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The antifungal efficacy of Guayule resin
1987 - IRG/WP 3429
The Naval Research Laboratory is evaluating the non-rubber-producing portion of guayule (Parthenium argentatum) resin as a protectant for wood in terrestrial and marine service. This study phase, in collaboration with the universities of Arizona and Mississippi State, evaluates the resin's fungicidal worth. Resin-impregnated pine sapwood was exposed to brown rot fungi (Gloeophyllum trabeum, Antrodia carbonica, Formitopsis cajanderi, Lentinus ponderosa), white rot fungi (Dichomitus squalens, Trametes versicolor, Ganoderma sp.), and a natural inoculum of soft rot fungi from unsterile soil. The exposures for the brown and white rot fungi lasted 20 weeks, using malt agar chambers inoculated 2 weeks prior to the introduction of the treated wood; the soft rot exposure lasted 12 weeks and included treated birch specimens. Weight loss data showed a definite inhibition of decay of the treated wood by the brown and white rot fungi, however there was some decay caused by Lentinus ponderosa (closely related to creosote-tolerant Lentinus lepideus) and by Antrodia carbonica, a common utility pole fungus. None of the resin-impregnated pine or birch specimens were attacked by the soft rot fungi, even those specimens containing the lowest of the three resin concentrations in the wood. In both sets of exposures all of the controls were decayed.
J D Bultman, R L Gilbertson, T L Amburgey, J E Adaskaveg, S V Parikh, C A Bailey

Detection of Anti-Fungal Sapwood Extractives in Non-Durable Scots Pine (Pinus sylvestris), Rubberwood (Hevea brasiliensis) and Jelutong (Dyera costulata)
2007 - IRG/WP 07-10634
A general laboratory bioassay method of Woodward and Pearce (1985) was adopted to detect anti-fungal activity of sapwood or heartwood extractives of 5 Malaysian hardwoods [dark red meranti heartwood (Shorea spp.), red balau heartwood (Shorea spp.), kulim heartwood (Scorodocarpus borneensis), jelutong sapwood (Dyera costulata) and rubberwood sapwood (Hevea brasiliensis), including the temperate Pinus sylvestris (Scots pine sapwood). The heartwoods of these species and Scots pine sapwood are known to be highly resistant to decay by soft-rotting Ascomycetes and anamorphic fungi (about 1-7% wood mass loss), while the sapwoods of rubberwood and jelutong had much reduced soft rot resistance (respectively 35, 32% wood mass loss) but obviously prone to sapstain and mold attack, including that of Scots pine. Crude methanol extracts of woodmeal samples of each wood species were loaded on to thin-layer chromatography plates at between 0.003 and 0.1 g fresh mass equivalent of woodmeal per spot so as to optimize resolution of separated compounds, and developed with chloroform:methanol solvent (ratio 19:1). The dried plates were sprayed with fresh fungal spores of Cladosporium cucumerinum and incubated at >90% RH for 5 days in the dark. Presence of anti-fungal compounds was revealed by white regions along the solvent transect for each extract of each species where inhibited spore germination and mycelial growth of C. cucumerinum occurred. Comparisons of anti-fungal activity of extracts between species and between sapwood and heartwood were made. Results revealed that several zones of inhibitory activity, indicated by their Rf-values, were clearly visible on chromatographic separations of methanol extracts of these 5 wood species. The inhibitory zones for 2 heartwood extracts (except kulim) did not move from the origin which was also resistant to infection. However inhibition zones were also detected for the sapwoods of rubberwood, jelutong and Scots pine against C. cucumerinum despite the known sapstain and decay susceptibility of these wood substrates. The presence of hitherto unidentified anti-fungal compounds in the sapwoods of these species may elicit limited potency or narrow spectrum protection from fungal infection and onset of stain or decay.
A H H Wong, R B Pearce

Antinomic natural self-protection mechanism in long-lasting woods: a case study with three tropical species from French Guiana
2009 - IRG/WP 09-10696
We demonstrate in this work through 3 examples that Amazonian trees may specialize long-lasting woods by means of at least to different approaches. Wallaba impregnates its wood with large amounts of weakly antifungal compounds acting in synergy, while tatajuba and louro vermelho woods are naturally impregnated with antifungal agents. Comparison of biological activities in vitro and concentrations in the woods indicate that these compounds alone may account for the natural durability of the two woods.
A Rodrigues, M Royer, N Amusant, J Beauchêne, G Herbette, V Eparvier, A Thibaut, L Salmen Espíndola, B Thibaut, D Stien

Antifungal activity of wood extractives from waste products of steam distillation of Aniba rosaeodora
2012 - IRG/WP 12-10779
Aniba rosaeodora, is a slow growing evergreens of the Lauraceae family which are indigenous over a wide range of the Greater Amazon Region (the Guianas and Venezuela, Brazilian Amazon…). The essential oil obtained from the wood has a characteristic aroma and is a long-established ingredient in the more expensive perfumes. Around the olfactive characteristic of the essential oil is due to the presence of levogyre linalol. The steam distilled wood oil is obtained in a yield ranging around 1% and up to 90% of the oil consists of optically active linalol. This work is focused on the valorization of steam distillated sawdust, waste obtained from extraction of essential oil. After steam distillation, the sawdust was extracted by ethyl acetate and methanolic solvents and the antifungal activity was evaluated against basidomycetes fungi. The both extracts were active in vitro against white and brown rot fungi and allowed to propose these extractives as wood preservative agent.
N Amusant, A Digeon, E Hoüel, J Beauchène

Antifungal activities of acetone-soluble Eusideroxylon zwageri and Potoxylon melagangai crude extracts against white rot
2012 - IRG/WP 12-30591
The development of natural wood extracts as a wood preservative is a potentially attractive prospect for the wood preservation industry. This study attempts to evaluate the toxicity of Eusideroxylon zwageri and Potoxylon melagangai extractives as potential wood preservatives. These two species are well-known as among the heaviest and very durable timbers. It has been established that natural durability of timbers are associated by their extractives contain. In this study acetone was used to remove extractives from both wood samples and later was purified by using rotoevaporation process. The toxicity of various extract concentrations against two white rot fungi, Pycnoporus cocinneus and Schizophyllum commune was evaluated on MEA agar for seven days period. Results showed that the mean growth rate of fungi decreased with increased in level of concentrations. Toxicity test indicated that in 1000 ppm concentration, the extractives of E. zwageri reduced the growth rate of P. cocinneus and S .commune by 26% and by 36% while P. melagangai extractives reduced P. cocinneus and S. commune growth rate by 36% and 41%, respectively. Various extract concentrations were used to treat Hevea brasiliensis wood blocks. Following exposure to the white rot fungi for eight weeks it was observed that the weight loss reduced significantly when treated with 15% acetone-soluble extractives. This suggests that transferred extractives have the potential to control decay. However, further studies are required before any concrete inferences can be made on extractives for natural wood preservatives.
I Jusoh, A Tida Henry, Z Assim, F Badruddin Ahmad, S Ujang

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

Wood properties modification by an enzymatic assisted treatment with phenolic extractives
2016 - IRG/WP 16-30696
Extractives of sawdust and bark from P. pinaster and, condensed tannins (CTs) from P. radiata bark were used to treat beech and pine veneers in combination with an oxidative enzyme, in order to stably graft such extractives onto the veneers. First, the antifungal activity of P. pinaster phenolic extractives against wood decay fungi was studied. These extractives were also used to hydrophobize pine and beech wood by means of the treatment with laccase enzyme. The same treatment was performed with CTs from P. radiata and chemically derivatized CTs (HPTs) to modify the physiochemical properties of beech wood. Sawdust extractives of P. pinaster showed a high growth inhibition of P. ostreatus and C. puteana. Besides the biological activity, the treatment with laccase and the mentioned phenolic extractives provided stable hydrophobic properties to pine and beech wood. The chemical derivatization of CTs enhanced the hydrophobic properties of native CTs. After the inclusion of such HPTs in the enzymatic treatment of wood veneers, a higher resistance to water absorption was obtained. Thus, the stable graft of P.pinaster phenolic extractives onto wood provided biological and hydrophobic properties. The chemical derivatization of natural phenolic extractives improved their chemical and biological properties which opens a new perspective for future applications of these compounds.
D Filgueira, C Fernández-Costas, D E García, D Moldes

Identification of Antifungal Compounds in Konjac Flying Powder and Assessment against Wood Decay Fungi
2019 - IRG/WP 19-30737
The antifungal activity of konjac (Amorphophallus rivieri) flying powder (a by-product produced during mechanical processing of konjac flour) ethanol extract was evaluated against wood decay fungi in culture. Compounds associated with antifungal activity in the extracts were isolated and purified by silica gel column chromatography. The antifungal active fractions were identified by ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-QE-MS). The ethanol extract showed good activity against the white-rot fungus, Trametes versicolor, and the brown-rot fungus, Gloeophyllum trabeum. The antifungal active fractions were mainly composed of organic acids and plant essential oils. Salicylic acid, 2,4,6-trichlorophenol and vanillin were presented in the active fractions. The preliminary results indicate that konjac extracts have potential as natural wood protectants. Further tests in wood are planned.
Z Bi, F Yang, Y Lei, J J Morrell, L Yan

Extraction, identification and antifungal activity of polar extractives originated from various wood species
2020 - IRG/WP 20-20673
Extractives are non-cell wall small molecules present in wood and other lignocellulosic materials that can be removed by solvents. Although they represent a minor fraction in comparison with the structural cell wall components, they are an important source of functional groups or molecules with bioactivity or antioxidant properties, that could be used in medicine, cosmetic or wood preservation. The increasing social and economic interest in obtaining chemical compounds from sustainable sources has motivated this research study. It is expected that the identification of alternative uses of native and tropical wood by-products coming from the wood processing industries, will promote the circular bioeconomy which demands a truthful environmental development. This study includes the preparation of samples, accelerated extraction and chemical identification of polar components from different wood species, and finally, complementary tests on possible antifungal activities focused on the creation of novel wood preservation products. The preliminary results indicate potential of some compounds as natural additives for wood preservation. Additional tests in wood samples are required to guarantee its feasibility and upscaling.
R Herrera, F Poohphajai, J Labidi, S Willför, A Sandak

Antifungal and antitermite activities of acetonic extractives from Cedrus Atlantica heartwood
2022 - IRG/WP 22-10990
Cedrus atlantica is a woody species present in France, which in a context of climate change can be privileged in the next years. In addition, this woody species presents great ecological and socio-economic interest as it is mainly recognized for its durable timbers and its essential oil presenting some interesting chemical properties. Therefore, the studies of its heartwood formation and properties of its extractives are interesting, spite of very few studies have been conducted till now. The radial repartition of water/acetone extractives within the tree (bark, sapwood, transition wood, outer heartwood and inner heartwood), at different tree height levels, were screened. HPLC analyses were performed, especially to characterized flavonoid compounds of these extractives fractions. The radial variation of the extractive composition obtained, highlighted the phenomenon of heartwood formation. Hypotheses on the metabolic pathways involved in the heartwood formation process of cedar wood were suggested, especially based on the occurrence and the radial evolution of catechin, taxifolin and flavan compounds. Then, the antifungal and anti-termite activities of the extracts were tested. The water/acetone extractives from Cedrus atlantica showed a strong repellent activity against termites and a moderate antifungal activity against crops and fruits pathogens. Thus, the results show a possible valorisation of the extractives of the Atlas cedar, as wood preservatives and/or as biocontrol products against pathogens of lignocellulosic agricultural crops.
R Dijoux, R Ducruet, E Kieny, D Aznar, C Cayzac, L Bidel, C J Allemand, K Candelier

The effect of certain wood extractives on the growth of marine micro-organisms
1977 - IRG/WP 438
S E J Furtado, E B G Jones, J D Bultman

Biological control with Trichoderma harzianum in relation to the formation for spores the production of soluble metabolites
1994 - IRG/WP 94-10073
The amount of spores produced by three strains of Trichoderma harzianum on the aerial mycelium of agar cultures and in shake cultures, respectively, correlated with the inhibition zones exerted against Phanerochaete chrysosporium in an agar diffusion test. The amount of soluble antifungal metabolites as well as the protein content also correlated with the inhibition zones and the amount of spores produced. The antifungal metabolites were identified to be trichorzianines. They were the only compounds with antifungal activity. It is concluded that the trichorzianines are responsible for the biocontrol effect by soluble metabolites and that they are produced during conidiogenesis.
J Bürgel, E Horvath, J Haschka, K Messner

Chemical compounds from Eperua falcata and Eperua grandiflora heartwood and their biological activities against wood destroying fungus (Coriolus versicolor)
2005 - IRG/WP 05-30373
The chemistry analysis of the compounds present in dichloromethane and ethanolic fraction as well as bioassays enables to understand the durability differences of Eperua falcata and Eperua grandiflora. The principal distinction between these two species is the acidic subfraction of diterpenoic extract, which is antifungic in Eperua falcata when tested in in-vitro conditions. This study also enables to show that ethanolic fraction plays an important role in the mechanism of natural durability. It also reports the first isolation of cativic acid in Eperua falcata wood.
N Amusant, C Moretti, B Richard, E Prost, J M Nuzillard, M-F Thévenon

Methodology challenges in developing a transfer of natural durability from sawmill residues, illustrated by experiences with white cypress (Callitris glaucophylla)
2000 - IRG/WP 00-20203
The transfer of durability-conferring extractives from durable to non-durable wood has been accomplished often, but usually as an educational exercise rather than as a commercially oriented process. In the latter environment, many factors previously overlooked become vitally important. How to study them, in the absence of well-developed methodology and given the shorter timeframes being demanded by industry research funding organisations, presents real challenges. These challenges will be illustrated by experiences with the development of such a process for the 'waste' durability components of white cypress. Factors to be considered include: identification of active components; quantification of their individual and collective activities against target organisms; optimisation of source material handling, storage and extraction techniques; extract standardisation and batch-to-batch reproducibility; compatible yet cost-effective carriers for the actives into treated wood; effects on durability and other wood properties such as strength and handling safety; regulatory obstacles including acceptance into wood preservation standards; and quality control methods for penetration and retention of the treated product.
M J Kennedy, M A Powell

Efficacy of some extractives from Pinus heartwood for protection of Pinus radiata sapwood against biodeterioration. Part 1: Fungal decay
1995 - IRG/WP 95-30072
Chemical compounds thought to contribute to the natural durability of heartwood of Pinus spp. were either chemically synthesised in the laboratory or extracted from the heartwood of Pinus elliottii or Pinus caribaea. These compounds included the stilbenes, pinosylvin and its mono- and di-methyl ethers, and the flavonoids, pinobanksin and pinocembrin. Small blocks of Pinus radiata sapwood were impregnated with methanolic solutions of pure compounds or heartwood extracts, to a range of retentions extending above and below the concentration of each compound known to occur in the heartwood of Pinus spp.. Fungicidal efficacy of these compounds has been evaluated by exposure of treated blocks to pure cultures of a white and a brown rot, in addition to an unsterile soil test.
M J Kennedy, J A Drysdale, J Brown

About the relations between the natural durability of some tropical species and their extractives content
1983 - IRG/WP 1208
G R Y Déon

Co-operative research at the Naval Research Laboratory on wood extractives and related compounds as antiborer agents
1977 - IRG/WP 429
J D Bultman, K K Parrish

Antifungal mechanism of dichloro-N-octylisothiazolone
1998 - IRG/WP 98-30183
4,5-dichloro-N-octylisothiazolin-3-one (DCOI) is a member of the isothiazolone class of preservatives, whose antimicrobial mechanism of action has been intensively studied over the last decade. DCOI has also been intensively studied for use in wood preservation. The isothiazolones are electrophilic molecules that rapidly react with thiol groups to form covalently bonded isothiazolone-thiol adducts. This ability to bond with thiol groups is crucial to their ability to act as preservatives. Thiol groups are present in proteins as part of the amino acid cysteine, where they play an important role in maintaining protein structure and function. A number of enzymes have thiol groups at the site where the enzyme function is performed, and these thiol groups may participate in the enzyme reaction. If the isothiazolone reacts with this thiol group, the activity of the enzyme is inhibited. Our studies have shown that there are several enzymes in the Krebs cycle that are inhibited by isothiazolones and these enzymes are required to generate energy and perform many biosynthetic functions. Reflective of this, DCOI has been shown to be a rapid inhibitor of cellular respiration, causing the cell to cease consuming oxygen almost immediately upon contact with DCOI. The multiplicity of targets and their central importance to the metabolism of the cell, as well as the fact that all microbes use at least parts of the Krebs cycle, can be related to the low use levels and broad spectrum of activity of DCOI. The antimicrobial mechanism of DCOI results in a potent rapid-acting preservative with a broad spectrum of antifungal and antibacterial activity that is effective at low levels.
J S Chapman, M A Diehl, K B Fearnside, L E Leightley

Antifungal activity of a stilbene glucoside from the bark of Picea glehnii
2001 - IRG/WP 01-10402
Stilbene glucosides are widely distributed as phenolic extractives in the bark of Picea glehnii, a commercially species planted in the northern area of Japan, and its content reaches to more than 10% by the dried weight of the bark. Although antifungal activities of these compounds have been reported, the mechanism of growth inhibition is still unclear. Isorhapontin (5,4'-dihydroxy-3'-methoxystilbene-3-ß-D-glucoside) is the major constituent of the stilbene glucosides in the bark of P. glehnii. In the present work, the relation between metabolism and antifungal activities of isorhapontin for the white-rot fungus Phanerochaete chrysosporium and the wood staining fungus Trichoderma viride was investigated. Inhibition of fungal growth was obviously depending on the conversion of isorhapontin to the aglycone isorhapontigenin (3'-methoxy-3,5,4'-trihydroxystilbene) by ß-glucosidic activities in the cultures. Exogenous addition of ß-glucosidase also enhances the antifungal activity of isorhapontin. Moreover, less than 100 ppm addition of the stilbene aglycone isorhapontigenin is sufficient to inhibit the growth of both fungi. However, further metabolism of isorhapontigenin was observed after prolonged incubation of the fungi and resulted in detoxification.
S Shibutani, M Samejima

Estimation of service life of durable timber species by accelerated decay test and fungal cellar test
2002 - IRG/WP 02-20249
Many kinds of durable wood species for outdoor uses has been imported from all over the world to Japan. However information on the natural durability of these species is not sufficient to estimate the service life of them in the climate of Japan. Highly durable species such as Jarrh, Teak, Ipe, Ekki, Selangan batu, Red wood, Western red cedar showed no significant percent mass losses by accelerated decay test according to the JIS Z2101, but some of them are degraded during fungal cellar test for 4 years . The decay rating (0:sound to 5:totally decayed) of them after 4 years exposure was 1.0, 2.0, 0.0, 1.0, 0.0, 2.3, 5.0 respectively. This results indicated that the conventional accelerated decay test could not evaluate the natural durability of these highly durable species at all. Solid wood specimens treated with boiling water at 120? for one hour are subjected to the same JIS test, and the obtained percent mass losses of these species are 1.2, 2.9, 1.9, 3.8, 4.7, 17.5, 0.0 % by a brown rot fungus, Fomitopsis palustris, and 17.5, 14.3, 3.3, 8.2, 4.2, 0.0, 18.3 % by a white rot fungus, Trametes versicolor respectively. Pre-treatment of solid wood specimens for removal of heartwood extractives before a accelerated decay test would be an effective way to evaluate the natural durability of highly durable species in a laboratory.
K Yamamoto, I Momohara

Autoxidation of beech condensate
2003 - IRG/WP 03-40261
Liquid effluent from steaming beech wood was studied. The effluent contains many phenolic compounds which can present a significant toxicity. The effluent was treated by oxidation was carried out at 250 rpm for 30 min with NaOH. This was followed flocculation with CaCl2 for 30 min. The influence of parameters such as pH, time of autoxidation were studied. Experimental results reveal the electrostatic interaction between the oppositely charged wood extracts after oxidation and flocculation. The increase in aqueous phase pH resulted in enhanced removal of wood extracts from water. The effect of pH is explained based on oxygen uptake.
M Irmouli, J P Haluk

Antifungal properties of new quaternary ammonium and imidazolium salts against wood decay, staining and mould fungi
2004 - IRG/WP 04-30347
The biological activity of twenty-four potential wood preservatives – imidazolium and quaternary ammonium salts with a modified anion structure was determined employing screening agar-plate and agar-block methods. Experiments were carried out on Scots pine (Pinus sylvestris L.) wood. The aim of the performed studies was to investigate the effect of structure modification of IC and QAC with organic anions or copper (ll) and zinc complexes on their biological activity against wood decay, staining and mould fungi. The fungicidal value of new compounds for Coniophora puteana ranged from 0.64 kg/m3 to 2.2 kg/m3. Aspergillus niger turned out to be the most resistant fungus to the action of modified IC and QACs, whereas Sclerophoma pityophila was effectively inhibited by the examined salts. The performed soil-block tests showed that the IC and QAC were leached from the experimental wood in conditions of contact with moist soil and revealed their fungal detoxification by mould fungi, especially by Gliocladium roseum. Observations made using the scanning electron microscope of the colonization and decay of treated wood by mould fungi confirmed tolerance of mould fungi to QACs.
J Zabielska-Matejuk, W Wieczorek

Decay resistance of Scots pine (Pinus sylvestris) heartwood against brown rot
2002 - IRG/WP 02-10433
Natural decay resistance of wood is mainly restricted in the heartwood and based on wood microstructure and chemical composition. The genetic variation in the durability of Scots pine (Pinus sylvestris L.) wood against decay and the relationship between resistance and chemical composition was studied. The laboratory tests of 6 and 8 weeks were carried out with a brown rot fungus Coniophora puteana (Schum. ex Fr) Karst (strain Bam EBW 15). The increment core samples of sapwood and juvenile heartwood, obtained from about 30-year-old half-sib progenies, were decayed using a modification of the standardised EN 113 method. The average density of the sapwood was 391 mg/cm3 (one stand) and that of heartwood samples 337 and 376 mg/cm3 (two stands). The average mass loss of the sapwood samples was 114 mg/cm3 (6 weeks, stand 1) and that of the heartwood samples 80 mg/cm3 (6 weeks, stand 1) and 123 mg/cm3 (8 weeks, stand 2). The variation among heartwood samples was high. The additive genetic component was small in stand 1 but quite large in stand 2, which resulted in a low narrow sense heritability h2 in stand 1 (0.07) but high in stand 2 (0.37). New samples were taken from the most resistant and susceptible trees for chemical analyses. The concentration of resin acids was higher in the group of decay resistant trees than in the group of decay susceptible trees. About 90 % of the resin acids in the heartwood were of the abietane type, abietic acid being the most abundant.
H Viitanen, A M Harju, P Kainulainen, M Venäläinen

Effect of permeability and extractives on the decay rate of southern pine sapwood in above grund exposure
2005 - IRG/WP 05-20310
The effects of wood permeability and hydrophilic and hydrophobic extractives on the decay rate of southern pine sapwood in above ground exposure were investigated. Permeability was determined by water sorption measurements, and the effect of extractives was studied by pre-extracting the test samples prior to outdoor exposure using water to extract hydrophilic extractives or sequential methanol/cyclohexane extractions to remove hydrophobic extractives. Initial water permeability of the wood prior to outdoor exposure was highly correlated to decay rate, with the more permeable samples decaying more rapidly. Removal of the hydrophilic extractives prior to exposure decreased the decay rate, but the effect was not statistically significant at the 0.05 level. Conversely, removal of the hydrophobic extractives significantly increased the rate of decay, even though it had no effect on the initial water permeability.
D D Nicholas, T Schultz, L Sites, D Buckner

The chemical analysis and biological evaluation of wood extractives as potential timber preservatives
1995 - IRG/WP 95-30090
Work involved the biological performance of water and organic solvent soluble extractives of four naturally durable wood species, namely; Matumi, Tamboti, Sneezewood and the Turpentine tree. These timber species are known to be naturally durable against termites and fungi (±25 to 35 years). The extractives were evaluated against termites and fungi using impregnated pine pencil stakes in field tests and soil burial trials over a 2 year period. C13NMR analysis of extractives isolated from the wood was carried out to try and identify the key chemical components which might impart durability with a view to prediction of new potential wood preservative formulations.
P Turner, D Conradie

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