Structural characterization of lignin from leaf sheaths of "dwarf cavendish" banana plant

resumo

Dioxane lignin (DL) isolated from leaf sheaths of banana plant (Musa acuminata Colla var. cavendish) and in situ lignin were submitted to a comprehensive structural characterization employing spectroscopic (UV, FTIR, solid state C-13 CP-MAS NMR, liquid state C-13 and H-1 NMR) and chemical degradation techniques (permanganate and nitrobenzene oxidation). Results obtained showed that banana plant leaf sheath lignin is of HGS type with a molar proportion of p-hydroxyphenyl (H)/guaiacyl (G)/syringyl (S) units of 12:25:63. Most of the H units in DL are terminal phenolic coumarates linked to other lignin substructures by benzyl and C-gamma-ester bonds in contrast to ferulates that are mainly ether linked to bulk lignin. It is proposed that banana plant leaf sheath lignin is chemically bonded to suberin-like components of cell tissues by ester linkages via essentially hydroxycinnamic acid residues. beta-O-4 structures (0.31/C-6), the most abundant in DL, comprise mainly S units, whereas a significant proportion of G units is bonded by beta-5, 5-5', and 4-O-5' linkages contributing to ca. 80% of condensed structures in DL.

palavras-chave

CHEMICAL-COMPOSITION; HIBISCUS-CANNABINUS; EUCALYPTUS-GLOBULUS; ABACA FIBER; SUBERIN; SAMPLES; ESTERS

categoria

Agriculture; Chemistry; Food Science & Technology

autores

Oliveira, L; Evtuguin, DV; Cordeiro, N; Silvestre, AJD; Silva, AMS; Torres, IC

nossos autores

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