Sakae Shibutani

Effects of stilbenes from bark of Picea glehnii (Sieb. et Zucc) and their related compounds against feeding behaviour of Reticulitermes speratus (Kolbe)

The effects of stilbene glucosides and related compounds on termite feeding behavior were investigated using paper disc methods against the subterranean termite Reticulitermes speratus. The stilbene-rich fraction and isorhapontin (3′-methoxy-3,4′, 5-trihydroxystilbene-3-β-d-glucoside) from bark extracts of Picea glehnii showed avoidance by termites in choice tests. In the no-choice tests using compounds purified from the stilbene-rich fraction, the largest feeding deterrent effect was observed for piceid (3,4′,5-trihydroxystilbene-3-β-d-glucoside), followed by isorhapontin, and astringin (3,3′,4′,5-tetrahydroxystilbene-3-β-d-glucoside), at the concentrations from 0.63 to 2.5 µmol/disc. No change in activity was observed at retentions of more than 5.0 µmol/disc. When the activities of isorhapontin and its aglycone derivative (isorhapontigenin: 3′-methoxy-3,4′,5-trihydroxystilbene) were compared with that of taxifolin (3,3′,4′,5,7-pentahydroxyflavanone) in the no-choice test, the stilbenes exhibited a larger antifeedant potential. Methylation of isorhapontigenin increased its termiticidal activity.

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) I: changes in hygroscopicity due to heating

The effect of heating on the hygroscopicity of Japanese cedar wood was investigated as a simple evaluation of thermal degradation in large-dimension timber being kiln-dried at high temperatures (>100°C). Small wood pieces were heated at 120°C in the absence of moisture (dry heating) and steamed at 60°, 90°, and 120°C with saturated water vapor over 2 weeks, and their equilibrium moisture contents (M) at 20°C and 60% relative humidity (RH) were compared with those of unheated samples. No significant change was induced by steaming at 60°C, while heating above 90°C caused loss in weight (WL) and reduction in M of wood. The effects of steaming were greater than those of dry heating at the same heating temperature. After extraction in water, the steamed wood showed additional WL and slight increase in M because of the loss of water-soluble decomposition residue. The M of heated wood decreased with increasing WL, and such a correlation became clearer after the extraction in water. On the basis of experimental correlation, the WL of local parts in large-dimension kiln-dried timber was evaluated from their M values. The results indicated that the thermal degradation of inner parts was greater than that of outer parts.

Effects of high temperature kiln drying on the practical performances of Japanese cedar wood (Cryptomeria japonica) II: Changes in mechanical properties due to heating

Japanese cedar wood specimens were steamed at 80°, 100°, and 120°C over 14 days, and their equilibrium moisture content (M) at 20°C and 60% relative humidity, longitudinal dynamic Young’s modulus (E), bending strength (σmax), and breaking strain (εmax) were compared with those of unheated specimens. Steaming for a longer duration at a higher temperature resulted in a greater reduction in M, σmax, and εmax. The E of wood was slightly enhanced by steaming at 100°C for 1–4 days and 120°C for 1–2 days, and thereafter it decreased. The slight increase in the E of sapwood was attributable to the reduction in hygroscopicity, while sufficient explanation was not given for a greater increase in the heartwood stiffness. Irrespective of the steaming temperature, the correlations between M and the mechanical properties of steamed wood were expressed in terms of simple curves. M values above 8% indicated a slight reduction in E and s max, whereas M values below 8% indicated a marked decrease in the mechanical performances. In addition, the e max decreased almost linearly with a decrease in the value of M. These results suggest that hygroscopicity measurement enables the evaluation of degradation in the mechanical performances of wood caused by steaming at high temperatures.

Quantitative comparisons of antitermite extractives in heartwood from the same clones of Cryptomeria japonica planted at two different sites

The quantities of some extractives in the heartwood of 25 plus tree clones of Japanese cedar (Cryptomeria japonica) from two different sites were investigated to clarify the differences in antitermite properties in relation to clones and environmental factors. The measured compounds were cubebol, epicubebol, sandaracopimarinol, and ferruginol. The total amounts of extractives were calculated from gas chromatogram peak areas. The heartwoods from Tano (Tano Forest Research Station, Miyazaki University; 31° N, 131° E, 130 m asl) tended to contain more of the individual extractives and total extractives than those from Komenono (Komenono Forest Research Station, Ehime University; 33° N, 132° E, 700 m asl). There was a significant difference (calculated by analysis of variance) at the 1% level among clones at both sites in quantities of total and individual extractives. This result suggests that the qualities and quantities of heartwood extractives are largely affected by genetic factors. Spearman’s rank correlation with the average of the extractive quantities at the sites was investigated. The correlation coefficients of total extractives, cubebol, epicubebol, sandaracopimarinol, and ferruginol were 0.61, 0.85, 0.76, 0.67, and 0.74, respectively. This result means that the order of the amounts of these compounds among the cultivars could be maintained at different sites. It is apparent that both environmental and genetic factors affected the quantities of these extractives in the heartwoods of Japanese cedar.

Characteristic Raman bands for Artocarpus heterophyllus heartwood

The Raman spectrum of Artocarpus heterophyllus heartwood, which proved to be a rich source of flavonoids, exhibited two characteristic bands, at 1247 cm−1 and 745 cm−1. The bands also appeared in the Raman spectrum of the yellow-brown needles extracted from the heartwood with methanol. Based on the Raman measurements of flavones and related compounds, it was predicted that the Raman band at 1247 cm−1 may be attributed to flavonoid-type compounds. No vibrational band corresponding to the characteristic Raman bands was observed by diffuse reflectance infrared spectroscopy. Thus, it was suggested that observation of the characteristic bands is an advantage of Fourier transform-Raman spectroscopy for nondestructive analysis of wood.

Swelling of acetylated wood II: effects of delignification on solvent adsorption of acetylated wood

To clarify the role of lignin in the affinities of acetylated wood for organic solvents, the effects of delignification on the solvent adsorption of acetylated wood were investigated. Acetylated wood meals rapidly adsorbed organic solvents that were hardly adsorbed by unmodified wood. For nonpolar and low-polarity organic solvents, a clear positive correlation was observed between the amount of adsorption and the lignin content. This indicated that acetylated lignin was responsible for the excellent affinities of acetylated wood for hydrophobic organic solvents. On the other hand, for lower alcohols and water, the amount of adsorption reduced with an increase in the lignin content. It was suggested that the adsorption of such polar solvents was dominated by insufficiently acetylated hydrophilic polysaccharides.

Evaporation of volatiles from essential oils of Japanese conifers enhances antifungal activity

The antifungal properties of evaporation residue of essential oils (EOs) derived from the needles of the three Japanese planted conifer species Cryptomeria japonica, Pinus thunbergii and Thujopsis dolabrata var. hondae were evaluated. Open system mild heat treatments (MHTs) enhanced the volatilities of the EOs, leading to changes in their chemical composition. The activities of all EOs increased according to the monoterpene hydrocarbons evaporated, and then gradually decreased with the component degradation. These results indicated that the terpenoid components in lower volatile phase together with a variety of components could be responsible for the antifungal activities of these EOs. Further investigation also showed that the C. japonica EO showed the highest antifungal potential of the three EOs because it contained the major sesquiterpene alcohol elemol. This study represents the first reported time course investigation of changes in the chemical composition and antifungal properties of conifer needle EOs based on their volatility.

Chemical composition of the terpenoids in wood and knots of Abies species

Oily constituents were obtained from sapwood and knots of Abies balsamea and A. alba using steam-distillation, and the chemical compositions were determined by gas chromatography and gas chromatography–mass spectrometry. The oily constituents of sapwood and knots of A. balsamea were mainly oxygenated diterpenes with manoyl oxide (1), epi-13-manoyl oxide (2), manool (3), and epi-13-manool (4). Moreover, 2 and 3 were found to be components in A. alba. The constituents of sound knots were dominated by oxygenated diterpenes, together with 2 and 3. Comparison of the content of oxygenated diterpenes from the material revealed that dead knots of A. balsamea contained a large quantity of 4, which was higher than in sapwood. Knots of both Abies spp. contained large quantities of oxygenated diterpenes that were also higher than in sapwood.