resumo
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.
palavras-chave
CHEMICAL-COMPOSITION; REPRODUCTION CORK; MACROMOLECULAR COMPONENTS; FTIR SPECTROSCOPY; SAPONIFIED CORK; GRAPE STALKS; GC-MS; VARIABILITY; METHANOLYSIS; PYROLYSIS
categoria
Agriculture, Multidisciplinary; Chemistry, Applied; Food Science & Technology
autores
Branco, DG; Santiago, C; Lourenco, A; Cabrita, L; Evtuguin, DV
nossos autores
Dmitry Evtyugin
Professor Associado com AgregaçãoProjectos
Novas Abordagens na desinfecção e branqueamento de rolhas de cortiça. (NEWASHCORK)
CICECO - Aveiro Institute of Materials (UIDB/50011/2020)
agradecimentos
This work was developed within the scope of the project NEWASHCORK (POCI-01-0247-FEDER-034048) financed by ANI, cofinanced by FEDER, and supported by the CICECO-Aveiro Institute of Materials (UIDB/50011/2020 and UIDP/50011/2020) financed by national funds through the FCT/MEC and when appropriate cofinanced by FEDER under the PT2020 Partnership Agreement. The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No. 022161 (cofinanced by FEDER through COMPETE 2020, POCI, and PORL and by FCT through PIDDAC). The pyrolysis analysis was supported by the Forest Research Centre (financed by FTC through UIDB/00239/2020 project). A.L. thanks FCT for her research contract (DL 57/2016/CP1382/CT0007).