NMR Studies of Lignins. 6. Interpretation of the 1H NMR Spectrum of Acetylated Spruce Lignin in a Deuterioacetone Solution.

Lundquist, Knut; Paterson, Alistair; Ramsey, Lee

doi:10.3891/acta.chem.scand.37b-0734

Cited by 18 publications

(9 citation statements)

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“…The dimers recovered from the degradation of pinoresinol structures could be observed äs prominent ones among the main dilignols recovered from this dehydropolymer, whereas they were observed äs traces from softwood lignin. This result confirms that the pinoresinol linkage pattern is not significant in softwood lignins (Sakakibara 1981;Lundquist et al·, 1983;Lundquist and Unge 1986), which is not the case in dehydropolymers (Freudenberg 1968;Nakatsubo and Higuchi 1975;Brunow and Lundquist 1980).…”

Section: Identification Of the Main Products Recovered From Spruce LIsupporting

confidence: 87%

Thioacidolysis of Spruce Lignin: GC-MS Analysis of the Main Dimers Recovered After Raney Nickel Desulphuration

Lapierre¹,

Pollet²,

Monties³

et al. 1991

Holzforschung

152

167

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KeywordsSpruce lignin Softwood lignin Carbon-carbon bonds in Thioacidolysis Desulphuration Rancy nickcl lignin SummaryThe GC-MS Identification of the main dimcrs rccovcrcd aftcr thioacidolysis, thcn dcsulphuration ovcr Rancy nickcl of sprucc lignin allowcd to charactcrizc the vurious typcs of Condensed linkagcs in softwood lignin. The major carbon-carbon bonds wcrc obscrvcd to bc rcprcscnted by the ß-5, 5-5 and ß-1 intcrunitary linkagcs cstablishcd bctwccn two guaiacyl units, in agrccmcnt with litcraturc data. Bcsidcs, minor linkagc patterns wcre rcprcscnted by dimcrs providcd with the diphcnyl cthcr, the phcnylisochroman and the tctrahydrofuran structurcs. This fingcrprint of Condensed structurcs in softwood iignin was obtaincd from a fcw milligrarns of sample, by mcans of a rcproduciblc and mild routinc proccdurc.

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Section: Identification Of the Main Products Recovered From Spruce LIsupporting

confidence: 87%

Thioacidolysis of Spruce Lignin: GC-MS Analysis of the Main Dimers Recovered After Raney Nickel Desulphuration

Lapierre¹,

Pollet²,

Monties³

et al. 1991

Holzforschung

152

167

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“…However, there are invariably hydroxycinnamyl aldehyde end-groups in normal lignins (26), in structures 6, so their products are not diagnostic for CAD deficiency, and they do not qualify as molecular maker compounds for CAD deficiency.…”

Section: Cadmentioning

confidence: 99%

Identification of the Structure and Origin of Thioacidolysis Marker Compounds for Cinnamyl Alcohol Dehydrogenase Deficiency in Angiosperms

Kim

Ralph

et al. 2002

Journal of Biological Chemistry

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Molecular marker compounds, derived from lignin by the thioacidolysis degradative method, for cinnamyl alcohol dehydrogenase (CAD) deficiency in angiosperms have been structurally identified as indene derivatives. They are shown to derive from hydroxycinnamyl aldehydes that have undergone 8 -O-4-cross-coupling during lignification. As such, they are valuable markers for ascertaining plant responses to various levels of CAD down-regulation. Their derivation illustrates that hydroxycinnamyl aldehydes incorporate into angiosperm lignins by endwise coupling reactions in much the same way as normal monolignols do, suggesting that the hydroxycinnamyl aldehydes should be considered authentic lignin precursors.Perturbations of the lignin biosynthetic pathway have the potential to enhance the utilization of plant cell walls in various natural and industrial processes. In forages fed to ruminant animals, for example, lignins inhibit the rumen degradability of potentially digestible polysaccharides (1). In chemical pulping for the production of fine paper, the aim is to selectively remove the lignin from the cellulose fibers. Recently it has become evident that there is potential beyond down-regulating lignification to produce low lignin plants; inducing structural and compositional changes in the polymer may also be beneficial for many processes (2-8).The definitive way to determine the response of a plant to upor down-regulation of lignin biosynthetic pathway genes/enzymes and the impact on the lignification process itself is by lignin structural analysis. Molecular marker compounds that allow the degree of change to be elucidated are vital particularly when various levels of down-regulation need to be assessed. CAD1 (cinnamyl alcohol dehydrogenase) is the last enzyme on the pathway to the monolignols, primarily coniferyl and sinapyl alcohols 4 (Fig. 1), from which polymeric lignin is derived. One of the most prominent effects of CAD down-regulation is an increased incorporation of hydroxycinnamyl aldehydes 1 into the lignin polymer (7, 9 -19). Such an incorporation is logical; the hydroxycinnamyl aldehyde 1 precursors to the hydroxycinnamyl alcohol monolignols 4 are anticipated to build up when the flux to the monolignols is reduced and can be used for polymerization in much the same way as the monolignols themselves (9, 13, 18 -20).2 What was not obvious a priori is that these aldehydes, products of incomplete monolignol synthesis, would necessarily be exported to the wall, but that appears to be the case.In softwoods, in which their (guaiacyl) lignins are overwhelmingly derived from coniferyl alcohol 4G, coniferyl aldehyde 1G is not well incorporated (18,19).2 This is largely due to simple chemical cross-coupling propensities; coniferyl aldehyde 1G does not 8 -O-4-cross-couple efficiently with guaiacyl units 2G in the evolving polymer in plants (18). The prime incorporation mechanism then is by dimerization, or by cross-coupling with a coniferyl alcohol monomer (Fig. 1b) (13,19,22). Coniferyl alcohol 4G overwhelmingly...

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“…Although this correspondence cannot generally be expected for proton NMR, good lignin model compounds and their counterpart units in the polymer also closely match proton NMR chemical shifts (11)(12)(13). Despite the broad featureless one-dimensional (1D) proton spectra, which have nevertheless allowed substantive interpretation (14), homoand hetero-nuclear, two-and three-dimensional (2D and 3D) spectra are rich in information that is extremely useful in polymer characterization (7,8). NMR has already proven invaluable in revealing structural aspects of other ligninbiosynthetic-pathway mutants and transgenics (15,16).…”

mentioning

confidence: 99%

NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5-hydroxylase

Marita

Ralph

Hatfield

et al. 1999

Proc. Natl. Acad. Sci. U.S.A.

162

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Nuclear magnetic resonance (NMR) of isolated lignins from anArabidopsis mutant deficient in ferulate 5-hydroxylase (F5H) and transgenic plants derived from the mutant by overexpressing the F5H gene has provided detailed insight into the compositional and structural differences between these lignins. Wild-type Arabidopsis has a guaiacyl-rich, syringyl-guaiacyl lignin typical of other dicots, with prominent ␤-aryl ether (␤-O-4), phenylcoumaran (␤-5), resinol (␤-␤), biphenyl͞dibenzodioxocin (5-5), and cinnamyl alcohol end-group structures. The lignin isolated from the F5H-deficient fah1-2 mutant contained only traces of syringyl units and consequently enhanced phenylcoumaran and dibenzodioxocin levels. In fah1-2 transgenics in which the F5H gene was overexpressed under the control of the cauliflower mosaic virus 35S promoter, a guaiacyl-rich, syringyl͞guaiacyl lignin similar to the wild type was produced. In contrast, the isolated lignin from the fah1-2 transgenics in which F5H expression was driven by the cinnamate 4-hydroxylase promoter was almost entirely syringyl in nature. This simple lignin contained predominantly ␤-aryl ether units, mainly with erythro-stereochemistry, with some resinol structures. No phenylcoumaran or dibenzodioxocin structures (which require guaiacyl units) were detectable. The overexpression of syringyl units in this transgenic resulted in a lignin with a higher syringyl content than that in any other plant we have seen reported. transgenic plants ͉ mutant ͉ syringyl lignin ͉ heteronuclear single quantum coherence (HSQC) ͉ guaiacyl lignin T he biotechnological manipulation of lignin content and͞or structure in plants is seen as a route to improving the use of plant cell wall polysaccharides in various agricultural and industrial processes. The aims of these efforts range from enhancing cell wall digestibility in ruminants to reducing the energy demand and negative environmental impacts of chemical pulping and bleaching required in the papermaking process. To achieve these goals, many researchers (1-3) have down-regulated the expression of genes of the monolignol biosynthetic pathway in attempts to decrease lignin deposition. This approach has sometimes had negative side effects, including the collapse of tracheary elements under the tension generated by transpiration. One of the most desirable strategies for modifying lignin is to produce a less crosslinked, syringyl-rich lignin. It is hoped that this modified lignin would have improved industrial and͞or agricultural properties, yet remain fully functional in planta.Through the identification of the fah1-2 mutant, it has been shown that ferulate 5-hydroxylase (F5H) activity is required for syringyl lignin deposition in Arabidopsis (4). The Arabidopsis F5H gene was subsequently cloned by T-DNA tagging (5). F5H expression was shown to be rate limiting for syringyl lignin accumulation by overexpression of the gene in the fah1-2 mutant background (6). The lignin in transgenic plants, in which the F5H gene was expressed under the control of ca...

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NMR Studies of Lignins. 6. Interpretation of the 1H NMR Spectrum of Acetylated Spruce Lignin in a Deuterioacetone Solution.

Cited by 18 publications

References 0 publications

Thioacidolysis of Spruce Lignin: GC-MS Analysis of the Main Dimers Recovered After Raney Nickel Desulphuration

Thioacidolysis of Spruce Lignin: GC-MS Analysis of the Main Dimers Recovered After Raney Nickel Desulphuration

Identification of the Structure and Origin of Thioacidolysis Marker Compounds for Cinnamyl Alcohol Dehydrogenase Deficiency in Angiosperms

NMR characterization of lignins in Arabidopsis altered in the activity of ferulate 5-hydroxylase

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