Tocotrienols are structurally and functionally similar to vitamin E and other tocopherols. Like tocopherols, several forms of tocotrienols are known (alpha-, beta-, delta-, and gamma-tocotrienols). Tocotrienols have much less vitamin activity than tocopherols, but are generally better antioxidants in vitro. For example, alpha-tocotrienol is 6.5-60x more effective than alpha-tocopherol as an antioxidant.
Similar to vitamin E, tocotrienols also protect against lipid peroxidation (the damaging of fats by oxidation).
The primary sources of tocotrienols in the average diet are vegetable oils, including palm and rice bran oil.