Vicelina B. Sousa

Wood properties of teak (Tectona grandis) from a mature unmanaged stand in East Timor

The wood quality from 50- to 70-year-old Tectona grandis trees from an unmanaged forest in East Timor was assessed. The aim was to evaluate teak in mature stands that had undergone uncontrolled disturbances, e.g., fire and local community usage. Heartwood represented 91% of the tree radius at a height of 1.7 m, and sapwood contained on average nine rings. The mean ring width showed within-tree and between-tree variability. The chemical compositions of heartwood and sapwood were similar. Within-tree chemical variation occurred only in terms of extractives, which increased from the pith (8.3%) to the heartwood-sapwood transition (12.7%) and decreased in the sapwood (9.2%). Overall, the wood properties of teak from a unmanaged forest in East Timor were comparable to those reported for plantation teaks of other origin: 607 kg/m3 basic density, 3.5% and 5.2% radial and tangential shrinkage, 141 N/mm2 modulus of rupture, 10684 N/mm2 modulus of elasticity, and 50 N/mm2 maximum crushing strength in compression parallel to the grain. Disturbances on individual tree growth arising from the unmanaged status of the stand were evidenced by higher within-tree variability of ring width. However, the longitudinal and radial variations of wood density and mechanical properties were of low magnitude and in a degree that did not negatively impact on timber quality.

Characterization of cork oak (Quercus suber) wood anatomy.

The cork oak (Quercus suber L.) is important for ecological and socioeconomic sustainability and nature conservation in the Mediterranean area. Anatomical and structural features of cork oak wood were characterized at two sites in Portugal, including never-debarked trees and trees under cork production. Cork oak wood showed semi-ring porosity, solitary vessels with simple perforation plates, and large rays. Vessels were arranged in a diagonal to radial pattern, larger and more abundant in earlywood, and gradually decreasing in intermediate and latewood. In trees under cork production vessel distribution and frequency were altered, with more frequent and smaller pores, and a less distinct porosity pattern. Vessel diameter, element length and frequency were 133 ± 49 μm, 433 ± 103 μm and 2.9 ± 0.5 vessels/mm2 for never-debarked trees and 139 ± 50 μm, 341 ± 100 μm and 5.1 ± 1.5 vessels/mm2 for debarked trees. Multiseriate ray width ranged 0.15–1.04 mm, and uniseriate ray height 9.1–791.3 μm. Fibres had a mean length of 1.15 ± 0.20 mm. Vasicentric tracheids were frequent. Tyloses and crystals were commonly present. The anatomical features of cork oak wood favour water conduction and mechanisms of drought adaptation to the Mediterranean climate. The wood can also adapt to cork removal.

Age trends in the wood anatomy of Quercus faginea

The wood anatomy of Quercus faginea, an oak native to the Iberian Peninsula and the Maghreb in Africa, is described and age trends of fibres and ray dimensions are recorded. The analysis was made on a total of 20 trees from two different sites in Portugal. The wood structure within both sites was similar. Quercus faginea shares its microscopic characteristics with other species of the white oak group; i.e., it was not easily distinguishable from other European oaks. The wood is ring porous with wide multiseriate rays and a high proportion of fibres and vasicentric tracheids. There was an increase of fibre and ray dimensions from the pith outwards. Fibre length started to stabilize around 30 years of age up to 50–60 years and decreased afterwards under a traditional rotation period (100–150 years). Linear and polynomial adjustments fitted better the fibre variation at younger and older ages, respectively. Rays were quite homogeneous within the trees. Cambial age accounted less to total variation than individual trees at both sites; i.e., tree-to-tree variation is greater than variation related to maturation or cambial age. The average dimensions of fibres and rays were similar between sites.

Chemical characterization and extractives composition of heartwood and sapwood from Quercus faginea

Heartwood and sapwood of Quercus faginea were evaluated in relation to summative chemical composition and non-polar and polar extracts composition, including an assessment of antioxidant properties (DPPH and FRAP). Twenty trees from two sites in Portugal were analysed. Heartwood had approximately two times more solvent extractible compounds than sapwood (on average 19.0% and 9.5%). The lipophilic extractible compounds were below 1%, and most of them were polar e.g. ethanol-soluble compounds corresponded to 65% of total extractives in heartwood and 43% in sapwood. Lignin content was similar in sapwood and heartwood (28.1% and 28.6% of extractive-free wood respectively) as well as the sugar composition. Site did not influence the chemical composition. The lipophilic extractible compounds from both sapwood and heartwood included mainly saturated fatty acids (23.0% and 36.9% respectively) and aromatic compounds were also abundant in sapwood (22.9%). The ethanol-water extractibles had a high content of phenolic substances (558.0 and 319.4 mg GAE/g extract, respectively of heartwood and sapwood). The polyphenolic composition was similar in heartwood and sapwood with higher content of ellagitannins (168.9 and 153.5 mg tannic acid/g of extract in sapwood and heartwood respectively) and very low content of condensed tannins. The antioxidant activity was very high with IC50 of 2.6 μg/ml and 3.3 μg/ml for sapwood and heartwood respectively, as compared to standard antioxidants (IC50 of 3.8 μg/ml for Trolox). The ferric reducing ability was 2.8 and 2.0 mMol Trolox equivalents/g extract of heartwood and sapwood respectively. The variability between trees was low and no differences between the two sites were found. Q. faginea showed a very good potential for cooperage and other applications for which a source of compounds with antioxidant properties is desirable.

Copaifera langsdorffii Bark as a Source of Chemicals: Structural and Chemical Characterization

The chemical composition and the anatomy of Copaifera langsdorffii bark are reported here for the first time by studying trees grown in a native forest area in the Amazon region, Brazil. The bark is thin, dark reddish brown, and exfoliates in irregular flakes. It is very dense, showing highly lignified cells and abundant sclereids, and cellular fillings of phenolic nature. It includes a poorly developed rhytidome and a periderm with thin- and thick-walled phellem cells. The mean chemical composition was: ash 3.7%, total extractives 21.3%, mainly corresponding to polar compounds soluble in ethanol and water, suberin 0.8%, and lignin 36.6%. The polysaccharides showed a predominance of glucose and xylose (66.4% and 23.5% of total monosaccharides, respectively). The ethanol-water bark extract had a high content in phenolics: total phenolics 589.2 mg gallic acid/g extract, flavonoids 441.9 mg catechin/g extract, and tannins 54.8 mg catechin/g extract. The antioxidant activity was high, comparable to known antioxidant reference compounds: 720.3 mg Trolox per g of extract or 92.1 mg Trolox per g of bark. After bark grinding, the finest fraction was enriched in polar extractives (40.6%). C. langsdorffii bark is a potential source of functional extractives, therefore representing a valorization of the residual bark obtained during the industrial tree processing for timber.

Chemical composition of barks from Quercus faginea trees and characterization of their lipophilic and polar extracts

The bark from Quercus faginea mature trees from two sites was chemically characterized for the first time. The barks showed the following composition: ash 14.6%, total extractives 13.2%, suberin 2.9% and lignin 28.2%. The polysaccharides were composed mainly of glucose and xylose (50.3% and 35.1% of all monosaccharides respectively) with 4.8% of uronic acids. The suberin composition was: ω-hydroxyacids 46.3% of total compounds, ɑ,ω-alkanoic diacids 22.3%, alkanoic acids 5.9%, alkanols 6.7% and aromatics 6.9% (ferulic acid 4.0%). Polar extracts (ethanol-water) had a high phenolic content of 630.3 mg of gallic acid equivalents (GAE)/g of extract, condensed tannins 220.7 mg of catechin equivalents (CE)/g extract, and flavonoids 207.7 mg CE/g of extract. The antioxidant activity was very high corresponding to 1567 mg Trolox equivalents/g of extract, and an IC50 of 2.63 μg extract/ml. The lipophilic extracts were constituted mainly by glycerol and its derivatives (12.3% of all compounds), alkanoic acids (27.8%), sterols (11.5%) and triterpenes (17.8%). In view of an integrated valorization, Quercus faginea barks are interesting sources of polar compounds including phenols and polyphenols with possible interesting bioactivities, while the sterols and triterpenes contained in the lipophilic extracts are also valuable bioactive compounds or chemical intermediates for specific high-value market niches, such as cosmetics, pharmaceuticals and biomedicine.