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DOI: 10.1055/s-2006-949873
Trypanocidal Flavonoids from Ageratum conyzoides
The crude extract (MeOH sol. part of DCM extract) of Ageratum conyzoides L. (Asteraceae) was found to be active against the trypomastigote forms of Trypanosoma brucei rhodesiense (IC50 =0.78µg/mL), the protozoan that causes East African sleeping sickness. Bioassay-guided fractionation of this extract so far afforded four polyoxygenated flavonoids (1-4) and a chromene (5). Compounds 1–4 were active with IC50 values of 16µM, 18µM, 21µM and 11µM, respectively, whereas compound 5 was almost inactive with an IC50 of 316µM. The cytotoxicity level of all compounds against murine L6 cells was negligibly low. Although polyoxygenated flavonoids have previously been reported from A. conyzoides [1] no information was hitherto available on the trypanocidal activity of the crude extract or pure compounds. These results suggest that the polyoxygenated flavone skeleton deserves further investigation as a template for novel trypanocidal compounds. Structure-activity studies in relation with other flavonoids, see, e.g. [2], are under way. Search for further active constituents from this species is still in progress.
Acknowledgements: Amal Nour acknowledges a scholarship from the German Academic Exchange Service (DAAD).
References: 1. Vyas, A.V. et al. (1986), Phytochemistry 25: 2625–27. 2. Tasdemir, D. et al. (2006), Antimicr. Agents Chemother. 50: 1352–64.