Preparation, bioactivities, structure-activity relationships, applications, and safety concerns of Inonotus obliquus...

Inonotus obliquus polysaccharides (IOPs) are β-glucan-rich heteropolysaccharides whose structural diversity underlies their immunomodulatory, antioxidant, and gut-organ-axis-mediated activities. This review synthesizes recent advances in IOPs extraction, purification, and structural characterization, clarifying how molecular weight distribution, monosaccharide composition, glycosidic linkage patterns, branching topology, and triple-helix integrity collectively determine biological performance. Emerging green extraction technologies-such as subcritical water and enzyme-assisted approaches-have improved yield while better preserving native structural features. Practical criteria for raw-material selection and key extraction parameters are further outlined to promote standardized preparation and improve inter-study reproducibility. By integrating current knowledge and refining understanding of IOPs structure-activity relationships, this review seeks to identify critical knowledge gaps and suggest directions for future research and development, including the optimization of extraction strategies, integration of multi-omics technologies to deepen structure-activity elucidation, and expansion of IOPs applications in food, biomedical, and sustainable material fields.