Abstract: Response surface methodology was employed to optimize the ultrasound-assisted extraction of flavonoids from Radix Puerariae. The effects of extraction time, solid-to-liquid ratio, and temperature on the extraction yield of flavonoids were studied by one-factor-at-a-time method. A regression model for the yield of flavonoids was established using a Box-Behnken design involving the above three factors at three levels. The results showed that the optimal extraction conditions were as follows: distilled water as extraction solvent, extraction time of 43 min, solid-to-liquid ratio of 1:10 (g/mL), and temperature of 68 ℃. Under these conditions, the observed yield of flavonoids was 5.28% in comparison with the predicted yield of 5.36%, and the relative error was only 1.49%, suggesting that the optimal extraction conditions are reliable.

Key words: Radix Puerariae, flavonoids, ultrasound-assisted extraction, response surface methodology (RSM)