Abstract: In order to maximize extraction efficiency of flavonoids from Euryale ferox leaves, Plackett-Burman design was used to screen 4 main variables (ratio of material to liquid, ultrasonic power, ethanol concentration and extraction time) that influence extraction efficiency out of 5 process parameters (ratio of material to liquid, ultrasonic power, ethanol concentration, temperature and extraction time) and the selected variables were then optimized using orthogonal array design. The optimum conditions for flavonoid extraction from Euryale ferox leaves were determined as follows: 1:25 ratio of material to liquid (g/mL), 175 W ultrasonic power, 85% ethanol as extraction solvent, and 40 min extraction time. Under such conditions, the extraction efficiency of flavonoids was 90.28 mg/g.

Key words: Euryale ferox leaves, flavonoids, ultrasonic extraction