HSQC-NMR analysis of lignin in woody (Eucalyptus globulus and Picea abies) and non-woody (Agave sisalana) ball-milled plant materials at the gel state

8 páginas, 2 tablas, 2 figuras.

In situ analysis of lignin by 2D NMR of whole plant material was carried out by swelling finely ball-milled samples in deuterated dimethylsulfoxide (DMSO-d6) and sonicated so that a gel was formed in the NMR analysis tube. Solution HSQC NMR spectra of different plant materials representative for hardwood (Eucalyptus globulus), softwood (Picea abies), and non-woody plants (Agave sisalana) are presented here. The spectra show signals corresponding to those of the main plant constituents such as lignin and polysaccharides. The lignin signals were assigned by comparing the HSQC spectra of the whole plant materials with the HSQC spectra of their respective milled-wood lignins (MWL). In general terms, the major lignin structural features, such as the relative abundances of the main lignin substructures, the syringyl/guaiacyl ratios and the extent of γ-acetylation of the lignin side-chain observed in the HSQC spectra of the whole plant materials, matched those obtained from the HSQC spectra of the isolated MWL. Therefore, this technique, which needs only minor amounts of lignocellulosic material and minimal sample preparation, can be useful for the rapid screening of plant lignins without the need for tedious and time-consuming lignin isolation procedures.

This study has been supported by the Spanish Ministry of Science and Innovation (projects AGL2005-01748, BIO2005-03569 and BIO2008-01533), CSIC (project 2006-4-0I-039) and European Commission (BIORENEW project NMP2-CT-2006-026456). J.R. thanks the CSIC for a I3P fellowship and GM thanks the Spanish MEC for a FPI fellowship.

Peer reviewed