Characterization of Anacardium occidentale exudate polysaccharide

The composition, structure and molar mass distribution of Anacardium occidentale exudate polysaccharide of Brazilian origin was investigated. The composition from gas-liquid chromatography (GLC) and C-13 NMR was 72% beta-D-galactopyranose, 14% alpha-D-glucopyranose, 4.6% alpha-L-arabinofuranose, 3.2% alpha-L-rhamnopyranose and 4.5% beta-D-glucuronic acid. A thorough analysis of high resolution C-13 NMR spectra from intact, partially hydrolysed and Smith-degraded polysaccharide enabled reliable chemical shift assignments to be made, and indicated the presence of three types of unit within the branched galactan core: linked at C-1 and C-3, at C-1 and C-6, and at C-1, C-3 and C-6. The polysaccharide was fractionated with respect to molar mass using water/ethanol as a solvent/non-solvent system. The polysaccharide and fractions were characterized by gel permeation chromatography (GPC), intensity light scattering, dilute solution viscometry and sedimentation velocity. The intrinsic viscosity in 0.1 M aqueous NaCl at 25 degrees C was found to depend on molar mass according to: [eta]/(cm(3) g(-1))=0.052 M-0.42. The molar mass distribution for the whole polysaccharide, determined by GPC using a universal calibration, exhibited two main peaks at 28 000 and 67 000 gmol(-1), together with traces of much higher molar mass material. (C) 1998 SCI.