Antiparasitic activities of acridone alkaloids from Swinglea glutinosa (Bl.) Merr

Eleven acridone alkaloids isolated from Swinglea glutinosa (Bl.) Merr. were examined for in vitro activity against chloroquine-sensitive Plasmodium falciparum 3D7, Trypanosoma brucei rhodesiense STIB900 and Leishmania donovani L82. An assay with KB cells was developed in order to compare in vitro toxicity of alkaloids with the selective action on the parasites. Nine of the compounds had IC50 values ranging from 0.3 to 11.6 μM against P. falciparum. In contrast, a small number of compounds showed significant activity against T. brucei rhodesiense and none had activity against L. donovani. Among the alkaloids three had IC50 < 1.0 μM against P. falciparum, whereas against T. b. rhodesiense five had IC50 < 10 μM. The characterization of the acridone alkaloids, 1,3,5-trihydroxy-4-methoxy-10-methyl-2,8-bis(3-methylbut-2-enyl)acridin-9 (10H)-one (1), 2,3-dihydro-4,9-dihydroxy-2-(2-hydroxypropan-2-yl)-11-methoxy-10-methylfuro [3,2-b] acridin-5(10H)-one (2) and 3,4-dihydro-3,5,8-trihydroxy-6-methoxy-2,2,7-trimethyl-2Hpyrano[ 2,3-a]acridin-12(7H)-one (3), is discussed, as well as the structure-activity relationship of all compounds assayed. Isolation and spectral data of alkaloids 1-3 are described for the first time although their cytotoxicities to cancer cells have been described before. (author)