Unmasking the structural features and property of lignin from bamboo

In this study, a simple method based on DMSO/NMI (dimethylsulfoxide/N-methylimidazole) dissolved system for the isolation of dissolved lignin (DL) from bamboo was presented. The lignin extracted was studied as compared to milled wood lignin (MWL) and alkali lignin (AL). Quantitative C-13 and 2D-HSQC NMR analysis indicated that all lignin preparations are HGS-type and partially acylated (below 12%) at the gamma-carbon of the side chain by p-coumarate. In addition, some LCC linkages and acetylated beta-D-xylopyranoside were distinguished from HSQC spectra in the specific lignin preparations. The abundances (Ar/100Ar) of beta-O-4, beta-beta and beta-5. S/G ratios, acylation degree, phenolic hydroxyl. aliphatic hydroxyl and methoxy groups (mmol/g) were also observed in the lignin preparations. Furthermore, the amount of beta-O-4 coupling and molecular weight of the lignin decreased in the order of DL < MWL < AL. The in vitro antioxidant activity results showed that the radical scavenging index (RSI) is correlated to the phenolic hydroxyl groups (Ar-OH) involved in the lignin preparations. (C) 2012 Elsevier B.V. All rights reserved.