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.
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 (s max ), and breaking strain (e max ) were compared with those of unheated specimens. Steaming for a longer duration at a higher temperature resulted in a greater reduction in M, s max , and e max . 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.
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