Natural vitamin E (tocopherol and tocotrienol) is separated from byproduct of vegetable oil refining by conventional process with mainly multistep molecular distillation. However, its recovery yield and purity are low due to poor thermal stability and separation selectivity, which causes high production cost. In order to overcome these problems, many separation processes under mild conditions, such as supercritical CO₂ extraction and adsorption/desorption, has been proposed. These processes have been applied to the separation of tocotrienol from distillate from rice bran or palm oils.

Rice bran oil contains various bioactive compounds, including tocotrienol (T3; unsaturated vitamin E), ferulic acid (FA), γ-oryzanol, β-sitosterol, and thus much attention has been focused on the health benefits of its components. We previously demonstrated that T3 has potent anti-tumor activity, and that δ-T3 has the most potent anti-cancer activity (i.e., antiangiogenesis and telomerase inhibition) of the four T3 isomers. Since the bioavailability of orally ingested T3 is lower than that of tocopherol (well-known vitamin E), several studies are in progress to screen for molecules that can synergize with T3 in order to augment its potency. In this review, we summarize the current status of synergistic effects of rice bran oil components, especially T3 and FA, on cancer cell growth and cellular telomerase.

Epidemilogical studies have shown that whole grains consumption prevents obesity and type 2 diabetes. Brown rice induces less postprandial blood glucose increase compared with white rice. Recently, brown rice consumption has been proved to exhibit anti-obese effect in humans. Whereas several components in rice bran have been shown to have beneficial function for prevention of obesity and type 2 diabetes, active components in brown rice have not been fully clarified. Our recent studies have demonstrated that dietary consumption of triterpene alcohol and sterol preparation (TASP) from rice bran prevented high-fat diet-induced obesity and reduced postprandial blood glucose increase in mice. Moreover, TASP consumption significantly reduced postprandial hyperglycemia in humans. Reduction in postprandial glucose-dependent insulinotropic peptide increase in blood and inhibition of sodium-dependent glucose transporter 1 translocation to the plasma membrane are likely to underlie the beneficial function of TASP. Brown rice-derived TASP can be industrially produced from rice bran that is being discarded on a massive scale. Application of TASP to functional food development can be expected to be quite useful for prevention and improvement of obesity and type 2 diabetes. Present paper would review our recent findings of physiological function of rice bran-derived TASP and its underlying mechanisms.