Objective: To optimize ultrasonic-assisted extraction technology of total flavonoids from Penthorum chinense and evaluate its in vitro antioxidant activity. Method: With yield of total flavonoids as index

the concentration of ethanol

extraction time

liquid-material ratio were optimized by response surface methodology based on single-factor tests

and its in vitro antioxidant activity were evaluated by multi-test systems. Result: Optimal extraction technology conditions were:extracted 20 min with 26 times the amount of 60% ethanol at 50℃. Under these conditions

yield of total flavonoids reached 4.14%

which was agreed with model predictions.In vitro antioxidant activities results showed that total flavonoids from P. chinense had good antioxidant activities of scavenging DPPH free radical and hydroxyl free radical

but also had strong reducing power and total antioxidant capability. Conclusion: Optimized ultrasonic-assisted extraction technology was simple

rapid and efficient.Total flavonoids from P. chinense had good antioxidant activity which was worth of further study.