title: Structural characterization of the lignin in the cortex and pith of elephant grass (Pennisetum purpureum) stems.
abstract: The structure of the lignin in the cortex and pith of elephant grass (Pennisetum purpureum) stems was studied both in situ and in isolated milled "wood" lignins by several analytical methods. The presence of p-coumarate and ferulate in the cortex and pith, as well as in their isolated lignins, was revealed by pyrolysis in the presence of tetramethylammonium hydroxide, and by 2D NMR, and indicated that ferulate acylates the carbohydrates while p-coumarate acylates the lignin polymer. 2D NMR showed a predominance of alkyl aryl ether (β-O-4') linkages (82% of total interunit linkages), with low amounts of "condensed" substructures, such as resinols (β-β'), phenylcoumarans (β-5'), and spirodienones (β-1'). Moreover, the NMR also indicated that these lignins are extensively acylated at the γ-carbon of the side chain. DFRC analyses confirmed that p-coumarate groups acylate the γ-OHs of these lignins, and predominantly on syringyl units.
authors.affiliation: Instituto de Recursos Naturales y Agrobiología de Sevilla (IRNAS), CSIC, Seville, Spain. delrio@irnase.csic.es
authors.forename: José C
authors.initials: JC
authors.lastname: del Río
authors.forename: Pepijn
authors.initials: P
authors.lastname: Prinsen
authors.forename: Jorge
authors.initials: J
authors.lastname: Rencoret
authors.forename: Lidia
authors.initials: L
authors.lastname: Nieto
authors.forename: Jesús
authors.initials: J
authors.lastname: Jiménez-Barbero
authors.forename: John
authors.initials: J
authors.lastname: Ralph
authors.forename: Angel T
authors.initials: AT
authors.lastname: Martínez
authors.forename: Ana
authors.initials: A
authors.lastname: Gutiérrez
mesh_terms: D000215:Acylation; D003373:Coumaric Acids / Q000032:analysis / Q000737:chemistry; D008401:Gas Chromatography-Mass Spectrometry; D006358:Hot Temperature; D008031:Lignin / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D008970:Molecular Weight; D031782:Pennisetum / Q000737:chemistry*; D018547:Plant Stems / Q000033:anatomy & histology / Q000737:chemistry*; D011422:Propionates
chemical_list: D003373:Coumaric Acids; D011422:Propionates; D008031:Lignin; C004999:ferulic acid; C495469:p-coumaric acid