Among the many sterols present in the unsaponifiable fraction of rice bran oil, oryzanols and tocotrienols are two distinctly different component groups that have been intensively studied for their health benefits (Rogers et al., 1993; Rong et al., 1997).

Oryzanol
Crude rice bran oil contains about 1.5% or more gamma-oryzanol, a group of ferulate esters of triterpene alcohols and phytosterols. The high antioxidant property of gamma-oryzanol has been widely recognized. Studies have shown several physiological effects related to gamma-oryzanol and related rice bran oil components. These include its ability to reduce plasma cholesterol (Lichenstein et al., 1994), reduce cholesterol absorption and decrease early atherosclerosis (Rong et al., 1997), inhibit platelet aggregation (Seetharamaiah et al., 1990), and increase fecal bile acid excretion (Seetharamaiah and Chandrasekhara, 1990). Oryzanol has also been used to treat nerve imbalance and disorders of menopause (Nakayama et al., 1987).

Tocotrienols
Rice bran oil is the only readily available oil, other than palm, that contains significant levels (approximately 500 ppm) of tocotrienols (Eitenmiller, 1997). These occur in at least four known forms and are similar to the tocopherols in chemical structure. They belong to the vitamin E family and are powerful natural antioxidants (Tomeo et al., 1995). The protective benefits of dietary antioxidants in the prevention of cardiovascular disease and some forms of cancer have been widely publicized (Eitenmiller, 1997; Nesaretnam et al., 1998).