Health Benefits of Polysaccharides in Red Algae: A Comprehensive Review

Humans have long consumed red algae (especially by the Asian community), and their polysaccharide extracts (carrageenan, agar) are extensively used in the food industry as gel thickeners. Furthermore, due to the wide variety of habitats red algae inhabit, red algal polysaccharides possess many interesting structures, possessing unique structures and monosaccharides which are not found in other organisms. These unique structures have allowed red algal polysaccharides to display many bioactivities such as anticoagulant, antiviral, antioxidant, and anti‐inflammation. However, the use of red algal polysaccharides as nutraceuticals is rare despite displaying such promising bioactivities. One key reason for this is the same complex structure that enables bioactivity, also complicates studies of red algal polysaccharides as direct comparisons between studies can rarely be done due to the large amount of changed variables. Thus, this review aims to provide a high‐level overview of red algal polysaccharides to ease further delving into red algal polysaccharides, particularly in a nutraceutical context. The review starts by introducing the basic structure of well‐known red algal polysaccharides. This is followed by highlighting current extraction and characterization methods of algae. Various bioactivities displayed by red algal polysaccharides in the nutraceutical (gastrointestinal) context are then highlighted. Among the bioactivities, the potential health benefits resulting from the interaction of red algal polysaccharides with the gut microbiota stood out, and more effort can be invested in such studies. Finally, the major challenges of turning red algae polysaccharides into a nutraceutical product are raised. These include difficulty in accounting for algae variability and a lack of understanding of structure–activity relationships.