Structure-Function Correlations of Commercial Fucoidan Extracts: Antioxidant, Antiviral, Antifungal, Antibacterial and Prebiotic Activities

Fucoidan is a sulfated polysaccharide derived from brown seaweed, reported to possess diverse biological activities that make it a molecule of great interest for nutraceutical and biomedical applications. A significant challenge to its wider use is the limited understanding of the relationship between fucoidan’s structural and chemical characteristics with biological activity. This gap was addressed by detailed chemical characterization of commercial fucoidan extracts and biological activity testing (antioxidant, antiviral, antifungal, antibacterial and prebiotic) to elucidate potential relationships for further study. Fucoidan extracts exhibited multiple bioactivities, notably antioxidant activity, antiviral activity against Nipah virus, antifungal activity against Candida dubliensis and prebiotic effects on Lactobacillus casei. No antifungal activity against Candida albicans, Candida auris and Cryptococcus neoformans, nor antibacterial effects against Klebsiella pneumoniae, were observed. A correlation analysis to identify potential key quality attributes of fucoidan was employed, suggesting that high fucose content may be important for antioxidant, antiviral, antifungal, and prebiotic activities. A high sulfation degree was also identified as potentially optimal for these bioactivities. This work also addressed a debate in the literature regarding the optimal molecular weight for bioactivity, demonstrating that this likely depends on the specific microbe to which a fucoidan extract is applied, with smaller molecular weights required for antioxidant and antiviral bioactivities and larger molecular weights for antifungal and prebiotic activities. This study demonstrates that a formalized comparative approach linking chemical and structural data with results from biological activity assessments can effectively identify important fucoidan characteristics underpinning specific bioactivity. The results of which are worthy of further validation.