Extraction Optimization of Polyphenols from Phoenix Dan Cong and Its in vitro Antioxidant Capacity and Inhibitory Activity of α-Glucosidase

To promote the development and utilization of regional tea resources,the polyphenols in Phoenix Dan Cong,a typical oolong tea from Chaoshan district,was extracted by ultrasound-assisted treatment. The ethanol concentration,liquid/solid ratio,extraction time and temperature were investigated by single factor test and Box-Behnken response surface methodology to acquire the optimum extraction process. Meanwhile,the antioxidant capacity and α-glucosidase inhibitory effect of extracted polyphenols were also evaluated. The results indicated that the optimum extraction parameters were as follows:Ethanol concentration 70%,extraction temperature 57 ℃,extraction time 34 min,liquid/solid ratio 42∶1 mL/g,and the extraction rate of polyphenols reaches 18.18%±0.23%. The in vitro antioxidant test showed that the extracted polyphenols had significant DPPH and OH free radical scavenging activity which were mass concentration-dependent. The IC₅₀ values were 8.42 and 24.70 μg/mL respectively,which were lower than V_C at the same mass concentration. Moreover,the extracted polyphenols exhibited strong inhibitory activity against α-glucosidase better than acarbose,with an IC₅₀ of 7.24 μg/mL. These results provided a theoretical basis for utilization of the natural antioxidation and hypoglycemic effect of Phoenix Dan Cong.