Submitted to: International Symposium on Wood and Pulping Chemistry
Publication Type: Proceedings
Publication Acceptance Date: 12/1/2008
Publication Date: 6/15/2009
Citation: Ralph, J., Kim, H., Lu, F., Grabber, J.H., Leple, J., Berrio-Sierra, J., Mir, D., Jouanin, L., Boerjan, W., Lapierre, C. 2009. Thioacidolysis Marker Compound for Ferulic Acid Incorporation into Angiosperm Lignins (and an Indicator for Cinnamoyl-coenzyme-A Reductase Deficiency. In: Proceedings of the Fifteenth International Symposium on Wood, Fiber, and Pulping Chemistry, Oslo, Norway, (2009); pp Paper P-071. Interpretive Summary:
Technical Abstract: A molecular marker compound, derived from lignin by the thioacidolysis degradative method, for structures produced when ferulic acid is incorporated into lignification in angiosperms (poplar, Arabidopsis, tobacco) has been structurally identified as 1,2,2-trithioethyl ethylguaiacol [1-(4-hydroxy-3-methoxyphenyl)-1,2,2-tris(ethylthio)ethane]. Its truncated sidechain and distinctive oxidation state suggest it derives from ferulic acid that has undergone bis-8–O–4-(cross-)coupling during lignification, as validated by model studies. A diagnostic contour for such structures is found in 2D 13C–1H correlated (HSQC) NMR spectra of lignins isolated from CCR-deficient poplar. As low levels of the marker are also released from normal (i.e. non-transgenic) plants in which ferulic acid may be present during lignification, notably in grasses, we term this only an indicator for CCR-deficiency in general, but a reliable marker in woody angiosperms such as poplar. Its derivation, along with evidence for 4-O-etherified ferulic acid, strongly implies that ferulic acid incorporates into angiosperm lignins. Its endwise radical coupling reactions suggest that ferulic acid should be considered an authentic lignin precursor.