Eucalyptus globulus Stumps Bark: Chemical and Anatomical Characterization Under a Valorisation Perspective

The chemical and anatomical properties of Eucalyptus globulus stumps barks collected from fresh stumps (SB) and from industrial stumps bark piles (ISB) were determined. The stump bark showed similar anatomical structure to that of the stem bark, however with abundant prismatic crystals in the axial parenchyma cells. Stumps barks (ISB) presented a great amount of ashes (19.2%) that were incorporated during forest and mill processing, and lower content in extractives (4.1%), lignin (18.5%) and polysaccharides (48.5%). The non-polar (DCM) extracts were composed essentially by triterpenoids, fatty acids (C-8 to C-28), phytosterols (sterols and steroid ketones) and fatty alcohols (C-15 to C-28). The polar extracts (ethanol and water) were rich in phenolic compounds, condensed tannins and flavonoids, with higher values for the ethanol extracts and for SB. The antioxidant activity of ethanol extracts from SB was higher although only moderate (IC50 6.8). The lignin monomeric composition (H:G:S) was similar in SB (1:12:45) and in ISB (1:9:26). Sugar-derived compounds formed by Py-GC/MS included more low molecular compounds in ISB than in SB (45.5% vs.20.3%) indicative of a more degraded structure. [GRAPHICS] .

Automated summary

The study found that industrial stump bark has higher ash content, while fresh stump bark contains more extractives, lignin, and polysaccharides. In addition, eucalyptus stump bark also contains abundant fatty acids, phytosterols, and phenolic compounds, with antioxidant activity.