EXTRACTION OF PHENOLIC-CARBOHYDRATE COMPLEXES FROM GRAMINEOUS CELL-WALLS

Barley straw and a preparation of perennial ryegrass were sequentially extracted with oxalic acid, dimethyl sulphoxide (DMSO) and a ''cellul olytic'' enzyme preparation Driselase and the fractions studied by met hylation analysis, C-13 NMR and other methods. Oxalic acid, as expecte d, solubilised the bulk of the arabinose and ferulic acid in both samp les, although appreciable amounts of xylose were also solubilised. DMS O yielded polymeric lignin-carbohydrate complexes (LCC), both of which consisted predominantly of a beta(1 --> 4) xylan. From the results of methylation analysis, sensitivity to oxalic acid hydrolysis and size- exclusion chromatography after alkaline hydrolysis, it was evident tha t lignin polymers were attached to arabinosyl acid xylosyl residues by both ester and aryl-ether linkages. After cellulolytic hydrolysis of the residues, thioacidolysis analysis of the lignin component in the D MSO-soluble and Driselase-insoluble fractions from ryegrass revealed d ifferences in every measurable aspect. The DMSO-soluble lignin was fou nd to be more highly condensed, have a higher S/G ratio and have a hig her terminal G/internal G ratio.