Structure and antioxidant activities of sulfated guar gum: Homogeneous reaction using DMAP/DCC catalyst

It was essential to understand the chemical structure of polysaccharides for further research and biochemical or medical application of this natural biopolymer. In the present study, sulfated derivatives of guar gum with high degree of sulfation (DS) were synthesized using 4-dimethylaminopyridine (DMAP)/dimethylcyclohexylcarbodiimide (DCC) as catalyst in homogeneous conditions. The effects of the ratio of chlorosulfuric acid to pyridine, the content of catalyst and reaction temperature were investigated. Results of FT-IR, 1H and 13C NMR indicated that C-6 substitution was predominant in sulfated polysaccharide. In the sulfation reaction, a sharp decrease in MW was observed. The enhanced antioxidant activities of sulfated polysaccharides were not a function of a single factor but a combination of high DS and low molecule weight.

► An efficient catalyst system was studied. So far, there are not similar reports in this area.
► The current studies are focus on structure characterization and antioxidant activities of sulfated polysaccharides.
► The originality of this work is obvious. We hope it could provide valuable information on polysaccharides research.