Optimization of ultrasound-assisted extraction of quercetin, luteolin, apigenin, pinocembrin and chrysin from Flos populi by Plackett-Burman design combined with Taguchi method

The objective of this study was to optimize for the extraction of five flavonoids: quercetin, luteolin, apigenin, pinocembrin and chrysin from Flos populi. A combination of the Plackett-Burman design (PBD) with Taguchi method was used to optimize the process parameters of ultrasound-assisted extraction (UAE). Based on the single-factor analysis, a Plackett-Burman design was initially employed and it was found that Temperature (°C), Particle diameter (mm), Ultrasonic time (min) and Ultrasonic intensity (W/cm2) were key variables that effecting extraction yield. The optimal conditions were further determined using the Taguchi method. Results showed that the optimum temperature, ethanol concentration, particle diameter, ultrasonic time, liquid-solid ratio, ultrasonic intensity and experimental runs were 70 °C, 60%, 0.18 mm, 35 min, 25 mL/g, 3.3 W/cm2, and two experimental runs respectively. Under these optimum conditions, approximately 16.26 mg of quercetin, 9.97 mg of luteolin, 8.57 mg of apigenin, 119.71 mg of pinocembrin, and 16.12 mg of chrysin could be obtained from 1 g of Flos populi, which well correlated with predicted values (15.91 mg of quercetin, 6.09 mg of luteolin, 7.49 mg of apigenin, 114.37 mg of pinocembrin, and 14.91 mg of chrysin).