Abstract: The present study aimed to optimize the process parameters for the ultrasonic-assisted enzymatic extraction of total flavonoids from old leaves of Toona sinensis. Using one-factor-at-a-time method, enzyme dosage, pH, temperature, and solid to liquid ratio were identified as important factors affecting the total flavonoid yield. These factors were by response surface methodology. An HPLC method to determine total flavoids in T. sinensis was established. The results showed that the optimum conditions were as follows: hydrolysis with 0.6% cellulose at pH 4.6 and 45 ℃ for 120 min, followed by two cycles of 40 min extraction at 62 ℃ with 60% ethanol as the extraction solvent at a solid to liquid ratio of 1:25 (g/mL) under 140 W ultrasonic irradiation. Under these conditions, the total flavonoid yield was 14.98%, which was significantly increased compared with traditional enzymatic extraction. The results of HPLC showed that the flavonoids extracted contained 0.16% rutin, 0.06% quercetin and 0.03% kaempferol.

Key words: leaves of Toona sinensis, response surface methodology, total flavonoids, high performance liquid chromatography (HPLC)