-mesoporphyrin functionalized by two helical decapeptides
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A new metalloenzyme formed by a Fe(III)-mesoporphyrin IX functionalized by two helical decapeptides was synthesized to mimic function and structural features of a hemoprotein active site. Each decapeptide comprises six 2-aminoisobutyric acid residues, whi
- Venanzi, Mariano,Cianfanelli, Sabrina,Palleschi, Antonio
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- Electrochemical determination of L-dopa in pharmaceutical samples using metallophtalocyanines modified carbon nanotubes paste electrodes
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Levodopa (L-dopa), the biological precursor of catecholamines, is the most widely prescribed drug in the treatment of Parkinson's disease. The present work presents an application of a carbon nanotubes paste electrode (CNTPE) modified with metallo-phthalo
- Andrei, Cristina-Cassiana,Bala, Daniela,Ciucu, Anton Alexandru,Ciurea, Ana,Mihailciuc, Constantin
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p. 835 - 843
(2015/06/30)
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- An efficient preparation of mulberroside a from the branch bark of mulberry and its effect on the inhibition of tyrosinase activity
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A bioactive ingredient in an ethanol extract from the branch bark of cultivated mulberry Husang-32 (Morus multicaulis Perr.) was isolated using a macroporous resin column. The primary component, which was purified by semi-preparative highperformance liqui
- Wang, Shu,Liu, Xian-Ming,Zhang, Jian,Zhang, Yu-Qing
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- Voltammetric analysis of the possibility of derivatization of levodopa in the presence of aniline derivatives
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Electrochemical oxidation of levodopa (LD) as one of the most well-known neurotransmitters has been studied in the presence of some aniline derivatives. The electron transfer of LD is followed by two competitive reactions in the presence of these amines.
- Khalafi, Lida,Rafiee, Mohammad,Khoshnam, Mojgan,Shoaei, Seyed Mohammad
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p. 1257 - 1262
(2013/11/06)
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- Investigating the selectivity of metalloenzyme inhibitors
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The inhibitory activity of a broad group of known metalloenzyme inhibitors against a panel of metalloenzymes was evaluated. Clinically approved inhibitors were selected as well as several other reported metalloprotein inhibitors in order to represent a broad range of metal binding groups (MBGs), including hydroxamic acid, carboxylate, hydroxypyridinonate, thiol, and N-hydroxyurea functional groups. A panel of metalloenzymes, including carbonic anhydrase (hCAII), several matrix metalloproteinases (MMPs), angiotensin converting enzyme (ACE), histone deacetylase (HDAC-2), and tyrosinase (TY), was selected based on their clinical importance for a range of pathologies. In addition, each inhibitor was evaluated for its ability to remove Fe3+ from holo-transferrin to gauge the ability of the inhibitors to access Fe 3+ from a primary transport protein. The results show that the metalloenzyme inhibitors are quite selective for their intended targets, suggesting that despite their ability to bind metal ions, metalloprotein inhibitors are not prone to widespread off-target enzyme inhibition activity.
- Day, Joshua A.,Cohen, Seth M.
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p. 7997 - 8007
(2013/11/06)
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- Kinetic characterisation of o-aminophenols and aromatic o-diamines as suicide substrates of tyrosinase
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We study the suicide inactivation of tyrosinase acting on o-aminophenols and aromatic o-diamines and compare the results with those obtained for the corresponding o-diphenols. The catalytic constants follow the order aromatic o-diamines max/KmS, follows this order: o-diphenols > o-aminophenols > aromatic o-diamines.
- Munoz-Munoz, Jose Luis,Garcia-Molina, Francisco,Berna, Jose,Garcia-Ruiz, Pedro Antonio,Varon, Ramon,Tudela, Jose,Rodriguez-Lopez, Jose N.,Garcia-Canovas, Francisco
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experimental part
p. 647 - 655
(2012/08/08)
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- Synthesis of novel 3,5-diaryl pyrazole derivatives using combinatorial chemistry as inhibitors of tyrosinase as well as potent anticancer, anti-inflammatory agents
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In the present article, we have synthesized a combinatorial library of 3,5-diaryl pyrazole derivatives using 8-(2-(hydroxymethyl)-1-methylpyrrolidin-3- yl)-5,7-dimethoxy-2-phenyl-4H-chromen-4-one (1) and hydrazine hydrate in absolute ethyl alcohol under the refluxed conditions. The structures of the compounds were established by IR, 1H NMR and mass spectral analysis. All the synthesized compounds were evaluated for their anticancer activity against five cell lines (breast cancer cell line, prostate cancer cell line, promyelocytic leukemia cell line, lung cancer cell line, colon cancer cell line) and anti-inflammatory activity against TNF-α and IL-6. Out of 15 compounds screened, 2a and 2d exhibited promising anticancer activity (61-73% at 10 μM concentration) against all selected cell lines and IL-6 inhibition (47% and 42% at 10 μM concentration) as in comparison to standard flavopiridol (72-87% inhibition at 0.5 μM) and dexamethasone (85% inhibition at 1 μM concentration), respectively. Cytotoxicity of the compounds checked using CCK-8 cell lines and found to be nontoxic to slightly toxic. Out of 15, four 3,5-diaryl pyrazole derivatives exhibiting potent inhibitory activities against both the monophenolase and diphenolase actions of tyrosinase. The IC50 values of compounds (2a, 2d, 2h and 2l) for monophenolase inhibition were determined to range between 1.5 and 30 μM. Compounds 2a, 2d, 2h and 2l also inhibited diphenolase significantly with IC50 values of 29.4, 21.5, 2.84 and 19.6 μM, respectively. All four 3,5-diaryl pyrazole derivatives were active as tyrosinase inhibitors (2a, 2d, 2h and 2l), and belonging to competitive inhibitors. Interestingly, they all manifested simple reversible slow-binding inhibition against diphenolase.
- Bandgar, Babasaheb P.,Totre, Jalinder V.,Gawande, Shrikant S.,Khobragade,Warangkar, Suchita C.,Kadam, Prasad D.
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experimental part
p. 6149 - 6155
(2010/09/15)
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- Selective determination of L-dopa in the presence of uric acid and ascorbic acid at a gold nanoparticle self-assembled carbon nanotube-modified pyrolytic graphite electrode
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Gold nanoparticle-functionalized carbon nanotubes (AuNP-CNT) have been prepared by a novel self-assembly method. The new material has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) and utilized for constructing Au
- Hu, Guangzhi,Chen, Long,Guo, Yong,Wang, Xiaolai,Shao, Shijun
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experimental part
p. 4711 - 4716
(2010/10/01)
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- Tyrosinase inactivation in its action on dopa
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Under aerobic or anaerobic conditions, tyrosinase undergoes a process of irreversible inactivation induced by its physiological substrate l-dopa. Under aerobic conditions, this inactivation occurs through a process of suicide inactivation involving the fo
- Mu?oz-Mu?oz,Acosta-Motos,Garcia-Molina,Varon,Garcia-Ruíz,Tudela,Garcia-Cánovas,Rodríguez-López
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experimental part
p. 1467 - 1475
(2011/12/01)
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- Tyrosinase inhibitory polyphenols from roots of Morus Ihou
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Twelve polyphenols (1-12) possessing tyrosinase inhibitory properties were isolated from the methanol (95%) extract of Morus Ihou. The isolated compounds consisted of four flavanones (1 -4), four flavones (5-8), and four phenylbenzofuranes (9-12). Moracin derivative 12 proved to be new a compound which was fully characterized. Compounds 1-12 were evaluated for both monophenolase and diphenolase (the two steps catalyzed by tyrosinase) inhibition to identify the structural characteristics required for mushroom tyrosinase inhibition. We observed that all parent compounds (1, 5, and 9) possessing an unsubstituted resorcinol group were highly effective inhibitors of monophenolase activity (IC50 values of 1.3, 1.2, and 7.4 μM). The potency of the inhibitors diminished with alkyl substitution on either the aromatic ring or the hydroxyl functions. Interestingly, flavone 5 was shown to possess only monophenolase inhibitory activity, but flavanone 1 and phenylbenzofuran 9 inhibited diphenolase as well as monophenolase significantly. The inhibitory mode of these species was also dependent upon the skeleton: phenylbenzofuran 9 manifested a simple competitive inhibition mode for monophenolase and diphenolase; on the other hand flavanone 1 (monophenolase, K3 = 0.1966 min-1 μM-1 k4= 0.0082 min ~1, and Kiapp = 0.0468 μM; diphenolase, k3 = 0.0014 min-1 μM-1 k4 = 0.0013 min-1, and Kiapp = 0.8996 μM) and flavone 5 both showed time-dependent inhibition against monophenolase. Compound 1 operated according to the simple reversible slow binding model whereas compound 5 operated under the enzyme isomerization model.
- Jeong, Seong Hun,Ryu, Young Bae,Curtis-Long, Marcus J.,Ryu, Hyung Won,Baek, Yoon Su,Kang, Jae Eun,Lee, Woo Song,Park, Ki Hun
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experimental part
p. 1195 - 1203
(2010/06/14)
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- Stereospecificity of mushroom tyrosinase immobilized on a chiral and a nonchiral support
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Mushroom tyrosinase was immobilized from an extract onto glass beads covered with the cross-linked totally cinnamoylated derivates of D-sorbitol (sorbitol cinnamate) and glycerine (glycerine cinnamate). The enzyme was immobilized onto the support by direct adsorption, and the quantity of immobilized tyrosinase was higher for sorbitol cinnamate, the support with the higher number of esterified hydroxyls per unit of monosacharide, than for glycerine cinnamate. The results obtained from the stereospecificity study of the monophenolase and diphenolase activity of immobilized mushroom tyrosinase are reported. The enantiomers L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, DL-α-methyldopa, L-isoprenaline, DL-isoprenaline, L-adrenaline, DL-adrenaline, L-noradrenaline, and D-noradrenaline were assayed with tyrosinase immobilized on a chiral support (sorbitol cinnamate), whereas L-tyrosine, DL-tyrosine, D-tyrosine, L-dopa, DL-dopa, D-dopa, L-α-methyldopa, and DL-α-methyldopa were assayed with tyrosinase immobilized on a nonchiral support (glycerine cinnamate). The same Vmaxapp values for each series of enantiomers were obtained. However, the Kmapp values were different, the L isomers showing lower values than the DL isomers, whereas the highest K mapp value was obtained with D isomers. No difference was observed in the stereospecificity of tyrosinase immobilized on a chiral (sorbitol cinnamate) or nonchiral (glycerine cinnamate) support.
- Marin-Zamora, Maria Elisa,Rojas-Melgarejo, Francisco,Garcia-Canovas, Francisco,Garcia-Ruiz, Pedro Antonio
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p. 4569 - 4575
(2008/02/09)
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- Metallo-ROS in Alzheimer's disease: Oxidation of neurotransmitters by CuII-β-amyloid and neuropathology of the disease
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A clear mind: The CuII-β-amyloid (Aβ) complex has been shown to exhibit enzyme-like metal-centered oxidative and hydroxylation catalyses. Metal-centered oxidation of various neurotransmitters by CuAβ under biomimetic conditions has verified the bio-relevance of the metal-centered catalyses and is expected to provide a chemical basis for the better understanding of the etiology of Alzheimer's disease. ROS = reactive oxygen species. (Figure Presented).
- Da Silva, Giordano F. Z.,Ming, Li-June
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p. 3337 - 3341
(2008/03/12)
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- Probing biocatalytic transformations with CdSe-ZnS QDs
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CdSe/ZnS QDs enable the optical probing of the biocatalytic oxidation of tyrosine derivatives and of the scission of peptides by thrombin. CdSe/ZnS QDs were modified with tyrosine methyl ester or with a tyrosine-containing peptide. The tyrosine units were reacted with tyrosinase/O2 to yield the respective l-DOPA and quinone derivatives. The luminescence of QDs modified by the enzyme-generated quinone units is quenched. The quinone-functionalized peptide associated with the QDs was cleaved by thrombin, a process that restored the luminescence of the QDs. Copyright
- Gill, Ron,Freeman, Ronit,Xu, Jian-Ping,Willner, Itamar,Winograd, Shira,Shweky, Itzik,Banin, Uri
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p. 15376 - 15377
(2007/10/03)
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- Protection of mesopore-adsorbed organic matter from enzymatic degradation
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Synthetic mesoporous alumina and silica minerals with uniform pore geometries, and their nonporous analogues, were used to test the role of mineral mesopores (2-50 nm diameter) in protecting organic matter from enzymatic degradation in soils and sediments
- Zimmerman, Andrew R.,Chorover, Jon,Goyne, Keith W.,Brantley, Susan L.
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p. 4542 - 4548
(2007/10/03)
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- Models for biological trinuclear copper clusters. Characterization and enantioselective catalytic oxidation of catechols by the copper(II) complexes of a chiral ligand derived from (S)-(-)-1,1'-binaphthyl-2,2'-diamine.
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The dinuclear and trinuclear Cu(II) complexes of an octadentate ligand derived from (S)-1,1'-binaphthyl-2,2'-diamine have been prepared and characterized by UV/Vis, CD, EPR and NMR spectroscopy. The ligand contains two tridentate aminobis(benzimidazole) d
- Mimmi, Maria Chiara,Gullotti, Michele,Santagostini, Laura,Battaini, Giuseppe,Monzani, Enrico,Pagliarin, Roberto,Zoppellaro, Giorgio,Casella, Luigi
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p. 2192 - 2201
(2007/10/03)
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- Synthesis of N-substituted N-nitrosohydroxylamines as inhibitors of mushroom tyrosinase
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A series of N-substituted N-nitrosohydroxylamines including six new compounds were synthesized and examined for inhibition of mushroom tyrosinase. Corresponding hydroxylamines were reacted with n-butyl nitrite to give substituted nitrosohydroxylamines as their ammonium salt. The N-substituted hydroxylamines were prepared from the primary amines via the oxaziridine, or from the carbonyl compounds via the oxime. Most of the nitrosohydroxylamines tested inhibited mushroom tyrosinase. Among them, N-cyclopentyl-N-nitrosohydroxylamine exhibited the most potent activity (IC50=0.6 μM), as powerful as that of tropolone, one of the most powerful inhibitors. As removal of nitroso or hydroxyl moiety, the enzyme inhibitory activity was completely diminished. Both N-nitroso group and N-hydroxy group were suggested to be essential for the activity, probably by interacting with the copper ion at the active site of the enzyme. Lineweaver-Burk plotting showed that cupferron was a competitive inhibitor but that N-cyclopentyl-N-nitrosohydroxylamine was not.
- Shiino, Mitsuhiro,Watanabe, Yumi,Umezawa, Kazuo
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p. 1233 - 1240
(2007/10/03)
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- Oxidation of 3-(3,4-dihydroxy phenyl)-L-alanine (levodopa) and 3-(3,4,dihydroxy phenyl)-2-methyl-L-alanine (methyl dopa) by manganese(III) in pyrophosphate media: Kinetic and mechanistic study
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Manganese(III) (Mn(III)) has been stabilized in weakly acidic solution by means of pyrophosphate and the nature of the complex was elucidated spectrophotometrically. Stoichiometry of Mn(III)-oxidation of levodopa and methyl dopa in pyrophosphate medium wa
- Sherigara,Kumara Swamy,Subrahmanyam,Ishwar Bhat
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p. 449 - 457
(2007/10/03)
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- Oxidation of benzenediols by hexabromoiridate(IV): Kinetics at ambient and elevated pressures
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The kinetics of oxidation of several benzenediols by the hexabromoiridate(IV) ion have been studied spectrophotometrically by the stopped-flow method. In 0.010 mol dm-3 HClO4 and an ionic strength of 0.10 mol dm-3 (NaClO4) at 25.0°C the second-order rate constants (the reaction is first order in each reactant concentration), vary from 1.26 × 102 to 9.3 × 104 dm3 mol-1 s-1. The enthalpies of activation range from about 44 kJ mol-1 for the slowest reacting substrate to about 20 kJ mol-1 for the faster reactions. The ΔS? values do not vary over a wide range; the reaction rates are governed more by the enthalpy barrier. Application of pressure (up to 125 MPa) causes significant rate accelerations, giving rise to ΔV? values in the -17 to -26 cm3 mol-1 range, consistent with the large, negative ΔS? values. This indicates that the rate limiting step is largely characterised by an increase in species ordering and electrostriction, and in the present case slightly less than for the corresponding reactions with the less bulky hexachloroiridate(IV) ion.
- Ciosto, Cornelia,Bajaj, Hari C.,Van Eldik, Rudi,Hubbard, Colin D.
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p. 1503 - 1507
(2007/10/03)
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- Selective inhibition of Src protein tyrosine kinase by analogues of 5- S-glutathionyl-β-alanyl-L-dopa
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Twelve analogues of the antibacterial phenolic peptide 5-S- glutathionyl-β-alanyl-L-dopa (5-S-GA-L-D: 1) were synthesized via orthoquinones using tyrosinase. Several synthesized compounds inhibited the v-Src autophosphorylation tyrosine kinase reaction with an IC50 value comparable to that of herbimycin. The inhibition of c-Src substrate phosphorylation was much less active than v-Src autophosphorylation inhibition. The analogues showed no effects on substrate phosphorylation by epidermal growth factor receptor (EGFR), and this selectivity is the most characteristic feature of the analogues (1-12).
- Zheng, Zhe-Bin,Nagai, Sachie,Iwanami, Naoko,Kobayashi, Ayako,Hijikata, Mariko,Natori, Shunji,Sankawa, Ushio
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p. 1950 - 1951
(2007/10/03)
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- Screening test for insecticides interfering with cuticular sclerotization
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The potential of known and new insecticides to interfere with cuticle sclerotization was investigated using assays for key enzymes such as phenoloxidase, quinone methide isomerase and DOPA decarboxylase. Homogenates from the blowfly Lucilia cuprina and from the epithelial cell line from Chironomus tentans were used to examine the compounds under investigation. Phenoloxidases are known to oxidize DOPA, the substrate for DOPA decarboxylase. Since phenoloxidases were not detectable in C. tentans cell homogenates, inhibitor and kinetic studies were done for comparison with DOPA decarboxylase of this insect cell line. DOPA decarboxylase and phenoloxidase of L. cuprina exerted highest specific activities at early pupal stages (day 7). The apparent K(m) values for the two enzymes were 0.47(±0-21) mM and 0.71(±0.16) mM, respectively, using L-DOPA as substrate. DOPA decarboxylase from C. tentans had a K(m) value of 0.42(±0.18) mM. Quinone methide isomerase was most active in young pupae. In terms of substrate specificity for enzymic (mushroom-tyrosinase) production of different quinones from their corresponding catechols, that with dopamine quinone proved to be the most efficient. Synthesis of derivatives of L-DOPA and L-tyrosine led to a compound which inhibited both phenoloxidase and quinone methide isomerase. DOPA decarboxylase from L. cuprina and from cells of C. tentans was inhibited by carbidopa (IC50 values of 0.021(±0.011) μM and 0.031(±0.019) μM, respectively) and indomethacine (IC50 values of 22.6(±7.1) μM and 18.8(±9.7) μM). Both compounds exerted a competitive type of inhibition and were able to interfere with development of L. cuprina.
- Londershausen,Turberg,Spindler-Barth,Peter
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p. 315 - 323
(2007/10/03)
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- Role of Azide Concentration in Pulse Radiolysis Studies of Oxidation: 3,4-Dihydroxyphenylalanine
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The radiolysis of aqueous solutions of 3,4-dihydroxyphenylalanine (dopa) using N3 as a one-electron oxidant leads to the formation of dopasemiquinone and, successively, dopaquinone and dopachrome.It is now shown that under pH conditions where significant protonation of N3(1-) to HN3 occurs, dopachrome formation is supressed, probably due predominantly to addition of HN3 to dopaquinone.The possibility of such nucleophilic reactions occuring needs to be considered in studies of quinone intermediates generated using N3 as oxidant.
- Lambert, Chris,Truscott, T. George,Land, Edward J.,Riley, Patrick A.
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p. 2939 - 2942
(2007/10/02)
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- TRANSITION STATE EFFECTS IN STEREOSELECTIVE ELECTRON-TRANSFER REACTIONS
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Electron-transfer between optically active catecholamines and iron(III) complex ions bound to sodium poly(L-glutamate) or poly(D-glutamate) has been studied at pH 7.Remarkable stereoselective effects - corresponding to an enantiomeric excess as high as 65percent - have been observed when structurally ordered and partially shielded reaction centres prevent easy approach for redox partners.Steady-state kinetic data show that stereoselectivity is chiefly controlled by transition state effects.A hypothetical model of the diastereomeric non-covalent electron-transfer complexes has been constructed by conformational energy calculations.The models are consistent with a number of experimental findings and support the hypothesis that chiral discrimination is coupled with a remote attack mechanism on the central metal ion where oxidant-reductant interactions are mediated by the orderd polypeptide matrices.Relevance of solvent reorganization energy changes associated with the diastereomeric charge-transfer steps in the observed phenomena is briefly discussed.
- Pispisa, Basilio,Palleschi, Antonio,Paradossi, Gaio,Chiavarini, Salvatore
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p. 423 - 430
(2007/10/02)
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- Stereoselective Electrone Transfer between Chiral Catecholamines and Iron(III) Complex Ions Anchored to Asymmetric Polymers. A Kinetic and Conformational Investigation
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The oxydation of L-dopa (3,4-dihydroxyphenylalanine) and L-adrenaline (epinephrine) by + complex ions anchored to poly(L-glutamate) (FeTL) or poly(D-glutamate) (FeTD) was studied at pH 7 (tetpy = 2,2':6',2'':6'',2'''-tetrapyridy
- Pispisa, Basilio,Palleschi, Antonio,Barteri, Mario,Nardini, Stefanella
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p. 1767 - 1775
(2007/10/02)
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- Early Steps in the Free Radical Polymerisation of 3,4-Dihydroxyphenylalanine (Dopa) into Melanin
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Pulse radiolysis and flash photolysis-initiated one-electron oxidation of 3,4-dihydroxyphenylalanine (dopa) and other catecholamines have allowed the direct measurement of the kinetics of semiquinone disproportionation leading successively to the corresponding melanin precursors dopaquinones and dopachromes.
- Chedekel, Miles R.,Land, Edward J.,Thompson, Ambler,Truscott, T. George
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p. 1170 - 1172
(2007/10/02)
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- Method of preparing aldehydes
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A novel method for preparing substituted actaldehydes comprising subjecting a specific sulfoxide derivative to an acidic hydrolysis.
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