Chemical composition and structural features of the macromolecular components of plantation Acacia mangium wood

The wood of Acacia mangium, a prominent fast-growing plantation species used in the pulp-and-paper industry and, so far, poorly investigated for its chemical structure, was submitted to a detailed characterization of its main macromolecular components. Lignin (28% wood weight) isolated by mild acidolysis and characterized by permanganate oxidation, H-1 and C-13 NMR, and GPC, showed a very low content of syringylpropane-derived. units (S:G:H of 48:49:3), a high degree of condensation, a low content of beta-O-4 (similar to 0.40-0.43 per C6) structures, and a M-w of 2230. Glucuronoxylan (14% wood weight) isolated by alkaline (KOH) or by dimethyl sulfoxide extraction was characterized by methylation analysis, H-1 NMR, and GPC. About 10% of the xylopyranose (Xylp) units constituting the linear backbone were substituted at O-2 with 4-O-methylglucuronic acid residues. Almost half of the Xylp units (45%) were O-2 (18%), O-3 (24%) or O-2,3 (3%) acetylated. X-ray diffraction analysis of cellulose (46% wood weight), isolated according to the Kurschner-Hoffer method, showed a degree of crystallinity of 67.6%.