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).
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).
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.,