title: Characterization of lignin structures and lignin-carbohydrate complex (LCC) linkages by quantitative 13C and 2D HSQC NMR spectroscopy.
abstract: To characterize the lignin structures and lignin-carbohydrate complex (LCC) linkages, milled wood lignin (MWL) and mild acidolysis lignin (MAL) with a high content of associated carbohydrates were sequentially isolated from ball-milled poplar wood. Quantification of their structural features has been achieved by using a combination of quantitative (13)C and 2D HSQC NMR techniques. The results showed that acetylated 4-O-methylgluconoxylan is the main carbohydrate associated with lignins, and acetyl groups frequently acylate the C2 and C3 positions. MWL and MAL exhibited similar structural features. The main substructures were β-O-4' aryl ether, resinol, and phenylcoumaran, and their abundances per 100 Ar units changed from 41.5 to 43.3, from 14.6 to 12.7, and from 3.7 to 4.0, respectively. The S/G ratios were estimated to be 1.57 and 1.62 for MWL and MAL, respectively. Phenyl glycoside and benzyl ether LCC linkages were clearly quantified, whereas the amount of γ-ester LCC linkages was ambiguous for quantification.
authors: Institute of Biomass Chemistry and Technology,  Beijing Forestry University , Beijing, China.
authors: Tong-Qi
authors: TQ
authors: Yuan
authors: Shao-Ni
authors: SN
authors: Sun
authors: Feng
authors: F
authors: Xu
authors: Run-Cang
authors: RC
authors: Sun
mesh_terms: D000215:Acylation; D002236:Carbohydrate Conformation; D002241:Carbohydrates / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008970:Molecular Weight; D014934:Wood / Q000737:chemistry
chemical_list: D002241:Carbohydrates; D008031:Lignin