Ultrasound-assisted aqueous two-phase extraction of total flavonoids from and antioxidant activity of extracted flavonoids.

Here, the extraction of total flavonoids from (TF) by aqueous two-phase extraction combined with ultrasound is presented. The extraction was optimized via a single-variable approach using the variables of mass fraction of ethanol and NaHPO, ultrasonication time, and TF sample amount. Response surface methodology (RSM) was then applied to determine the best conditions for extraction using the following three key parameters: ultrasonication time, ethanol mass fraction, and NaHPO mass fraction. The optimum conditions were as follows: an aqueous two-phase system of ethanol/NaHPO, an ethanol mass fraction of 23%, a NaHPO mass fraction of 27.18%, and an extraction time of 8.25 min. Under these conditions, the maximum extraction rate of total flavonoids was 0.158 mg/g. The scavenging rates for superoxide anion and hydroxyl radical, as well as the antioxidant activity of total flavonoids in TF, were studied. Total flavonoids from TF showed some scavenging ability, but the scavenging effects were lower than those of vitamin C (Vc) at the same concentrations. Nevertheless, ultrasound-assisted two-phase extraction was considered an efficient and rapid method that can be used to extract total flavonoids from TF.