Novel flavanones with anti-trypanosomal activity isolated from Zambian and Tanzanian propolis samples

Alenezi, Samya S. and Natto, Manal J. and Igoli, John O. and Gray, Alexander I. and Fearnley, James and Fearnley, Hugo and de Koning, Harry P. and Watson, David G. (2020) Novel flavanones with anti-trypanosomal activity isolated from Zambian and Tanzanian propolis samples. International Journal for Parasitology: Drugs and Drug Resistance, 14. pp. 201-207. ISSN 2211-3207 (

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A bioassay-guided phytochemical investigation of propolis samples from Tanzania and Zambia that screened for activity against Trypanosoma brucei has led to the isolation of two novel flavanones with promising antitrypanosomal activity. The compounds were characterized based on their spectral and physical data and identified as 6-(1,1-dimethylallyl) pinocembrin and 5-hydroxy-4",4"-dimethyl-5"-methyl-5"-H-dihydrofuranol [2",3",6,7] flavanone. The two compounds, together with the propolis extracts and fractions, were assayed against a standard drug-sensitive strain of T. b. brucei (s427 wild-type), multi-drug resistant-resistant T. b. brucei (B48), drug-sensitive T. congolense (1L300) and a derived diminazene-resistant T. congolense strain (6C3), and for toxicity against U947 human cells and RAW 246.7 murine cells. Activity against T. b. brucei was higher than against T. congolense. Interestingly, the Tanzanian propolis extract was found to be more active than its fractions and purified compounds in these assays, with an IC50 of 1.20 μg/mL against T. b. brucei. The results of a cytotoxicity assay showed that the propolis extracts were less toxic than the purified compounds with mean IC50 values > 165.0 μg/mL.