Antioxidant activity and constituents of propolis collected in various areas of Japan

Propolis is a resinous substance collected by honeybees from various plant sources. We examined the antioxidant activity of Japanese propolis from various areas of Japan: Hokkaido, Akita (Minamiakita and Kazuno), Fukushima (Aizuwakamatsu and Futaba), Gifu, Nagano, Tokyo, Kanagawa, Shizuoka, Okayama, Tottori, Fukuoka and Okinawa. We prepared ethanol extracts of propolis (EEP), and evaluated the antioxidant activity of EEP samples by the beta-carotene bleaching and 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical scavenging assay systems. Further, we identified the major constituents in 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 (Minamiakita) contained large amounts of the antioxidative compounds, caffeic acid and phenethyl caffeate. Propolis from Okinawa appeared to have antioxidants not seen in propolis from other areas.