Chemical Synthesis and Biological Evaluation of Sulfated DK4 Derivatives from Escherichia coli K4 Polysaccharide

Three sulfated derivatives were synthesized using microbially derived defructosylated K4 (DK4) polysaccharide as a chondroitin-like polysaccharide backbone. The obtained derivatives were structurally characterized by nuclear magnetic resonance spectroscopy, Fourier-transform infrared spectroscopy, elemental analysis, and disaccharide composition analysis. The results demonstrated that sulfate groups were successfully introduced into the DK4 structure, while the main chondroitin-like polysaccharide backbone of DK4 was largely preserved after sulfation. Further biological evaluation indicated that the sulfated DK4 derivatives differentially altered the expression levels of Ras homolog family member A/Rho-associated coiled-coil-containing protein kinase 1 (RhoA/ROCK1) and myelin basic protein (MBP). This work provides an experimental basis for further elucidating the structure–activity relationship between sulfation patterns and glial cell functions.