The Chemistry of Vitamin E.

Smith, Lee Irvin

doi:10.1021/cr60087a001

Cited by 25 publications

(8 citation statements)

References 76 publications

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“…In an effort to combine the best features of “classical” ARGET (non‐initiating reducing agents) and ICAR ATRP (non‐reactive towards epoxides reducing agents), the suitability of α‐TOH (a component of vitamin E) as a reducing agent was investigated. The compound is a well‐known antioxidant, able to reduce a variety of oxidizing agents including high oxidation state metal ions such as Cu II and Fe III . The projected benefits of α‐TOH over traditionally used reducing agents were its ecological amiability, oil solubility, and, importantly, its minimal reactivity with epoxides.…”

Section: Resultsmentioning

confidence: 99%

Epoxides as Reducing Agents for Low‐Catalyst‐Concentration Atom Transfer Radical Polymerization

Woodruff

Davis

Tsarevsky

2013

Macromol. Rapid Commun.

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Activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) conditions utilizing a low concentration of catalyst are successfully applied for the preparation of well-defined poly(glycidyl methacrylate) without the addition of external reducing agents. The living character of polymerization is evidenced by successful chain extensions with methyl methacrylate and methyl acrylate, again, in the absence of additional reducing agents, yielding block copolymers. The epoxide groups in glycidyl methacrylate or the corresponding polymer can serve as an intrinsic reducing agent to continuously regenerate the Cu(I) -based ATRP activator from the Cu(II) halide complex present in the systems. The reactivity of various epoxides in the reduction of the Cu(II) Br2 complex of tris(2-pyridylmethyl)amine is compared.

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Section: Resultsmentioning

confidence: 99%

Epoxides as Reducing Agents for Low‐Catalyst‐Concentration Atom Transfer Radical Polymerization

Woodruff

Davis

Tsarevsky

2013

Macromol. Rapid Commun.

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“…In the sixties and seventies many efforts were devoted to clarify how separation of currents due to faradaic or nonfaradaic (double-layer charging currents) processes should be handled whenever the electroactive species influence the double-layer capacity (i.e., as with adsorption) [1]. These efforts were focused on Phase Sensitive Alternating Current Polarography (ACP in the text) because of its ability to discriminate between capacitive and faradaic currents if measurements are made at a convenient phase angle relative to the applied AC potential function [2 -4].…”

Section: Introductionmentioning

confidence: 99%

“…Assuming that complete discrimination of I f against I c should be possible by measurements done either in phase or at 1808 out of phase. However, the procedure to establish the more convenient angle in each case is not clear because I c is not the same in the presence that in the absence of faradaic process, as Smith discussed in detail [1].…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, it is very well known that adsorption phenomena affect the double layer and, as a consequence, the measured currents [1,2]. Although this fact is exploited in Adsorptive Stripping Voltammetry [5] and some polarographic determinations [6], in the case of voltammetric determination of stability constants of metal complexes the usual methods are based on the hypothesis of absence of adsorption phenomena [7 -11].…”

Section: Introductionmentioning

confidence: 99%

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Phase Sensitive Alternating Current Polarography: A Chemometric Approach for the Selection of Phase Angles

et al. 2006

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A method based on the combined use of multivariate curve resolution by alternating least squares (MCR-ALS) with phase sensitive alternating current polarography (ACP) is proposed to evaluate the phase angle where capacitive current is minimized in a much more accurate way than the visual inspection of ACP signals. The method allows, through the analysis of series of AC polarograms measured at different phase angles out the potential, to distinguish between faradaic and capacitive contributions. Then the angle at which the capacitive current is negligible can be shown and, in some cases, the influence of adsorption on measured currents minimized.

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“…Three dif'ferent phases of current research activities on the metabolic function of vitamin E are included in this report. These are: (1) the isolation and tentative characterization of a reversible oxidation product of tocopherol; (2) the effect of a-tocopheryl phosphate and other compounds of similar properties on the succinoxidase system; and (3) a re-evaluation of the biological activity of compounds related to vitamin E.…”

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confidence: 99%

Chemical and Biological Studies Related to the Metabolic Function of Vitamin E

Boyer¹,

Rabinovitz²,

Liebe³

1949

Ann NY Acad Sci

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Three dif'ferent phases of current research activities on the metabolic function of vitamin E are included in this report. These are: (1) the isolation and tentative characterization of a reversible oxidation product of tocopherol; (2) the effect of a-tocopheryl phosphate and other compounds of similar properties on the succinoxidase system; and (3) a re-evaluation of the biological activity of compounds related to vitamin E.Evidence for the existence of a reversible oxidation product of tocopherol was first obtained in this laboratory two years ago in spectrophotometric studies of the oxidation of a-tocopherol. In these experiments, tocopherol was oxidized by two equivalents of ferric iron in the presence of excess 2 , 2'bipyridine to react with the ferrous iron produced. When the oxidized tocopherol was reduced by ascorbic acid immediately following the completion of the oxidation, the product showed the same ultraviolet absorption curve as a-tocopherol. If the reduction was carried out a t subsequent intervals up to 20 hours, the presence of increasing amounts of the irreversible oxidation product, tocopheryl quinone, was evident. These observations suggested that the tocopherol was first converted to a primary oxidation product which could be readily reduced to the original tocopherol or converted irreversibly to the tocopheryl quinone. Experiments were then undertaken to find if such a product existed.Further experiments showed that by careful oxidation of the tocopherol a t -5"C., followed by extraction and chromatographic separation on alumina, the primary oxidation product could be obtained as a colorless oil. Elementary analyses of the product indicated that it has the composition CsaHsoOs. Thus it is isomeric with the tocopheryl quinone and differs from tocopherol only in the presence of an additional oxygen atom. The relationships existing between tocopherol and its oxidation products are summarized in FIGURE 1. a-Tocopherol may be converted by a reversible, bivalent oxidation to a primary oxidation product. The semiquinone radical of tocopherol' is probably an intermediate in the formation of the product. Upon exposure to very dilute acids, the primary oxidation product is converted irreversibly to tocopheryl quinone, the first oxidation product of tocopherol previously attainable? The tocopheryl quinone is reduced much less readily than the primary oxidation product, and the reduction gives rise to tocopheryl hydroquinone.2 Interest in the primary oxidation product was heighteneJ by the observation that it was biologically active. When fed orally, the product had 3$ of the activity of d,l-a-tocopherol, as measured by the conventional rat assay, When administered by intrsperitoneal injection as a suspen-A Reversible Oxidation Product of Tocopherol.

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The Chemistry of Vitamin E.

Cited by 25 publications

References 76 publications

Epoxides as Reducing Agents for Low‐Catalyst‐Concentration Atom Transfer Radical Polymerization

Epoxides as Reducing Agents for Low‐Catalyst‐Concentration Atom Transfer Radical Polymerization

Phase Sensitive Alternating Current Polarography: A Chemometric Approach for the Selection of Phase Angles

Chemical and Biological Studies Related to the Metabolic Function of Vitamin E

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