Koetsu Takahashi

Antitermitic Activities of Abietane-type Diterpenes from Taxodium distichum Cones

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.

Three Oxygenated Cyclohexenone Derivatives Produced by an Endophytic Fungus

Three cyclohexenone derivatives, (4S,5S,6S)-5,6-epoxy-4-hydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one (1), (4R,5R)-4,5-dihydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one (2), and (4R,5S,6R)-4,5,6-trihydroxy-3-methoxy-5-methyl-cyclohex-2-en-1-one (3), were isolated from unpolished rice fermented with an xylariaceous endophytic fungus (strain YUA-026). The structures of three compounds were established on the basis of spectroscopic analyses and chemical conversion. The minimum inhibitory concentrations of 1 and 3 were 100 μg/ml and 400 μg/ml against Staphylococcus aureus, 100 μg/ml and 200 μg/ml against Pseudomonas aeruginosa, and 200 μg/ml and >400 μg/ml against Candida albicans, respectively. In addition, 1 and 3 exhibited phytotoxic activity against lettuce.

Antifungal Abietane-Type Diterpenes from the Cones of Taxodium distichum Rich

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-C6H14 extract, was evaluated and its antifungal properties were identified. Twelve diterpenoids including ten abietane-type components were isolated from the n-C6H14 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.

Variation in the natural termite resistance of teak (Tectona grandis Linn. fil.) wood as a function of tree age

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.Résumé• L’âge de l’arbre est un des facteurs les plus importants de la durabilité du bois.• Le propos de cette étude était de déterminer la résistance naturelle du bois de cœur et de l’aubier de teck (Tectona grandis Linn. fil.) aux termites, pour des arbres âgés de 8, 30 et 51 ans. Reticulitermes speratus Kolbe a été utilisé comme termite test dans un essai d’alimentation sans choix.• Le bois de cœur et l’aubier de tous les arbres ont été testés pour leur activité anti-termite. En se basant sur la perte moyenne de masse de bois résultant des activités des termites, l’aubier et le bois de cœur des arbres de 8 ans se sont révélés les plus sensibles, alors que le bois de cœur des arbres de 30 ans a montré une résistance aux termites semblable à celle des arbres de 51 ans.• La perte de masse était modérément corrélée au contenu de l’extrait n-hexane, à celui de l’extrait total, ainsi qu’à la brillance et à la rougeur du bois.

Extractives relating to heartwood color changes in sugi (Cryptomeria japonica) by a combination of smoke-heating and UV radiation exposure

Abstract Sugi green logs with red or black heartwood were smoke-heated, and the changes in the color of the heartwood after ultraviolet (UV) (λ = 365 nm) radiation exposure were then observed. After UV radiation exposure, the redness and yellowness increased in both the red and black heartwoods, whereas the brightness decreased. In the black heartwood, the resulting color turned from yellowish white to reddish brown. Reddening in black heartwood after exposure to a combination of smoke heating and UV radiation is thought to be due to a decrease in brightness and an increase in both redness and yellowness. However, the degree of change in heartwood color by UV radiation exposure was not greatly affected by smoke-heating treatments of various lengths. When methanol extracts were fractionated and exposed to UV radiation, the yellowness increased in the n-hexane-soluble portion and the redness increased in the acetone-soluble fractions from the n-hexane-insoluble portion. These results suggest that the n-hexane-soluble fraction contains the substances that allow heartwood color to change to yellow after UV radiation exposure, and the acetone-soluble-fraction from the n-hexane-insoluble portion contains the substances that allow it to change to red.

Radial distribution of quinones in plantation teak (Tectona grandis L.f.)

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.Résumé• 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 cœur des arbres de 8, 30 et 51 ans de même qu’entre la partie interne et externe du bois de cœur.• 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.

Reddening by UV irradiation after smoke-heating in sugi (Cryptomeria japonica D. Don) black heartwood

Summary Sugi (Japanese cedar, Cryptomeria japonica D. Don) green logs with black heartwood were smoked, heated, and smoke-heated separately to improve the heartwood color. After each treatment, changes in heartwood color, pH, and extract amounts were examined. In addition, changes in heartwood color caused by UV irradiation were observed. Heating and smoke-heating of logs prevented the heartwood from discoloring to black, and the resulting color of thermally-treated heartwoods was yellow-white, whereas smoking alone allowed discoloration to black. The pH value decreased from the original 7.6 to 6.8 by smoking and to 6.5 by thermal treatment. The results obtained here suggest that a pH drop in heartwood by thermal treatment is involved in color changes of black heartwood. When thermally-treated black heartwood was exposed to UV light, redness and yellowness increased and brightness decreased. The resulting color tone was reddish brown. The color of non-thermally-treated woods, however, showed little change. Furthermore, acetone, ethanol, and methanol extracts of thermally-treated black heartwood showed an increase in redness by UV irradiation, but the residues showed little color change. The coloring substances relating to the reddening of heartwood could be extracted with these solvents, particularly with methanol. Reddening in black heartwood by a combination of smoke-heating and UV irradiation is considered to be due to a decrease in brightness and an increase in both redness and yellowness.

A norlignan, cryptoresinol, from the heartwood of Cryptomeria japonica

Abstract Cryptoresinol, a new norlignan has been isolated from the heartwood of Cryptomeria japonica and its structure was elucidated as 3,5-di(p-hydroxyphenyl)-2,5-epoxy-1-pentanol-3-en.

Antioxidant activity and mechanism of the abietane-type diterpene ferruginol

The antioxidant activity of the abietane-type diterpene ferruginol was evaluated by comparison with that of carnosic acid, ( ± )-α-tocopherol and dibutylhydroxytoluene using 2,2-diphenyl-1-picrylhydrazyl, β-carotene bleaching and linoleic acid assays. Ferruginol had the lowest antioxidant activity of this group using the 2,2-diphenyl-1-picrylhydrazyl and β-carotene methods in polar solvent buffer. However, ferruginol exhibited stronger activity than carnosic acid and α-tocopherol for linoleic acid oxidation under non-solvent conditions. Five peaks corresponding to ferruginol derivatives were detected through GC-MS analysis of the reaction between ferruginol and methyl linoleate. The three reaction products were identified as dehydroferruginol, 7β-hydroxyferruginol and sugiol, and the other two peaks were assumed to be 7α-hydroxyferruginol and the quinone methide derivative of ferruginol. The time course of the reaction suggests that the quinone methide was produced early in the reaction and reacted further to produce dehydroferruginol, 7-hydroxyferruginol and sugiol. Thus, we inferred that quinone methide formation was a key step in the antioxidant reaction of ferruginol.

Color and chemical characterization of partially black-streaked heart-wood in teak (Tectona grandis)

The heartwood of teak in certain areas of Java Island displays irregular black streaks along the annual rings. We investigated the color and chemical characteristics in a radial direction of partially black-streaked heartwood samples. Color properties (pH value, inorganic element, extractive content and extractive characterization) were measured in the color co-ordinates CIELAB system. The results show that the black streak part was 12–15 brightness (L*) value units less than the normal heartwood. Furthermore, the black streak part had more red (a*) but less yellow (b*), hue (h) and chroma (C*) than the normal wood. The pH value, ash content and calcium contents of the black streak part were slightly higher than those obtained for the normal wood. The content of the low-polar extractive (n-hexane and ethyl acetate) of the black streak part was considerably higher than that for the normal wood. The blackening process was speculated to be a kind of defense mechanism indicated by remarkable amount of bioactive compound called tectoquinone.