Functional ingredients for human health have recently become the focus of research. One such potentially versatile therapeutic component is fucose-containing sulfated polysaccharides (FCSPs), referred to as fucoidans. The exploitation of marine brown algae provides a rich source of FCSPs because of their role as a structural component of the cell wall. Fucoidans are characterized by a sulfated fucose backbone. However, the structural characterization of FCSPs is impeded by their structural diversity, molecular weight, and complexity. The extraction and purification conditions significantly influence the yield and structural alterations. Inflammation is the preliminary response to potentially injurious inducements, and it is of the utmost importance for modulation in the proper direction. Improper manipulation and/or continuous stimuli could have detrimental effects in the long run. The web of immune responses mediated through multiple modulatory/cell signaling components can be addressed through functional ingredients, benefiting patients with no side effects. In this review, we attempted to address the involvement of FCSPs in the stimulation/downregulation of immune response cell signaling. The structural complexity and its foremost influential factor, extraction techniques, have also attracted attention, with concise details on the structural implications of bioactivity.

The previous study suggested that the sulfated polysaccharides from Hizikia fusiforme (HFPS) possess strong antioxidant activity. The purpose of this study is to isolate fucoidan from HFPS and to investigate its antioxidant activity. A fucoidan (HFPS-F4) with a molecular weight of 102.67 kDa was isolated from HFPS. HFPS-F4 contains 99.01% of fucoidan (71.79 ± 0.56% of carbohydrate and 27.22 ± 0.05% of sulfate content). The fucoidan increased the viability of H₂O₂-treated Vero cells by 5.41, 11.17, and 16.32% at the concentration of 12.5, 25, and 50 μg/mL, respectively. Further results demonstrated that this effect act diminishing apoptosis by scavenging intracellular reactive oxygen species (ROS) via increasing the expression of the endogenous antioxidant enzymes, which was induced by elevating total nuclear factor (erythroid-derived 2)-like 2 (Nrf2) levels. In addition, the in vivo test results displayed that the pretreatment of fucoidan improved the survival rates and decreased heart-beating rate, ROS, cell death, and lipid peroxidation in H₂O₂-stimulated zebrafish. Taken together, these results demonstrated that fucoidan isolated from HFPS has strong in vitro and in vivo antioxidant activities and it could be utilized in pharmaceutical, nutraceutical, and cosmeceutical industries.

Elevated levels of reactive oxygen species (ROS) damage the internal cell components. Padina boryana, a brown alga from the Maldives, was subjected to polysaccharide extraction. The Celluclast enzyme assisted extract (PBE) and ethanol precipitation (PBP) of P. boryana were assessed against hydrogen peroxide (H₂O₂) induced cell damage and zebra fish models. PBP which contains the majority of sulfated polysaccharides based on fucoidan, showed outstanding extracellular ROS scavenging potential against H₂O₂. PBP significantly declined the intracellular ROS levels, and exhibited protection against apoptosis. The study revealed PBPs’ ability to activate the Nrf2/Keap1 signaling pathway, consequently initiating downstream elements such that catalase (CAT) and superoxide dismutase (SOD). Further, ROS levels, lipid peroxidation values in zebrafish studies were declined with the pre-treatment of PBP. Collectively, the results obtained in the study suggest the polysaccharides from P. boryana might be a potent source of water soluble natural antioxidants that could be sustainably utilized in the industrial applications.