Individual and combined antiparasitic effect of six plant metabolites against Leishmania amazonensis and Trypanosoma cruzi

Six plant metabolites including isobavachalcone (1), 4-hydroxylonchocarpine (2), and (E)-1-(2,2-dimethyl-2H-chromen-6-yl)-3-(4-hydroxyphenyl)prop-2-en-1-one (3), 6,8-(di-3-methyl-but-2-enyl)eriodictyol (4), damnacanthal (5), and buesgenine (6) were evaluated for their leishmanicidal and trypanocidal activities against intracellular amastigotes of Leishmania amazonensis and Trypanosoma cruzi. Compounds 2–4 and 6 displayed antileishmanial activity while 3 and 5 showed trypanocidal effect. The leishmanicidal activity of 6 was expressed with the lowest IC50(5.70 μg/mL) whereas the most trypanocidal metabolite (5) showed its activity with IC50at 11.14 μg/mL. In addition, antiprotozoal effect of mixtures of 1–6 prepared at different ratios (3:1, 1:1, and 1:3) was also investigated. Interestingly, 1 and 2 initially inactive against T. cruzi, displayed trypanocidal activities when mixed together. This activity increased when 3 (13.63 μg/mL) was combined with 1 in ratios 1:1 (10.01 μg/mL) and 3:1 (7.78 μg/mL). Moreover, the leishmanicidal effect of 4 against L. amazonensis increased in the mixture 6/4 (1:3).