Separation, Purification and Identification of Antioxidant Compositions in Black Rice

To separate, purify and identify the antioxidative compositions of black rice, using total antioxidation capacity (TAC) as an activity-monitoring parameter, different fractions of black rice antioxidative extracts were obtained using solvents of different polarities such as petroleum ether, chloroform, ethyl acetate and normal butyl alcohol. The main antioxidative components were separated from the strongest antioxidative fractions by using Sephadex LH-20 resin and the structures were analyzed by ultraviolet-vis, infra-red, ESI-MS, 1H-NMR and 13C-NMR spectrums. Results showed that the water fraction and normal butyl alcohol antioxidative extract fraction of black rice had the strongest antioxidation capacities and their TACs reached 383 and 392 ku g−1, respectively. Four main antioxidative components were separated from the water fraction and their TACs reached 976, 878, 1134 and 1 087 ku g−1, respectively. The spectroscopy analysis indicated that the four active components of the antioxidative extract of black rice were four anthocyanin compounds of malvidin, pelargonidin-3, 5-diglucoside, cyaniding-3-glucoside and cyaniding-3, 5-diglucoside. It is concluded that the anthocyanin compounds are the most important substantial foundations for antioxidation.