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The activity of propolis against protozoa.

Dr David G Watson

During the past ten years we have investigated the antiprotozoal activity of propolis. In our most recent work, ethanolic extracts of four samples of propolis from the UK and one from Poland were tested against three strains of Trypanosoma brucei. The extracts displayed EC50 values of < 20 µg/ml against T. brucei. The extracts were fractionated by using several chromatographic techniques and this resulted in the isolation of 13 compounds and one two component mixture which were characterized by NMR and high-resolution mass spectrometry. The compounds isolated include: 3-acetoxypinobanksin, 7-methoxychrysin, kaempferol, pinocembrin, 4’-methoxykaempferol, galangin, chrysin, apigenin, pinostrobin, cinnamic acid, coumaric acid cinnamyl ester/ coumaric acid benzyl ester (mixture), 4’,7-dimethoxykaempferol and Naringenin 4',7-dimethyl ether. The isolated compounds were tested against three strains of T. brucei and two strains of Leishmania mexicana. Most of the isolated compounds had EC50 values of < 100 µM. The most active compounds against T. brucei were 4’,7 naringenin dimethylether and 4’methoxy kaempferol with activity of ca 20 µM against the three strains of T. brucei. The most active compound against L. mexicana was the coumaric acid ester mixture.