New Earth Healing

Tocopherol

Vitamin E is the collective term given to a group of fat-soluble compounds first discovered in 1922 by Evans and Bishop; these compounds have distinct antioxidant activities essential for health.1 Vitamin E is present in fat- containing foods2 and, as the fat-soluble property of the vitamin allows it to be stored within the fatty tissues of animals and humans, it does not have to be consumed every day. The vitamin E group (i.e. chroman-6-ols), collectively termed tocochromanols (divided into tocopherols and tocotrienols), includes all of the tocol and tocotrienol derivatives which qualitatively exhibit the biological activity of d-alpha-tocopherol. There are eight naturally occurring forms of vitamin E; namely, the alpha, beta, gamma and delta classes of tocopherol and tocotrienol, which are synthesised by plants from homogentisic acid. Alpha- and gamma-tocopherols are the two major forms of the vitamin, with the relative proportions of these depending on the source. The richest dietary sources of vitamin E are edible vegetable oils as they contain all the different homologues in varying proportions [Table 1]. Among the tocopherols, the alpha- and gamma-tocopherols are found in the serum and the red blood cells, with alpha-tocopherol present in the highest concentration.3 Beta- and delta-tocopherols are found in the plasma in minute concentrations only. The preferential distribution of alpha-tocopherol in humans over the other forms of tocopherol stems from the faster metabolism of the other forms and from the alpha-tocopherol transfer protein (alpha-TTP). It is due to the binding affinity of alpha-tocopherol with alpha-TTP that most of the absorbed beta-, gamma- and delta-tocopherols are secreted into the bile and excreted in the faeces, while alpha-tocopherol is largely excreted in the urine. The alpha-tocopherol form also accumulates in the non-hepatic tissues, particularly at sites where free radical production is greatest, such as in the membranes of the mitochondria and endoplasmic reticulum in the heart and lungs. This review mainly focuses on the current developments in vitamin E research in the context