Effects of sulfation on the physicochemical and functional properties of psyllium.

The sulfation of psyllium was carried out with sulfur trioxide-pyridine in dimethyl formamide. Three sulfated psyllium derivatives, named SP1, SP2, and SP3, were characterized by sulfur content determination, elemental analysis, FT-IR, and surface charge analysis. The sulfated derivatives were also evaluated for their morphological and rheological properties, water uptake capacities, swelling volumes, and in vitro bile acid-binding abilities. The results showed that sulfation reduced the gelling capacity of psyllium and the viscosity of its solution, and significantly increased its bile acid-binding capacity. Sulfation might also increase the water uptake ability of psyllium but might decrease its swelling capacity. The three sulfated psyllium derivatives had in vitro binding capacities against cholic and chenodeoxycholic acids comparable to that of cholestyramine resin on a per same as it is weight basis. The bile acid-binding capacity of SP1 was about 8.4-fold of that observed for the original psyllium preparation under the same assay conditions. The results from this study suggest that sulfation is a possible approach to obtain novel psyllium derivatives with desirable physicochemical, functional, and biological properties for utilization in functional foods or supplemental and pharmaceutical products.