Solid-state spectroscopic analysis of lignins from several Austral hardwoods

In order to gain information about lignin molecular characteristics with a direct bearing on the remarkable susceptibility of some Austral hardwoods t o biological delignification, milled-wood lignins were isolated and analyze d by spectroscopic techniques in the solid state. Cross polarization and ma gic-angle spinning C-13 nuclear magnetic resonance (C-13 CPMAS NMR) and Fou rier-transform infrared (FTIR) spectra of the lignin preparations were obta ined. The most diagnostic peaks were assigned and quantified as percentages of the total spectral area, and the differences observed discussed in term s of lignin composition. The spectral patterns obtained revealed that the w oods from Gevuina avellana, Eucryphia cordifolia and Nothofagus dombeyii ha ve lignin with high syringyl/guaiacyl ratio, as evidenced by relative areas of C-13 NMR signals at 153 and 148 ppm, and FTIR bands at 1335 and 1275 cm (-1). The presence of syringyl-rich lignins, characterized by lower redox p otential and condensation degree than guaiacyl-rich lignins, could be a str uctural factor contributing to the ease of extensive delignification of the se woods by white-rot fungi. (C) 1999 Elsevier Science B.V. All rights rese rved.