Vitamin E Research Today is a free monthly online journal that collates and summarizes the latest research about Vitamin E, including details on benefits, dosage, supplements, antioxidants.

Vitamin E chemistry. Studies into initial oxidation intermediates of alpha-tocopherol: disproving the involvement of 5a-C-centered "chromanol methide" radicals.

Rosenau T, Kloser E, Gille L, Mazzini F, Netscher T

Department of Chemistry, University of Natural Resources and Applied Life Sciences, Muthgasse 18, A-1190 Vienna, Austria. thomas.rosenau@boku.ac.at

Contrary to concepts handed down in the literature from the early days of vitamin E research, one-electron oxidation of vitamin E does not involve 5a-C-centered radicals. A combined approach of analytical techniques, in particular electron paramagnetic resonance spectroscopy (EPR), organic synthesis of special derivatives, isotopic labeling, kinetic studies, and computational chemistry was used to re-evaluate the one-electron and two-electron oxidation chemistry of alpha-tocopherol (alpha-toc). EPR in combination with 5a-13C-labeled compounds provided no indication of the involvement of 5a-C-centered radicals. Oxidation of special tocopherol derivatives were used to disprove the occurrence of 5a-C-centered one-electron intermediates. Additionally it was shown that those vitamin E reactions that were commonly evoked to plead for the involvement of C-centered tocopheryl radicals actually proceeded via heterolytic, i.e., non-radical, intermediates. The results will help to clear widely spread misunderstandings about the chemistry of vitamin E and will have mechanistic implications for the synthesis of tocopherol-based supramolecular structures and 5a-substituted alpha-tocopherol derivatives.

Published 20 April 2007 in J Org Chem, 72(9): 3268-81.
Full-text of this article is available online (may require subscription).

© 2004-2008 Vitamin E Research Today. All Rights Reserved.