Gas chromatographic and mass spectrometric (GC-MS) analysis of lignin-derived products from Cryptomeria japonica treated in supercritical water

Abstract

Sugi (Cryptomeria japonica D. Don) wood was treated with supercritical water (≫374°C, ≫22.1 MPa), and fractionated into the water-soluble portion, the methanol-soluble portion, and the methanol-insoluble residue. The methanol-soluble portion mainly consisted of the lignin-derived products. To characterize the compounds in the methanol-soluble portion, gel permeation chromatographic (GPC) and gas chromatographic-mass spectrometric (GC-MS) analyses were performed. The GPC analysis indicated that the methanol-soluble portion contained lignin-derived monomeric and dimeric products. GC-MS analysis detected 31 products which were expected to be monomeric compounds, and 18 of these were identified to be guaiacol, methylguaiacol, ethylguaiacol, vinylguaiacol, eugenol, propylguaiacol, vanillin, cis-isoeugenol, homovanillin, trans-isoeugenol, acetoguaiacone, propioguaiacone, guaiacylacetone, 2-methoxy-4-(1-hydroxypropyl)phenol, homovanillic acid, 2-methoxy-4-(prop-1-en-3-one)phenol, coniferyl aldehyde, and ferulic acid. In addition, 22 dimeric products were detected, and 4 of these were believed to be compounds with biphenyl type (5-5), diphenylethane type (Β-1), stilbene type (Β-1), and phenylcoumaran type (Β-5) structures. These results clearly indicated that the methanol-soluble portion included various monomeric and dimeric compounds produced as a result of the cleavage of ether linkages and propyl chains of lignin.