Leishmanicidal activity of synthetic chalcones in Leishmania (Viannia) braziliensis

• New synthetic chalcones (1–4) showed inhibitory activity in vitro to promastigotes of L. (V.) braziliensis.
• All synthetic chalcones (1–4) exhibited low cytotoxicity to macrophages J774 and red blood cells.
• The four synthetic chalcones (1–4) reduced the infection index of macrophages by L. (V.) braziliensis.
• Synthetic chalcones 2 and 3 stimulated nitric-oxide production in macrophages infected with L. (V.) braziliensis.

The treatment of American cutaneous leishmaniasis (ACL) is based on a small group of compounds that were developed decades ago, all of which are highly toxic and have a high rate of treatment failure. The chalcones show leishmanicidal activity, yet few studies have evaluated this activity against Leishmania (Viannia) braziliensis, one of the most important species of Leishmania across Latin America. Four new synthetic chalcones (1–4) were evaluated for inhibitory activity in vitro against promastigotes and intracellular parasites 24 h post infection of L. (V.) braziliensis, cytotoxicity for macrophages J774.A1 and red blood cells, and the ability to stimulate nitric oxide production. The results for the inhibitory concentration for 50% of the promastigotes (IC50) (1.38 ± 1.09–6.36 ± 2.04 μM), cytotoxic concentration for 50% of the macrophages (CC50) (13.49 ± 3.13–199.43 ± 4.11 μM), and selectivity index (SI) (3.76 to 33.94) indicate that all chalcones (1–4) showed an effect on promastigotes of L. (V.) braziliensis; chalcone 2 had the highest SI. The haemolytic assay with chalcones 1 (301.93 μM), 2 (534.18 μM), 3 (419.46 μM) and 4 (381.11 μM) showed 0.00%, 2.33%, 0.57% and 1.74% haemolysis, respectively. All chalcones significantly reduced the infection index of macrophages by parasites; for chalcones (1–3) this effect may be dependent on nitric-oxide production by macrophages. The chalcones tested exhibited inhibitory activity for promastigotes and intracellular parasites of L. (V.) braziliensis, with low toxicity for macrophages and red blood cells. The anti-Leishmania activity of chalcones (1–3) may depend on the stimulation of nitric-oxide production in the initial stage of infection. These results show an initially encouraging potential for the use of chalcones (1–4) to treat ACL.

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