title: Regioselective synthesis of sulfated guar gum: comparative studies of structure and antioxidant activities.
abstract: We reported here a new synthesis of C-2 and C-3 sulfated guar gum (SRSGG) with low degree of substitution (DSS) of 0.58, employing triphenylchloromethane (TrCl) as a protected precursor. The yield and DSTr (calculated from the weight of triphenylmethanol) of triphenylmethylated GG (GGTr) was 165.6% and 0.71, respectively. In addition, low ratio (1:4) of chlorosulfuric acid to pyridine (1:4) was chosen in sulfation reaction since the protecting group was slightly sensitive to acid. Results of FT-IR and (13)C NMR spectroscopy indicated that C-2 and C-3 substitution was predominant but not fully sulfated in SRSGG. Size-exclusion chromatograph combined with multi-angle laser photometer (SEC-LLS) showed a decrease in molecular weight in the reaction. This might be due to the degradation in sulfation and deprotection process. Finally, we investigated the effect of structure features on the antioxidant activities in vitro. Vitro antioxidant experiments revealed that the regioselective sulfation at C-2 and C-3 and low molecular weight afforded strong antioxidant activities showing a much higher scavenging abilities of 1,1-diphenyl-2-picrylhydrazyl (DPPH) and hydroxyl radical than that by the known C-6-sulfated derivative. The antioxidant activities of sulfated polysaccharides were not a function of a single factor but a combination of molecular weight, DSS and substitution positions.
authors.affiliation: College of Life Science, Northwest Normal University, Lanzhou 730070, China; Bioactive Products Engineering Research Center for Gansu Distinctive Plants, Lanzhou 730070, China. Electronic address: nuno-vai@163.com.
authors.forename: Junlong
authors.initials: J
authors.lastname: Wang
authors.forename: Shengfan
authors.initials: S
authors.lastname: Niu
authors.forename: Baotang
authors.initials: B
authors.lastname: Zhao
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Wang
authors.forename: Jian
authors.initials: J
authors.lastname: Yao
authors.forename: Ji
authors.initials: J
authors.lastname: Zhang
authors.forename: Weiwei
authors.initials: W
authors.lastname: Zhao
authors.forename: Yuting
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000975:Antioxidants / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D005685:Galactans / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D017665:Hydroxyl Radical / Q000037:antagonists & inhibitors; D008351:Mannans / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D019906:Nuclear Magnetic Resonance, Biomolecular; D010084:Oxidation-Reduction / Q000187:drug effects; D053149:Plant Gums / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D017550:Spectroscopy, Fourier Transform Infrared; D013463:Sulfuric Acid Esters / Q000737:chemistry*; D013481:Superoxides / Q000037:antagonists & inhibitors
chemical_list: D000975:Antioxidants; D005685:Galactans; D008351:Mannans; D053149:Plant Gums; D013463:Sulfuric Acid Esters; D013481:Superoxides; D017665:Hydroxyl Radical; C007894:guar gum
keywords: Antioxidant activity; Guar gum; Regioselective sulfated