abstract
Milled wood lignin (MWL) and dioxane lignin (DL) from different morphological regions (nodes and internodes) of Arundo donax reed were subjected to a comprehensive structural characterization by C-13, H-1 NMR, FTIR, and UV spectroscopies and functional analysis. The permanganate and nitrobenzene oxidation methods were also applied to the in situ lignins. Both node and internode lignins are HGS-type lignins, with a significant amount of H units (including p-coumaric acid type structures). The S/G ratio (1.13-1.32), the weight-average molecular weight (20400-24500), the methoxyl group content (0.90-0.98), the phenolic hydroxyl group content (0.23-0.27), and the aliphatic hydroxyl group content (1.00-1.09) are not very different in the lignins from nodes and internodes. However, some structural differences between node and internode lignins were observed. The former has much more phenolic acids (p-coumaric and ferulic), 8.8% in node versus 1.2% in internode and less beta-O-4 (0.32 and 0.49 per aromatic unit in node and internode, respectively). In situ node lignin is more condensed than internode lignin.
keywords
DIFFERENT BOTANICAL ORIGINS; MILLED WOOD LIGNIN; HYDROXYL-GROUPS; WHEAT STRAW; SPECTROSCOPY; FRACTIONS
subject category
Agriculture; Chemistry; Food Science & Technology
authors
Seca, AML; Cavaleiro, JAS; Domingues, FMJ; Silvestre, AJD; Evtuguin, D; Neto, CP
our authors
Armando Jorge Domingues Silvestre
Full professor
Carlos Pascoal Neto
Raiz Director