Biological mechanisms of glycan- and glycosaminoglycan-based nutraceuticals

A nutraceutical is defined as a standardized pharmaceutical-grade nutrient. Among hundreds of nutraceuticals, polysaccharide or glycan-based products such as those containing chondroitin sulfate glycosaminoglycan isolated from animal cartilage have been on the top nutraceutical selling list for many years. It is expected that the nutraceutical market will reach $250 billion dollars worldwide by 2018. Glycans are most abundant biopolymers on earth those are synthesized by bacteria, fungi, plants, insects, and animals. Glycans that are synthesized by animals or from all marine sources can be modified with covalently linked sulfates or containing acidic monosaccharides whereas glycans that are synthesized by terrestrial plants or fungi usually do not contain sulfates. Glycans such as starch are common sources of energy for animals, therefore they are on the nutrient-side of nutraceuticals. Undigestible polysaccharides from plants could serve as dietary fiber for humans that change the contents of the gastrointestinal tract and affect how other nutrients and chemicals are absorbed, thus dietary fibers could be called nutraceuticals. Other intra- and extracellular glycans from different sources serve as biological active components that regulate a myriad of physiological functions. The reported biological functions for such glycans are not limited to immune system regulatory, anti-coagulating, anti-tumor, anti-viral, anti-oxidant, anti-aging, and lipid-lowing activities, which make them pharmaceutical-side nutraceuticals. This review will present the full spectrum of glycan-based nutraceuticals and summarize current knowledge (published data from 1960s to current) of the structure, biological function, and mechanisms of glycans from both terrestrial and marine sources.