Abstract: In this study, ultrasound assisted extraction was used to extract polyphenols from testa of Quercus mongolica Fischer. Response surface methodology (RSM) combined with Box-Behnken central composite design was applied for modeling and optimizing of three variables that influence the extraction, namely ethanol concentration, extraction time and ratio of liquid to solid. The yields and the contents of polyphenols were selected as responses to optimize the extraction process. The optimum conditions for the extraction of polyphenols were as follows: ethanol concentration 60.56%, ratio of liquid to solid 30.72∶1 mL·g^-1, ultrasound time 42.39 min. Under the optimum conditions, the yield and the purity of polyphenols were 0.38% and 18.8%, respectively and EC₅₀ of DPPH free-radical scavenging ability of these polyphenols is 176 μg·mL^-1, which is higher than BHA and BHT.

Key words: Quercus mongolica Fischer, testa, polyphenols, response surface methodology, ultrasound extraction, antioxidant activity