Abstract:To use polyphenols from sorghum bran, this study employed ultrasonic-assisted deep eutectic solvent (DES) extraction method. The most efficient DES system for extracting polyphenols from sorghum bran was selected from 16 candidates. Subsequently, based on the results of single-factor experiments, the optimal extraction conditions for sorghum bran polyphenols were determined using the response surface methodology. Finally, the antioxidant activity of the extracted polyphenols for sorghum bran was assessed. The results indicate that the optimal solvent for extracting polyphenols from sorghum bran was 1,3-butylene glycol-malonic acid with a solvent molar ratio of 1:1 and water content of 20% (V/V). Under the conditions of solid-liquid ratio of 1:26 g/mL, ultrasonic temperature of 47 ℃ , and ultrasonic time of 50 min, the extraction yield of sorghum bran polyphenols was 19.47 mg/g, which was 2.21 and 1.68 times higher than that obtained by 70% (V/V) ethanol and 70% (V/V) methanol, respectively. The half maximal inhibitory concentration (IC50) values of DES extract against 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) cation radical, 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical, superoxide anion, and hydroxyl radical were 105.85, 122.94, 145.42, and 146.29 g/mL, respectively, which were significantly lower than those of the 70% (V/V) ethanol and 70% (V/V) methanol extracts (P<0.05). At equivalent polyphenol concentrations, the ferric reducing ability of plasma (FRAP) value of the DES extract was significantly higher than that of the 70% (V/V) ethanol and 70% (V/V) methanol extracts (P<0.05). These results indicate that the ultrasonicassisted DES extraction method effectively extracts polyphenols from sorghum bran with high antioxidant activity. This research contributes to the green, efficient extraction and high-value application of polyphenols from sorghum bran.
