Abstract: Based on one-factor-at-a-time experiments, uniform experimental design followed by regression analysis using the software SPSS 13.0 was carried out to optimize the microwave-assisted and ultrasonic-assisted extraction of total flavonoids from navel orange residue (left over from juicing). The optimal microwave-assisted extraction conditions were microwave power 390 W, irradiation time 7 min, ethanol concentration 50%, and material/liquid ratio of 1:45 (g/mL) and the extraction rate of total flavonoids was 19.3 mg/g under these conditions. The optimal ultrasonic-assisted extraction conditions were temperature 70 ℃, ultrasonic treatment time 60 min, ethanol concentration 50%, and material/liquid ratio of 1:45 (g/mL), and the resulting extraction rate of total flavonoids was 16.6 mg/g.

Key words: navel orange residues, microwave-assisted extraction, ultrasonic-assisted extraction, total flavonoids