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United States Department of Agriculture

Agricultural Research Service

Title: The "dfrc" Method for Lignin Analysis. Part 6. Simple Modification for Identifying Natural Acetates on Lignins

Authors
item Ralph, John
item Lu, Fachuang - UNIV OF WISCONSIN-MADISON

Submitted to: Journal of Agricultural and Food Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 15, 1998
Publication Date: 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 a modification to the analysis that allows us to determine acetates on lignins. Although the functions of acetates in the plant are not clear, they alter the lignin and affect its processing. They also implicate new enzymes whose genes may be targeted for genetically modifying lignins. This study reinforces the value of the mild reactions in the DFRC method and its power to determine new structures of importance in basic and applied research. Scientists can use the DFRC method in a wide variety of studies ranging from optimization of pulping processes in pulp mills to the identification of how a plant responds to various genetic mutations that are forced on it. Such studies are at the heart of efforts to improve agricultural sustainability and maximize our plant resources.

Technical Abstract: By modifying the DFRC (derivatization followed by reductive cleavage) procedure to be completely acetate-free, the presence and regiochemistry of acetates on lignins can be determined. Derivatization is therefore with propionyl bromide in propionic acid (instead of acetyl bromide in acetic acid); reductive cleavage uses zinc in propionic acid (instead of in acetic cacid), and the final derivatization step uses propionic anhydride (instead of acetic anhydride). Applying the modified procedure to lignins or cell walls from kenaf bast fibers proved that their lignins are highly gamma- acetylated, mainly on syringyl units, supporting previous NMR work. Application to hardwood isolated lignins or cell walls confirmed the reported low-level acetylation and elucidated the gamma-regiochemistry. The DFRC method therefore provides a convenient screen for many types of lignin acylation.

Last Modified: 10/30/2014
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