Advances in fucoidan extraction and structure-bioactivity relationships

Fucoidan is a sulfated polysaccharide from brown seaweeds whose heterogeneous structure and broad bioactivities have stimulated extensive investigation. While primarily composed of fucose, its composition varies in monosaccharide content (e.g. galactose, xylose, mannose, glucuronic acid), backbone architecture, branching, and sulfation patterns, with these features influenced by species, environmental factors, and extraction conditions. Because extraction methods can preserve or degrade structural motifs essential to bioactivity, methodological variation has contributed to longstanding inconsistencies in reported structure-bioactivity relationships. This review critically explores advances in fucoidan extraction, including emerging optimization strategies and sequential extraction approaches, and evaluates their effects on yield, purity, and structural integrity. We further examine recent developments in understanding structure-bioactivity relationships, highlighting insights derived from molecular docking, multi-omics platforms, and integrative systems-level analyses. Together, these perspectives provide a consolidated framework for relating extraction conditions, structural characteristics, and biological function in fucoidan research.