Preparation, structural characterization and biological activities evaluation of non-carboxymethylated water-soluble polysaccharides derived from Monascus-fermented Poria cocos.

The main reason of low utilization for Poria cocos is primarily attributed to its extremely low content of water-soluble polysaccharides (WSP), which are associated with various biological effects. In this work, a water-soluble Poria cocos polysaccharide (F-WSP-1, 105.58 kDa) fermented by Monascus has been isolated and purified through water extraction, alcohol precipitation, and DEAE-52 cellulose column chromatography. Structural analysis by HPLC, GPC, and NMR confirmed F-WSP-1 as a non-carboxymethylated polysaccharide. Compared with native Poria cocos polysaccharide (PCP), F-WSP-1 showed a 25.62 % decrease in glucose content, while mannose, galactose, and fucose increased by 3.40 %, 10.46 %, and 11.95 %, respectively. Its molecular weight (Mw) increased by 48.66 %, and it exhibited a triple-helix conformation with porous, rough morphology. However, functional group composition and crystalline properties remained similar to PCP. The immunomodulatory and antitumor activities of F-WSP-1 were evaluated against RAW264.7 mouse macrophages and cancer cells (A549 lung cancer cells and SGC-7901 gastric cancer cells) using carboxymethylated Poria cocos polysaccharides (CMP) as a positive control, and the immunomodulatory of F-WSP-1 on the RAW264.7 cells without any toxicity and significantly promoted their proliferation, secretion of extracellular Nitric oxide (NO) and cytokine IL-1β, but the inhibitory effect on the proliferation of cancer cells was not obvious. The above results indicated that F-WSP-1 has certain immunomodulatory activity but no relevant antitumor activity, and the increase in immunomodulatory activity may be attributed to the characteristic structure related to the triple-helix structure, Mw, monosaccharide composition, and microscopic morphology, especially the formation of the glycan chain structure with α-D-galactose as the major monosaccharide component and galactose residues as the main backbone. The above results indicated that PCP can be biotransformed by Monascus to produce WSP with immunomodulatory activity, and provided a new insight for the high value utilization of Poria cocos biotransformation.