The Chemistry of Lignin.

Phillips, Max

doi:10.1021/cr60047a005

Cited by 43 publications

(16 citation statements)

References 88 publications

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“…30 chemical nature of lignins: various proponents described it as either a polysaccharidederived polymer, arising from degradation of hemicelluloses, cellulose or pectins (24), and others proposed that even the terpenoids were products of altered lignin metabolism (25). Yet, much earlier, Ferdinand Tiemann (26) and Peter Klason (27) had speculated that lignin was derived from £-coniferyl alcohol 1 (Figure 4), and in 1933 Holgar Erdtman suggested that the monolignol (a term coined later) was converted into lignin via a dehydrogenative polymerization process (28).…”

Section: Brief Historical Development Of Ideasmentioning

confidence: 99%

Lignin and Lignan Biosynthesis: Distinctions and Reconciliations

Lewis

Davin

Sarkanen

1998

ACS Symposium Series

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Before 1996, the framework within which lignin biosynthesis was understood at the molecular level had not fundamentally changed for 4 decades. During the same period nothing at all had been explicitly proposed about the mechanistic basis for lignan formation in vivo. The associated deficit in plant biochemistry was not minor: lignins and lignans together account for roughly 30% of the organic carbon in vascular plants. On the other hand, the biochemical transformations in phenylpropanoid metabolism leading, via the shikimate-chorismate pathway through phenylalanine or tyrosine, to the so-called monolignols (namely, the monomeric lignin/lignan precursors) came to be reasonably well documented. Indeed, attention has more recently been drawn to the identification of de facto rate-limiting steps in the various metabolic segments of the pathway as potential control-points for biotechnological manipulation. The most curious characteristic usually attributed to the lignin/lignan biosynthetic pathway is that the monolignol-derived radical coupling processes leading to lignans are regio-and stereospecific, whereas those resulting in lignin macromolecules ostensibly are not. Now that the molecular basis for the dehydrogenative dimerization of monolignols to lignans has been unraveled, however, it appears likely that an analogous mechanism may be operative in the dehydrogenative polymerization of monolignols to lignins. The investigation of this possibility has indeed become a central concern in the field of lignin biosynthesis.It has been almost three decades (7) since a comprehensive attempt had been made to summarize and evaluate contending views about lignin biosynthesis. Accordingly, the present volume draws together the current, yet conceptually vastly differing, ideas about how lignin composition and structure are established in living plants. It differs from all prior contributions, not only in introducing fresh evidence to support a compelling new paradigm that seeks to understand how lignin structure is established in vivo, but also in including lignan biosynthesis for comparative purposes. Indeed it appears that the first committed step in lignan biosynthesis bears an important relationship to the manner in which the configurations of lignins are specified in vivo.

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Section: Brief Historical Development Of Ideasmentioning

confidence: 99%

Lignin and Lignan Biosynthesis: Distinctions and Reconciliations

Lewis

Davin

Sarkanen

1998

ACS Symposium Series

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“…However, there is evidence that lignin is not a totally inert compound. Phillips (1934) concluded that some lignin could be degraded during digestion. Reports by Ellis et al (1946), Richards and Reid (1952), Allinson and Osbourn (1970), Minson (1971), Grant et al (1974), Kornegay (1978) and Fahey et al (1979) indicated that lignin was partly digested.…”

Section: Introductionmentioning

confidence: 99%

Phenolic Compounds in Roughages and Their Fate in the Digestive System of Sheep

Fahey

Al-Haydari

Hinds

et al. 1980

Journal of Animal Science

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Three experiments were conducted to determine the concentrations of phenolic monomers (para-coumaric acid, ferulic acid, vanillin, acetovanillone, para-hydroxybenzaldehyde and para-hydroxyacetophenone) and polymers (lignin) in roughages and to assess the fate of these compounds in the ruminant digestive system. In Exp. 1, low quality timothy hay and cottonwood, silver maple and red oak sawdusts were fed to mature wethers. Apparent digestibilities of dietary dry matter, hemicellulose and starch were similar among treatments. Cellulose digestibility of timothy hay was greater than that of the wood cellulose diets. Digestibility of klason acid detergent lignin (ADL) of timothy hay and the maple sawdust diet was greater than that of the cottonwood and oak diets. Lower concentrations of phenolic monomers were present in fecal lignins than in feed lignins when animals were fed any of the three sources of sawdust. In Exp. 2, cottonwood sawdust was fed fresh or after drying, ensiling or treatment with propionic acid. No differences in dry matter digestibility or hemicellulose digestibility were observed among treatments, but cellulose digestibility of fresh sawdust was greater than that of the treated roughages. Lignin of dry sawdust was more poorly utilized than was the lignin of the treated materials. As in Exp. 1, smaller amounts of phenolic monomers were present in feces than in feed. In Exp. 3, growing lambs were fed alfalfa or bromegrass hay to enable us to monitor selectively the disappearance of phenolic material from various sections of the

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“…By 1933-34, there was considerable disagreement and confusion about the very constitution of lignin, with various investigators proposing that it was derived either from cellulose (76)(77)(78)(79), pentoses/pentosans (80,81) or pectin (82), as summarized by Max Phillips (83). On the other hand, Karl Freudenberg had proposed that lignin was a linear polymer derived from coniferyl alcohol, linked via 9-0-4' linkages ( Figure 3), based upon perceived dehydration reactions occurring in vivo (84,85).…”

Section: Early Theories Of Lignification and Lignan Formationmentioning

confidence: 99%

The Biochemical Control of Monolignol Coupling and Structure During Lignan and Lignin Biosynthesis

Lewis

Davin

1998

ACS Symposium Series

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Over the last six decades or so, various theories and views have emerged to account for lignin and lignan assembly mechanisms. None have yet been able to satisfactorily describe all of the biochemical, structural and anatomical observations associated with formation of either distinct metabolic class in vivo. In this chapter a quite different perspective in terms of substance, approach and conclusion is given which now appears to account for all of the observations hitherto made. It is based primarily on results from the definitive elucidation of monolignol biochemical reactions, established at both the protein and gene levels, which reveals that monomer coupling processes do not occur haphazardly as often depicted. In this context, the first example of regio-and stereochemical control of monolignol bimolecular phenoxy radical coupling was that which gave the dimeric 8-8' linked lignan, (+)-pinoresinol, through the participation of a dirigent protein. The gene encoding this protein has no sequence homology to that of any other of known function, perhaps helping to explain further why stereoselective bimolecular phenoxy radical coupling, as controlled by this new class of proteins, had previously gone undiscovered. It is now contemplated that distinct arrays of dirigent protein sites (or some equivalent) stipulate macromolecular assembly mechanisms in the cell wall leading to the various lignins encountered. That is, to specifically account for the well-defined heterogeneous nature of lignin biopolymers within particular cell-wall types, it is proposed that arrays of dirigent protein sites in the developing wall specify the nature (monomer composition and bond frequency) of the primary lignin chain. There is growing evidence to show that specific lignin-related proteins are translocated to predetermined areas within the pre-lignified cell wall. An array of lignin monomers are then targeted to presumed specific sites on these proteins within the wall at about the same time. Although the precise mechanistic details need to be elucidated, lignification is then envisaged to occur via end-wise polymerization of the aligned monomers thereby generating the initial primary lignin chain(s), with chain replication occurring via a template polymerization effect as proposed by Sarkanen. Such a mechanism for lignin biosynthesis does not, however, readily account for formation of minor (reduced) substructures (e.g. dihydrodehydrodiconiferyl alcohol), supposedly present in the lignin macromolecule, which would suggest pre-or post-coupling modifications. As discussed elsewhere, these are viewed instead to be the products of a distinct pathway to the lignans. 334

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The Chemistry of Lignin.

Cited by 43 publications

References 88 publications

Lignin and Lignan Biosynthesis: Distinctions and Reconciliations

Lignin and Lignan Biosynthesis: Distinctions and Reconciliations

Phenolic Compounds in Roughages and Their Fate in the Digestive System of Sheep

The Biochemical Control of Monolignol Coupling and Structure During Lignan and Lignin Biosynthesis

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