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Antioxidant Activity of Tocopherols, Tocotrienols, and γ-Oryzanol Components from Rice Bran against Cholesterol Oxidation Accelerated by 2,2‘-Azobis(2-methylpropionamidine) Dihydrochloride 

Department of Food Science, Louisiana Agricultural Experimental Station, Louisiana State University Agricultural Center, Baton Rouge, Louisiana 70803
The antioxidant activities of vitamin E (α-tocopherol, α-tocotrienol, γ-tocopherol, and γ-tocotrienol) and γ-oryzanol components (cycloartenyl ferulate, 24-methylenecycloartanyl ferulate, and campesteryl ferulate) purified from rice bran were investigated in a cholesterol oxidation system accelerated by 2,2‘-azobis(2-methylpropionamidine) dihydrochloride. All components exhibited significant antioxidant activity in the inhibition of cholesterol oxidation. The highest antioxidant activity was found for 24-methylenecycloartanyl ferulate, and all three γ-oryzanol components had activities higher than that of any of the four vitamin E components. Because the quantity of γ-oryzanol is up to 10 times higher than that of vitamin E in rice bran, γ-oryzanol may be a more important antioxidant of rice bran in the reduction of cholesterol oxidation than vitamin E, which has been considered to be the major antioxidant in rice bran. The antioxidant function of these components against cholesterol oxidation may contribute to the potential hypocholesterolemic property of rice bran.