β-Tocotrienol is an antioxidant.

There are four tocopherols (α, β, δ, and γ) and four tocotrienols (α, β, δ, and γ) forms of vitamin E, which is known for its antioxidant activity. Tocotrienols are present in high concentrations in palm oil and wheat germ.

In vitro: The antioxidant activity of the tocopherols and tocotrienols was found to be mainly due to their ability to donate their phenolic hydrogens to lipid free-radicals. Although it is generally agreed that the relative antioxidant activity of the tocopherols was in the order α>β>γ>δ [1].

In vivo: In a previous study, mice were fed a nonpurified control diet, an atherogenic diet alone or the atherogenic diet supplemented with α- and β-tocopherols. Results showed that compared with mice fed the control diet, plasma cholesterol was fourfold greater in mice fed the atherogenic diet. Mice fed the atherogenic diet had much higher VLDL, intermediate density lipoprotein (IDL) and LDL cholesterol and markedly lower HDL cholesterol than the controls. Moreover, in mice fed the atherogenic diet, the hepatic cholesterol plus cholesterol ester concentration was 4.4-fold greater than in mice fed the control diet. Mice fed the atherogenic diet had large atherosclerotic lesions at the level of the aortic valve. The 0.5 g/100 g alpha-tocopherol and palm carotenoid supplements had no effect [2].

Clinical trial: So far, no clinical study has been conducted.

References:
1.  Kamal-Eldin, A., and Appelqvist, L.. The chemistry and antioxidant properties of tocopherols and tocotrienols. Lipids 31, 671-701 (1996).
2.  Black, T.M.,Wang, O.,Maeda, N., et al. Palm tocotrienols protect ApoE +/- mice from diet-induced atheroma formation. Journal of Nutrition 130(10), 2420-2426 (2000).