Orchid polysaccharides: Structural characteristics, bioactivities, and applications in biomaterials

Orchid polysaccharides (OPs) have emerged as a focal point in biomedical research due to their distinctive antioxidant, anti-inflammatory, and immunomodulatory properties. This review systematically examines the structural characteristics, bioactivities, structure-activity relationships (SAR), and biomedical applications of these polysaccharides. Characterized by glucomannan backbones with β-1,4-glycosidic linkages and acetyl modifications, their chain heterogeneity, fibrous network morphology, and exceptional thermal stability are intrinsically linked to biological functionality. Mechanistically, OPs demonstrate therapeutic efficacy by modulating key antioxidant/anti-inflammatory pathways, enhancing the immune system, and remodeling the gut microbiota, thereby exhibiting broad-spectrum therapeutic potential in oxidative stress mitigation, tumor suppression, neuroprotection, metabolic regulation, tissue repair, and the protection of multiple organs. SAR studies reveal that chemical modifications such as sulfation and selenization significantly enhance bioactivity, while enzymatically derived oligosaccharides retain critical functional domains. Innovative applications encompass transdermal delivery systems, targeted nanoparticles, microneedle patches, and injectable hydrogels, highlighting their promise in precision drug delivery and regenerative medicine. Current challenges involve scaling up production processes, elucidating molecular mechanisms, and achieving clinical translation. Future research should integrate omics technologies, artificial intelligence, and advanced characterization methods to advance OPs as multi-indication therapeutics and intelligent biomaterials.