Abstract:[Objective] This study optimized the extraction process of polyphenols from Camellia japonica (C. japonica) flowers and preliminarily explored the antioxidant and blood glucose-lowering effects of the extracted polyphenols, aiming to improve the utilization of C. japonica flowers. [Method] With the flowers of Xinyang Maojian as raw materials, the ultrasonic-assisted method was adopted to extract polyphenols from C. japonica flowers, and the antioxidant and blood glucose-lowering activities of the extracted polyphenols were analyzed. With the extraction rate of polyphenols from C. japonica flowers as the evaluation index, the response surface methodology was adopted to explore the effects of ethanol volume fraction, solid-liquid ratio, extraction time, and ultrasonic power on the extraction rate of polyphenols from C. japonica flowers. [Result] Under the conditions of the ethanol volume fraction of 54%, the solid-liquid ratio of 1 g∶33 mL, the extraction time of 49.5 min, and the ultrasonic power of 210 W, the actual extraction rate obtained from verification experiment was 12.60%, with a relative standard deviation (RSD) of 2.28%, which indicated that the optimization results were reliable. In addition, the polyphenols from C. japonica flowers had strong scavenging abilities against DPPH, hydroxyl, and ABTS+ free radicals. The scavenging abilities were positive correlated with the mass concentration of the extracted polyphenols, and the half-inhibitory mass concentrations (IC50) were 0.044, 0.065, and 0.068 mg/mL, respectively. The extracted polyphenols had good inhibitory effects on the activities of α-glucosidase and α-amylase, with the IC50 of 0.054 and 0.057 mg/mL, respectively. [Conclusion] The polyphenols from C. japonica flowers can be used as a good natural antioxidant and blood glucose-lowering agent, demonstrating potential application value. This study provides a theoretical foundation for the refined processing of C. japonica flowers.
