熱分解ガスクロマトグラフィーによるリグニンの構造解析（第２報） 腐朽材リグニンの分析

Abstract

Pyrolysis-gas chromatography (Py-GC) was applied to the characterization of lignin in decayed woods. Recently, Py-GC becomes one of the powerful tools for analyses of synthetic polymers. Very small amounts of solid materials are analyzed rapidly by using PyGC. In the structural analysis of lignin in woods, lignin can be analyzed by Py-GC without being isolated from woods.When sugi (Ctyptomeria japonica) woods is analyzed by Py-GC, the eight main ligninderived pyrolysis products (guaiacol, 4-methylguaiacol, 4-vinylguaiacol, vanillin, trans-isoeugenol dihydroconiferyl alcohol, coniferaldehyde and trans-coniferyl alcohol) can be detected. Pyrolysis of woods decayed by Coriolus versicolor and Tyromyces palustris provided the eight pyrolysis products in a smaller yield than that of the sound wood.In pyrolysis of sugi woods decayed by C. versicolor, the ratios of the peak area of guaiacol to the combined peak areas of the eight pyrolysis products (cpaG) increased with decreasing combined peak areas. On the other hand, in pyrolysis of sugi woods decayed by T. palustris, no cleas relationship was found between the ratios of the peak area of pyrolysis products to cpaG and cpaG per sample weight.Beech (Fagus crenata) woods were also decayed by C. versicolor, Daedalea dickinsii, Ganoderma lucidum and T. palustris, and analyzed by Py-GC. All decayed beech woods showed the smaller ratios of the combined peak areas of the four main syringyl type compounds (Syringol. 4-methylsyringol, 4-vinylsyringol, trans-4-propenylsyringol) (sumS) to the combined peak areas of the four main guaiacyl type compounds (guaiacol, 4-methylguaiacol, 4-vinylguaiacol, trans-isoeugenol) (sumG) than that of sound wood. This suggests that syringyl units of lignin were preferentially degraded to guaiacyl units. The ratios of the peak area of guaiacol to sumG and the ratios of the peak area of syringol to sumS increased in pyrolysis of beech woods decayed by the above four fungi.To clarify the convincing pyrolytic origins of the lignin structures giving syringol and guaiacol in high yields, some lignin dimer model compounds were subjected to Py-GC : syringlglycol-β-guaiacyl ether (SG-OH), dehydrodiisoeugenol (DDI) and α-guaiacoxyacetosyringone (SG=O). A phenylocoumaran type lignin model compound, DDI, did not give guaiacol. Similarly syringol was not formed from SG-OH, which is the β-O-4 analogue having a hydroxyl group at the Cα-position. On the other hand, the β-O-4 analogue having a carbonyl group at the Cα-position, SG=O, gave syringol by the pyrolytic cleavage of the bond between the Cα atom and aromatic ring in a 3 mol% yield. These findings suggest that the formation of α-carbonyl groups in the lignin macromolecule by fungal treatments should be one of the reasons why the ratios of guaiacol and syringol increased in Py-GC of the decayed woods. Py-GC is expected to be a promising method for characterization of the decayed wood lignin.