α-Thujaplicin, a minor component of Aomori Hiba (Thujopsis dolabrata SIEB. et ZUCC. var. hondai MAKINO), showed rather strong antifungal activity against seven kinds of plant-pathogenic fungi, their minimum inhibitory concentrations (MICs) being in the range of 12.0—50.0 μg/ml. α-Thujaplicin and hinokitiol (the major component of Aomori Hiba) also showed clear antibacterial activity against Legionella pneumophila SG 1 and L. pneumophila SG 3, and their MICs are in the range of 6.25—50 μg/ml. This compound showed strong insecticidal activity against Reticulitermes speratus [50%-lethal concentration (LC50): 0.02 g/m2], and it also had clear acaricidal activity against Dermatophagoides farinae (LC50: 0.66 g/m2). At 24 h after treatment, α-thujaplicin at 0.63 μg/ml inhibited the cell growth of murine P388 lymphocytic leukemia by 78%, and its cytotoxic activity at a concentration higher than 0.63 μg/ml was as high as that of vincristine, used as a positive control. On the other hand, the cytotoxic effect of α-thujaplicin at 0.63 μg/ml was weaker than that of vinblastine. In this respect, the strong cytotoxic effect of α-thujaplicin on murine P388 lymphocytic leukemia cell line should be emphasized, considering that it has recently been found to be low in toxicity to mice.
2004 The Pharmaceutical Society of Japan