Sulfated modification, characterization and structure–antioxidant relationships of Artemisia sphaerocephala polysaccharides

Sulfated polysaccharides exerted potent biological property which was relative to degree of sulfation (DS), Mw, substitution position and chain conformation. In the present study, sulfated derivatives of Artemisia sphaerocephala polysaccharide (ASP) with different DS were synthesized by chlorosulfuric acid/pyridine method. FT-IR and 13C NMR analysis indicated that C-6 substitution was predominant in sulfated ASP (SASP) compared with other positions at C-2. In the sulfation reaction, a sharp decrease in Mw was observed in SASP. The df values from 1.96 to 2.77 indicated that the –SO3H groups leading to the relatively expanded conformation of SASP. Antioxidant assays showed that SASP had better antioxidant activities. The data obtained in vitro models indicated that high DS and moderate Mw showed the best antioxidant capacities.