Volume 66, Issue 5

In a hydrophilic extract of Norway spruce knotwood, the dominating lignan, 7-hydroxymatairesinol, was partially removed by precipitation, and the resulting mixture was fractionated by flash chromatography and preparative high-performance liquid chromatography (HPLC). In the HPLC fractions, 7 S - and 7 R -todolactol A, 7′-hydroxylariciresinol, and two stereoisomers of 9′-hydroxylariciresinol were identified by gas chromatography-mass spectrometry (GC-MS) analyses, and their structures were confirmed by nuclear magnetic resonance spectroscopy. The 9′-hydroxylariciresinols were suggested to have the 7 S ,8 R ,8′ R ,9′ R and 7 R ,8 R ,8′ R ,9′ R configurations, and (-)-7′-hydroxylariciresinol 7 S* ,7′ R* ,8 R* ,8′ S* , which indicates a configuration of this structure that has not been reported previously. 7 S - and 7 R -isoliovil were identified by comparison with previously published GC-MS data, and 7′-oxolariciresinol was tentatively identified on the basis of its mass spectrum. Of these lignans, only 7′-hydroxylariciresinol has been identified previously in Norway spruce. Several other lignans with similar mass spectra as the todolactols, isoliovils, and 7′-hydroxylariciresinol were detected, indicating that they are different stereoisomers of these lignans and/or of liovils. In addition to these lignans, the mass spectra of several other unidentified minor lignans indicated the presence of several tens of previously unidentified minor lignans in Norway spruce knotwood, accounting altogether for approximately 6% of the dry weight of the ethanol extract. 7 S -Todolactol A, which was dominating among the new lignans, was found to be very unstable in aqueous solutions. Identification of more of these unidentified lignans may be possible only by access to pure reference compounds.

Chamaecyparis formosensis is a precious conifer endemic in Taiwan. To understand the sesquiterpene synthesis mechanism in this tree, full-length cDNA of a putative sesquiterpene synthase (sesqui-TPS), designated Cf-Cad , was obtained by rapid amplification of complementary DNA ends-polymerase chain reaction. Cf-Cad is 1812 bp in length. To identify its function, recombinant protein from Escherichia coli was incubated with farnesyl diphosphate, which produced one major product, the structure of which was elucidated by gas chromatography/mass spectrometry (GC/MS) analysis. GC/MS analysis, GC retention time and MS matching with authentic standards revealed that the major product was β-cadinene. This is the first report of the cloning, functional expression in E. coli and identification of a sesqui-TPS from a Cupressaceae conifer.

The most active phenolics in Quercus sideroxyla Humb. & Bonpl. residual bark were identified and evaluated following a chromatographic fractionation. Bark powder was defatted with hexane and crude extract (CE) was obtained by extraction with aqueous acetone (70%). A liquid partition with ethyl acetate was performed to produce an organic extract (OE), which was subsequently purified by column chromatography (Toyopearl HW-40F, methanol), and resulted in six methanolic fractions (MF1 to MF6) and an oligomeric fraction (OLF) eluted with acetone 67%. Extraction yields, total phenolic and flavanol contents were determined. The antioxidant activity of bark extracts was measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH), Trolox (6-hydroxy-2,5,7,8-tetramethyl-chroman-2-carboxylic-acid)-equivalent antioxidant capacity (TEAC), and ferric ion reducing antioxidant power (FRAP) assays. Their median effective concentration (EC 50 ) data and rate constants for DPPH radical scavenging were also estimated. Identification of major phenolics was carried out by high performance liquid chromatography with diode array detection (HPLC-DAD) and high performance liquid chromatography with electrospray ionization coupled to mass spectrometry (HPLC-ESI-MS) instruments. Bioactive gallic acid, catechin, epicatechin, gallocatechin, catechin gallate, dimeric procyanidins, galloylated dimeric proanthocyanidins, trimeric procyanidins, and tetrameric proanthocyanidins were detected and identified in Q. sideroxyla bark extracts. MF2 was the most active fraction containing gallocatechin as its major compound; MF5 and OLF contain galloylated procyanidins, which may explain their higher antiradical activity. OLF besides galloylated procyanidins has gallocatechin, which presumably contributes to its higher antiradical activity. Consequently, Q. sideroxyla bark could be a good source of therapeutic health products or nutraceutical ingredients that may exert a potential prevention or treatment action against diseases in biological systems.

From the heartwood of Lindera glauca Blume three new diarylpropanoids have been isolated and identified, which were named lindeglaucol, lindeglaucone, and lindeglaucoside A. Chipped heartwood was extracted repeatedly with 80% aqueous methanol (MeOH) at room temperature, and the concentrated methanolic extract was successively partitioned with ethyl acetate (EtOAc), n -butanol, and H 2 O. From the EtOAc fraction, three new diarylpropanoids and a known chalconoid were isolated through repeated column chromatography with silica gel, octadecyl silica gel, and Sephadex LH-20. The chemical structures of the compounds were elucidated by interpretation of extensive spectroscopic data such as nuclear magnetic resonance, fast atom bombardment mass spectroscopy, and infrared. In addition, a known chalconoid, cilicicone B, was isolated for the first time from the heartwood of L. glauca .

Xylose solutions have been produced from Eucalyptus globulus wood by autohydrolysis (with hot, compressed water) and post-hydrolysis (in presence of sulfuric acid). This two-stage process led to solids enriched in cellulose and lignin (suitable as a substrate for pulping) and liquors containing xylose as the major component. The liquid phase from post-hydrolysis also contained other sugars (glucose, arabinose) and acetic acid. Neutralized liquors (as obtained, or after membrane concentration), were employed (directly or after detoxification by ion exchange) as fermentation media for the production of hemicelluosic bioethanol with the yeast Pichia stipitis CECT 1922T. Under the best conditions assayed (fermentation of neutralized, concentrated and detoxified two-stage hydrolysis liquors), bioconversion took place at nearly stoichiometric yield, with a volumetric productivity of 0.37 g l -1 ·h -1 .

The dissolution of pulps with varying characteristic properties, for example cellulose chain length or content of hemicellulose, has been investigated in two alkaline solvent systems [sodium hydroxide (NaOH)/urea/thiourea (8:8:6.5 by wt.) and NaOH/zince oxide (ZnO) (9:0.5 by wt.)]. One standard paper pulp, two dissolving pulps and three pretreated pulps were selected for this study. The dissolution parameters in focus were the fiber dimensions, average degree of polymerization (DP), polydispersity, water retention value and content of hemicelluloses. The solubility was not influenced by the fiber dimensions. The only significant properties, according to variable importance plot, were DP and composition of the hemicelluloses. It was also established that mass transfer effects during the dissolution stage plays an important role in the dissolution of cellulose derived from pulp fibers.

A method for nuclear magnetic resonance (NMR) characterization of whole cell wall components, including lignin, cellulose and hemicelluloses, was recently developed in our laboratory. The method described for fir ( Abies sachalinensis ) as a softwood consists of ball-milling of cell wall, dissolution in an ionic liquid 1-butyl-3-methylimidazolium chloride ([Bmim]Cl), in situ acetylation, recovery of the material from the solution, and characterization of the product by 1 H- 13 C correlation heteronuclear single quantum coherence (HSQC) NMR spectroscopy in dimethyl sulfoxide (DMSO)- d 6 . In the present paper, the performance of the method should be tested for a hardwood and a bamboo. Thus, Japanese white birch ( Betula platyphylla ) and hachiku bamboo ( Phyllostachys nigra ) have been investigated. Finely ball-milled birch and bamboo materials were completely dissolved in [Bmim]Cl at 100°C without severe chemical modification of the cell wall components. The dissolved cell walls were then subjected to in situ acetylation, and the ball-milled and fully acetylated cell walls were recovered from [Bmim]Cl. Longer ball-milling time was required for birch and bamboo cell walls, because of the lower solubility of acetylated birch and bamboo materials in DMSO- d 6 compared to the acetylated fir material. However, HSQC NMR experiments were successfully conducted, and the acetylated whole cell wall components in the birch and bamboo could be fully characterized. This method is applicable for the analysis of cell wall components of various plant biomasses without previous isolation. Further studies are necessary to improve the method.

The adhesion of single and associated lignin chains to a substrate has been studied by means of single-molecule force spectroscopy (SMFS). Softwood kraft lignin (KL) and two lignin polymer models (dehydrogenation polymers, DHPs) based on coniferyl alcohol (DHP c.alc. ) and coniferaldehyde (DHP c.ald. ) were in focus. The desorption force from the “silicon nitride SMFS tip” for the KL was significantly greater than that of the DHPs. The higher desorption force was interpreted as being due to the interaction of carboxyl groups through hydrogen bonding with the tip as well as to the less compact polymeric layer at the interface. The distribution of the extended chain lengths was determined, and self-association of lignin chains was observed. For both KL and the DHP c.ald. , chains were extended significantly beyond the limit that would be expected for polymers with the corresponding degree of polymerization. The α-carbon on the DHP c.alc. has a strong intramolecular hydrogen bonding interaction with the adjacent aryl ether, which inhibits the possibility of the ether to participate in intermolecular hydrogen bonding with nearby lignin chains. Thus, the self-association for KL and DHP c.ald. was found to be dominated by intermolecular hydrogen bonding with carboxylic groups and aryl ether functionalities.

Experimental results for the fracture behavior under mixed-mode in-plane loading conditions of adhesively bonded wood specimens are reported. The material systems considered involved yellow-poplar ( Liriodendron tulipifera ), a hardwood of the Magnoliaceae family, as adherends bonded with two different adhesives, a moisture-cure polyurethane (PU) and a phenol/resorcinol/formaldehyde (PRF) resin. A dual actuator test frame permitted fine scanning of fracture behavior over a full range of mixed-mode I/II levels for double cantilever beam (DCB) geometry specimens. These tests showed that, in the considered material systems, the critical strain energy release rate, c , tends to increase as the mode-mixity of the loading increases. In particular, the increase is steeper in proximity to pure mode II loading for the PRF bonded specimens. The experimental values of c obtained were fairly scattered, as is common when testing wood systems. This variability is due in part to the natural variability of wood but also to other factors such as the orientation of the grain in the bonded beams and variations of bondline thickness. In particular, measurements of adhesive layer thickness were performed. This analysis was implemented with microscopic examination of samples cut from untested DCB specimens, where the bondline had not been disrupted by the test. Although the wood parts were power planed prior to bonding, rather large variations of the adhesive layer thickness were observed: on the order of 1–100 μm for specimens bonded with the PU resin and 10–50 μm for specimens bonded with the PRF resin, which showed somewhat more consistent fracture behavior.

Grading tests were performed on 338 poplar wood samples ( Populus × euramericana I-214) with dimensions of 150×50 mm 2 , 150×80 mm 2 , and 200×100 mm 2 prepared for structural utilization. The non-destructive testing methods included ultrasound (Sylvatest) and induced vibrations (Portable Lumber Grader) combined with visual grading criteria. Additionally, screw withdrawal resistance was tested by the instrument Fakopp. These results were compared with those obtained by a four-point bending test according to the EN 408 (2004) standard. Ultrasound and induced vibrations overestimated the quality of this type of wood. Correlation equations are proposed to determine the true characteristics for each testing method. It can be concluded that poplar timber from clone I-214 has acceptable flexural strength, but a comparatively low elastic modulus, whereby it is not graded within a high strength class according to the EN 338 (2009) standard.

Dimensional stability is one of the most important properties of lumber. Shrinkage is especially critical in this regard. In this study, longitudinal, radial and tangential shrinkages in jack pine ( Pinus banksiana ) have been found to be 0.4, 3.3 and 5.7%, respectively, by means of three dimensional digital image correlation (3D DIC). Full field shrinkage data were extracted from two types of specimen. It was demonstrated that the 3D DIC method is a suitable method of providing localized shrinkage values. The shrinkages in the three anatomical dimensions exhibit different variation patterns from pith to bark. Detailed shrinkage measurements provided data for a better understanding and modeling of shrinkage within a tree stem, which could be useful for lumber distortion simulation.

To understand internal stress (IS) development within lumber during drying of rubberwood, restoring force measurements on half-sawn specimens has been performed at drying temperature of 90°C under various patterns of wet-bulb (WB) temperature: (1) single-step drying, (2) two-step drying, (3) oscillation drying, and (4) stress control drying. Two extreme single-step drying conditions designated as “severe” and “conservative” at WB temperatures of 40°C and 80°C, respectively, were applied as control drying. It was shown that the measured force, which strongly correlates with the released strain data obtained by the McMillen slice test, indicates the level of IS developed within the lumber. In two-step drying, when the time of abrupt WB temperature change from conservative to severe drying conditions is extended up to the time of stress reversal, the force detected after stress reversal decreases from the level of severe drying to that of conservative drying. Once the time of stress reversal is exceeded, the force profile is largely unaffected by the parameters of the severe drying condition. Gradual reduction in WB temperature beyond the time of peak stress also reduces the force detected later after stress reversal under severe drying conditions. Oscillation of the WB temperature between conservative and severe conditions periodically changes the magnitude of the measured force. After stress reversal, the force amplitude monotonically decreases after each drying cycle. In addition, longer oscillation cycles seem to produce larger initial force amplitudes, which decline quicker than those created under the shorter ones. The possible application of the measured force as a controlling parameter of rubberwood drying has also been demonstrated.

The aim of this study was to obtain tensile elastic modulus (EM) information for radiata pine ( Pinus radiata D. Don) sapwood in tangential grain direction, over a temperature range of 70°C to 150°C for a wide range of moisture contents. Such information is scarce, probably because of difficulties with research equipment design and process control strategies to perform accurate tests. As expected, EM dramatically decreased with increasing temperature and moisture content. The results were modelled to yield a relationship between stress and strain. The results were also successfully transposed into a mastercurve based on temperature-moisture equivalence through a modified form of the Williams, Landel, and Ferry equation for amorphous polymers. This result is consistent with the view that wood is visco-plastic around the glass transition zone of the ligno-hemicellulosic matrix. It is demonstrated that moisture and temperature can play a significant role in reducing stress during drying, regardless of the drying time. Properties of wood, such as tensile elastic information at elevated temperatures, are important for mechanical design, distortion modelling and understanding the fundamental behaviour of wood in general.

Industrially produced high-density fibreboard fibres are inhomogeneous in structure and chemical composition. Changes in polysaccharide chemistry during processing have an impact on strength loss, fibre separation and structural alterations. In the present study, carbohydrate composition of extracted wood chips and refiner fibres was monitored for a year at an industrial HDF plant. The polysaccharides were analysed via methanolysis and quantification of the monomeric sugars released. Significant reductions of arabinose, xylose, rhamnose and galacturonic acid were observed. The amount of glucose and extractable substances increased. The depletion of galacturonic acid and rhamnose indicates a degradation of pectin located in the compound middle lamella. The diminishing amounts of the other sugars and elevated extractive contents are a result of hemicellulose degradation. A pronounced seasonal variability of the data was observed depending on the processed wood species and degree of chemical degradation.

Wood species, carbohydrate composition and the content of extractives were determined from extracted wood chips and refiner fibres over 1 year of sampling at an industrial high-density fibreboard (HDF) plant. Correlations were found among processing variables (discharge screw flow, digester and refiner pressure, and refiner power consumption) and the analysed composition of raw materials and semi-finished product based on partial least squares regression (PLSR) analysis. Moreover, correlations between the degree of hemicellulose degradation and process variables were found. Panel thickness swell (PTS) was found to be affected by several raw and fibre material characteristics (based on PLSR), in which PTS was lower in the case of good fibre quality. These results demonstrate the potential impact of variable raw material properties on product properties and processing conditions in an industrial environment.

The effect of grain angle (GA) on shear strength of Douglas-fir has been evaluated. Shear block specimens with a GA varying from 0 to 90° was loaded in the shear plane, resulting in failure mode transitioning from parallel to grain shear to rolling shear. As expected, shear strength decreased as the GA increased from 0° to 90°. A root-mean-square equation was found to be suitable to predict the relationship between GA and shear strength. Traditional Hankinson formula and the Tsai-Wu criteria were less effective with this regard.

No abstract available.