Comparative analysis of bioactive-phytochemical characteristics, antioxidants activities, and anti-inflammatory properties of selected black rice germ and bran (Oryza sativa L.) varieties

Black rice has numerous health benefits and one of the well-known functional foods throughout the world. To encourage the increasing trend of the consumer interest in health-promoting functional foods, special varieties of rice have been developed offering greater nutrient values and exhibiting biological activities that are beneficial to the consumer. In this study, we aimed to evaluate the associations of the phytochemical contents, antioxidants, and anti-inflammatory properties among eight selected black rice germ and bran extracts (BR extracts) from 4 non-glutinous and 4 glutinous rice varieties. Accordingly, glutinous BR extracts possessed higher degree of Cyanidin-3-O-glucoside (C3G), Peonidin-3-O-glucoside (P3G) contents, antioxidant and anti-inflammatory properties than the non-glutinous BR extracts. Pearson’s correlation indicated that the amount of C3G in the BR extracts had a strong positive association with the antioxidant properties (DPPH; r = 0.846, ABTS; r = 0.923, and FRAP; r = 0.958, p < 0.01). While P3G exhibited a strong positive association with the anti-inflammatory properties (r value = 0.717 and 0.797 for IL-6 and TNF-α inhibition, respectively, p < 0.05). Lastly, the principal component analysis (PCA) categorized the black rice varieties into three groups: Group A with high C3G content and superior antioxidant properties, Groups B with a high amount of P3G and potent anti-inflammatory properties, and Group C with a lower amount of phytochemical contents and less potent bioactivities. Overall, the outcomes of this study could provide vital information to food industries in selecting the variety of black rice for the functional food based on the anthocyanin contents that could benefit to consumers for new normal healthy lifestyle.