Inonotus hispidus Polysaccharides Prepared by Graded Ethanol Precipitation Modulate the Gut-Immune Axis in Cyclophosphamide-Induced Immunosuppressed Mice.
Inonotus hispidus polysaccharides (IHP) from this edible medicinal fungus exhibit notable immunological benefits, yet fraction specific effects on host immunity and the gut microbiota remain unclear. This study investigated the differential bioactivities of three graded ethanol-precipitated fractions (IHP-65, IHP-75, and IHP-85) in a cyclophosphamide (CTX)-induced immunosuppressed mouse model. Structural characterization revealed that IHP-65 was a 1098 kDa complex heteropolysaccharide, whereas IHP-85 comprised a highly uniform 19.7 kDa glucan core. Following oral administration, all fractions mitigated CTX induced weight loss, significantly increased spleen and thymus indices, and restored IL-2 and TNF-α toward normal levels. Efficacy was strictly fraction dependent, with the low molecular weight IHP-85 consistently outperforming IHP-75 and IHP-65. Microbiota analysis showed a marked reversal of CTX induced dysbiosis, significantly expanding Bacteroidetes and Firmicutes while suppressing Proteobacteria. At the genus level, Alistipes and Lactobacillus rose and Alloprevotella declined, collectively tracking a recovery trajectory toward the normal control community. These findings demonstrate distinct structure activity relationships among IHP fractions, establishing a clear mechanistic framework for utilizing specific low molecular weight glucans as functional food ingredients to modulate host health via the gut immune axis. PRACTICAL APPLICATIONS: This research demonstrates that graded ethanol precipitation is an effective method for isolating high-activity polysaccharides from Inonotus hispidus. Specifically, the fraction precipitated at high ethanol concentrations shows superior potential for boosting immunity and regulating gut health. These findings provide a scientific basis for food manufacturers to optimize processing techniques and develop effective, natural functional food ingredients targeted at immune support.