102-32-9Relevant articles and documents
Hydroxylation of p-substituted phenols by tyrosinase: Further insight into the mechanism of tyrosinase activity
Munoz-Munoz, Jose Luis,Berna, Jose,Garcia-Molina, Maria del Mar,Garcia-Molina, Francisco,Garcia-Ruiz, Pedro Antonio,Varon, Ramon,Rodriguez-Lopez, Jose N.,Garcia-Canovas, Francisco
, p. 228 - 233 (2012)
A study of the monophenolase activity of tyrosinase by measuring the steady state rate with a group of p-substituted monophenols provides the following kinetic information: kcatm and the Michaelis constant, KMm. Analysis of these data taking into account chemical shifts of the carbon atom supporting the hydroxyl group (δ) and σp+, enables a mechanism to be proposed for the transformation of monophenols into o-diphenols, in which the first step is a nucleophilic attack on the copper atom on the form Eox (attack of the oxygen of the hydroxyl group of C-1 on the copper atom) followed by an electrophilic attack (attack of the hydroperoxide group on the ortho position with respect to the hydroxyl group of the benzene ring, electrophilic aromatic substitution with a reaction constant ρ of -1.75). These steps show the same dependency on the electronic effect of the substituent groups in C-4. Furthermore, a study of a solvent deuterium isotope effect on the oxidation of monophenols by tyrosinase points to an appreciable isotopic effect. In a proton inventory study with a series of p-substituted phenols, the representation of kcatfn/kcatf0 against n (atom fractions of deuterium), where kcatfn is the catalytic constant for a molar fraction of deuterium (n) and kcatf0 is the corresponding kinetic parameter in a water solution, was linear for all substrates. These results indicate that only one of the proton transfer processes from the hydroxyl groups involved the catalytic cycle is responsible for the isotope effects. We suggest that this step is the proton transfer from the hydroxyl group of C-1 to the peroxide of the oxytyrosinase form (Eox). After the nucleophilic attack, the incorporation of the oxygen in the benzene ring occurs by means of an electrophilic aromatic substitution mechanism in which there is no isotopic effect.
A kinetic investigation of the pulmonary metabolism of dopamine in rats shows marked differences compared with noradrenaline
Scarcella,Bryan-Lluka
, p. 491 - 499 (1995)
The aim of this study was to investigate the deamination of dopamine in the intact pulmonary circulation of isolated lungs of the rat. The first part of the study showed that dopamine is not converted to noradrenaline by dopamine-β-hydroxylase (DBH) when dopamine is perfused through isolated lung preparations with monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) inhibited. Hence, it was not necessary to inhibit DBH in subsequent experiments. The metabolite profile for deamination of dopamine in the lungs was examined by determining whether MAO and semicarbazide-sensitive amine oxidases (SSAO) contribute to the deamination of dopamine (and noradrenaline), and by determining the activity of MAO (k(MAO)) for the metabolism of dopamine. Lungs were perfused with 1 nmol/l 3H-dopamine or 3H-noradrenaline with COMT inhibited and, in experiments to determine the contribution of SSAO to deamination, with MAO inhibited. Inhibition of MAO reduced the deamination of dopamine and noradrenaline by 99.8% and 98.6%, respectively, indicating that MAO, and not SSAO, was responsible for deamination of the catecholamines in the lungs. The k(MAO) value for deamination of dopamine was 3.89 min-1. Further experiments were carried out to determine the contributions of MAO-A and MAO-B to the deamination of dopamine in lungs perfused with 1 nmol/l3H-dopamine and 100 nmol/l lazabemide or 300 nmol/l Ro41-1049, respectively. The values of k(MAO-A) and k(MAO-B) were 3.05 min-1 and 0.626 min-1, respectively.
A Heterogeneous Recyclable Rhodium-based Catalyst for the Reduction of Pyridine Dinucleotides and Flavins
Deng, Yifan,Odziomek, Mateusz,Sanchez, Clement,Back, Olivier,Mougel, Victor,Fontecave, Marc
, p. 1236 - 1243 (2020)
Reduced pyridine nucleotides and flavins are important enzyme cofactors that require continuous regeneration for biotechnological development of the corresponding enzymes. This can be achieved with the assistance of a dehydrogenase system or by reduction with formate catalysed by a soluble organometallic {[Cp*Rh(bpy)(H2O)]2+} (Cp=pentamethylcyclopentadienyl; bpy=bipyridine) complex. Here, we report that this Rh complex, once immobilized on bypiridine-periodic mesoporous organosilica, displays catalytic activity for flavin (including FAD, FMN and riboflavin) and NAD(P)+ reduction by formate. The recyclability of this solid catalyst makes it possible to achieve up to 20 cycles of FAD reduction without activity loss. This recyclable heterogeneous catalyst can also be used to assist a complex NADH-, FAD- and O2-dependent monooxygenase system, allowing several cycles of transformation of a phenol into the corresponding catechol.
Bioavailability and pharmacokinetics of an oral dopamine prodrug in dogs.
Murata,Noda,Kohno,Samejima
, p. 812 - 814 (1989)
The bioavailability and pharmacokinetics of an oral dopamine prodrug, N-(N-acetyl-L-methionyl)O,O-bis(ethoxycarbonyl)dopamine (1), were examined in dogs, and the mechanism of its absorption and bioactivation was discussed. Compound 1 showed a plasma dopamine concentration that was several times higher than that of dopamine (DA) following oral administration to dogs, while the plasma concentrations of dopamine-30-sulfate (DA-SO4) and 3,4-dihydroxyphenylacetic acid (DOPAC) are lower in comparison with that of DA. The conversion of 1 to DA occurred in proportion to the dose administered. Compound 1 also showed a plasma DA concentration that was several times higher than that of other DA prodrugs reported hitherto. In dog plasma, in vitro, 1 was converted to its deethoxycarbonylated form, N-(N-acetyl-L-methionyl)dopamine (2), while other related compounds, N-(L-methionyl)dopamine (3), N-(L-methionyl)O,O-bis(ethoxycarbonyl)-dopamine (4), and O,O-bis(ethoxycarbonyl)dopamine (5), were rapidly converted to DA (however, 2 was stable in plasma). Bioavailability, based on the AUC of DA, 1, 2, and 5 following oral administration to dogs, increased in the following order: 1, 2, 5, and DA. Thus, it was shown that the two protective groups introduced in 1 served to reduce the first-pass metabolism of the DA moiety in the absorption process. It was also confirmed that 1 is converted to 2 or DA in blood, liver, and intestine.
Toward a high added value compound 3, 4-dihydroxyphenylacetic acid by electrochemical conversion of phenylacetic acid
Trabelsi, Souhel Kallel,Dridi Gargouri, Olfa,Gargouri, Boutheina,Abdelhèdi, Ridha,Bouaziz, Mohamed
, p. 370 - 376 (2015)
Abstract The development of the effective procedure to recover the potentially high-added-value phenolic compound, 3,4-dihydroxyphenylacetic acid (3,4-DHPAA) was investigated using electrochemical conversion of phenylacetic acid (PAA). The proposed mechanism is based on the hypothesis of two-electron oxidation of PAA molecule leading to 3-hydroxyphenyl acetic acid. The latter underwent a second bi-electronic transfer by means of a radical cation, thus leading to the formation of the 2,5 dihydroxyphenylacetic (2,5-DHPAA) acid and 3,4-DHPAA as major products. The 3,4-DHPAA was synthesized by anodic oxidation of PAA at lead dioxide electrode and identified by cyclic voltammetry and spectrophotometry UV-visible. It was also confirmed by mass spectrophotometry using LC-MS/MS apparatus. According to their voltammetric behavior during electrolysis, the oxidation potential of 3,4-DHPAA was lower than that of PAA. The antioxidant activity was measured by DPPH assay, showing that the strongest antiradical activity was detected when the 3,4-DHPAA concentration was higher during electrolysis experiments.
Novel mild synthesis of high-added-value p -hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid using the acidic clay/hydrogen peroxide catalytic system
Bouguerra Neji, Soumaya,Azabou, Samia,Contreras, Sandra,Medina, Francisco,Bouaziz, Mohamed
, p. 285 - 291 (2016)
Acid-activated clays KSF and KSF/0 were successfully used in the hydrogen peroxide conversion of phenyl acetic acid to high-added phenolic compounds: p-hydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid, endowed with a powerful antioxidant capacity. The catalytic conversion enhancement could be correlated to the total surface acidity and the high iron content of the catalysts KSF/0 and KSF, respectively. The synthetic route described here was conducted under mild conditions with very low degree of mineralization and without significant Fe ion leaching observations. The synthesis reaction is operationally simple and could find application for industrial purposes.
Acidity and stability of 10-substituted 1,8-dihydroxy-9(10H)-anthracenones
Muller,Gawlik,Wiegrebe
, p. 359 - 362 (1995)
The decomposition of 10-substituted anthralin derivatives in dimethyl sulfoxide and ethanol was determined. While 10-ω-phenylalkylidene derivatives were thoroughly stable, 10-ω-phenylacyl-substituted compounds were slowly degraded to danthron and the corresponding carboxylic acids. However, the stability of these derivatives was markedly improved as compared to that of anthralin. Determination of the pK(a) values showed that the ω-phenylacyl derivatives were somewhat stronger acids than anthralin, while ω-phenylalkylidene-substitution generally leaves the acidity of the anthralin part unchanged.
Tyrosinase catalyzed production of 3,4-dihydroxyphenylacetic acid using immobilized mushroom (Agaricus bisporus) cells and in situ adsorption
Kampmann, Markus,Riedel, Natascha,Mo, Yee Li,Beckers, Laura,Wichmann, Rolf
, p. 113 - 121 (2016)
3,4-Dihydroxyphenylacetic acid (DHPAA), a catechol derivative with proposed beneficial human health applications, was synthesized in this work from 4-hydroxyphenylacetic acid (HPAA) using an unpurified, tyrosinase-containing, cell preparation from the fruiting body of the edible mushroom Agaricus bisporus which were immobilized in silica alginate matrix capsules. The formation of DHPAA was equimolar to the conversion of HPAA, as long as ascorbic acid was present in amounts sufficient for reduction of o-quinones generated by oxidation of DHPAA. With a concentration of 5 mM HPAA and 5, 10, or 25 mM ascorbic acid, the maximum yields of DHPAA were 26, 36, or 56%, respectively. When aluminum oxide, pretreated with ammonium acetate, was added for an in situ adsorption of DHPAA, the yield obtained with 5 or 10 mM ascorbic acid was increased to 42 or 52%, respectively, with a reaction time reduced by ～25%. In contrast to experiments without in situ adsorption, the yield remained almost constant after depletion of ascorbic acid. After desorption, the concentration of DHPAA in the eluent was up to 32 times higher than the concentration of HPAA. The results presented here will be useful for the design of production and purification processes for DHPAA.
BIOISPIRED PROTEASOME ACTIVATORS WITH ANTIAGEING ACTIVITY
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Page/Page column 8; 20, (2019/10/01)
The present invention relates to novel bio-inspired hybrid compounds of formula I which act as proteasome activators and exhibit anti-ageing activity, as well as methods for their synthesis. These hybrid compounds combine the structural features of hydroxytyrosol and the natural antioxidant vitamin E or its bioisosteres in one molecular scaffold. The compounds of formula I, which include structural proteasome activators (activation by stereochemical interaction), can be used in the production of anti-ageing products, such as cosmetic preparations. Additionally, they can be used in conditions and diseases where the proteasome is down-regulated, as well as proteasome-activation control compounds.
Synthesis and biological evaluation of 3-arylcoumarins as potential anti-Alzheimer's disease agents
Yang, Jie,Zhang, Pingping,Hu, Yuheng,Liu, Teng,Sun, Jie,Wang, Xiaojing
, p. 651 - 656 (2019/02/19)
Alzheimer's disease, a neurodegenerative illness, has the extremely complex pathogenesis. Accumulating evidence indicates there is a close relationship between several enzymes and Alzheimer's disease. Various substituted 3-arylcoumarin derivatives were synthesised, and their in vitro activity, including cholinesterase inhibitory activity, monoamine oxidase inhibitory activity, and antioxidant activity were investigated. Most of the compounds exhibited high activity; therefore 3-arylcoumarin compounds have the potential as drug candidates for the treatment of Alzheimer's disease.
