jf8b02014_si_001.pdf (429.73 kB)
Structural Characterization of Lignins from Willow Bark and Wood
journal contribution
posted on 2018-06-22, 00:00 authored by Jinze Dou, Hoon Kim, Yanding Li, Dharshana Padmakshan, Fengxia Yue, John Ralph, Tapani VuorinenUnderstanding the chemical structure
of lignin in willow bark is
an indispensable step to design how to separate its fiber bundles.
The whole cell wall and enzyme lignin preparations sequentially isolated
from ball-milled bark, inner bark, and wood were comparatively investigated
by nuclear magnetic resonance (NMR) spectroscopy and three classical
degradative methods, i.e., alkaline nitrobenzene oxidation, derivatization
followed by reductive cleavage, and analytical thioacidolysis. All
results demonstrated that the guaiacyl (G) units were predominant
in the willow bark lignin over syringyl (S) and minor p-hydroxyphenyl (H) units. Moreover, the monomer yields and S/G ratio
rose progressively from bark to inner bark and wood, indicating that
lignin may be more condensed in bark than in other tissues. Additionally,
major interunit linkage substructures (β-aryl ethers, phenylcoumarans,
and resinols) together with cinnamyl alcohol end groups were relatively
quantitated by two-dimensional NMR spectroscopy. Bark and inner bark
were rich in pectins and proteins, which were present in large quantities
and also in the enzyme lignin preparations.
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Keywords
fiber bundlesreductive cleavagedegradative methodscell wallnitrobenzene oxidationwillow barkenzyme lignin preparationsStructural Characterizationcinnamyl alcohol end groupsNMR spectroscopychemical structuremonomer yieldsenzyme lignin preparations sequentiallyWillow Barkwillow bark ligninball-milled bark
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