Sterculia striata exudate polysaccharide:: characterization, rheological properties and comparison with Sterculia urens (karaya) polysaccharide

The exudate polysaccharide from Sterculia striata trees was investigated regarding its composition, structure and rheological properties and metal ion interactions. This polysaccharide contains galactose, rhamnose galacturonic and glucuronic acids as the main monosaccharide components. C-13 NMR spectroscopy revealed that the anomeric composition is similar to that of Sterculia urens exudates, except for the presence of xylose, not identified in the latter polysaccharide. The empirical stiffness parameter B was determined for S striata (B = 0.043), suggesting that the polysaccharide exists in a semi-rigid chain conformation, with no conformational change being demonstrated. Deacetylation led to a more flexible polymer chain (B = 0.058). The counter ion affinity of the polysaccharide aqueous solution was determined by intrinsic viscosity measurements, resulting in Al3+ > Ca2+ > Na+. (C) 2004 Society of Chemical Industry.