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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Research » Publications at this Location » Publication #90009
Title: THE "DFRC" METHOD FOR LIGNIN ANALYSIS. PART 5. CYCLIC LIGNIN TRIMERS FROM DFRC-DEGRADED PINUS TAEDA

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

Submitted to: Phytochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/23/1998
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 the identification of a new type of structure in lignin, one that is logical but has never been considered in the past. It also suggests that certain structures identified by prior analytical methods have been incorrectly assigned. This study reinforces the value of the mild reactions in the DFRC method and its power to correctly 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: A pair of new aryl isochroman lignin trimers, 7-acetoxy-1-[2-acetoxy-1-[4- acetoxyprop-2-enyl)-2-methoxyphenoxy]-3-(4-acetoxy-3 -methoxyphenyl)-4- acetoxymethyl-6-methoxy-isochromans, that we have named taedate and isotaedate, along with three related dimers were isolated from the DFRC (Derivatization Followed by Reductive Cleavage) degraded loblolly pine (Pinus taeda L.) wood following gel permeation and reversed-phase TLC and HPLC. Their structures were elucidated by means of 2D-NMR, FAB-MS and GC-MS analyses. These two trimers contained a unique beta-1 inter-unit linkage with a 6-membered di-alpha-ether ring and with the side chain migrated. The mechanistic plausibility of the lignification pathway, the isolation of expected DFRC degradation dimers and trimers, and the tentative identification of the aryl isochroman structure in pine milled wood lignins by NMR all suggest that such structures are present in native lignins (in their un-acetylated forms).