Lignin-hydrolyzable tannin interactions in wood

A series of investigations were carried out to ascertain the relationship between lignin and hydrolyzable tannins in white oak (Quercus alba) and American chestnut (Castanea dentata) milled wood lignins as well as synthetic co-DHPs. Acidolysis and chromatographic analysis of chestnut and white oak milled wood lignins revealed the presence of ellagic acid in the chestnut sample but not in the white oak sample. Synthetic protocols were developed to prepare theorized lignin-gallate dimers, and these compounds served as a database for assessing American chestnut and white oak milled wood lignin by NMR spectroscopy. While dehydrogenative co-polymerization of C-13-labeled pentagalloyl D-glucopyranoside (PGG) with coniferyl alcohol and sinapyl alcohol showed evidence for hydrolyzable tannin/lignin interactions, unambiguous identifications in native milled wood lignin could not be made. The observed results are discussed in relation to natural wood durability.