Studies on plant gums. Isolation and characterisation of the major polysaccharide from Neem (Azadirachta indica) gum

Abstract

Azadirachta indica (neem) exudate gum was treated with pronase for 48 h followed by chromatography on TEAE-cellulose and the major polysaccharide was isolated. The polysaccharide covalently associated with remnant protein, was homogeneous as indicated by rechromatography on TEAE-cellulose, paper electrophoresis, gel chromatography under dissociating conditions on Bio-Gel P-l00 and P-300. The monosaccharide units, galactose, arabinose, glucuronic acid, fucose and glucosamine were present in a molar ratio of 86 ∶ 70 ∶ 30 ∶ 10 ∶ 1. Thirteen amino acids constituted the protein portion. The linkage between the polysaccharide and the protein was a glucosaminyl asparginyl bond. Limited hydrolysis showed that fucose and arabinose were at the non-reducing ends of the polysaccharide and galactose and glucuronic acid were in the central core.