This work studies how pressure and temperature affect supercritical carbon dioxide extraction of rice bran oil from powdered rice bran, followed by the concentration and isolation of gamma-oryzanols by column partition purification. The two purest gamma-oryzanols (>98 wt.%) were isolated from reagent chemical gamma-oryzanols by preparative reverse-phase high-pressure liquid chromatography. In searching for a suitable range of extraction conditions, supercritical extraction at 350 bar and 313 K yielded 17.5% oil and the extraction efficiency of gamma-oryzanols was 84.9%, using 1200 g of carbon dioxide over 4 h. Finally, supercritical extractions at pressures from 250 to 350 bar and at temperatures from 313 to 333 K were chosen based on the response surface methodology to determine their effects on concentration of gamma-oryzanols in the extracted oil. Pressure proved more significant than temperature in increasing the concentration of gamma-oryzanols. A significant amount of the purest oil that contained 37.0 wt.% gamma-oryzanols was obtained following a normal-phase medium-pressure column partition fractionation of the extracted oil. (C) 2007 Elsevier B.V. All rights reserved.