Structure–antioxidant relationships of sulfated galactomannan from guar gum

Sulfated polysaccharides exerted potential biological property which was relative to degree of sulfation (DS), Mw, substitution position and chain conformation. In the present study, commercial guar gum was purified and its sulfated derivates with different DS and Mw were synthesized. FT-IR and 13C NMR analysis indicated that C-6 substitution was predominant in sulfated samples compared with other positions. In the sulfation reaction, a sharp decrease in Mw was observed. The df values from 1.92 to 2.85 indicated that the –SO3H groups led to the relatively expanded conformation of sulfated polysaccharides. Antioxidant assays showed that sulfated polysaccharides had better antioxidant activities. The data obtained in in vitro models indicated that high DS and low Mw showed the best antioxidant capacities.