Tocotrienols

Tocotrienols are a family of fat-soluble compounds within the naturally occurring vitamin E family. Four forms are recognized: alpha-, beta-, gamma-, and delta-tocotrienol. Like tocopherols, they contain a chromanol ring and a long hydrocarbon side chain. The four tocotrienols differ in the number and positions of methyl groups attached to the chromanol ring .^1,2

The defining structural difference between tocotrienols and tocopherols is their side chain. Tocotrienols contain three carbon-carbon double bonds in this chain, whereas the corresponding side chain of tocopherols is saturated. Both families can act as lipid-soluble antioxidants because the hydroxyl group on their chromanol ring can participate in reactions that intercept lipid peroxyl radicals .²

Although tocotrienols are among the eight naturally occurring forms of vitamin E, they are not equivalent to alpha-tocopherol in human vitamin E nutrition. The liver preferentially retains alpha-tocopherol through alpha-tocopherol transfer protein, while tocotrienols have substantially lower affinity for this protein and are more extensively metabolized. Consequently, tocotrienol concentrations in human plasma and tissues are generally lower than those of alpha-tocopherol .^1,2

Vitamin E can therefore refer broadly to a family containing four tocopherols and four tocotrienols, while established human vitamin E requirements are based specifically on alpha-tocopherol rather than tocotrienols .¹