CHOLLA GUM: I. STRUCTURE OF THE DEGRADED CHOLLA GUM

Abstract

Purified cholla gum (Opuntiafulgida) contains L-arabinose (51.6%), D-galactose (31.7%), D-xylose (15.0%), L-rhamnose (2-3%), and D-galacturonic acid (11.2%). Partial hydrolysis of the gum by cold acid produced a polymer which contained only D-galactose and D-galacturonic acid in the proportion 9:2. Methylation and hydrolysis of the degraded gum produced 2,3,4,6-tetra-O-methyl-D-galactose (2 moles), 2,3,4-tri-O-methyl-D-galactose (1 mole), 2,4,6-tri-O-methyl-D-galactose (2 moles), 2,4-di-O-methyl-D-galactose (4 moles), and 2,3,4-tri-O-methyl-D-galacturonic acid (2 moles). Smith-type degradation of the degraded gum produced D-galactose (6 moles), glycolaldehyde (? moles), glycerol (2.5 moles), and glyceronic acid (2.5 moles).Hydrolysis of the undegraded gum produced an aldobiouronic acid, which was proved to be 3-O-(β-D-galactopyranosyl uronic acid)-D-galactose by its reduction, methylation, and the identification of the methylated sugars obtained by the hydrolysis of the octamethyl galactobioside.Based on these results, a possible structure for the average chain length of the degraded gum has been proposed.