Antioxidative Compounds in the Extracts of Black Rice Brans

Abstract

Recently we found that extracts from ancient rice brans, especially those from black rice bran, possess strong scavenging activities for reactive oxygen species (ROS). In this study, we examined the origin of the ROS-scavenging activities in the black rice bran extracts, and identified candidate scavengers such as cyanidin-3-glucoside (Cy3-glu) and cyanidin. Although ferulic acid is known to be an antioxidative component of bran in currently available common white rice varieties, it was not found in the black rice bran extracts. The ROS-scavenging activities of Cy3-glu and cyanidin, which were identified in this study, were examined using the ESR-spin trap method and in terms of protective activity against effects of ultraviolet (UVB) irradiation on an epidermal cell line (HaCaT cell). These anthocyanin compounds were found to possess both strong ROS-scavenging activities and to suppress cell-damaging effects of UVB, indicating that both Cy-3-glu and cyanidin are the active components involved in the antioxidative activity of black rice bran extracts.