Monomeric and dimeric phenolic constituents of plant cell walls—possible factors influencing wall biodegradability

A range of plant cell walls fiom graminaceous and leguminous plants were examined qualitatively and quantitatively for monomeric and dimeric phenolic constituents that were released by treatment with sodium hydroxide. The total amounts of phenolics released fiom the walls of the graminaceous plants varied fiom 8 to 28 mg g−1 walls compared with less than 3 mg g−1 walls jiom the legumes. p‐Coumaric and ferulic acids were the major components of the monomeric fraction. The cell walls also contained substituted cyclobutanes having molecular weights equal to two p‐coumaric acid molecules, two ferulic acid molecules or one p‐coumaric plus one ferulic acid molecule, All the walls contained dehydrodiferulic acid. If it is assumed that the substituted cyclobutanes and dehydrodiferulic acid arise from dimerisation of feruloyl and p‐coumaroyl groups linked to cell wall polysaccharides, then, for the graminaceous walls, it is calculated that between 5 and 14% of these groups had converted to dimers. This dimerisation process may limit the biodegradability of the wall polysaccharides.