Can Fucoidans of Brown Algae Be Considered as Antioxidants?

The ability of fucoidans to scavenge reactive oxygen species still remains a subject of debate in scientific literature, as shown by an analysis of the results of recent studies on the antioxidant activity (AOA) of fucoidans. On the one hand, in vitro and in vivo experiments provide evidence that fucoidans of brown algae can modulate diseases associated with oxidative stress by regulating the antioxidant defense systems and signaling pathways. On the other hand, the use of cell-free assay systems has revealed a relationship between the antioxidant activity attributed to fucoidans and the polyphenolic compounds extracted along with them. The polyphenolic compounds of brown algae referred to as phlorotannins are also known as potent antioxidants. Since the vast majority of studies use various commercial preparations or extracts containing fucoidan and polyphenolic compounds without measuring the level of the latter in polysaccharide samples, there is still no clear understanding of whether fucoidans or co-extracted polyphenolic compounds are a priority component providing AOA.