Cholla gum (Opuntiafulgida) has partially been degraded to yield several oligosaccharides and a degraded polymer. The structure of the degraded polymer was reported in an earlier paper. Six of the oligosaccharides formed have been isolated in a pure state and identified. They are (i) 6-O-β-D-galactopyranosyl-D-galactose, (ii) 3-O-β-D-galactopyranosyl-D-galactose, (iii) 3-O-α-L-arabinofuranosyl-L-arabinose, (iv) 5-O-β-D-xylopyranosyl-L-arabinose, (v) 3-O-β-D-galactopyranosyl-L-arabinose (?), and (vi) a new trisaccharide O-β-D-xylopyranosyl-(1 → 5)-O-α-L-arabinofuranosyl-(1 → 3)-L-arabinose. The purified gum was subjected to Smith-type degradation, and the results of this experiment are compared with the methylation studies carried out earlier. On the basis of all this information plus the suggested structure for the degraded gum, it is proposed that the repeating unit of the polysaccharide consists of a total of 36 sugar residues with a backbone of 1 → 6 linked galactose residues.
V. Parikh, J. K. Jones
Canadian Journal of Chemistry