Chemical and biological studies of propolis and its origin plants

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Propolis is a resinous substance collected by honeybees from various plant sources. We studied the constituents and biological activities of propolis and its origin plants. In Japan, Brazilian propolis is widely used. To identify the plant origin of Brazilian propolis directly, we observed of honeybees in Minas Gerais State of Brazil and analyzed chemically the plant used by honeybees. We identified that plant origin of Brazilian propolis is Baccharis dracunculifolia. Further we examined the antioxidant activity of propolis from various areas of Japan. We identified the major constituents in ethanol extracts of propolis (EEP) by HPLC analysis by a photodiode array (PDA) and mass spectrometric (MS) detection, and quantitatively analyzed each component. EEP from Akita (Minamiakita) and Okinawa had relatively strong antioxidant activity, and was correlated with total polyphenol contents. Propolis from Akita (Minakiakita) contained large amounts of the antioxidative compounds, caffeic acid and phenethyl caffeate. Propolis from Okinawa had antioxidants not seen in propolis from other areas. These antioxidants were isolated and identified by spectroscopic methods to be novel prenylated flavonoids. Also concerning with Korean propolis, we examined the antioxidant activity. Further we investigated the absorption and metabolism of the components in propolis. We administered EEP orally to rats and analyzed their plasma and urine by HPLC with PDA and MS detection, and detected several flavonoids in it. On the other hand, we proved that honeybees use different origin plants by seasons.