Optimization of Polyphenol Extraction Process, Analysis of Components and Antioxidant Activity of Jujube

The polyphenol compounds in red jujube were extracted by ultrasonic-assisted extraction process. The methanol concentration, ultrasonic time, ultrasonic temperature and solid-liquid ratio were selected to conduct the single factor experiments. On this basis, the response surface methodology was used to optimize the process parameters, and the high-resolution liquid-mass spectrometer was used to determine the polyphenol components in red jujube to evaluate the antioxidant activity of the polyphenol based on its ability to remove DPPH and superoxide anion radicals. The results showed that, the optimal ultrasonic-assisted extraction conditions were as follows: Methanol concentration 70%, ultrasonic time 40 min, ultrasonic temperature 60℃, solid-liquid ratio 1:40 (g/mL). Under these conditions, the polyphenol yield was 1.397%±0.08%. A high-resolution liquid chromatography-mass spectrometry (HPLC-MS) method was developed for the determination of 19 components in jujube polyphenols, including phenolic acids and their derivatives, flavonoids and triterpenoids. The results of antioxidant experiments showed that the maximum clearance of DPPH was 77.63% when the polyphenol concentration of jujube was 0.3 mg/mL. The maximum clearance of superoxide anion radical was 82.48% when the concentration was 0.8 mg/mL, and with the increasing of polyphenol concentration, the clearance was close to V_C, indicating that the polyphenol compound extracted from jujube had strong antioxidant activity and was a natural antioxidant with great development potential.