Negative pressure cavitation based ultrasound-assisted extraction of main flavonoids from Flos Sophorae Immaturus and evaluation of its extraction kinetics

In this study, an efficient process of negative pressure cavitation based ultrasound-assisted extraction (NPC-UAE) was invented, and applied for the extraction of main flavonoids from Flos Sophorae Immaturus (FSI) for the first time. After the optimization of single factor and Box-Behnken design (BBD) experiments, the optimum technological conditions of NPC-UAE were determined as follows: ethanol concentration 72%, time 16 min, liquid to solid ratio 25:1 mL/g, ultrasonic intensity 0.347 W/cm(2), negative pressure - 0.07 MPa and temperature 60 degrees C. The extraction yields of rutin, nicotiflorin, narcissin, quercetin, kaempferol and isorhamnetin were 125.17, 15.02, 25.61, 51.89, 4.32 and 6.30 mg/g, respectively. The advantages of NPC-UAE were demonstrated by mass transfer kinetics. Under the optimal parameters, the extraction yields of NPC-UAE for six compounds were 1.27-1.62 and 1.17-1.40 folds to those of negative pressure cavitation extraction (NPCE) and ultrasound-assisted extraction (UAE), respectively. In terms of DPPH radical scavenging activity, the effect of NPC-UAE extracts was superior to other methods (UAE, NPCE). The results showed that NPC-UAE could not only extract flavonoids from FSI efficiently, but also have great advantages in extracting active components from sample matrix.