Abstract: This study aimed to investigate the structural characteristics and biological activity of polysaccharides from selenium-enriched Cordyceps militaris. A homogeneous polysaccharide (SeCMP0.2) was isolated and purified from the fruiting bodies of selenium-enriched C. militaris by water extraction and alcohol precipitation, followed by anion exchange column chromatography. The structural characteristics of SeCMP0.2 were characterized by high-performance gel permeation chromatography (HPGPC), high-performance liquid chromatography (HPLC), nuclear magnetic resonance spectroscopy (NMR), and atomic force microscopy (AFM). The immunoregulatory activity of SeCMP0.2 was evaluated by using RAW264.7 mouse macrophages. Results showed that the weight average molecular mass and selenium content of SeCMP0.2 were 440.7 kDa and 49.1 μg/g, respectively. SeCMP0.2, with a triple-helix conformation, was aggregated in aqueous solution. Moreover, it was a heteropolysaccharide mainly composed of galactose (53.1%), glucose (8.2%), and mannose (37.1%), containing both α- and β-type glycosidic linkages. The dominant residues in SeCMP0.2 including T-Galp-(1→, →2)-Galp-(1→, and →6)-Manp-(1→ accounted for 16.6%, 29.4% and 26.9%, respectively. Additionally, the in vitro immunomodulatory assays showed that SeCMP0.2 could significantly upregulate the mRNA expression levels of inducible nitric oxide synthetase (iNOS), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-1β (IL-1β) by activating the mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB) signaling pathways, thereby exerting immunoregulatory activity. These results will lay the foundation for further development and utilization of selenium-enriched C. militaris resources.

Key words: selenium-enriched Cordyceps militaris; polysaccharide; structural characteristics; immunoregulatory activity