Biological Activity of β-Dolabrin, γ-Thujaplicin, and 4-Acetyltropolone, Hinokitiol-Related Compounds

β-Dolabrin, γ-thujaplicin, and 4-acetyltropolone, the components of Aomori Hiba (Thujopsis dolabrata SIEB. et ZUCC, var. hondai MAKINO), showed antifungal activity on seven kinds of plant-pathogenic fungi, antibacterial activity against two kinds of Legionella sp., and in vitro cytotoxic effect on murine P388 lymphocytic leukemia cell line. Firstly, β-dolabrin, γ-thujaplicin and 4-acetyltropolone had clear antifungal activity against seven kinds of plant-pathogenic fungi tested. In particular, β-dolabrin and 4-acetyltropolone showed strong antifungal activity against Pythium aphanidermatum IFO 32440, with minimum inhibitory concentration (MIC) values of 6.0 μg/ml. Secondly, β-dolabrin, γ-thujaplicin and 4-acetyltropolone had obvious growth-inhibitory effect on two kinds of Legionella sp. 4-Acetyltropolone especially had strong antibacterial activity toward Legionella pneumophila SG 1, and its MIC value was 3.1 μg/ml. These three compounds showed cytotoxic effects against murine P388 lymphocytic leukemia cell line in vitro. The cytotoxic effect of three compounds in the murine P388 lymphocytic leukemia cell line were clear when cell growth was measured using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. At 48 h after treatment, γ-thujaplicin and 4-acetyltropolone at 0.63 μg/ml inhibited cell growth of murine P388 lymphocytic leukemia by 85% and 65%, respectively. At the same time after treatment, the growth of the murine P388 lymphocytic leukemia cell line was completely suppressed by the three compounds at concentrations higher than 5.0 μg/ml. Among these three compounds, γ-thujaplicin had the strongest cytotoxic activity on the growth of this tumor cell line in vitro.