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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #179634
Title: STRUCTURAL ELUCIDATION OF NEW FERULIC ACID-CONTAINING PHENOLIC DIMERS AND TRIMERS ISOLATED FROM MAIZE BRAN

Author
item BUNZEL, MIRKO - U OF HAMBURG
item Ralph, John
item FUNK, CAROLA - U OF HAMBURG
item STEINHART, HANS - U OF HAMBURG

Submitted to: Tetrahedron Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/15/2005
Publication Date: 7/14/2005
Citation: Bunzel, M., Ralph, J., Funk, C., Steinhart, H. 2005. Structural elucidation of new ferulic acid-containing phenolic dimers and trimers isolated from maize bran. Tetrahedron Letters. 46:5845-5850.

Interpretive Summary: A plant's fiber component provides a great deal of structural strength as well as considerable nutrition to ruminant animals. Grain fiber also has significant human health benefits. The fiber is reinforced in the plant by cross-linking of the polysaccharide polymers, on a micro-scale rather akin to the cross-bracing we use when building wooden structures. Some time ago we discovered new mechanisms by which wall cross-linking could be achieved by chemical coupling of two so-called ferulate molecules (that were each tied to one polysaccharide chain) to create ferulate “dimers.” Such findings have opened up avenues of research into improving the utilization of large classes of plant fiber and other food commodities. A short time ago we reported the first structural evidence for three ferulates coupling together making a ferulate "trimer." It is tempting to infer that polysaccharide chains may be very heavily cross-linked, but in fact we think that it is attached twice to one polysaccharide chain and once to another, so that the entity still only cross-links two chains. In proving that this was not some singular event, and is a common mechanism for plants to tie their fibers together, we have now discovered two more ferulate trimers, with quite different but reasonably predictable structures, along with two further dimers, at least one of which is implicated in cross-linking. The significance is that cross-linking is even more prevalent than we previously thought, and that ferulates are capable of creating the cross-links in a variety of ways. Future efforts are aimed at minimizing this cross-linking in forage plants to improve ruminant digestibility, and to ascertain the human and animal health benefits of the ferulates in cereal grains.

Technical Abstract: Four new phenolic dimers and trimers that contain ferulic acid moieties were isolated from the alkaline hydrolyzate of insoluble maize bran fiber and their structures were established by 1D/2D NMR and mass spectrometry. The biological role of one dimer remains unclear whereas the dimeric vanillin-ferulic acid-cross-product probably represents an oxidative degradation product from the corresponding diferulate. Both ferulic acid dehydrotrimers are able to cross-link polysaccharide chains. However, the 5-5/8-O-4(H2O)-triferulic acid may be a cross-link in its identified structure whereas we assume that the identified 8-O-4/8-5(noncyclic)-triferulic acid arose from a natural 8-O-4/8-5(cyclic)-triferulate analog during the saponification process.