Optimization of ultrasonic-assisted extraction of total saponins from Semen Ziziphi Spinosae and evaluation of their antioxidant activity and pH stability.

This study aimed to optimize the ultrasonic-assisted extraction (UAE) process for Semen Ziziphi Spinosae total saponin (SZS-TS) from defatted Semen Ziziphi Spinosae powder and to assess the antioxidant activity and pH stability of the SZS-TS obtained under these conditions. Single-factor experiments, along with a four-factor, three-level Box-Behnken response surface methodology, were utilized to optimize the UAE process parameters. The optimal extraction conditions included an ultrasonic temperature of 50℃, an ethanol concentration of 70%, a solid-liquid ratio of 1:20 (g/mL), an ultrasonic power of 360 W, and an ultrasonic time of 50 min, with an average SZS-TS extraction yield of 2.719%. Compared with the traditional water decoction method (WDM), the optimized UAE significantly increased (P < 0.001) the yields of SZS-TS and jujuboside A by 137.88% and 161.15%, respectively, while no significant difference was observed in the yield of jujuboside B (P > 0.05). In vitro antioxidant assays showed that SZS-TS exhibited concentration-dependent scavenging effects against ABTS+·, DPPH·, ·OH, and O2⁻· free radicals, with the scavenging rates of 83.30%, 75.18%, 57.20%, and 13.00% at the maximum tested concentration of 2.5 mg/mL, respectively, but its antioxidant activity was lower than that of vitamin C at the same mass concentration. In vivo experiments utilizing a diquat-induced oxidative stress model in broilers confirmed the antioxidant effect of SZS-TS, which dose-dependently increased serum superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities, and enhanced total antioxidant capacity (T-AOC). Furthermore, pH stability tests indicated that SZS-TS exhibited the highest stability under weak acidic conditions (pH 5.77), with a total retention rate of 85.51% after 12 d of storage at 4°C. This study provides a scalable, green extraction strategy for SZS-TS, laying a theoretical foundation for its industrial applications in functional foods and pharmaceuticals.