Structure of a galactomannan from the seeds of Cassia angustifolia Vahl

Cassia angustifolia Vahl (family: Caesalpiniaceae) is a fast growing and spreading Indian shrub of which seeds, pods and leaves are extensively used for pharmaceutical applications. The seeds have been found to be an alternative source of commercial gums. The structural aspects of the galactomannans have been determined for a better understanding of its properties. The purified seed galactomannan contains mannose:galactose in a ratio of 2.90. The average molecular weight ( M̄ w) is 9.66×10 4 and the intrinsic viscosity ( η) is 209 mL/g. Methylation analysis, periodate oxidation, Smith degradation and 13C NMR studies confirm that the gum has the basic structure of legume 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. Man/Gal ratio 2.90 (HPLC) M̄ w =9.66×10 4 2.92 (GLC) d n/d c =0.15 2.63 ( 13C NMR) [ η] =209 mL/g 2.82 (1H NMR) Methylation, periodate oxidation, Smith degradation and NMR studies reveal that the gum possesses the basic structure of legume galactomannans. The seeds have been identified as a new source of commercial gums.