Gamma-oryzanol content, phenolic acid profiles and antioxidant activity of rice milling fractions

This study was aimed to determine gamma-oryzanol content and total phenolics, individual phenolic acid profile and the antioxidant activity of the free and bound extracts of rice milling fractions namely, brown rice, unpolished rice, white rice, chalky rice, raw seed and rice bran. Gamma-oryzanol content of milling fractions which is designated with a simple chromatographic method was in the range of 12.19-3,296.5 mg/kg. The whitening and polishing steps reduced approximately 94% of gamma-oryzanol of the brown rice when becoming the white rice. The contribution of bound phenolics to the total phenolic content was approximately 40%. Ferulic and p-coumaric acids were the most abundant phenolic acids in bound phenolic extracts and their amounts were 119.98 and 18.10 mu g/g, respectively, in rice bran. The best source of gamma-oryzanol, phenolics and antioxidants was clearly rice bran and followed by raw seed and brown rice.