Optimization of Ultrasonic‐Assisted Enzymatic Hydrolysis for the Extraction of Luteolin and Apigenin from Celery

The extraction of flavonoids is of increasing interest because of their various pharmacological effects. This study is the first attempt for the ultrasonic-assisted enzymatic hydrolysis (USAEH) applied in the extraction of 2 bioactive flavonoid compounds in celery--luteolin and apigenin. The quantitative yields of luteolin and apigenin were determined by high-performance liquid chromatography (HPLC). To achieve high yields of extracted compounds, the procedure was optimized with regard to the relative parameters involved. The optimal conditions for enzymatic hydrolysis using pectinase treatment were a reaction time of 30 min and a concentration of 0.4 mg/mL at pH 3 for luteolin and pH 5.5 for apigenin. The optimal ultrasonic parameters were an exposure period of 30 min at a temperature of 25 °C using a power source of 80 W. Under these optimal conditions, the yields of luteolin and apigenin were increased to 42.5 and 25.3 mg/g, respectively, which represented a 26.1-fold and a 32.2-fold increase in the yields of these 2 compounds, respectively, compared with the control model of aqueous extraction without enzyme or ultrasonic treatment.