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.