The studies presented in this thesis fall into three
distinct groups.a) Analytical characterizations have been made of the gum exudates,
not hitherto investigated, from 3 species of the genus Parkia, 6
species of the genus Grevillea, 9 species of the Series Phyllodineae
and Gummiferae of the genus Acacia, and 15 specimens of gum obtained
from Acacia karroo growing in different locations in Africa. Several
of the new species of gum have exceptional features e.g. the intrinsic
viscosities of the gums from Grevillea caahlabroides and Grevillea
wickhamii (521 and 575 nlg⁻¹ respectively) and the nitrogen content
(7.5%) of A. dictyophleba gum are the highest values reported to
date for these parameters in plant gums.b) A study of some of the structural features of Acacia xanthophloea
gum by Smith-degradation, methylation and acid hydrolysis showed the
complex acid heteropolysaccharide to be based on a highly-branched
ß - 1,3 - linked galactose framework which also contained some ß - 1,6 - linkages. Glucuronic acid and rhamnose were present as end-groups; arabinose was present in short side-chains, up to three units long, attached to the branched galactan core.c) The applicability of natural abundance carbon - 13 nuclear
magnetic resonance spectroscopy to structural studies of complex
acid heteropolysaccharides of high molecular weight was evaluated
by examining the sequence of progressively simpler spectra given by
the whole gum and its different degradation products.A preliminary study of the applicability of proton magnetic
resonance spectra to complex gum molecules showed that an indication
of the amounts of different sugar components present and a rapid
non -destructive evaluation of the degree of structural similarity
of different gum samples can be obtained
