Structural characteristics of a mixed linkage β-d-glucan from sorghum (Sorghum bicolor)

Hemicellulose B, obtained by alkali extraction of sorghum flour on DEAE-cellulose chromatography gave a water-eluted neutral polysaccharide composed exclusively of d-Glc. Further purification on Sephacryl S-400 gave a major fraction (Fra.II) which was homogeneous by electrophoretic and SEHPLC methods. It had a MW of 3.6×104 Da and showed a bathochromic shift (19 nm) in the λmax of its complex with Congo Red. Permethylation and GC–MS analysis revealed (1→4)- and (1→3)-glucosidic linkages in a ratio of 2.3:2 which were corroborated by 13C NMR and CD spectral measurements. The β configuration of the glucan was further confirmed by treatment with β-glucanase and also by its low [α]D value of +12.5°.