Radical scavenging activity and identification of anthocyanin pigments in Shikokumai (Oryza sativa)

Shikokumai 105 (Oryza sativa), which was bred in Shimane Agricultural Technology Center, is a black rice that contains anthocyanin pigment in its rice bran. We found that this pigment consists mainly of cyanidin-3-glucoside and peonidin-3-glucoside. As various functions in anthocyanin are well known, we measured DPPH radical and superoxide radical scavenging activity of Shikokumai by colorimetry and electron spin resonance spectroscopy to examine Shikokumai as a functional material. We confirmed strong activity for cyanidin-3-glucoside, which contributed to more than 55% of superoxide radical scavenging activity of the extracted pigment fraction. Protocatechuic acid contributed about 12% of the radical scavenging activity. In total, the identified pigments and protocatechuic acid contributed to 71% of all radical scavenging activity of the extracted pigment fraction.