Cassia grandis Linn. f. seed galactomannan:: structural and crystallographical studies

Cassia grandis is a small or medium sized tree, found in abundance throughout India. The seeds contain about 50%, endosperm gum and possess the characteristics of becoming a potential source of seed gum. The purified polysaccharide has been characterized as a pure galactomannan having a mannose-galactose ratio of 3.15 molecular weight (M-w) 80,200; polydispersity (M-w/M-n), 1.35 and intrinsic viscosity [eta], 848 mL/g. Methylation, periodate oxidation, Smith degradation and C-13 NMR Studies confirm that the polysaccharide has the basic structure of legume galactomannans consisting of a beta-(1-->4)-linked main mannan backbone to which galactose units are attached at O-6. The orthorhombic lattice constants of the hydrated gum are as follows: a = 9.00, h = 24.81 c 10.30 Angstrom. The crystallographic data establish that the probable space group symmetry of the unit cell is P2(l)2(l)2. The results are in contradiction to earlier reports (Indian J. Chem. 16B (1978) 966 J. Indian Chem. Soc. 55 (1978) 1216) in which a non-galactomannan polysaccharide structure has been assigned having a main chain of (1-->4)-linked galactose and mannose units in the molar ratio 6:3, where 50% of the galactose units branched with two galactose and one mannose through 1-->3 linkage. (C) 2003 Elsevier Ltd. All rights reserved.