Relationship between trace metal concentration and antioxidative activity of ancient rice bran (red and black rice) and a present-day rice bran (Koshihikari)

Antioxidative activity and polyphenol and trace metal content in bran from ancient rice varieties (red and black rice) and a present-day variety of rice (Koshihikari) were measured. The antioxidative properties of rice bran in terms of scavenging and quenching activity for reactive oxygen species (ROS), including superoxide anion radicals (·O2−), hydroxyl radicals (·OH), singlet oxygen (1O2) and lipid peroxide (LOO·), correlated well with polyphenol and trace metal content. In particular, the possibly that Mn content greatly contributes to the antioxidative properties of rice bran was revealed.