New structural features of Spondias purpurea gum exudate

Spondias purpurea L. (Anacardiaceae), disseminated in Venezuela, produces a polysaccharide gum constituted by galactose (59%), arabinose (9%), mannose (2%), xylose (2%), rhamnose (2%) and uronic acids (26%). It also contains a proteinaceous material (2%). The original gum was subjected to two successive Smith-degradation process to obtain polysaccharide II. Application of 2D-NMR techniques, including COSY, HMQC and HMBC, to the original gum and the structure backbone, in combination with chemical methods, led to confirm interesting structural features of the gum. It was demonstrated unequivocally that the backbone of the gum structure is mainly a β-(1→3) galactan and amino acids. A sequence of α-l-arabinose residues in the branches of the polysaccharide was observed by spectral data. The presence of amino acids, in the structure backbone, demonstrated by chemical and 2D-NMR spectral data, is a new and interesting finding for the complex gum structure.