AFFINITIES OF MONOLIGNOLS AND SACCHARIDES DETERMINED BY THE SOLUBILITY METHOD

To estimate the difference of affinities between monolignols and sacch arides, solubilities of p-coumaryl alcohol (HL), coniferyl alcohol (GL ), and sinapyl alcohol (SL) for D-glucose (Glc), D-galactose (Gal), D- mannose (Man), and D-xylose (Xyl) aqueous solutions were measured. The results showed that the solubilities increased with increases in the concentrations of all saccharides except the GL and Glc pair. This beh avior indicates that an attractive interaction exists in saccharides a nd monolignols. The apparent association constant (K(app)) in each sac charide and monolignol pair was estimated by Janado's equation. The va lues of K(app) were in the order of Glc < Gal almost-equal-to Xyl < Ma n for HL, Glc < Gal < Man < Xyl for GL, and Glc almost-equal-to Xyl < Man < Gal for SL. These results inform us that the affinities of monol ignols are greater for hemicellulose residues, for example, Xyl, Man, and Gal, than for cellulose residue, that is, Glc.