Structural characterization and in vitro antioxidant and immunomodulatory activities of a water-soluble...

Polysaccharides are recognized as the primary functional components of Angelica sinensis. While a significant correlation between structural characteristics and biological activities of polysaccharides is established, this relationship for A. sinensis polysaccharides remains largely elucidated. In this study, we isolated a hydrosoluble low-molecular-weight polysaccharide from A. sinensis, designated as ASP-4. We subsequently characterized its structure and determined its biological activities. Structural analysis revealed that ASP-4 possessed a molecular weight of 23.18 kDa and was rich in uronic acids, with glucose and mannose as its principal constituent monosaccharides. Scanning electron microscope (SEM) imaging demonstrated that ASP-4 presented as amorphous aggregates with irregular circular lamellae and discernible pores. Further detailed structural elucidation indicated that the backbone of ASP-4 primarily comprised →4)-α-d-Glcp-(1→ and α-d-Glcp-(1→ units, with side chains predominantly composed of α-d-Manp-(1→ units. In terms of biological activities, ASP-4 was found to increase SOD, CAT and GPx activities, decrease MDA content, ameliorate nuclear damage and apoptosis, and suppress caspase-9 and caspase-3 activities in HepG2 cells. Furthermore, ASP-4 significantly inhibited the secretion of tumor necrosis factor-α (TNF-α) and stimulated the secretion of interleukin-10 (IL-10) in RAW 264.7 cells (p < 0.05). Immunoblotting analysis indicated that ASP-4 dose-dependently inhibited the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) signaling pathways at the cellular level. It also attenuated the phosphorylation of p65 and NF-κB inhibitor-α (IκB-α), thereby improving acute inflammatory infiltration. This study supported a structure-activity hypothesis for A. sinensis polysaccharide. Our findings open a new avenue for the utilization of medicinal and edible plant and provide a potential bioactivity exploitation for its polysaccharide.