Extraction of Polyphenols from Dry Roselle Calyx and its Antioxidant Activity

Abstract

Dried Roselle calyxes were used to extract polyphenols by ultrasonic technology. By using single factor test and orthogonal test, the ultrasonic extraction process of roselle dry calyxes polyphenols was optimized. Antioxidant effect of the extraction was measured by the clearance rate of diphenyl picryl hydrazinyl radicals. The optimized extraction conditions were determined as follows:extraction temperature, 45°C; solid-liquid ratio, 1:15; extraction time, 20 min; ethanol solvent, 75%. Antioxidant activity was examined by the comparison between the sample with the highest polyphenol content and butylated hydroxytoluene. The result shows that the sample has stronger antioxidant ability than butylated hydroxytoluene.