18920-62-2Relevant academic research and scientific papers
Tunneling effect in regeneration reaction of vitamin e by ubiquinol
Ouchi, Aya,Nagaoka, Shin-Ichi,Mukai, Kazuo
, p. 6601 - 6607 (2010)
A kinetic study of the regeneration reaction of vitamin E by ubiquinol was carried out by means of double-mixing stopped-flow spectroscopy. A substantial deuterium kinetic-isotope effect was observed on the second-order rate constant and the activation energy. In the regeneration reaction of α-tocopherol, deuteration of ubiquinol increased and decreased the activation energy and the second-order rate constant by 6.1 kJ/mol and a factor of 18.3, respectively. From this result, it is considered that proton tunneling plays an important role in the regeneration reaction of vitamin E by ubiquinol. The conditions under which the tunneling effect becomes an important factor were discussed in conjunction of our experimental results.
Rate constants for hydrogen atom abstraction by α-tocopheroxyl radical from lipid, hydroperoxide and ascorbic acid
Watanabe, Akira,Noguchi, Noriko,Takahashi, Mareyuki,Niki, Etsuo
, p. 613 - 614 (1999)
The rate constants for each reaction of α-tocopheroxyl radical with methyl linoleate, t-butyl hydroperoxide and ascorbic acid, and also the bimolecular reaction of α-tocopheroxyl radicals were measured by a stopped-flow ESR technique in order to understand the antioxidant action of α-tocopherol. It was suggested that α-tocopheroxyl radical is primarily reduced by ascorbic acid in vivo.
Antioxidative effects of flavonols and their glycosides against the free-radical-induced peroxidation of linoleic acid in solution and in micelles
Zhou, Bo,Miao, Qing,Yang, Li,Liu, Zhong-Li
, p. 680 - 691 (2005)
The antioxidative effect of flavonols and their glycosides against the peroxidation of linoleic acid has been studied in homogeneous solution (tBuOH/H2O, 3:2) and in sodium dodecyl sulfate and cetyl trimethylammonium bromide micelles. The peroxidation was initiated thermally by the water-soluble initiator 2,2′-azobis(2-methyl-propionamidine) dihydrochloride, and the reaction kinetics were studied by monitoring the formation of linoleic acid hydroperoxides. The synergistic antioxidant effect of the flavonols with α-tocopherol (vitamin E) was also studied by following the decay kinetics of α-tocopherol and the α-tocopheroxyl radical. Kinetic analysis of the antioxidative process demonstrates that the flavonols are effective antioxidants in solution and in micelles, either alone or in combination with α-tocopherol. The antioxidative action involves trapping the initiating radicals in solution or in the bulk-water phase of the micelles, trapping the propagating lipid peroxyl radicals on the surface of the micelles, and regenerating α-tocopherol by reducing the α-tocopheroxyl radical. It was found that the antioxidant activity of the flavonols and their glycosides depends significantly on the position and number of the hydroxy groups, the oxidation potential of the molecule, and the reaction medium. The flavonols bearing ortho-dihydroxy groups possess significantly higher antioxidative activity than those without such functionalities, and the glycosides are less active than their parent aglycones. The activity of the flavonols is higher in micelles than in solution, while the activity of α-tocopherol is lower in micelles than in solution. This is because the predominant factor for controlling the activity is the hydrogen-bonding interaction of the antioxidant with the micellar surface in the case of hydrophilic flavonols, while it is the inter- and intramicellar diffusion in the case of lipophilic α-tocopherol.
Catalytic performance of nanoscopic, aluminium trifluoride-based catalysts in the synthesis of (all-rac)-α-tocopherol
Coman,Wuttke,Vimont,Daturi,Kemnitz
, p. 2517 - 2524 (2008)
A novel nanoscopic, partly hydroxylated aluminium fluoride was prepared in a sol-gel fluorination synthesis and characterised by IR probe molecules. It was shown that this material has, in contrast to high surface area aluminium fluoride (HSAlF3) which is one of the strongest Lewis acids, a low amount of strong Lewis acid sites combined with weak and medium strength Br?nsted sites. Both materials were tested in the synthesis of (all-rac)-α-tocopherol through the condensation of 2,3,6- trimethylhydroquinone (TMHQ) with isophytol (IP). The activity data indicate the partly hydroxylated aluminium fluoride to be a very efficient and highly selective catalyst for (all-rac)-α-tocopherol (>99.9%, for an IP conversion of 100%) whereas high surface area aluminium fluoride is a poor catalyst for this reaction.
Synthesis of triphenylphosphonium Vitamin E derivatives as mitochondria-targeted antioxidants
Jameson, Victoria J.A.,Cochemé, Helena M.,Logan, Angela,Hanton, Lyall R.,Smith, Robin A.J.,Murphy, Michael P.
, p. 8444 - 8453 (2015)
A series of mitochondria-targeted antioxidants comprising a lipophilic triphenylphosphonium cation attached to the antioxidant chroman moiety of vitamin E by an alkyl linker have been prepared. The synthesis of a series of mitochondria-targeted vitamin E derivatives with a range of alkyl linkers gave compounds of different hydrophobicities. This work will enable the dependence of antioxidant defence on hydrophobicity to be determined in vivo.
Novel sol-gel synthesis of acidic MgF2-x(OH)x materials
Wuttke, Stefan,Coman, Simona M.,Scholz, Gudrun,Kirmse, Holm,Vimont, Alexandré,Daturi, Maro,Schroeder, Sven L. M.,Kemnitz, Erhard
, p. 11488 - 11499 (2008)
Novel magnesium fluorides have been prepared by a new fluorolytic sol-gel synthesis for fluoride materials based on aqueous HF. By changing the amount of water at constant stoichiometric amount of HF, it is possible to tune the surface acidity of the resulting partly hydroxylated magnesium fluorides. These materials possess medium-strength Lewis acid sites and, by increasing the amount of water, Br?nsted acid sites as well. Magnesium hydroxyl groups normally have a basic nature and only with this new synthetic route is it possible to create Br?nsted acidic magnesium hydroxyl groups. XRD, MAS NMR, TEM, thermal analysis, and elemental analysis have been applied to study the structure, composition, and thermal behaviour of the bulk materials. XPS measurements, FTIR with probe molecules, and the determination of N 2/Ar adsorption-de-sorption isotherms have been carried out to investigate the surface properties. Furthermore, activity data have indicated that the tuning of the acidic properties makes these materials versatile catalysts for different classes of reactions, such as the synthesis of (all-rac)-[α]-tocopherol through the condensation of 2,3,6- trimethylhydroquinone (TMHQ) with isophytol (IP).
A short route to α-tocopherol
Liu, Kegang,Chougnet, Antoinette,Woggon, Wolf-D.
, p. 5827 - 5829 (2008)
(Chemical Equation Presented) Short and sweet: A simple and practical route to α-tocopherol is described (see scheme; TES=triethylsilyl). The key step is a remarkably diastereoselective domino aldol/oxa-Michael reaction, which is promoted by proline derivative 1.
Synthesis of 2,2-dialkyl chromanes by intramolecular Ullmann C–O coupling reactions toward the total synthesis of D-α-tocopherol
Tsubogo, Tetsu,Aoyama, Saki,Takeda, Rika,Uchiro, Hiromi
, p. 843 - 846 (2018)
The complete synthesis of D-α-tocopherol was achieved using our developed-Ullmann C–O coupling reaction as a key reaction. The synthesis of the core structure of D-α-tocopherol, which is a chiral chromane, has never been reported using intramolecular Ullmann C–O coupling reactions owing to the low reactivity of electron-rich iodoarenes with tertiary alcohols. Because the developed intramolecular C–O coupling reactions prefer electron-rich iodoarenes with tertiary alcohols, we successfully synthesized the chiral chromane core and achieved the total synthesis of D-α-tocopherol.
D,L-α-tocopherol synthesis catalyzed by the Bronsted acidic ionic liquids
Xing, Huabing,Wang, Tao,Zhou, Zhenhuan,Dai, Youyuan
, p. 2433 - 2439 (2006)
The synthesis of D,L-α-tocopherol from trimethylhydroquinone and isophytol using the Bronsted acidic SO3H-functionalized ionic liquids as catalysts was explored. The catalytic activities of the SO 3H-functionalized ionic liquids were dependent on their anions. The yield of D,L-α-tocopherol also depended on the solvent, which was the reaction medium. A yield of 94.3% was obtained using the SO3H- functionalized ionic liquid with [BF4-] anion as catalyst in propylene carbonate/heptane. The reaction mixture exhibited good biphasic behaviors, so that the produced D,L-α-tocopherol could be separated by decantation. The SO3H-functionalized ionic liquids could be reused after the removal of water. Copyright Taylor & Francis Group, LLC.
Zinc catalyst recycling in the preparation of (all-rac)-α-tocopherol from trimethylhydroquinone and isophytol
Goemoery, Juraj,Kralik, Milan,Kaszonyi, Alexander
, p. 427 - 436 (2011)
Recycling of ZnCl2 as a catalyst in the cyclocondensation of trimethylhydroquinone and isophytol to all-rac-a-tocopherol was studied. ZnCl2 was recycled at over 98 % efficiency in required purity by repeated extraction of the reaction streams with water, followed by switching of solvent to butyl acetate and then back to water. Recycled ZnCl2 had no negative effect on the yield of all-rac-a- tocopherol (maintaining over 90 %) at nearly total conversion of isophytol and only a 3 % molar excess of trimethylhydroquinone.
