Extraction Optimization and Antioxidant Activity of Saponins from Hovenia dulcis Pedicels

In order to improve the resource utilization rate of Hovenia dulcis pedicels (HDPS), the purpose of this study was to optimize the extraction process of saponins and evaluate their antioxidant activity. HDPS was extracted by the homogenization-assisted ultrasonic extraction. On the basis of a single-factor experiment, the extraction process parameters were optimized by the response surface methodology, and the crude extract was purified by D101 macroporous resin. The structure and composition of the purified product were characterized by Fourier transform infrared spectroscopy (FT-IR) and ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Finally, the DPPH·, ABTS⁺·, ·OH radicals, and the ferric reducing power of HDPS were verified by an in vitro antioxidant model. The results showed that the optimum extraction conditions were as follows: ethanol concentration 49%, liquid-to-solid ratio 30:1 mL/g, homogenization ultrasonic time 21 min, ultrasonic power 400 W, homogenization power 500 W. Under these conditions, the yield of HDPS was 4.41%±0.13%. After purification by D101 macroporous resin, the purity of HDPS was significantly increased from 34.37% to 67.12%. UPLC-MS/MS analysis showed that HDPS mainly contained saponins such as echinacoside B, jujuboside B, and so on. In vitro antioxidant experiments showed that HDPS had significant scavenging ability to DPPH·, ABTS⁺·, and ·OH radicals, and its IC₅₀ values were 165.3, 56.2, and 168.7 μg/mL, respectively, and had a certain iron reducing power. This study provides a theoretical basis and technical support for the comprehensive development and utilization of Hovenia dulcis fruit stem and its application in the field of functional food.