Biological activity of alpha-thujaplicin, the minor component of Thujopsis dolabrata SIEB. et ZUCC. var. hondai MAKINO.

Alpha-thujaplicin, a minor component of Thujopsis dolabrata SIEB. et ZUCC. var. hondai MAKINO, which was synthesized, showed the antibacterial activity, phytogrowth-inhibitory effect, inhibition of carboxypeptidase A and cytotoxic effect. Antibacterial activity of alpha-thujaplicin on Enterococcus faecalis IFO-12965 [minimum inhibitory concentration (MIC): 1.56 microg/ml] was higher than that of gentamicin (MIC: 6.25 microg/ml) used as a positive control. Inhibitory activity of alpha-thujaplicin on carboxypeptidase A [50% inhibitory concentration (IC50): 3.24 x 10(-5) M] was higher than that of 1,10-phenanthroline used as a positive control. Alpha-thujaplicin showed germination inhibition toward the seed of Echinochloa utilis Ohwi et Yabuno even at the low concentration of 10 ppm and its growth inhibitory effect was stronger than that of sodium 2,4-dichlorophenoxyacetate used as a standard. Alpha-thujaplicin at 1.25 microg/ml inhibited cell growth of human stomach cancer KATO-IIl by 86%, and Ehrlich's ascites carcinoma by 87%, respectively. This compound even at the low concentration of 0.32 microg/ml also inhibited cell growth of the former by 66%, and the latter by 75%, respectively. The acute toxicity of alpha-thujaplicin [50% lethal dose (LD50) value: 256 mg/kg] in mice was as strong as those of beta-dolabrin (LD50 value: 232 mg/kg) and gamma-thujaplicin (LD50 value: 277 mg/kg).