Antifungal Activity of Hinokitiol-Related Compounds on Wood-Rotting Fungi and Their Insecticidal Activities

Hinokitiol (β-thujaplicin), β-dolabrin and γ-thujaplicin isolated from Thujopsis dolabrata SIEB, et ZUCC. var hondai MAKINO showed antifungal activities against all of the wood-rotting fungi examined. The antifungal activity of three compounds on Daedalea dickinsii IFO-4979 was especially strong, their mininum inhibitory concentration (MIC) values being 0.2 μg/ml. Their antifungal activities on D. dickinsii IFO-4979 were as high as that of amphotericin B used as a positive control. Three compounds had strong insecticidal activities on Tyrophagus putrescentiae [50%-lethal concentration (LC50 : g/m2) 0.25 in hinokitiol, 0.02 in β-dolabrin and γ-thujaplicin]. Their insecticidal activities were higher than that of N, N-diethyl-m-toluamide (DEET, LC50 : 1.46 g/m2) used as a positive control. Three compopunds also showed strong insecticidal activity on Coptotermes formosanus [LC50 (g/m2) 0.07 in hinokitiol, 0.05 in β-dolabrin and γ-thujaplicin], although their insecticidal activities were much lower than that of commerical chloropyrifos (LC50 : 0.00016 g/m2).