Structural Features of Cork Dioxane Lignin from Quercus suber L.
authors Branco, DG; Santiago, C; Lourenco, A; Cabrita, L; Evtuguin, DV
nationality International
journal JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
author keywords cork; dioxane lignin; permanganate oxidation; H-1 NMR; C-13 NMR; HSQC; FTIR; SEC; Py-GC-MS
keywords CHEMICAL-COMPOSITION; REPRODUCTION CORK; MACROMOLECULAR COMPONENTS; FTIR SPECTROSCOPY; SAPONIFIED CORK; GRAPE STALKS; GC-MS; VARIABILITY; METHANOLYSIS; PYROLYSIS
abstract The dioxane lignin was isolated from extractives- and suberin-free cork (Quercus suber L.) by a modified acidolytic procedure and submitted to structural analysis by permanganate oxidation, analytical pyrolysis coupled with gas chromatography and mass spectrometry (Py-GC-MS), liquid- and solid-state nuclear magnetic resonance (NMR) spectroscopy, and Fourier transform infrared (FTIR) spectroscopy. The molecular weight (M-w = 2500 Da) was assessed by size exclusion chromatography (SEC). The results obtained show that the cork lignin is of syringyl (S)/guaiacyl (G) type with a small proportion of p-hydroxyphenyl (H) units (S:G:H molar ratio of 23:72:5). Among a dozen detected lignin structures, those linked by ether bonds, such as beta-O-4' (38 mol %) and 4-O-5' (5 mol %), were the most abundant. The frequency of occurrence of beta-5', beta-beta', 5-5', tetrahydrofuran type, and structures arising from the condensation with concomitant procyanidins was assessed. Ferulates were the only cinnamic structure detected in the cork dioxane lignin.
publisher AMER CHEMICAL SOC
issn 0021-8561
isbn 1520-5118
year published 2021
volume 69
issue 30
beginning page 8555
ending page 8564
digital object identifier (doi) 10.1021/acs.jafc.1c01961
web of science category 10
subject category Agriculture, Multidisciplinary; Chemistry, Applied; Food Science & Technology
unique article identifier WOS:000683727500022
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