Extraction, purification, structural characterization and immunomodulatory activity of a polysaccharide from Hirudo...

Hirudo nipponica Whitman has been utilized in traditional medicine for centuries for its bioactive components. In this study, a novel polysaccharide, which was called SZ, was isolated from H. nipponica Whitman through enzymatic hydrolysis, alkaline extraction, and chromatographic purification. The structure of SZ was characterized using high-performance liquid chromatography (HPLC), Fourier-transform infrared spectroscopy (FT-IR), gas chromatography-mass spectrometry (GC-MS), and nuclear magnetic resonance (NMR) spectroscopy. The results revealed that SZ has a prevalent component monosaccharide of glucose (Glc) and a backbone of →4-)α-D-Glcp-(1 → residues, with branches attached at O-3 and O-6 positions. The molecular weight of SZ was determined to be 221.28 kDa. SZ exhibited potent immune-enhancing activity in vitro, as demonstrated by its ability to modulate the expression of inflammatory cytokines in RAW264.7 macrophages. Real-time quantitative PCR analysis further confirmed the immunomodulatory effects of SZ on RAW264.7 cells, showing significant upregulation of iNOS, TNF-α, and IL-6 mRNA expression. This study suggests that SZ has the potential to serve as an immunomodulatory agent.