Structural characterization and antiviral activity of polysaccharide from Codonopsis pilosula

Codonopsis polysaccharides exhibit diverse biological activities, but their antiviral effects against the H1N1 influenza A virus and how these activities change after sulfation modification remains unclear. In this study, crude Codonopsis polysaccharide (COP) was obtained via water extraction and alcohol precipitation, and COP-1 (2.1 × 103 Da, β-D-(2 → 1)-fructan) was isolated and purified. Both COP and COP-1 were modified by sulfation using the sulfur trioxide-pyridine method, yielding derivatives SCOP and SCOP-1 with degrees of substitution of 1.792 and 1.403, respectively. Antiviral activity was evaluated in MDCK cells using MTT and TCID₅₀ assays, revealing that COP, SCOP, and SCOP-1 all inhibited H1N1 replication, with sulfation significantly enhancing antiviral activity. Time-of-addition experiments indicated that inhibition occurred during the early phase of infection (0-4 h). Annexin V-PI staining confirmed that these compounds reduced virus-induced early apoptosis. In H1N1-infected A549 cells, they suppressed NF-κB p65 phosphorylation and downregulated the expression of IL-6, IL-8, MCP-1, CCL-5, TNF-α, and TRAIL. Overall, Codonopsis polysaccharides and their sulfated derivatives exert anti-influenza effects through a triple mechanism involving inhibition of early viral replication, anti-apoptotic activity, and anti-inflammatory action, making them promising candidates for antiflu therapeutics.