期刊
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
卷 53, 期 25, 页码 9639-9649出版社
AMER CHEMICAL SOC
DOI: 10.1021/jf0515330
关键词
correlation 2D NMR; hardwood; lignin; milled wood lignin (MWL); quantitative C-13 NMR
The structure of Eucalyptus grandis milled wood lignin (MWL) was investigated by 2D H-1-C-13 HSQC, HMQC, and H-1-H-1 TOCSY correlation NMR techniques and by quantitative C-13 NMR as well as by the permanganate oxidation degradation technique. The combination of 2D NMR and quantitative 13C NMR spectroscopy of nonacetylated and acetylated lignin preparations allowed reliable identification and calculation of the amount of different lignin structures. About 85% of side-chain moieties were estimated on the structural level. This information was substantiated by data on the quantity of various functional groups and interunit linkages as a whole. A modified method for calculation of the h:g:s ratio has been suggested and compared with previously suggested approaches. E grandis MWL has been determined to have an h:g:s ratio of 2:36:62. The amounts of various phenolic/etherified noncondensed/condensed guaiacyl and syringyl moieties were approximately estimated. E grandis MWL contained similar to 0.60/Ar of beta-O-4 moieties along with small amounts of other structural units such as pino/syringyresinol (0.03/Ar), phenylcoumaran (0.03/Ar), and spirodienone (0.05/Ar). The degree of condensation was estimated at similar to 21%; the main condensed structures are 4-O-5 moieties (similar to 0.09/Ar). The structure of E grandis MWL was compared with those of other lignin preparations isolated from various hardwoods.
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