Optimization of Ultrasound-assisted Alkali Extraction of Bound Polyphenol from Rosa sterilis and Its Antioxidant Activity

In order to investigate the application and development of Rosa sterilis in the field of drug-food homology, the Box-Behnken method was used to optimize the extraction process of bound polyphenols from Rosa sterilis based on the single factor experiment. The study also examined the clearance rate of DPPH·, ABTS⁺·, and ·OH and total reducing power of bound polyphenols and free polyphenols from Rosa sterilis, with V_C as controls. The results showed that the optimal extraction conditions for the bound polyphenols of Rosa sterilis were a liquid-to-solid ratio of 24 mL/g, a lye concentration of 8 mol/L, an ultrasonic time of 47 min, and an ultrasonic power of 250 W. Under these conditions, the amount of extracted bound polyphenols was 135.73 mg GAE/g, which was close to the predicted value of the regression model (135.77 mg GAE/g). The model fit was excellent. The IC₅₀ values of the bound polyphenols to DPPH· and ABTS⁺· were 0.0599 and 0.0121 mg/mL, respectively. These values were significantly (P<0.05) lower than those of the free polyphenols (0.168, 0.0395 mg/mL). In the concentration range of 0.02~0.1 mg/mL, the scavenging ability of bound polyphenols on ·OH was strong, which was not significantly different from that of V_C (P>0.05). The total reducing power of the bound polyphenols was higher than that of the free polyphenols. Additionally, the total reducing power of both polyphenols was significantly influenced by the concentration of the solution. The extracted bound polyphenols can be used as natural antioxidants, providing a theoretical basis for the processing and utilization of Rosa sterilis.