title: Structural characterization of wheat straw lignin as revealed by analytical pyrolysis, 2D-NMR, and reductive cleavage methods.
abstract: The structure of the lignin in wheat straw has been investigated by a combination of analytical pyrolysis, 2D-NMR, and derivatization followed by reductive cleavage (DFRC). It is a p-hydroxyphenyl-guaiacyl-syringyl lignin (with an H:G:S ratio of 6:64:30) associated with p-coumarates and ferulates. 2D-NMR indicated that the main substructures present are β-O-4'-ethers (∼~75%), followed by phenylcoumarans (~11%), with lower amounts of other typical units. A major new finding is that the flavone tricin is apparently incorporated into the lignins. NMR and DFRC indicated that the lignin is partially acylated (~10%) at the γ-carbon, predominantly with acetates that preferentially acylate guaiacyl (12%) rather than syringyl (1%) units; in dicots, acetylation is predominantly on syringyl units. p-Coumarate esters were barely detectable (<1%) on monomer conjugates released by selectively cleaving β-ethers in DFRC, indicating that they might be preferentially involved in condensed or terminal structures.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, PO Box 1052, E-41080 Seville, Spain.
authors.forename: José C
authors.initials: JC
authors.lastname: del Río
authors.forename: Jorge
authors.initials: J
authors.lastname: Rencoret
authors.forename: Pepijn
authors.initials: P
authors.lastname: Prinsen
authors.forename: Ángel T
authors.initials: ÁT
authors.lastname: Martínez
authors.forename: John
authors.initials: J
authors.lastname: Ralph
authors.forename: Ana
authors.initials: A
authors.lastname: Gutiérrez
mesh_terms: D000107:Acetylation; D000215:Acylation; D002244:Carbon / Q000737:chemistry; D004952:Esters / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D008031:Lignin / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D019684:Magnoliopsida / Q000737:chemistry; D008970:Molecular Weight; D018547:Plant Stems / Q000737:chemistry*; D059748:Proteolysis; D014908:Triticum / Q000737:chemistry*
chemical_list: D004952:Esters; D002244:Carbon; D008031:Lignin