Biol. Pharm. Bull. 29(9) 1980—1982 (2006)

tention in the search for bioactive compounds to develop new drugs. We have taken note of brown algae of the genus Sargassum (Sargassacea, Fucales), which contain structurally unique secondary metabolites such as palstoquinones, chromanol, and chromenes. In the course of studies on search for bioactive molecules of algae, we isolated plastoquinones [hydroquinone (1) and quinone (2)] together with a novel chromene derivative (3) from a brown alga, Sargassum micracanthum (KUETZING) ENDLICHER, “Togemoku” in Japanese (Fig. 1). 1 and 3 exhibited antioxidant activity, while 2 and 3 exhibited antiviral effect on human cytomegalovirus. Osteoporosis, a disease characterized by low bone mass and structural deterioration of bone tissue, has been widely recognized as one of major public health problems. In order to prevent or treat osteoporosis, it is quite important to find novel candidates of lead compound for the development of clinically useful drugs. Thus, we evaluated the effects of 1, 2 and 3 on bone resorption. This paper describes their inhibitory effects on osteoclast-like cells (OCLs) formation, pit formation and survival of OCLs. MATERIALS AND METHODS