Stimulation of lymphocyte proliferation by oyster glycogen sulfated at C-6 position

In this study, glycogen was extracted from oyster Ostrea talienwhanensis Crosse and used as a model to investigate the structure–activity correlation of polysaccharides. Purified oyster glycogen was characterized by methylation analysis, nuclear magnetic resonance (NMR) spectroscopy and infrared spectroscopy (IR). The oyster glycogen was subsequently sulfated by chlorosulfonic acid–pyridine method, and a C-6 substituted species (SOG) was identified to be the primary sulfated oyster glycogen species by 13C NMR spectroscopy. The molecular weight and sulfate content of the SOG was determined to be 3.2 × 104 g/mol and 33.6%, respectively. Another sulfated oyster glycogen species (SOG1) with C-2 and C-3 substitution was also identified at a lesser amount in the final product. SOG exhibited a much stronger stimulation effect to splenic lymphocyte proliferation than SOG1 in vitro, indicating that the position of sulfate substitution is a major determining factor on the efficacy of sulfated glycogens to stimulate lymphocyte proliferation.