X-Ray Crystallographic Studies of Vitamin E Derivatives. Relationship between Antioxidant Activity and Molecular Structure

Mukai, Kazuo; Ohbayashi, Shigeru; Nagaoka, Shin‐ichi; Ozawa, Takehiro; Azuma, Nagao

doi:10.1246/bcsj.66.3808

Cited by 11 publications

(6 citation statements)

References 21 publications

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“…The room temperature crystal structures of compounds 6 and 7 have been previously determined by other authors, but the structure data deposited at The Cambridge Crystallographic Data Centre need a correction in the case of 6 (CCDC refcode WELHAW; a -axis and b -axis were erroneously interchanged) and nonstandard unit cell settings for 6 and 7 (CCDC refcode WELHEA) were used in addition.…”

Section: Methodsmentioning

confidence: 99%

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

et al. 2007

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In contrast to the alpha-form permethylated at the aromatic ring, non-alpha-tocopherols possess free aromatic ring positions which enable them to act as potent scavengers of electrophiles in vivo and in vitro. In preparation of enzymatic studies involving peroxynitrite and other nitrating systems, the behavior of non-alpha-tocopherols under nitration conditions was studied. The nitration products of beta-, gamma-, and delta-tocopherol were identified, comprehensively analytically characterized, and their structure was supported by X-ray crystal structure analysis on truncated model compounds. Even under more drastic nitration conditions, no erosion of the stereochemistry at 2-C occurred. The nitrosation of gamma-tocopherol and delta-tocopherol was re-examined, showing the slow oxidation of the initial nitroso products to the corresponding nitro derivatives by air to be superimposed by a fast equilibrium with the tautomeric ortho-quinone monoxime, which only in the case of gamma-tocopherol released hydroxyl amine at elevated temperatures to afford the stable ortho-quinone. Mononitration of delta-tocopherol selectively proceeded at position 5. This selectivity can be explained by the theory of strain-induced bond localization (SIBL) to the quinoid nitration intermediates. Bisnitration was only insignificantly disfavored by the first nitro group, so that under normal nitration conditions offering an excess of nitrating species only the bisnitration product was found.

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Section: Methodsmentioning

confidence: 99%

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

et al. 2007

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“…The XRD data for vitamin E as well as its derivatives are available only for tocopherol succinate [ 1 ]. Generally, the available XRD data were recorded for vitamin E model compounds: 2,2,5,7,8-pentamethylchroman-6-ol ( 2 ) (MOPHLB) [ 3 , 4 , 5 , 6 ] and Trolox C (DEWVOQ02) [ 7 ] as well as for its derivatives [ 8 , 9 , 10 ]. In the present work, the new X-ray structures of chroman-6-ol ethers, including THP 3 , methyl 4 and silyl 5 were presented.…”

Section: Resultsmentioning

confidence: 99%

“…They can successfully imitate the action of the d-α-tocopherol molecule in broad areas of structural research and the lower chroman-6-ol ( 2 ) lipophilicity [ 2 ] can help to obtain crystalline derivatives suitable for crystallographic research. The CCDC database contains crystallographic data for 2 [ 3 , 4 , 5 , 6 ] and 2a [ 7 ] as well as for their derivatives [ 8 , 9 , 10 ].…”

Section: Introductionmentioning

confidence: 99%

13C CP MAS NMR and DFT Studies of 6-Chromanyl Ethereal Derivatives

et al. 2022

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Vitamin E consists of a group of compounds including α- β- γ- and δ-tocopherols and α- β- γ- and δ-tocotrienols, containing the chroman-6-ol system. The recognition of the structural and dynamic properties of this system, present in all vitamers, seems to be important for the full explanation of the mechanism of the biological activity of vitamin E. This paper presents results of the structural analysis of the chosen 6-chromanyl ethereal derivatives using experimental (13 C NMR-in solution and solid state, as well as variable temperature experiments; single crystal X-ray diffraction) and theoretical (DFT) methods. For one of the studied compounds, 2,2,5,7,8-pentamethyl-6-((tetrahydro-2H-pyran-2-yl)oxy) chroman, the splitting of some signals was observed in the 13C dynamic NMR spectra. This observation was explained by the application of a conformational analysis and subsequent DFT optimization, followed by the calculation of NMR properties.

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“…The main difference appears in the conformation of the semi-unsaturated ring; the torsional angles between O-1-C-2, C-3-C-4 and the aromatic ring differ by 3.2°and 0.9°, respectively. 17 In order to diversify 13 C CP/MAS NMR signals coming from both molecules, variable contact time experiments were performed. 18 Because of signal overlap, only a few resonances could be observed for an individual form and the cross-polarization parameters were essentially the same.…”

Section: Resultsmentioning

confidence: 99%

¹³C CP/MAS NMR studies of vitamin E model compounds

Witkowski

Paradowska

Wawer

2004

Magnetic Reson in Chemistry

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13C cross-polarization magic angle spinning (CP/MAS) NMR data for 2,2,5,7,8-pentamethylchroman-6-ol (2), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox c) (3) and its acetate (4), 2-methoxy-2,2,5,7,8-pentamethylchroman-6-ol (5), 2-hydroxy-2,2,5,7,8-pentamethylchroman-6-ol (6) and 2,2,5,7,8-pentamethylchroman (7) are reported. A deshielding of 7.7 ppm for the carboxylic carbon was observed in solid Trolox due to formation of intermolecular hydrogen bonds within cyclic dimers. Such crystal packing permits effective cross-polarization and fast relaxation (short T1rho(H)). The impact of the proton concentration on the CP dynamics is reflected by the longer T(CP) and T1rhoH for Trolox-d2 (deuterated at mobile proton sites). The calculated GIAO RHF shielding constants are sensitive to intramolecular effects: rotation around the C-6-O bond (changes of sigma up to 8 ppm) and conformation at C-2.

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X-Ray Crystallographic Studies of Vitamin E Derivatives. Relationship between Antioxidant Activity and Molecular Structure

Abstract: Molecular structures of vitamin E derivatives were analyzed with X-ray diffraction. The relationship between the antioxidant activity and the molecular structure of vitamin E is discussed.

Cited by 11 publications

References 21 publications

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

13C CP MAS NMR and DFT Studies of 6-Chromanyl Ethereal Derivatives

¹³C CP/MAS NMR studies of vitamin E model compounds

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X-Ray Crystallographic Studies of Vitamin E Derivatives. Relationship between Antioxidant Activity and Molecular Structure

Abstract: Molecular structures of vitamin E derivatives were analyzed with X-ray diffraction. The relationship between the antioxidant activity and the molecular structure of vitamin E is discussed.

Cited by 11 publications

References 21 publications

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

Vitamin E Chemistry. Nitration of Non-α-tocopherols: Products and Mechanistic Considerations

13C CP MAS NMR and DFT Studies of 6-Chromanyl Ethereal Derivatives

13C CP/MAS NMR studies of vitamin E model compounds

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¹³C CP/MAS NMR studies of vitamin E model compounds