Structural Characterization and Biological Activities of a Novel Polysaccharide from Cultured Cordyceps militaris and Its Sulfated Derivative

A novel polysaccharide (CMPA90-1; compound 1) was isolated from the cultured fruiting bodies of Cordyceps militaris. The chemical structure of compound 1 was elucidated by acid hydrolysis, periodate oxidation, Smith degradation, and methylation analysis, along with Fourier transform infrared spectroscopy, high-performance anion-exchange chromatography coupled with pulsed amperometric detection, gas chromatography–mass spectrometry, and one-dimensional [1H and 13C nuclear magnetic resonance (NMR)] and two-dimensional NMR (heteronuclear single-quantum coherence and heteronuclear multiple-bond correlation). Sulfation of compound 1 by the chlorosulfonic acid–pyridine (CSA–Pyr) method led to synthesis of its sulfated analogue (CMPA90-M1; compound 2). The ultrastructures of both compounds 1 and 2 were further characterized by scanning electron microscopy and atomic force microscopy. The results of antioxidant assays showed that compounds 1 and 2 exhibited free-radical-scavenging effects, ferrous-ion-chelating ability, and reducing power. Also, in the cytotoxicity assay, compounds 1 and 2 showed inhibitory activity against A549 cells, with IC50 values of 39.08 and 17.33 μg/mL, respectively.