Abstract• Tree age is one of the most important factors to affect the natural durability of wood.• The purpose of this study was to determine the natural termite resistance of heartwood and sapwood of teak (Tectona grandis Linn. fil.) for trees aged 8, 30 and 51 years. Reticulitermes speratus Kolbe was employed as a test termite using a no-choice feeding method.• The heartwood and sapwood of all of the trees tested exhibited antitermitic activity. Based on the mean mass loss due to termite activity, the sapwood and heartwood regions of 8-year-old trees are the most susceptible to termites while the heartwood regions of the 30-year-old trees showed termite resistance similar to the termite resistance of 51-year-old trees.• The mass loss is moderately correlated with n-hexane extractive content, total extractive content, brightness and redness of the wood.

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Abstract• Quinones are primarily responsible for the natural durability of teak.• The previous paper in this series reported on the natural termite resistance of teak trees of different ages (8-, 30-and 51-year-old trees). In this study, the radial distribution of quinones (tectoquinone, lapachol, desoxylapachol and its isomer) and other components in the ethanol-benzene (1:2) extract were measured by means of gas chromatography.• Significant differences in desoxylapachol or its isomer content were found among the outer heartwood of 8-, 30-and 51-year old trees, as well as between the inner and outer parts of the heartwood.• All toxic quinone contents were positively correlated with the total extractive content. The highest correlation degree was measured in the isodesoxylapachol content.• Although linearly related, only modest correlations were observed between the natural termite resistance parameters and the content of tectoquinone and isodesoxylapachol. Mots-clés :Tectona grandis / extractibles / tectoquinone / desoxylapachol / âge des arbres Résumé -Distribution radiale des quinones dans du teak de plantation (Tectona grandis L.f.).• Les quinones sont à l'origine de la durabilité naturelle du teak.• Le précédant papier de la série traitait de la résistance naturelle contre les termites pour des arbres de 8,30 et 51 ans. Dans cette étude, la distribution radiale des quinones (tectoquinone, lapachol, deoxylapachol et son isomère) et des autres composés présents dans les extraits éthanol-benzène (1:2) est déterminée par chromatographie en phase gazeuse.• Le contenu en desoxylapachol ou ses isomères présente des différences significatives en périphérie du bois de coeur des arbres de 8, 30 et 51 ans de même qu'entre la partie interne et externe du bois de coeur.• Toutes les teneurs en quinones toxiques sont corrélées positivement avec le contenu total d'extractibles. Le degré de corrélation le plus élevé est mesuré pour la teneur en isodesoxylapachol.• Bien qu'il existe une relation linéaire entre les paramètres de résistance naturelle aux termites et la teneur en tectoquinone et isodesoxylapachol, les corrélations observées sont modestes.

Eight known abietane-type diterpenes were isolated from the weak acidic fraction of the n-hexane extract from cones of Taxodium distichum, one of the extant, living fossil conifers. They were identified as 6,7-dehydroroyleanone (1), taxodal (2), taxodione (3), salvinolone (4), 14-deoxycoleon U (5), 5,6-dehydrosugiol (6), sandaracopimaric acid (7), and xanthoperol (8). The structures of these compounds were determined by comparison of NMR spectral data with published data. The antitermitic (termicidal and antifeedant) activities of the compounds 1-8 against the subterranean termite, Reticulitermes speratus Kolbe, were evaluated. Compounds 1 and 3 showed potent termicidal activity, and 5 and 8 showed potent antifeedant activity. Compound 1 was found to be one of the representative bioactive compounds in the n-hexane extract of T. distichum cones. Compounds 1-8, with the exception of 7, were oxides of ferruginol (9). Therefore, the presence of various oxidation forms of the abietane-type structure reflects their various bioactivities.

The chemical composition of Taxodium distichum cones and the antifungal activities of twelve diterpenoids against two wood decay fungi, Trametes versicolor (white-rot) and Fomitopsis palustris (brown-rot) were examined. The chemical composition of the major extractive fraction, the n-C(6)H(14) extract, was evaluated and its antifungal properties were identified. Twelve diterpenoids including ten abietane-type components were isolated from the n-C(6)H(14) extract: 6,7-dehydroferruginol (1), ferruginol (2), 6,7-dehydroroyleanone (3), sandaracopimaric acid (4), taxodione (5), taxodal (6), taxodone (7), sugiol (8), xanthoperol (9), salvinolone (10), 5,6-dehydrosugiol (11), and 14-deoxycoleon U (12). Compounds 5 and 12 were highly active against both wood-decay fungi. In particular, the activities of these compounds against F. palustris were potent. The results suggest that the position and the number of hydroxyl groups on abietane-type structures may be related to antifungal activities against T. versicolor and F. palustris.

Summary The antifungal properties of 14 major oleoresin‐constitutive terpenoids of Norway spruce (Picea abies) against Heterobasidion parviporum were evaluated in vitro at three gradient concentrations, 0.1, 0.2 and 0.4 μmol/cm2, on potato dextrose agar medium. Eight monoterpene hydrocarbons (+)‐ and (−)‐α‐pinene, (−)‐β‐pinene, (+)‐3‐carene, myrcene, (+)‐ and (−)‐limonene, terpinolene; four oxygenated monoterpenes α‐terpineol, terpinen‐4‐ol, 1,8‐cineole, bornyl acetate; and two resin acids abietic acid and dehydroabietic acid were selected. Abietic and dehydroabietic acids showed the highest antifungal activities at all concentrations. Among oxygenated monoterpenes, bornyl acetate and α‐terpineol showed antifungal activity at the highest concentration. Among monoterpene hydrocarbons, (+)‐α‐pinene showed similar activity to terpinen‐4‐ol and 1,8‐cineole at the highest concentration; however, it was lower than α‐terpineol and bornyl acetate. Other monoterpene hydrocarbons inhibited mycelial growth by <10%. Re‐extraction of medium surfaces after the test period revealed that most α‐terpineol and terpinen‐4‐ol remained unchanged on the surface but monoterpene hydrocarbons completely disappeared. However, notable fungal transformed products were observed on surfaces applied with 1,8‐cineole and bornyl acetate. Thus, mycelial growth inhibition of monoterpenoids might be caused by complex functions such as biodegradation and/or detoxification by interaction between mycelium and compound. These results provide a basis for future studies considering the role of chemodiversity in the comprehensive chemical defence of P. abies.

Latifolin (1) and its derivatives were investigated with the aim of confirming the correlation between bioactivity (antitermite and antifungal activity) and chemical structure. Termite mortality in response to the derivatives 2'-O-methyllatifolin (2), latifolin dimethyl ether (4), and latifolin diacetate (5) increased 2-fold compared to compound 1. The mortality rate from 5-O-methyllatifolin (3) was not different from 1. The mass loss (feed consumption by termite) in response to compounds 3-5 was 3 times greater than compound 1, and the mass loss from compound 2 was twice as great as compound 1. The mortality rate from compounds 4 and 5 increased sharply 7 days after initial exposure. In assessing the antifungal activity of these compounds, it was found that the inhibition rates of white- and brown-rot fungi in response to all derivatives were less than that for compound 1. Our findings indicate that the phenolic hydroxyl group at C-5 of the A ring provides antitermite activities (mortality and mass loss). In addition, both C-5 and C-2' phenolic hydroxyl groups in the A and B rings have antifungal activity against white- and brown-rot fungi. In conclusion, the bioactivity of compound 1 depends upon the position of phenolic hydroxyl groups.

study 1 based on a study using individuals in which the main components were agatharesinol and sequirin-C. In the second report, 2 which precedes the present report, the relationship was based on a study using individuals in which the main components were sugiresinol and hydroxysugiresinol.In both studies, parts of heartwood that are normally red showed acidic pH values and a high content of sequirin-C, while the blackened parts of heartwood showed alkaline pH values and a low content of sequirin-C. The blackened parts had a significantly high content of potassium hydrogencarbonate.Ishiguri et al. also reported that sequirin-C has a definite relationship with the stabilization of heartwood color based on a series of studies involving the smoke heating of sugi. [3][4][5] These studies have suggested that changes in the quality of sequirin-C and the pH value in heartwood are important factors in the blackening of heartwood. Therefore, we investigated the coloration mechanism with alkaline treatment by using norlignans (known to exist in sugi) as the main samples. Materials and methods Sample materialFive norlignans (agatharesinol, sequirin-C, sugiresinol, hydroxysugiresinol, and cryptoresinol) were isolated from sugi heartwood, and two norlignans (hinokiresinol, yateresinol), and 1,4-bis-(p-hydroxyphenyl)-butadiene (C 16 compound) were isolated from damaged sugi wood as samples. Ferruginol, sugiol, and xantopherol were also isolated from sugi heartwood as samples of diterpene phenol. Alkaline treatment of norlignansFive milliliters of 0.4% potassium hydrogencarbonate solution (pH 8.6) was added to 1 mg of each sample.