| Abstract
| - 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 employingspectroscopic (UV, FTIR, solid state 13C CP-MAS NMR, liquid state 13C and 1H NMR) and chemicaldegradation techniques (permanganate and nitrobenzene oxidation). Results obtained showed thatbanana 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 linkedto other lignin substructures by benzyl and Cγ-ester bonds in contrast to ferulates that are mainlyether linked to bulk lignin. It is proposed that banana plant leaf sheath lignin is chemically bonded tosuberin-like components of cell tissues by ester linkages via essentially hydroxycinnamic acid residues.β-O-4 structures (0.31/C6), the most abundant in DL, comprise mainly S units, whereas a significantproportion of G units is bonded by β-5, 5−5‘, and 4-O-5‘ linkages contributing to ca. 80% of condensedstructures in DL. Keywords: Lignin; leaf sheaths; Musa acuminata Colla var. cavendish; banana plant; 13C NMR; 1HNMR; FTIR; lignin degradation methods
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