Sulfated modification of polysaccharides from Sophora flavescens: Impact on antioxidant, antitumor, and immunomodulatory activities

Three polysaccharides, namely SHC, SFH, and SFA, were extracted from Sophora sophora under various conditions. A single-factor experimental design was employed to investigate the influence of reaction solvent, sulfating reagent ratio, reaction time, and temperature on the yield of sulfated products, the degree of sulfate group substitution, and their inhibitory effects on HepG2 cell proliferation. Three sulfated derivatives, SHCS, SFHS, and SFAS, were synthesized and confirmed through Fourier Transform Infrared Spectroscopy, Ultraviolet Spectroscopy, and Nuclear Magnetic Resonance Spectroscopy. Among these, SFHS exhibited the highest degree of substitution (DS) at 1.22, followed by SFAS at 0.97 and SFCS at 0.56. In vitro analyses revealed that sulfated modification significantly enhanced free radical scavenging activity, tumor cell growth inhibition, and immune response enhancement. Specifically, SFHS exhibited scavenging activities against DPPH, hydroxyl, and superoxide anion free radicals with rates of 69.8 % ± 6.1 %, 50.4 % ± 4.2 %, and 58.5 % ± 5.1 %, respectively, at 5 mg/mL. Furthermore, it inhibited the proliferation of HepG2 cells by 51.9 % ± 5.6 % at 400 μg/mL and HeLa cells by 43.7 % ± 1.8 % at 800 μg/mL. At 800 μg/mL, SFHS treatment resulted in a phagocytosis rate of neutral red by RAW264.7 macrophages, which was 246.6 % ± 13.9 % relative to the control group, while nitric oxide production was measured at 237.6 % ± 6.2 %. These results suggest that sulfation can enhance the biological functions of polysaccharides derived from S. flavescens, indicating potential applications in functional foods and pharmaceuticals.