Simultaneous Extraction and Analysis of Seven Major Saikosaponins from Bupleuri Radix and the Exploration of Antioxidant Activity and Its Mechanism

Saikosaponins (SS) are the main active components of Bupleuri Radix. In this study, the yields of SS a, b(1), b(2), c, d, e, and f were simultaneously determined using the HPLC-DAD dual wavelength method, and the ultrasound-assisted extraction process of saikosaponins was optimized using the response surface methodology. The antioxidant effect of saikosaponins was investigated using the scavenging rate of 1, 1-diphenyl-2-picrylhydrazyl (DPPH), 2, 2-diazo-bis (3-ethyl-benzothiazole-6-sulfonic acid) diammonium salt (ABTS), and hydroxyl (-OH) groups, and the mechanism was clarified via network pharmacological analysis. The results showed that the optimal extraction process of SS was a 5% ammonia–methanol solution as an extraction solvent, a material–liquid ratio of 1:40, a temperature of 46.66 °C, an extraction time of 65.07 min, and an ultrasonic power of 345.56 W. The total content of the seven saikosaponins under this condition was up to 6.32%, which was close to the model’s predicted value of 6.56%, where the yields of the seven saikosaponins a, b(1), b(2), c, d, e, and f were 1.18%, 0.11%, 0.26%, 1.02%, 3.02%, 0.38%, and 0.44%, respectively. The saikosaponins have an obvious scavenging ability for DPPH, ABTS, and -OH radicals. The interactions of seven saikosaponins with antioxidant targets were studied, and a database was used to collate the core of saikosaponins and antioxidants through network pharmacology. The mechanisms of the antioxidant effects of the saikosaponins were derived via GO enrichment analysis and KEGG pathway analysis. Finally, the binding energy of the saikosaponins to the antioxidant targets was found to be less than −5.0 kcal·mol(−1) via molecular docking, indicating that the antioxidant capacity of the saikosaponins are good. Therefore, this study developed a rapid and efficient method for the extraction of saikosaponins, which provides a theoretical basis for an in-depth understanding of the rational utilization of saikosaponins and the development of their medicinal value.