Analytical and structural studies of acacia polysaccharides

Abstract

An analytical study of eleven Acacia gums from the subseries Juliflorae of the series Phyllodineae showed them to be more proteinaceous, more acidic and more viscous, with higher methoxyl contents and higher molecular weights but with lower proportions of rhamnose and arabinose than the majority of Acacia gums studied so far.A structural study of the gum from Acacia auriculiformis involving hydrolysis, Smith- degradation and methylation studies, revealed a ß -1, 3 - linked galactose backbone with side chains of ß -1, 6 - linked galactose. Glucuronic acid was present as end-groups, linked ß-1, 6 to galactose: 4-Ω-methyl glucuronic acid was present as end - groups, α -1, 4 - linked to galactose. Arabinose was present in short, ß-1, 3- linked chains, while rhamnose was present as end-group. Proteinaceous material was attached to the molecule by periodate- resistant linkages.The use of carbon 13-nuclear magnetic resonance spectroscopy for the study of gum exudates was examined. Spectra were obtained for the gum from Acacia auriculiformis and its degradation products, despite their high molecular weight and chemical complexity. The spectra substantiated the findings of the structural study.