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Wood Natural durability study source of biomolecules: case of Dicorynia guianensis Amsh. heartwood
2016 - IRG/WP 16-10871
The chemical investigations of Dicorynia Guianensis heartwood led to the isolation of four new indole alkaloids for the first time in this plant Compound (1) identified as spiroindolone 2’,3’,4’,9’ -tetrahydrospiro [indoline-3,1’pyrido[ 3,4-b]-indol ]- 2- one, and compound (3) described as nitrone 1-methyl-4,9 -dihydro-3H-pyrido [3, 4-b] indole 2 – oxide and were isolated for the first time as natural products ABTS antioxydant activity guided their isolation and showed the potential of these compounds in industrial sectors
J-B Say Anouhe, A A Adima, F B Niamké, D Stien, B Kassi Amian, D Virieux, J-L Pirate,S Kati-Coulibaly, N Amusant

Synergistic effects between 2-HPNO, Irganox 1076 and EDTA on the inhibition of wood degradation by Coriolus versicolor
2004 - IRG/WP 04-30331
The efficiency of 2-hydroxypyridine-N-oxide (2-HPNO) as wood preservative has been investigated. As shown using classical experiments as well as using response surface methodology, the efficiency of 2-HPNO as wood preservative is strongly improved in presence a chelator like EDTA and/or of Irganox 1076 an industrial antioxidant. In these conditions, wood preservative efficiency of the mixture the three previous compounds is quite similar to that of tebuconazole used alone. 2-HPNO exhibits an hydroxamic acid function and is a susbtrate of fungal peroxidase. These properties could explain the observed synergy. The implications of these data for the design of new wood preservation strategies are also discussed.
A Mabicka, S Dumarçay, N Rouhier, M Linder, J P Jacquot, P Gérardin, E Gelhaye

Susceptibility of angiosperm sapwood to white-rot fungal colonization and subsequent degradation: a hypothesis
1997 - IRG/WP 97-10211
It has long been recognized that angiosperm sapwood in nature is relatively easily and preferentially degraded by white-rot fungi. This susceptibility to white-rot fungi is generally believed to be mainly caused by the structure and concentration of angiosperm lignin. However, an explicit explanation as to why lignin structure makes a particular wood vulnerable to white-rot colonisation and subsequent degradation has apparently never been given. We propose that free phenolic groups in wood, such as those present in the lignin or heartwood extractives, can act as free radical scavengers (antioxidants) which disrupt the various white-rot free radical degradative mechanisms. Consequently the presence of a relatively high free phenolic "density", such as that present in gymnosperm sapwood or angiosperm heartwood, may inhibit white-rot degradation. Conversely, white-rot fungi may find wood with a relatively low free phenolic content, such as angiosperm sapwood, easy to colonize. The complex structure of angiosperm wood, in which different cell types have different amounts and types of lignin -- and consequently different levels of free phenolic "densities" -- influences the susceptibility of angiosperm wood to initial white-rot colonisation and, perhaps, also the subsequent decay rate. In addition to the free phenolic ``density" other factors, some as yet unknown, undoubtedly also affect the decay resistance of a particular wood.
T Schultz, D D Nicholas

Synergistic combination of an antioxidant and wood preservative: a preliminary study
1998 - IRG/WP 98-30172
We previously proposed that extractives in highly durable angiosperm heartwood may protect wood against white-rot fungal colonization and subsequent degradation by a dual mechanism: extractives have some fungicidal activity and are also free radical scavengers (antioxidants) and thus interfere with the fungal free radical degradative mechanisms. We tested this hypothesis using the commercial biocide DDAC, which has no antioxidant properties, in laboratory decay tests using angiosperm sapwood and white-rot fungi. When the commercial antioxidant BHT, which has no fungicidal activity, was present a dramatic increase in the efficacy of DDAC was observed. This synergistic effect may have commercial applications.
T Schultz, D D Nicholas, J Minn, K D McMurtrey, T H Fisher

Targeted inhibition of wood decay fungi: degradation of cotton cellulose
1999 - IRG/WP 99-10321
Brown-rot decay is responsible for 80% of the damage and replacement of wood in service. For nearly thirty years, researchers have postulated a one-electron oxidase system combining Fe+2 oxalic acid, and H2O2 in the production of hydroxy radicals which ultimately oxidize cellulose in situ. Recently, researchers have been investigating antioxicants, in combination with biocides (Schultz, et al.,1998), as targeted inhibitors of the decay process and potential wood preservatives. In order to target the cellulolytic mechanisms of brown-rot and white-rot decay fungi, cotton cellulose was treated with free radical scavengers, antioxidants, dyes and hydroxy-radical detectors 2,2'-Azino-bis (3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) in order to assess their ability to retard cellulose hydrolysis. Weight loss of cotton cellulose is the most reliable and accurate measure of exoglucanase activity. Cotton cellulose was exposed to G. trabeum MAD 617, T. palustris 6137 and T. versicolor MAD 697 in soil-block tests. After 12 weeks exposure, cotton was evaluated for weight loss, change in DP, and elemental analysis by ICP spectroscopy. Only 2 out of 11 compounds tested (NHA and ruthenium red) showed less than 1% weight loss for all three fungi tested. All other compounds were selective, underscoring difficulties in sharply targeting decay mechanisms. Weight loss and DP of cellulose are analogous to degradation and strength loss of wood caused by decay fungi.
F Green III, T A Kuster

Environmentally benign wood preservatives based on organic biocide antioxidant combinations: A brief review of laboratory and field exposure results and discussion of a proposed mechanism
2004 - IRG/WP 04-30335
The combination of various organic biocides with commercial antioxidants generally increased the biocides’ efficacy 2-3 fold against wood-destroying fungi in short-term laboratory decay tests, and some positive results have been obtained after 2-4 years of outdoor exposure. The two antioxidants principally examined, propyl gallate and butylated hydroxytoluene, are low cost and, since both are food additives, benign. The biocides studied have either been examined as potential wood preservatives or are used in commercial wood preservative systems. The purpose of this paper is to: 1) briefly summarize our prior laboratory decay results; 2) briefly discuss results obtained so far from outdoor exposure tests, both above-ground and ground-contact exposure; 3) discuss differences in results between laboratory decay tests and the outdoor exposure data; and 4) propose a mechanism by which antioxidants could protect wood.
T Schultz, D D Nicholas, W Henry, C Pittman, D Wipf, B Goodell

Prevention of non-microbial sapwood discolorations in hardwood lumber: chemical and mechanical treatments
1997 - IRG/WP 97-30137
Sapwood discolorations in hardwood lumber that are non-microbial in origin result from the formation of pigmented starch-like granules in ray parenchyma cells. These discolorations can be prevented by treating unseasoned lumber with an antioxidant (sodium bisulfite). Exposing unseasoned lumber to microwaves or treating logs with fumigants also will prevent these discolorations. Subjecting unseasoned lumber to mechanical stresses (compression and/or vibration) also prevents sapwood discolorations of non-microbial origin. A machine to mechanically stress lumber and thereby prevent these discolorations has been built and is being field-tested at cooperating sawmills.
T L Amburgey, S Kitchens

Investigation of new wood preservation formulations based on synergies between antioxidant, 2-HPNO and Propiconazole
2006 - IRG/WP 06-30401
Wood degradation by fungi is a complex phenomenon taking place in part through oxidative reactions involving many oxidizing agents like free radicals and hydroperoxide. In order to develop novel and more environmentally benign preservative systems, mixtures of Propiconazole and antioxidants with different stabilization mechanisms were investigated to detect possible synergies allowing to reduce the quantity of biocide to prevent wood biodegradation. Results obtained showed that the nature of the antioxidant had an important effect on the potential synergies. The most interesting results were obtained with 2-HPNO and hindered amine and to a weaker extend with H-donors like hindered phenol.
B Bakhsous, S Dumarçay, E Gelhaye, P Gérardin

A hypothesis on a second non-biocidal property of wood extractives, in addition to toxicity, that affects termite behavior and mortality
2008 - IRG/WP 08-10638
While it is has long been recognized that heartwood extractives affect termite behavior, the exact cause and relationship between total extractives, extractive types, and termite resistance remains unclear. Generally, researchers have proposed that the extractives are toxic and/or repel termites. We propose, based on the well known fact that many extractives have excellent antioxidant properties in addition to some termite toxicity, that: 1) the antioxidant properties of wood extractives interfere with the termite and symbiotic microbial digestion of lignocellulose; 2) thus, over time termites have learned to recognize and avoid wood with high levels of antioxidants; and 3) consequently, termites will also avoid wood treated with artificial and nontoxic antioxidants. Use of an artificial and nontoxic antioxidant will allow one to definitively test our hypothesis, while tests with natural extractives would be confounded by natural extractives often having both toxicity and antioxidant properties. We conducted some initial tests employing a man-made and benign antioxidant, BHT. In outdoor field trials, ground-contact stakes treated with only the antioxidant had less termite degradation than the control stakes at up to three years of exposure. An initial termite choice experiment using Reticulitermes flavipes Kollar (Eastern subterranean termite) was run with an untreated and 1- or 3%-BHT treated wafer in each jar, along with control jars that contained two untreated wafers. No termite feeding occurred on any of the BHT-treated wafers, indicting that the non-biocidal antioxidant was a strong feeding repellent. Furthermore, while only about 2% termite mortality occurred in the jars that contained two untreated wafers, in every jar that had an untreated wafer and a second BHT-treated wafer 100% mortality occurred. Recent no-choice laboratory tests with two subterranean termite species, R. flavipes and Coptotermes formosanus Shiraki (Formosan subterranean termite), and an exterior test with BHT-treated wood with Formosan termites, confirmed our initial results.
T P Schultz, K Ragon, D D Nicholas

Effect of amphiphilic antioxidant alkyl ammonium ascorbate on inhibition of fungal growth: Application to wood preservatives formulation
2008 - IRG/WP 08-30466
Amphiphilic surfactants were synthesized from ascorbic acid and different fatty amines and evaluated for formulation of wood preservation products. Characterization of physicochemical properties of the new compounds indicated classical behavior of cationic surfactants. Antioxidant properties, estimated using methyl linoleate oxidation inhibition method, were similar to that of ascorbic acid tested in the same conditions. Growth inhibition assays indicated that amphiphilic dodecylammonium ascorbate is able to inhibit Coriolus versicolor mycelium development, while butylammonium ascorbate deprived of surfactant properties has no effect. This compound was then investigated in the formulation of wood preservation mixtures containing propiconazole and compared to formulation obtained with an industrial surfactant. Biological tests based on the ability of these formulations to protect beech wood blocks exposed to a white rot fungus Coriolus versicolor were carried out under laboratory conditions. Results indicated that use of propiconazole formulation in aqueous solution allows to reduce the quantity of biocide compared to solutions of the same concentrations in ethanol. Protection achieved with antioxidant surfactant was slightly superior to that conferred by conventional surfactant.
C Gérardin , T Koumbi Mounanga, P Gérardin

Vacuum drying of European oakwood: Color, chemistry and anti-oxidant potency of wood. Improving appearance in forest value added products
2008 - IRG/WP 08-40432
In hardwoods used for decorative and appearance purposes, wood colour is one of the most important factors of wood quality; in addition colour is related with durability and biological decay of wood. Wood discolouration during drying is mainly affected by heat, light, physiological reactions, combinations of reactions, biochemical and chemical reactions, and micro-organisms attack. In freshly felled and stored round wood discolorations are initiated predominantly through physiological reactions of living parenchyma cells. Discolouration during kiln-drying decreases the commercial value of hardwoods, since hardwoods are used in the manufacture of furniture and cabinets. On one hand, heat modifies the cell wall components and induces chemical reactions of nutrients and extractives, by other hand the role of oxygen in kiln dryers is very important due to oxidation reaction of phenolic compounds. The formation of coloured substances from a phenolic compound oxidized with air and the formation of dark materials from hydrolysable extractives are considered causes of discolouration. In order to reduce oxidation reaction, vacuum drying process can be used. In addition, it offers reduced drying times and higher end-product quality in comparison with conventional drying operations. Operating at low pressures reduces the boiling temperature point of water and enables an important overpressure inside the material which is advantageous for drying and especially for species that do not support a high temperature level. In this work, experimental results for the vacuum drying of oakwood with conductive heating are presented for different drying conditions. In particular, surface-wood scans, antioxidant capacity of wood, Fourier Transform Infrared Spectra of dust-wood for different vacuum and convective drying conditions. Sample temperatures and pressure in the dryer are logged during drying. The experimental setup (Figure 1) is a vacuum chamber where pressure is regulated between two values (Pmin, Pmax). The chamber is built in glass; one balance is kept inside the chamber in order to log the mass variation of the sample. A thermometer gives the dryer temperature. The heating source is an electrical resistance which temperature is controlled with the help of a PID controller. Experiments are performed on Oakwood disks (7 cm diameter and 2.5 cm height). The conductive heat source is maintained at different temperatures (46°, 61° and 70°C) and pressure in the chamber is controlled at different intervals (60-100, 150-200, and 250-300 mbar). Temperature inside the wood sample is obtained at two different positions. Conventional drying is carried out for comparison in a tunnel dryer. Antioxidant potential in fresh and dry wood samples is determined by using ABTS+• radical cation method. The top surface of vacuum-dried specimens is imaged with an HP scan. Finally it is shown that oak wood which is prone to discolour is degraded by different mechanisms depending on drying method. Our results suggest that oxidation of extractives and thermal degradation of hemicelluloses are the principal mechanisms of degradation, but its importance depends on drying method. Oakwood can be dried under vacuum conditions with an acceptable diminution of discolorations due to low temperature and reduction of oxygen amount with acceptable drying rates.
S Sandoval, W Jomaa, F Marc, J-R Puiggali

Impact of an Antioxidant on the Efficacy of Quaternary Ammonium Compounds (Quats) and Triazoles – Seven Year Above-Ground Study
2009 - IRG/WP 09-30504
It has been reported that antioxidants have great potential for use with organic biocides in the area of wood protection. This paper demonstrates the impact of a low level of the antioxidant butylated hydroxytoluene (BHT) on the efficacy of quat-based and triazole-based formulations. A seven year lap joint test revealed a positive effect of BHT on the efficacy of quat-based formulations, especially at the low quat retention. The incorporation of BHT in a propiconazole-based system, however, showed an unexpected negative antioxidant effect at all levels tested. For tebuconazole- and cyproconazole-based formulations, the antioxidant effect on efficacy is slightly positive but insignificant. The influence of BHT on efficacy appears to diminish with increased active retentions in wood for both quat-based and triazole-based formulations, and in fact yields an adverse efficacy impact at high active retention levels. It is hypothesized that a larger amount of BHT is needed at high active retention levels to ensure the positive antioxidant effect. In addition, wood treated with BHT only showed slight protection for fungal decay, while the untreated controls exhibited severe decay with numerous failures.
Xiao Jiang, D Biro, W Holcombe

Effect of extractives on durability of Prosopis juliflora heartwood
2009 - IRG/WP 09-30518
The heartwood of Prosopis juliflora is resistant to fungal attack caused by different brown and white rot fungi. This durability due to the presence of high amounts of extractives decreases after extraction of these latter ones with different solvents. Heartwood extractives were effective in inhibiting the growth of the fungi. Depending on the concentration used, development of the fungal mycelium on the treated medium started after a more or less important inhibition period, suggesting that the extractives present rather fungistatic than fungicidal properties. Chemical characterization of extractives of P. juliflora was investigated by 1H NMR and GC-MS techniques to understand their contribution to heartwood durability. Results show that heartwood extractives contain mainly (-)-mesquitol possessing important antioxidant properties, which can be at the origin of durability to fungi. Durability of heartwood was also investigated towards Macrotermes natalensis, a subterranean termite commonly found in Kenya, on extracted or unextracted wood blocks. Weight losses on solvent extracted wood exposed to termites are higher than for the unextracted samples suggesting that heartwood resistance of P. juliflora heartwood to Macrotermes natalensis is associated to the presence of extractives. No-choice tests realized with filter papers impregnated with different amounts of extractives caused important termites mortality. Biological resistance of P. juliflora wood against termites and fungi seems therefore associated to the presence of extractives.
P Sirmah, K Iaych, B Poaty, S Dumarçay, P Gérardin

Direct estimation of the durability of high-pressure steam modified wood by ESR-spectroscopy
2010 - IRG/WP 10-40508
Heat generated persistent free radicals have been detected by electron spin resonance measurement of thermally modified wood, prepared by high pressure superheated steam treatment. The specific density of these radicals have been correlated with the durability against basidiomycetes, as measured by the European standard EN113 test. In the lower range of specific radical densities, the found correlation has revealed non-specificity for six different wood species, for two different treatment intensities and within different tree zones. This result promises a great potential for electron spin resonance to estimate the durability of high pressure steam modified wood. It also provides evidence for an antioxidant mechanism, responsible for the durability enhancement in heat treated wood.
W Willems, A Tausch, H Militz

Effect of an antioxidant on the efficacy of organic wood preservatives in an accelerated soil contact decay test
2012 - IRG/WP 12-30583
In comparison to inorganic wood preservatives, organic biocides in transient carriers are considerably less effective when the treated wood is exposed to soil contact. Various oils are used in some formulations with pentachlorophenol to improve the efficacy. However, use of these oils imparts unacceptable properties to products used in residential applications. Consequently, there is a need to develop additives other than heavy oils that improve the performance of organic biocides as wood preservatives. In this study the possibility of using the benign antioxidant BHT as a non-biocidal additive to improve the performance of wood treated with isothiazolone and azoles was investigated. The treated wood with and without BHT was exposed to unsterile soil and monitored for decay by dynamic MOE. It was found that the efficacy of both preservative systems was enhanced when BHT was added to the formulations. The use of Dynamic MOE to evaluate the progression of wood decay appears to be far superior to visual ratings.
D D Nicholas, J Shi, T P Schultz, L Sites

Investigations on the durability of several Congo basin wood species
2015 - IRG/WP 15-10840
The sawdust of ten wood species was studied to assess their natural resistance to decay. The extractives and lignin contents were primarily determined (between 2.7-16.0% and 26.8-35.9% respectively) to give an overview of the chemical distribution. Then, a phytochemical screening (colorimetric methods) characterized the different chemical functional groups in all extracts studied. Antioxidant activity indicated values comprised between 18 and 175 µmol AAE/µg of extract correlated to total phenolic content which were comprised between 51 and 935 mg eq. of gallic acid/g of extract. The resistance to decay of extracted and unextracted sawdust against the two white-rot fungi was evaluated and showed that extractives amounts and compositions partially influenced wood durability.
S Mounguengui, J-B Tchinda Saha, M Kor Ndikontar, S Dumarçay, C Attéké, D Perrin, E Gelhaye,

Chemical composition of extractives of different wood compartments of Pinus merkusii and their potential implication in wood durability
2015 - IRG/WP 15-10841
Amounts and nature of extractives differ strongly according to the compartment of wood and to the nature of the wood species. Previous studies reported that knotwood of several European Pinus sp. contains extractives contents much higher than stemwood consisting mainly of lignans which may find valuable applications in cosmetic, nutraceutic or pharmaceutic sectors. Different explanations have been proposed to explain these high amounts of lignans: the first one concerns their potential implications in the lignification process to reinforce knot tissues involved in branches support; the second one their role in wood durability and protection against biotic and abiotic agents. During the course of our studies concerning the identification of new sources of molecules with potential interest, we were interested in the characterization of knotwood extractives of Pinus merkusii a tropical wood species for which no data on the nature of extractives have been reported up to now. Determination of extractives amounts present in sapwood, heartwood and knotwood of Pinus merkusii has been performed and their chemical composition analyzed using GC-MS and LC-MS. Antioxidant and antifungal activities were also evaluated by DPPH method and growth inhibition method, respectively. The results showed that knotwood contains more extractives than heartwood, the latter containing more extractives than sapwood. Knotwood extracts contain mainly lignans, especially nortrachelogenin, stilbenes and resin acids, while heartwood extracts were constituted mainly of stilbenes, especially pinosylvin monomethyl ether, pinosylvin and pinosylvin dimethyl ether and of flavonoid like pinocembrin. Acetone knotwood extract presents the higher antioxidant activity, while acetone heartwood extract possesses the higher antifungal activities against the two tested fungi Trametes versicolor and Poria placenta.
A Wijayanto, S Dumarçay, R Kartika Sari, W Syafii, P Gérardin, C Gérardin-Charbonnier

Characterization of waste from Pinus radiata generated during industrial thermal-treatment
2016 - IRG/WP 16-20586
The thermal-treatment is an established chemical-free process to modify wood, improving the durability and physical properties of wood through its service life. During the hydro-thermolysis several reactions from wood components occur, releasing volatile and non-volatile compounds from wood to the chamber. Once the process is accomplished, solid residues agglomerate below the wood load and gaseous products are released and collected as condensed water from the gas stream. In order to identify and characterize the industrial residues generated during the industrial thermal-treatment of Pinus radiata, solid and liquid samples were analyzed. The results indicated thermal and chemical differences among the evaluated waste materials. In case of the solid sample, a superior thermal stability (above 300 °C) was displayed, mostly formed by sugars and lignin derived compounds, with unremarkable antioxidant capacity. In contrast, the liquid sample started to degrade at lower temperatures (around 200 °C) and predominantly was composed by a large amount of phenolic and volatile compounds. Moreover, this liquid fraction exhibited a positive scavenging activity against DPPH free radical (about 54%). Furthermore, the principal products detected by chromatographic analysis in both residues were sugar derivatives such as furfural (up to 30%), phenolic derivatives as guaiacol (~2%), Guaiacyl acetone (~5%), coniferyl aldehydes (12.5%), along with fatty and resin acids (~ 9%) in the solid sample.
R Herrera, D Thomas da Silva, R Llano-Ponte, J Labidi

Biocomposites based on PVA, cellulose nanofibrils and tannic acid
2022 - IRG/WP 22-40957
Biocomposite films based on a polyvinyl alcohol (PVA) with the addition of cellulose nanofibrils (CNF) as a reinforcing component and with the addition of the biologically active tannic acid (TA) were prepared. The influence of different additions of CNF and TA in the polymer matrix PVA on the mechanical properties, improvement of hydrophobicity of the prepared films was studied. In all cases, the addition of CNF and TA improved the value of tensile strength and elastic modulus. In one of the prepared films, the hydrophobicity of the film surface was greatly improved compared to the neat PVA film. The better properties of the produced composite films were probably due to hydrogen and ester bonds between the components of the composite, which was confirmed by FT-IR spectroscopy.
U Osolnik, V Vek, I Poljanšek, Poven