Biological Activity of b-Dolabrin, g-Thujaplicin, and 4-Acetyltropolone, Hinokitiol-Related Compounds

hinokitiol-related compounds (Chart) such as hinokitiol (b-thujaplicin), b-dolabrin, g-thujaplicin, a-thujaplicin and 4-acetyltropolone isolated from Aomori Hiba (Thujopsis dolabrata SIEB. et ZUCC. var. hondai MAKINO). Of these hinokitiol-related compounds, hinokitiol and b-dolabrin are the major components isolated from this plant by our group. On the other hand, g-thujaplicin, a-thujaplicin, and 4-acetyltropolone, the minor components, were chemically synthesized for various biological activity tests. It has been found by authors that these five compounds showed antimicrobial activity, metalloprotease inhibition, phytogrowth-inhibitory effects, insecticidal activity, and in vitro cytotoxic effect on human and murine tumor cell lines. Among these five compounds, hinokitiol has also been used as a preservative for vegetabls, flowers, and mushrooms as well as a plant growth stimulator because of its strong antibacterial activity. Hinokitiol has been widely used as a preservative, a toothpaste, a cosmetic, and a hair tonic. On the other hand, unlike hinokitiol, the other four hinokitiol-related compounds have not been used practically, because no basic toxicologic and histopathologic studies of these four compounds have been done. We have recently reported that in addition to the above-mentioned activities, a-thujaplicin, hinokitiol, and tropolone showed antifungal activity on plant-pathogenic fungi and antibacterial effect against Legionella sp., and in vitro cytotoxic effect on murine P388 lymphocytic leukemia cell line. However, no study has been done on the similar biological activities of b-dolabrin, g-thujaplicin, and 4-acetyltropolone. Therefore in the series of our basic studies on the biological activity of hinokitiol-related compounds isolated from T. dolabrata and their clinical application, antifungal activity on plant-pathogenic fungi and antibacterial activity against Legionella sp. of b-dolabrin, g-thujaplicin and 4-acetyltropolone were investigated. Cytotoxic effect on murine P388 leukemia lymphocytic cell line of b-dolabrin, g-thujaplicin and 4-acetyltropolone, the components of this plant was also examined in vitro and compared with that of hinokitiol.