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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #94083
Title: THE DFRC METHOD FOR LIGNIN ANALYSIS. PART 7. THE BEHAVIOR OF CINNAMYL END-GROUPS.

Author
item LU, FACHUANG - UNIV OF WISCONSIN-MADISON
item Ralph, John

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/25/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: A major component in all terrestrial plants, lignin is a polymer that limits digestion of plants by animals, and must be removed from wood to make paper. We recently developed a new analytical method, the "DFRC" method (for Derivatization Followed by Reductive Cleavage, but also identifying the Dairy Forage Research Center where it was developed) that cleanly degrades lignins to simple analyzable compounds that give insight into the structural details of the original lignin. This paper reports on what happens to units at the ends of the lignin polymer. These "end-groups" are important because they tell us how large the lignin polymer is, and about how the polymerization occurred. For example, a large number of end- groups implies that the lignin building blocks (monomers) are present in large quantities during lignin formation and that one monomer frequently reacts with another monomer before further polymerization. More typically, end-group concentrations are low, implying that new monomers are supplied slowly to the cell wall and react not with other monomers but with the growing lignin polymer. The DFRC method creates unique compounds from various types of end-groups in lignin, making it valuable for determining the lignification mechanism and for understanding the lignification of plants that have been genetically altered. Such studies are at the heart of efforts to improve agricultural sustainability and maximize our plant resources.

Technical Abstract: The behavior of cinnamyl end-groups of lignins during the DFRC procedure has been investigated by DFRC treatment of lignin model compounds. On AcBr treatment, hydroxycinnamyl alcohols give rise mainly to 1-aryl-1,3- dibromopropanes from which 1-aryl-3-bromopropanes and aryl-cyclopropanes are formed by zinc reduction. Aryl propene derivatives are also significant tin DFRC products of etherified cinnamyl end-group models. Major monomers from DFRC of hydroxycinnamaldehydes are aryl-cyclopropyl acetates produced by zinc reductive ring closure of 1-acetoxy-3-aryl-1,3-dibromopropanes. Although the reactions are not as clean as the ether-cleaving reactions that form the basis of the DFRC method, end-groups nevertheless produce diagnostic compounds which provide valuable markers for studying end-groups in lignins.