Study on macrophage activation and structural characteristics of purified polysaccharide from the liquid culture broth of Cordyceps militaris

The water-soluble crude polysaccharides obtained from the liquid culture broth of Cordyceps militaris by ethanol precipitation were fractionated by DEAE cellulose and Sepharose CL-6B column chromatography. This fractionation process resulted in three polysaccharide fractions that were termed CPSN Fr I, CPSN Fr II, and CPSN Fr III. Of the fractions, CPSN Fr II was able to upregulate the functional events mediated by activated macrophages, such as production of nitric oxide (NO) and expression of cytokines (IL-1β and TNF-α). Its structural characteristics were investigated by a combination of chemical and instrumental analyses, including methylation, reductive cleavage, acetylation, Fourier transform infrared spectroscopy (FT-IR), and gas chromatography–mass spectrometry (GC–MS). Results indicate that CPSN Fr II was a 1,6-branched-glucogalactomannan that had a molecular weight of 36 kDa. The configuration of the β-linkage and random coil conformation of CPSN Fr II were confirmed using a Fungi-Fluor kit and congo red reagent, respectively.