Structural features of a xylogalactan isolated from Hymenaea courbaril gum

The gum from Hymenaea courbaril (Caesalpiniaceae) produced gum at seed level. The gum is soluble in water, dextrorotatory and less viscous than the gum from Cyamopsis tetragonolobus (guar gum). The polysaccharide, isolated from this gum, contains galactose, glucose, xylose and arabinose. The preparation of degraded products by acid hydrolysis and Smith-degradation process led to obtain degraded gums A and B, and the polysaccharides I and II. Chemical methods in combination with 1D NMR (1H, 13C, DEPT-135) and 2D NMR (COSY, HMQC and HMBC) were applied. The backbone is a xylogalactan; β-d-galactose and β-d-xylose residues are 4-O- and 2-O-linked, respectively. The branches are constituted by xylose, arabinose and galactose. It was also observed 4,6-di-O-substituted galactose residues. This work shows interesting structural features of the polysaccharide isolated from H. courbaril gum.