Structural characterization of a sulfated glucan isolated from the aqueous extract of Hedysarum polybotrys Hand.-Mazz

A water-soluble sulfated glucan, SHG, was isolated from Hedysarum polybotrys Hand.-Mazz using anion-exchange and gel-permeation chromatography. Elemental analysis indicated that SHG was a sulfated polysaccharide containing small amount of sulfate groups (1.47 mass%). The molecular weight was estimated to be 1.72 × 105 Da by high-performance gel permeation chromatography (HPGPC) and size exclusion chromatography–multi angle laser light scattering (SEC–MALLS). SHG took random coil compact conformation in 0.1 M NaNO3. Compositional analysis revealed that SHG was composed of glucose only. On the base of partial acid hydrolysis, methylation analysis, gas chromatography–mass spectrometry (GC–MS), Fourier transform infrared (FT-IR) spectra, nuclear magnetic resonance (NMR) spectroscopy of 1H, 13C, β-correlation spectroscopy (β-COSY), total correlation spectroscopy (TOCSY), heteronuclear single quantum coherence (HSQC), and heteronuclear multiple bond correlation (HMBC), the results showed that SHG was composed of α-d-(1 → 4)-linked glucopyranosyl residues, with branches at C-6 consisting of non-reducing terminal approximately every eight residues. Sulfate groups may attach to the backbone at O-6, occasionally occurring per thirty-eight anhydrous glucose units.