Structural characterization and immunostimulatory activity in vitro of a glycogen from sea urchin-Strongylocentyotus internedius.

Sea urchin possesses both high nutritional and medicinal value. It contains diverse biological active polysaccharides. But there are few studies on its glycogen. In the current study, a glucan (MSGA) was separated from Strongylocentyotus internedius and purified by ion exchange and gel filtration column. Chemical analysis revealed that MSGA with 2.65 × 10 Da is made up entirely of glucose. The analysis of methylation, NMR and mass spectrum demonstrated that MSGA is a highly branched glycogen with α-(1→4) linked gluconic backbone and branched at C-6 (one branch per five residues). In addition, MSGA showed good in vitro immunostimulatory activity via NF-κB and MAPKs pathways. It is considered that high degree of branching is necessary for its activity. However, the relationship between structure and immunostimulatory activity of natural glycogens is difficult to elucidate because the difference in their structural properties. Therefore, much more research is needed in this area.