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Open Access item Structural characterization of milled wood lignin from different eucalypt species

Authors:Rencoret, Jorge
Río Andrade, José Carlos del
Marques, Gisela
Gutiérrez Suárez, Ana
Ibarra, David
Santos, José Ignacio
Jiménez-Barbero, Jesús
Martínez Ferrer, Ángel Tomás
Keywords:Eucalypt wood, Milled-wood lignin (MWL), Pyrolysis-GC/MS, 2D-NMR, HSQC, Thioacidolysis, Dimers, Trimers, Desulphuration, Eucalyptus globulus, Eucalyptus nitens, Eucalyptus maidenii, Eucalyptus grandis, Eucalyptus dunnii
Issue Date:2008
Publisher:Walter de Gruyter
Citation:Holzforschung 62: 514-526 (2008)
Abstract:The chemical structure of milled-wood lignins from Eucalyptus globulus, E. nitens, E. maidenii, E. grandis, and E. dunnii was investigated. The lignins were characterized by analytical pyrolysis, thioacidolysis and 2D-NMR that confirmed the predominance of syringyl over guaiacyl units and only showed traces of p-hydroxyphenyl units. E. globulus lignin had the highest syringyl content. The heteronuclear single quantum correlation (HSQC) NMR spectra gave information about relative abundances of inter-unit linkages in the whole polymer. All the lignins showed a predominance of β-O-4' ether linkages (66-72% of total side-chains), followed by β-β' resinol-type linkages (16-19%) and lower amounts of β-5' phenylcoumaran-type (3-7%) and β-1' spirodienone-type linkages (1-4%). The analysis of desulphurated thioacidolysis dimers provided additional information on the relative abundances of the various carbon-carbon and diaryl ether bonds, and the type of units (syringyl or guaiacyl) involved in each of the above linkage types. Interestingly, 93-94% of the total β-β' dimers included two syringyl units indicating that most of the β-β' substructures identified in the HSQC spectra were of the syringaresinol type. Moreover, three isomers of a major trimeric compound were found which were tentatively identified as arising from a β-β' syringaresinol substructure attached to a guaiacyl unit through a 4-O-5' linkage.
Description:Rencoret, Jorge et al.-- 13 pages, 7 figures, 6 tables, 49 references.
URI:http://hdl.handle.net/10261/34790
???metadata.dc.identifier.doi???:http://dx.doi.org/10.1515/HF.2008.096
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