Optimization of Purification of Tea Polyphenols with Macroporous Adsorption Resin and Research of Their Antioxidant Activity

To optimize the technical condition for purification of tea polyphenols with macroporous adsorption resin, the static adsorption and desorption performance of macroporous adsorption resin of fourteen types were compared to select the best type of resin. The optimal purification process conditions were determined by single factor and response surface experiments, and the reuse and regeneration times of the resin were further investigated. Meanwhile, the antioxidant activities of tea polyphenols before and after purification were investigated by in vitro experiments with V_C as the control. The results showed that LX-8 resin had the best adsorption-desorption effect on tea polyphenols, which could be reused 5 times and regenerated 6 times. The optimum purification conditions were as below: The sample concentration of 6.4 mg/mL, the sample pH value of 5.4, the loading volume of 100 mL, the sample flow rate of 1.0 mL/min, ethanol concentration of 76% eluting agent volume of 180 mL, and desorption rate of 1.0 mL/min. Under these conditions, the recovery rate of tea polyphenols was 86.9% and the purity was 74.6%. In vitro antioxidant activity studies revealed that the total antioxidant capacity, DPPH· scavenging capacity and ·OH scavenging capacity of the purified tea polyphenols were significantly increased. And with the increase of polyphenol concentration, its antioxidant capacity enhanced. The total antioxidant capacity of the purified tea polyphenol (1 mg/mL) was 80.59 U/mL. The IC₅₀ of the purified tea polyphenol on scavenging ability of DPPH· and ·OH were 0.0326 and 0.4167 mg/mL respectively. Although the antioxidant activity of pure extract was lower than that of V_C, it was higher than that of crude extract, indicating that the antioxidant activity of tea polyphenols could be significantly improved by this process, and when the concentration of the purified tea polyphenol was 1 mg/mL, its DPPH· scavenging rate was close to that of V_C. This research provided a theoretical reference for the industrial production and utilization of tea polyphenols.