Studies on the dehydrogenative polymerization of monolignol β-glycosides: Part 5. UV spectroscopic monitoring of horseradish peroxidase-catalyzed polymerization of monolignol glycosides
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Yuki Tobimatsu
Abstract
Horseradish peroxidase (HRP)-initiated dehydrogenative polymerizations of guaiacyl (G) and syringyl (S)-type monolignol γ-O-glucosides, isoconiferin (iso-G) and isosyringin (iso-S), which contain a hydrophilic glucosyl unit on γ-position of coniferyl alcohol (G-alc) and sinapyl alcohol (S-alc), respectively, were monitored by UV spectroscopy to study the formation of dehydrogenation polymer (DHP, lignin polymer model) in a homogeneous aqueous phase. During homopolymerization of iso-S, a new absorbance band at 325 nm (A325) rapidly increased in intensity and then gradually disappeared, whereas such stable changes in absorbance were not observed during homopolymerization of iso-G. During polymerization of iso-S, A325 rapidly disappeared when an acid, nucleophile or reductant was added to the reaction mixture, indicating that A325 can be attributed to S-type quinone methide intermediates (QMs). Similar to iso-S polymerization, temporary absorbance at 328 nm was observed during conventional polymerization of S-alc. We interpret this observation as follows: S-type QMs accumulated in the reaction mixture and the progress of subsequent DHP formation during oxidative polymerization of iso-S or S-alc was hindered. UV monitoring of iso-G and iso-S copolymerization revealed that the presence of iso-G promoted the disappearance of A325. Furthermore, S-type QMs generated in situ by iso-S polymerization disappeared more rapidly after guaiacol addition than after 2,6-dimethoxyphenol addition. The following mechanism for copolymerization of iso-G and iso-S can be proposed: G-type precursors with phenolic hydroxyl groups react readily by nucleophilic addition with the α-C of S-type QMs, and the molecular chains of DHPs increase via non-cyclic α-aryl ether bonds.
©2008 by Walter de Gruyter Berlin New York
Articles in the same Issue
- Original Papers
- Studies on the dehydrogenative polymerizations (DHPs) of monolignol β-glycosides: Part 4. Horseradish peroxidase-catalyzed copolymerization of isoconiferin and isosyringin
- Studies on the dehydrogenative polymerization of monolignol β-glycosides: Part 5. UV spectroscopic monitoring of horseradish peroxidase-catalyzed polymerization of monolignol glycosides
- Monolignol dehydrogenative polymerization in vitro in the presence of dioxane and a methylated β-β′ dimer model compound
- Structural characterization of milled wood lignins from different eucalypt species
- FTIR spectroscopy in combination with principal component analysis or cluster analysis as a tool to distinguish beech (Fagus sylvatica L.) trees grown at different sites
- Hydrothermal dissolution of mixed southern hardwoods
- Characterisation of fines from unbleached kraft pulps and their impact on sheet properties
- Effects of refining steam pressure on the properties of loblolly pine (Pinus taeda L.) fibers
- Elastic deformation mechanisms of softwoods in radial tension – Cell wall bending or stretching?
- Fiberboard bending properties as a function of density, thickness, resin, and moisture content
- Modification of Fagus sylvatica (L.) with 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU): Part 1. Estimation of heat adsorption by the isosteric method (Hailwood-Horrobin model) and by solution calorimetry
- Development of wooden block shear wall – Improvement of stiffness by utilizing elements of densified wood
- Significance of the heating rate on the physical properties of carbonized maple wood
- Exploring Scots pine fibre development mechanisms during TMP processing: Impact of cell wall ultrastructure (morphological and topochemical) on negative behaviour
- Pentachlorphenol migration from treated wood exposed to simulated rainfall
- Resistance of Trichoderma harzianum to the biocide tebuconazol – Proposed biodegradation pathways
- Short Notes
- On the variation of acid-labile aryl ether unit content in wood lignin
- Coumarins and secoiridoid glucosides from bark of Fraxinus rhynchophylla Hance
- Antifungal activities of heartwood extracts of Port-Orford cedar extractives
- Antifungal secoabietane dialdehyde and bisabolane-type terpenoids from the heartwood of Cryptomeria japonica D. Don
- Meetings
- Meetings
Articles in the same Issue
- Original Papers
- Studies on the dehydrogenative polymerizations (DHPs) of monolignol β-glycosides: Part 4. Horseradish peroxidase-catalyzed copolymerization of isoconiferin and isosyringin
- Studies on the dehydrogenative polymerization of monolignol β-glycosides: Part 5. UV spectroscopic monitoring of horseradish peroxidase-catalyzed polymerization of monolignol glycosides
- Monolignol dehydrogenative polymerization in vitro in the presence of dioxane and a methylated β-β′ dimer model compound
- Structural characterization of milled wood lignins from different eucalypt species
- FTIR spectroscopy in combination with principal component analysis or cluster analysis as a tool to distinguish beech (Fagus sylvatica L.) trees grown at different sites
- Hydrothermal dissolution of mixed southern hardwoods
- Characterisation of fines from unbleached kraft pulps and their impact on sheet properties
- Effects of refining steam pressure on the properties of loblolly pine (Pinus taeda L.) fibers
- Elastic deformation mechanisms of softwoods in radial tension – Cell wall bending or stretching?
- Fiberboard bending properties as a function of density, thickness, resin, and moisture content
- Modification of Fagus sylvatica (L.) with 1,3-dimethylol-4,5-dihydroxyethylene urea (DMDHEU): Part 1. Estimation of heat adsorption by the isosteric method (Hailwood-Horrobin model) and by solution calorimetry
- Development of wooden block shear wall – Improvement of stiffness by utilizing elements of densified wood
- Significance of the heating rate on the physical properties of carbonized maple wood
- Exploring Scots pine fibre development mechanisms during TMP processing: Impact of cell wall ultrastructure (morphological and topochemical) on negative behaviour
- Pentachlorphenol migration from treated wood exposed to simulated rainfall
- Resistance of Trichoderma harzianum to the biocide tebuconazol – Proposed biodegradation pathways
- Short Notes
- On the variation of acid-labile aryl ether unit content in wood lignin
- Coumarins and secoiridoid glucosides from bark of Fraxinus rhynchophylla Hance
- Antifungal activities of heartwood extracts of Port-Orford cedar extractives
- Antifungal secoabietane dialdehyde and bisabolane-type terpenoids from the heartwood of Cryptomeria japonica D. Don
- Meetings
- Meetings
