Optimization of ultrasonic-microwave synergistic extraction of total flavonoids and antioxidant activity from Davidia involucrata leaves

The purpose of this research was to investigate the optimization of the extraction process of total flavonoids from Davidia involucrata leaves and its bioactivity activity. The ultrasonic-microwave synergistic extraction (UMSE) method is used to extract total flavonoids from D. involucrata leaves. The effects of extraction time, extraction temperature, ethanol volume fraction, solid–liquid ratio, microwave power, and ultrasonic power on the yield of total flavonoids are investigated. Through the Plackett-Bruman design (PBD) experiment, the factors affecting the yield of total flavonoids the most are determined, including extraction temperature, extraction time, and solid–liquid ratio. Then, the optimum extraction conditions are obtained after Box-Behnken design (BBD) response surface design optimization, and the optimum extraction conditions are as follows: solid–liquid ratio 1:33 g/mL, extraction temperature 73 ℃, extraction time 45 min, ethanol volume fraction 60%, ultrasonic power 800 W, and microwave power 350 W. Under these conditions, the yield of total flavonoids extracted from D. involucrata leaves is 5.27 ± 0.04%. The scavenging ability of dove leaf total flavonoid extracts against both free radicals was ABTS· > DPPH. HPLC results revealed that the antioxidant substances had diverse flavonoids. The optimized extraction process with response surface design is reliable and can be used for the extraction of total flavonoids from D. involucrata leaves with better antioxidant capacity than the conventional extraction method.