Fucoidan: Structure–activity relationships, molecular mechanisms, and nanotherapeutic applications with perspectives from Traditional Chinese Medicine

Introduction Fucoidan is a sulfated polysaccharide derived from brown macroalgae that has attracted considerable attention due to its diverse biological activities and therapeutic potential. Its bioactivity is closely associated with structural characteristics such as molecular weight, sulfation pattern, monosaccharide composition, and branching architecture. Methods This narrative review summarizes recent advances in fucoidan research, focusing on its sources, structural characteristics, structure–activity relationships, molecular mechanisms, biological activities, nanotherapeutic applications, and perspectives from Traditional Chinese Medicine (TCM). Results Fucoidan exhibits a broad spectrum of biological activities, including antioxidants, anti-inflammatory, anticoagulant, antiviral, immunomodulatory, and anticancer effects. These activities are mediated through multiple signaling pathways, including Nrf2/ARE, NF-κB, MAPK, PI3K/Akt, and caspase-dependent apoptotic pathways. Recent studies have demonstrated the potential of fucoidan-based nanocarriers for targeted and controlled drug delivery, improving bioavailability, therapeutic efficacy, and tumor targeting. Furthermore, modern pharmacological evidence increasingly supports the traditional use of fucoidan-rich seaweed in TCM. Discussion The therapeutic efficacy of fucoidan is strongly influenced by its structure–activity relationships and physicochemical properties. Despite challenges related to structural heterogeneity, bioavailability, and limited clinical evidence, advances in nanotechnology and biomedical research continue to expand its potential applications. Fucoidan represents a promising marine-derived biomolecule for the development of future pharmaceuticals, nutraceuticals, and targeted therapeutic systems.