Isolation and structural identification of diarabinosyl 8-O-4-dehydrodiferulate from maize bran insoluble fibre.

The first saccharide ester of a dehydrodiferulic acid (DFA) other than 5-5-DFA has been isolated from maize bran insoluble fibre after acidic hydrolysis and fractionation by gel chromatography and semi-preparative RP-HPLC. HPLC-MS along with 1D, 2D and 3D NMR spectra provided the requisite structural evidence that it is the di-5-O-l-arabinosyl ester of 8-O-4-DFA. Although a range of DFAs have been well authenticated as components released from the cell walls of grasses, the only structural evidence for a DFA attached to polysaccharides had been from 5-5-DFA. The isolation of the 8-O-4-ester demonstrates that polysaccharides in maize cell walls, and presumably in all grasses, are cross-linked through dehydrodiferulates other than 5-5-dehydrodiferulate.