Characterization of lignin in heartwood, sapwood and bark from Tectona grandis using Py-GC-MS/FID

Sapwood, heartwood and bark of 70-year-old teak trees from an unmanaged stand in East Timor were characterized by pyrolysis (Py-GC-MS/FID). Sapwood and heartwood from teak presented a high lignin content (35.4 and 37.3 % of extractive-free wood) and similar composition. Teak wood is characterized by a GS type of lignin (56.0 % of G-units, 42.2 % of S-units and 1.8 % of H-units in extractive-free wood), with an S/G ratio of 0.8. The major lignin-derived compounds were 4-vinylsyringol (6.6 %), coniferyl alcohol (trans) (4.5 %), coniferaldehyde (2.0 %), 4-vinylguaiacol (1.6 %) and 4-methylguaiacol (1.6 %). Extractive-free teak bark presented 28.0 % of lignin, characterized by a GS type, with 53.3 % G-units, 42.1 % S-units and 4.6 % H-units, with S/G ratio of 0.8. The high lignin content and a composition with predominance of G-units may contribute to the durability and mechanical resistance of teakwood.