Ultrasonic-microwave-assisted extraction of total flavonoids from Seed oil residue of Passiflora edulis Sims

The seed oil residue of Passiflora edulis Sims was used as the study object，and the flavonoids in the seed oil residue were extracted by ultrasonic-microwave-assisted methodology. First single-factor experiments were taken，such as ethanol concentration，solid-to-solvent ratio，ultrasonic power，ultrasonic time，microwave power and microwave time. The results showed that ultrasonic power and microwave time had a significant effect on the extraction rate of flavonoids；ultrasonic time，ethanol concentration，solid-to-solvent ratio and microwave power had a more significant effect on the extraction yield of flavonoids. Response surface methodology（ RSM） was applied to optimize the extraction result and a maximum extraction yield of total flavonoids was achieved. The optimal extraction conditions were 73.78% of ethanol concentration，1∶56.02（g/mL） of ratio between solid and liquid，300 W of ultrasonic power，50 min of ultrasonic time，160 W of microwave power，90 s of microwave time，by which the yield of flavonoids reached 117.53 mg/g. The extraction yield of flavonoids by ultrasonic-microwave-assisted methodology is 14.81% higher than that of ethanol extraction.