Occurrence of naturally acetylated lignin units

Abstract

In this work, we have studied the occurrence of native acetylated lignin in a large set of vascular plants, including both angiosperms and gymnosperms, by a modification of the so-called Derivatization Followed by Reductive Cleavage (DFRC) method. Acetylated lignin units were found in all angiosperms selected for this study, including mono- and eudicotyledons, but were absent in the gymnosperms analyzed. In some plants (e.g. abaca, sisal, kenaf or hornbeam), lignin acetylation occurred at a very high extent, exceeding 45% of the uncondensed syringyl lignin units. Acetylation was observed exclusively at the -carbon of the lignin-side chain and predominantly on syringyl units, although a predominance of acetylated guaiacyl over syringyl units was observed in some plants. In all cases, acetylation appears to occur at the monomer stage and sinapyl and coniferyl acetates seem to behave as real lignin monomers participating in lignification.