Total Flavonoids from Xinjiang Ruoqiang Jujubes: Optimization of Extraction Conditions Using Response Surface Methodology and Antioxidant Activity

This study was undertaken to optimize condition for the extraction of total flavonoids from Xinjiang Ruoqiang jujubes.One-factor-at-a-time method was used to investigate the effects of ethanol concentration,temperature,extraction time and solid-to-solvent ratio on the extraction yield of total flavonoids.Maximum extraction yield of total flavonoids was reached after 90 min of extraction.Using a three-variable,three-level Box-Behnken experimental design coupled with response surface methodology,ethanol concentration,temperature and solid-to-solvent ratio were optimized to be 45%,90 ℃ and 1:35(g/mL),respectively.Under the optimized conditions,the actual extraction yield of total flavonoids was 14.34 mg kaempferol equivalent/g,which was 97.9% as compared to the predicted value(14.647 mg kaempferol equivalent/g).The obtained extract had an ethyl acetate fraction that revealed potent antioxidant activity and was comparable to BHT.