Localization of vitamin E in membranes.

Abstract

Vitamin E is a term encompassing a group of eight isomeric molecules which are characterized by a 6-chromanol ring structure and a side chain at the 2 position. The tocopherols possess a 4′,8′,12′-trimethyltridecyl phytol side chain, and the tocotrienols differ by the presence of double bonds at the 3′,7′, and 11′ positions of the side chain. The α, β, γ, and δ isomers of tocopherol and tocotrienols differ in the number and position of the methyl substituents attached to the chromanol ring. A total of eight optical isomers arise from the existence of three asymmetric carbons at the 2 position of the ring and the 4′ and 8′ positions of the phytol chain.