Abstract:Ultrasonic-assisted extraction of polyphenols from oil peony seed coats (OPSCP) was conducted, and the extraction yield was used as an evaluation index to optimize extraction conditions through single-factor experiments and response surface analysis. In addition, the antioxidant activity and in vitro fermentation characteristics of OPSCP were determined. The results showed that the optimal conditions of ultrasonic-assisted extraction of OPSCP are as follows: ethanol 60% V/V, solid-liquid ratio of 1:40, ultrasonic power of 480 W, and extraction time of 50 min. The polyphenol extraction yield equaled 83.11 mg GAE/g under the optimal conditions. The IC50 of DPPH, ABTS+ radical scavenging rate, and FRAP values of OPSCP in DPPH, ABTS, and FRAP assays were 8.19 mg GAE/g, 5.83 mg GAE/g, and 16.46 mg GAE/g, respectively, indicating good antioxidant activity. In vitro fermentation experiments showed that OPSCP can reduce the pH of the fermentation broth and increase the content of short-chain fatty acids (SCFAs) for both the normal and obese groups, with a more pronounced effect observed in the obese group. This study indicates that the polyphenols from oil peony seed coats exhibit significant in vitro antioxidant activity and have the effect potential to lower the pH and increase SCFAs in intestinal fermentation broth in vitro.