Effects of structural modifications on physicochemical and bile acid-binding properties of psyllium

The effects of sulfation, hydroxypropylation, and succinylation on gelling, water uptake, swelling, and bile acid-binding capacities of psyllium were examined and compared at the same molar substitution degree. Sulfated, hydroxypropylated, and succinylated psyllium were prepared with substitution levels of 1.02, 0.88, and 0.79, respectively, and their structures were characterized using FT-IR, SEM, and ζ-potential determination. All three derivatization methods reduced the gelling and swelling capacities of psyllium and increased the water uptake and bile acid-binding capacities compared to the original psyllium. Interestingly, it was observed for the first time that introduction of a stronger negatively charged group into the molecule might more effectively enhance the bile acid-binding capacity of psyllium. On the other hand, the steric effect of the substitution groups seemed to be more critical in altering the gelling and swelling properties of psyllium.