Extraction of Saponins from Black and White Quinoa and Comparison of Their Antioxidant Activities

Black and white quinoa seeds were used as materials in this study, and the methanol reflux extraction method was used to extract the total saponins from the quinoa seeds. The total saponins extraction rate was an important indicator, and the saponins content was compared the difference between the black and white quinoa seeds. At the same time, the reduction (Fe³⁺) ability, the hydroxyl radical (·OH), nitrite ion (\rm NO^-_2 ), superoxide anion (\rm O^-_2\cdot ) and 1, 1-Diphenyl-2-picrylhydrazine (DPPH·) scavenging ability were determined to analyze the antioxidant activity of black and white quinoa saponins. The results showed that the saponins content of black quinoa seeds was higher than that of white quinoa seeds, which were 17.37 and 1.89 mg/g, respectively. In addition, the reducing power and antioxidant activity of quinoa increased with the increase of concentration of saponins. Moreover, the reducing power and antioxidant activity of black quinoa seed saponins were higher than those of white quinoa seed saponins. As a contrast, the IC₅₀ values of black quinoa seed saponins for DPPH·, \rm O^-_2\cdot , ·OH, \rm NO^-_2 were 0.122, 1.106, 0.514, 0.832 mg/mL, respectively. The IC₅₀ values of white quinoa seed saponins for DPPH·, \rm O^-_2\cdot , ·OH, \rm NO^-_2 were 0.210, 5.530, 2.500, 1.569 mg/mL, respectively.