As interest in biomass utilization has grown, the manipulation of lignin biosynthesis has received significant attention, such that recent work has demanded more robust lignin analytical methods. As ...the derivatization followed by reductive cleavage (DFRC) method is particularly effective for structurally characterizing natively acylated lignins, we used an array of synthetic β‐ether γ‐acylated model compounds to determine theoretical yields for all monolignol conjugates currently known to exist in lignin, and we synthesized a new set of deuterated analogs as internal standards for quantification using GC–MS/MS. Yields of the saturated ester conjugates ranged from 40 to 90 %, and NMR analysis revealed the presence of residual unsaturated conjugates in yields of 20 to 35 %. In contrast to traditional selected‐ion‐monitoring, we demonstrated the superior sensitivity and accuracy of multiple‐reaction‐monitoring detection methods, and further highlighted the inadequacy of traditional standards relative to isotopically labeled analogs.
More than meets the eye: As plant breeding programs embrace the idea of the “biorefinery”, lignin has come to be seen as a feedstock for commodity chemicals. Without robust analytics capable of describing lignin's chemical structure, its true value will remain hidden. To this end, a powerful analytical method was developed using synthetic methodology and isotopic labeling to identify new and low‐abundance monolignols and their conjugates.
The cell walls of leaf base tissues of the Canary Island date palm (Phoenix canariensis) contain lignins with the most complex compositions described to date. The lignin composition varies by tissue ...region and is derived from traditional monolignols (ML) along with an unprecedented range of ML conjugates: ML-acetate, ML-benzoate, ML-p-hydroxybenzoate, ML-vanillate, ML-p-coumarate, and ML-ferulate. The specific functions of such complex lignin compositions are unknown. However, the distribution of the ML conjugates varies depending on the tissue region, indicating that they may play specific roles in the cell walls of these tissues and/or in the plant's defense system.
Invited for this month's cover is the group of Prof. John Ralph at the University of Wisconsin–Madison. The image shows the fragmentation of various lignins into monomeric components using the ...derivatization followed by reductive cleavage (DFRC) method, with the included mechanism providing the details for the derivatization of these lignins with acetyl bromide and their subsequent reductive cleavage using elemental zinc. The Communication itself is available at 10.1002/cssc.201800617.
“We consider derivatization followed by reductive cleavage (DFRC), especially with its focus on monolignol conjugates, to be a powerful…” This and more about the story behind the research that inspired the Cover image is presented in the Cover Profile. Read the full text of the corresponding research at 10.1002/cssc.201800617. View the Front Cover here: 10.1002/cssc.201800957.
The Front Cover shows how the derivatization followed by reductive cleavage (DFRC) lignin characterization assay fragments lignins into small monomeric components. Unlike other lignin degradation ...assays (e.g., thioacidolysis and nitrobenzene oxidation), the DFRC assay cleaves β‐aryl ethers without hydrolyzing the γ‐esters present in some lignin, especially grass lignin. This robust method works well on whole biomass, as well as lignins isolated from softwoods, hardwoods, and grasses. We have optimized each step of the DFRC method to provide highly accurate quantitative data for both the traditional monolignols (i.e., H, G, and S) and the less‐abundant γ‐ester‐containing monolignol conjugates. More information can be found in the Communication by Regner et al. on page 1600 in Issue 10, 2018 (DOI: 10.1002/cssc.201800617).
Phoenix canariensis leaf lignins vary between tissue region and contain an array of pendent groups.
The cell walls of leaf base tissues of the Canary Island date palm (
Phoenix canariensis
) contain ...lignins with the most complex compositions described to date. The lignin composition varies by tissue region and is derived from traditional monolignols (ML) along with an unprecedented range of ML conjugates: ML-acetate, ML-benzoate, ML-
p
-hydroxybenzoate, ML-vanillate, ML-
p
-coumarate, and ML-ferulate. The specific functions of such complex lignin compositions are unknown. However, the distribution of the ML conjugates varies depending on the tissue region, indicating that they may play specific roles in the cell walls of these tissues and/or in the plant’s defense system.
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