Similarity of monosaccharide, oligosaccharide and polysaccharide structures in gum exudate of Anacardium occidentale

The gum exudate from the Brazilian cashew-nut tree (Anacardium occidentale) contained traces of the reducing sugars, rhamnose (0.005%), arabinose (0.03%), mannose (0.007%), galactose (0.03%), glucose (0.02%), beta-D-Galp-(1-->6)-alpha beta-D-Gal (0.05%), alpha-L-Rhap-(1-->4)-alpha beta-D-GlcA (0.008%) and alpha-L-Rhap-(1-->3)-beta-D-GlcpA-(1-->6)-alpha beta-D-Gal (0.008%). Rhamnose, arabinose, glucose and the three oligosaccharides are components of the side-chains of the gum polysaccharide, which has a main chain of (1-->3)-linked beta-D-Galp units. The structure of this polysaccharide was determined and found to differ from that previously reported for the gum of a tree growing in India, lacking units of 4-O-methlglucuronic acid. Other new side-chain structures were characterized, particularly -alpha-D-Galp-(1-->6)-D-Galp- and alpha-L-Araf-(1-->6)-D-Galp-. (C) 1998 Elsevier Science Ltd. All rights reserved.