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Regioselective modification is an effective approach to synthesize polysaccharides with different structure features and improved properties. In this study, regioselective sulfation of Artemisia sphaerocephala polysaccharide (S RS ASP) was prepared by using triphenylchloromethane (TrCl) as protecting precursor. The decrease in fractal dimension ( d f ) values (1.56–2.04) of S RS ASP was observed in size-exclusion chromatography combined with multi angle laser light scattering (SEC-MALLS) analysis. Compared to sample substituted at C-6, S RS ASP showed a more expanded conformation of random coil, which was attributed to the breakup of hydrogen bonds and elastic contributions. Circular dichroism (CD), methylene blue (MB) and congo red (CR) spectrophotometric method and atomic force microscopy (AFM) results confirmed the conformational transition and stiffness of the chains after sulfation. S RS ASP exhibited enhanced antioxidant activities in the DPPH, superoxide and hydroxyl radical scavenging assay. Sulfation at C-2 or C-3 was favorable for the chelation which might prevent the generation of hydroxyl radicals. It concluded that the degree of substitution and substitution position were the factors influencing biological activities of sulfated polysaccharides. [ABSTRACT FROM AUTHOR]

Abstract: Selenium (Se) is an essential trace element for human beings and many other forms of life. Organic Se from natural foods has higher bioavailability and is safer than inorganic Se species. In the present study, selenium-containing derivatives of Artemisia sphaerocephala polysaccharide with the highest Se content of 1703μg/g were synthesized using H2SeO3/HNO3 and BaCl2 as a catalyst. The effects of the ratio of HNO3 concentration and reaction temperature were investigated. Results of Raman and 13C NMR spectroscopy indicated that C-6 substitution was predominant in selenized polysaccharide. A sharp decrease in M w was observed in the selenized reaction due to the acid environment. The in vitro antioxidant results suggest that selenium-containing polysaccharide should be applied as a novel selenium source in dietary supplements, with potent antioxidant properties. [Copyright &y& Elsevier]

Abstract: Sulfated polysaccharides exerted potent biological property which was relative to degree of sulfation (DS), M w, 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 M w was observed in SASP. The d f 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 M w showed the best antioxidant capacities. [Copyright &y& Elsevier]