The Gum of Fagara xanthoxyloides

Abstract

Fagara xanthoxyloides Lam. (Xanthoxylum Senegalense DC.), a common plant in West Africa, exudes a clear yellow gum during the dry season. The gum is partly acetylated and has a significant methoxyl content. A single unpurified nodule gave, on analysis, acetyl groups, 6.95 per cent; methoxyl groups, 2.6 per cent. The nodules dissolve with difficulty in water to give a viscous solution with a faintly acid reaction. The purified gum was obtained in the usual way¹, and after drying in a partial vacuum at 30° was a white amorphous powder,[α]²¹_D + 4° (c. 0.5 in N sodium hydroxide); equivalent weight by direct titration, 1,100; sulphated ash, 0.25 per cent; nitrogen, 0.23 per cent; acetyl groups, none; methoxyl groups, 2.6 per cent (a polysaccharide of equivalent weight 1,100 containing monomethyl-hexuronic residues would have a methoxyl content of 2.8 per cent). It gave a positive naphthoresorcinol test for uronic acid, and failed to reduce Fehling's solution. Specimens prepared from nodules from different trees did not show any significant differences in optical rotations and equivalent weights, indicating the essential homogeneity of the gum.