Study on the Extraction of Total Flavonoids from Chinese Kale Using Response Surface Methodology

The extraction process of total flavonoids in Chinese kale was studied. The mathematical models of extraction rate of total flavonoids related to ultrasonic time, ultrasonic temperature, liquid-to-material ratio and ethanol concentration were established by response surface methodology. Through the mathematical model, ultrasound assisted method is the optimum conditions to extract the total flavonoids from Chinese kale. The results showed that the optimum conditions for the extraction was: ultrasonic time 29 min, ultrasonic temperature 71 °C, liquid-to-material ratio 27 mL/g and ethanol concentration 77%. Based on these conditions, the extraction rate of total flavonoids in Chinese kale was 18.47 mg/g, with a relative error of 0.75% compared with the predicted value. The mathematical model had a high fitting degree and a better predictability about the extraction rate of total flavonoids in Chinese kale. The obtained conditions were reliable and could be used to optimize the extraction process of total flavonoids in Chinese kale.