Structural characteristics and immunomodulatory effects of sulfated polysaccharides derived from marine algae

Marine algae are becoming an important source of valuable candidates of functional food that remain unexplored. Compositional analysis showed that marine algae contain essential nutrients, such as carbohydrates, proteins, fats, and minerals, of which polysaccharides are the main bioactive component. Depending on the source, marine algae polysaccharides are sulfated, which have diverse structures and compositions that influence their biological activities. A growing body of evidence has demonstrated that sulfated polysaccharides derived from marine algae (SPs) exhibit various bioactivities, especially immunomodulation. This review aims at summarizing the structural characteristics of SPs, their immunomodulatory effects, and the structural-immunomodulatory activity relationships between them from articles in recent decade, in order to provide a theoretical basis for the further applications of SPs as promising food or feed additives and possible health products to modulate the immune response.