Natural vitamin E comprises 8 different analogues, the α-, β-, γ-, and δ-tocopherols and the α-, β-, γ-, and α-tocotrienols. However, only α-tocopherol is selectively enriched by the liver; the other vitamin E analogues and also excess α-tocopherol are converted to several metabolites and eliminated. Recently, a novel phosphorylated form of tocopherol, α-tocopheryl phosphate, was shown to occur naturally in animal and human tissues as well as in foods. Several synthetic vitamin E derivatives have been synthesized that are either converted by esterases to the natural form, or exert novel or vitamin E related biological activities. During the last years, specific cellular effects for each individual vitamin E analogue have been described that are the consequence of modulating signal transduction and gene expression. These effects possibly reflect specific interactions of each of the vitamin E analogues with enzymes, structural proteins, lipids and transcription factors. In this review, the different natural vitamin E analogues and synthetic derivatives are compiled in relation to their major molecular and cellular activities.
Keywords: Vitamin E, α-tocopheryl acetate, α-tocopheryl phosphate, tocopheryl succinate, tocopherol derivatives, tocopherol binding proteins, gene regulation, signal transduction, transport, metabolism
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