Propolis is a natural resinous product collected by honeybees from certain plants. It has gained popularity as a food and alternative medicine. However, the propolis from Okinawa, Japan, contains some prenylflavonoids not seen in other regions such as Europe and Brazil, suggesting that the plant origin of Okinawan propolis is a particular plant that grows in Okinawa. To identify the plant origin of Okinawan propolis, we obsereved the behavior of honeybees as they collected material from plants and caulked it inside the hive. Honeybees scraped resinous material from the surface of plant fruits of Macaranga tanarius and brought it back to their hive to use it as propolis. The chemical constituents and biological activity of the ethanol extracts of the plant did not differ from those of propolis. This indicates directly that the plant origin of Okinawan propolis is M. tanarius. We carried out the quantitative analysis of prenylflavonoids in various parts of M. tanarius such as leaf, petiol, atem, leaflet, flower, and fruit. Fruits were further separated into seed, pericarp, and glandular trichome, the surface of the fruits of M. tanarius. Large amounts of prenylflavonoids were present in glandular trichome. Next we observed the glandular trichome by a low vacuum scanning electron microscepe. It had the unique structure with a large cabity which is expected to produce prenylflavonoids. We prepared the ethanol extracts of M. tanarius and evaluated its antimicrobial and antiangiogenic activities. The extracts had significant antimicrobial activity against Gram-positive bacteria and also indicated the potent antiangiogenesis effects. Thus M. tanarius was proved to be an intersting plant with unique biological activities.
