Optimization of Ultrasonic-assisted Extraction of Flavonoids from Persimmon Leaf by Response Surface Methodology

Response surface methodology(RSM) was used to optimize the experimental conditions for ultrasonicassisted extraction of flavonoids from persimmon leaf. Box-Behnken design was employed to optimize four extraction variables including extraction temperature, ethanol concentration, ratio of aqueous ethanol to persimmon leaf and extraction time. The flavonoids content of persimmon leaf extract was the evaluation index. The results showed that the extraction temperature displayed the max impact on flavonoids content and followed by the ratio of aqueous ethanol to persimmon leaf, ethanol concentration and extraction time. The optimized conditions were: temperature 53℃, ethanol concentration 69%, ratio of aqueous ethanol to persimmon leaf 21 ∶1, extraction time 32min. Under the optimal conditions, the predicted flavonoids content of persimmon leaf extract was 35.05mg/g, while the experimental flavonoids content of persimmon leaf extract was 35.36mg/g. The RSM-predicted yield and the experimental flavonoids content of persimmon leaf extract were not significantly different from each other. The results showed that the empirical model developed by RSM was adequate to describe the relationships between the factors and response values. The ultrasonic-assisted extraction method could improve the extraction efficiency, shorten the extraction time and protect the bioactive compounds and possess the practical application value.