NEW ETHER-LINKED FERULIC ACID-CONIFERYL ALCOHOL DIMERS IDENTIFIED IN GRASS STRAWS

Grass cell walls are typified by ferulic esters linked to polysaccharides. In past research, these feruloylated esters have been repeatedly speculated to be cross-linking agents with lignins, via ether bonds. Whereas this hypothesis is strongly supported by degradative studies, model experiments, and NMR data, diagnostic fragments associating ferulic acid and lignin precursors, through an ether bond, have never been isolated from grass walls. This paper reports the isolation of such products by saponification of wheat and oat straws. New dimers associating ferulic acid to the beta position of coniferyl alcohol are characterized by gas chromatography/mass spectrometry and authenticated by independently synthesized compounds. The biochemical implication is that ferulate esters are copolymerized with lignin precursors through oxidative coupling. These ferulate esters thereby provide points of growth for the polymer Lignin, via ether bonds that anchor Lignins to wall polysaccharides.