Analysis of the structure of lignin-carbohydrate complexes by the specific13C tracer method |
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Authors: | Yimin Xie Sciichi Yasuda Hong Wu Huanbin Liu |
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Affiliation: | (1) State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, 510641 Guangzhou, China;(2) Laboratory of Forest Chemistry, School of Agricultural Sciences, Nagoya University, 464-8601 Nagoya, Japan |
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Abstract: | In the present study the specifically13C-enriched lignin precursors of biosynthesis (i.e., coniferin-[side chain–13C], coniferin-[side chain-–13C] and coniferin-[side chain-–13C]) were synthesized and administered exogeneously to ginkgo shoots (Ginkgo biloba L.) to obtain13C-enriched lignin-carbohydrate complexes (LCCs). The specifically13C-enriched LCCs were isolated from the newly formed xylem of ginkgo shoots administered with the13C-enriched precursors and degraded by enzymes. Lignin-rich fractions, so called enzyme-degraded LCCs (EDLCCs), were obtained. By determining their13C-NMR spectra, information related to the chemical structure of lignin building units and linkages between phenylpropane units of lignin and carbohydrates were obtained. It was found that these precursors were incorporated in natural lignin successfully. Three lignin-carbohydrates linkages (i.e., ether type, ester type, ketal type) were found at the C-position of the side chain of phenylpropane units in ginkgo LCC. No lignin-carbohydrate bond at the C- or C-position of the lignin side chain was observed in the13C-NMR spectra of the13C-enriched LCCs. This fact indicates that a specific13C tracer technique can be useful in NMR study of the chemical structure of LCCs.Part of this paper was presented at the 5th Pacific Polymer Conference, Kyongju, Korea, October 1997 |
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Keywords: | Lignin-carbohydrate complexes NMR 13C tracer Coniferin Ketal linkage |
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