MOLECULAR-STRUCTURES OF GUM EXUDATES FROM HAKEA SPECIES

Partial acid-hydrolysis of the gum exudates from Hakea sericea and H. gibbosa yields L-arabinose, D-galactose, D-xylose, D-mannose, D-glucur onic acid, the aldobiouronic acid GlcA (beta1,2)Man, and a dimer of th is acid alpha-linked from D-Man to O-4 of GlcA. Methylation analysis s howed the modes of linkage of the sugar units to be typical of those p resent in plant polysaccharide exudates of the arabinogalactan type, w hile partial acid hydrolysis and Smith degradations established the po sition of linkage of the peripheral sugar assemblies at O-3 of D-Man i n the interior core. Some minor differences were noted between the mol ecular structures of the gums from these two species of Hakea, the Gal :Ara ratio being higher for H. sericea gum.