Isolation, purification and characterization of galactomannans as an excipient from Senna tora seeds

Seed galactomannans are neutral, heterogeneous polysaccharides widely distributed in nature. The Mannose/Galactose ratios differ from gum to gum, resulting in a change in structure, which in turn, determines the various industrial applications of seed galactomannans. Senna tora (Family: Fabaceae) is a fast growing and spreading under shrub of which seeds, pods and leaves are extensively used for medicinal applications. The seeds have been found to be an alternative source of commercial gums. The present investigation deals with isolation, purification and characterization of galactomannans from the seeds of Senna tora (S. tora). The galactomannan extraction was based on mechanical separation of the endosperm, water dissolution, centrifugation and precipitation with acetone. The polysaccharide obtained from S. tora seeds was characterized by using physicochemical and chromatographic procedures, as well as FTIR, Mass, (13)C NMR and (1)H NMR spectroscopy. The results indicated that the gum has the basic structure of galactomannans with a main chain of (1→4)-linked β-D-mannopyranosyl units to which single α-(1→6)-D-linked galactopyranosyl units are attached through block pattern. The rheological studies indicated that the S. tora gum (1%, w/w) solution possesses pseudoplastic flow. The viscosity and other rheological properties confirmed its suitability as an excipient in the development of sustained release delivery systems.