Immune Enhancement Effects and Extraction Optimization of Polysaccharides from Peristrophe roxburghiana

The present study aims to optimize the extraction process and systematically investigate the bioactivity of polysaccharides derived from <i>Peristrophe roxburghiana</i> (Schult.) Brem. (CPPRs). To this end, the Box-Behnken design-response surface methodology was employed to optimize the extraction parameters of polysaccharides. The optimal extraction conditions were as follows: extraction temperature, 84 °C; extraction duration, 208 min; liquid-to-material ratio, 1:27 g/mL; extraction times, 4 times. The maximum extraction yield reached 17.89%, and the yield under non-optimal extraction conditions is 11-16%. This study systematically investigated the polysaccharides' physicochemical, structural, and morphological properties using multiple advanced techniques (FTIR, SEM, XRD, HPLC, rheology, and TGA). CPPRs are primarily composed of arabinose, galactose and glucose as the main monosaccharides, amorphous, and capable of low-viscosity gels at low shear rates. Furthermore, CPPRs displayed notable antioxidant activity in vitro, scavenging ABTS^•+ and DPPH^• and reducing Fe³⁺ (with scavenging/reducing rates exceeding 40% at a concentration of 1 mg/mL). Meanwhile, 3 mg/mL CPPRs reduced oxidative damage of red blood cells induced by AAPH, scavenging more than 50% of ROS, and reducing the hemolysis rate by 94.5%. Additionally, CPPRs significantly promoted secretion of cytokines (including TNF-α, IL-6, and IL-10) and NO in RAW264.7 macrophages in vitro compared with the untreated control group. These findings collectively highlight the potential of CPPRs-possessing both antioxidant and immune-enhancing properties-as promising functional ingredients for application in the food and pharmaceutical industries.