Release of Ferulic Acid Esters From Barley Aleurone. II. Characterization of the Feruloyl Compounds Released in Response to GA₃

Abstract

Two major feruloyl-containing compounds are released into the incubation medium, when isolated aleurone layers are treated with gibberellic acid (GA₃). These compounds were purified from 72 h, + GA₃ incubation medium and analysed, using methylation analysis, various chromatographic techniques, including gas chromatography-mass spectroscopy, and nuclear magnetic resonance spectroscopy. The compounds were shown in each case to contain arabinose and xylose residues with molar ratios consistent with a feruloylated trisaccharide and tetrasaccharide, and indicating that they were hydrolysis products of feruloylated arabinoxylans. Three possible alternative structures are given for the tetrasaccharide, and the trisaccharide was identified as O-[5-O-feruloyl-L-arabinofuranosyl]- (1͛4 3)-O-D-xylopyranosyl-(1͛4 4)-D-xylopyranose, with the feruloyl residue in the trans form. The implication of the results in relation to wall structure and hydrolysis, and the removal of ferulic acid from the walls, during the GA₃ response of barley aleurone is considered.