Antiparasitic Activity of Coumarin–Chalcone (3‐Cinnamoyl‐2 <i>H</i> ‐Chromen‐2‐Ones) Hybrids

Coumarin-chalcone hybrids are promising compounds that could be used as lead structures in the fight against parasitic diseases. In this work, 16 hybrids of coumarin-chalcone (3-cinnamoyl-2H-chromen-2-ones) were synthesized, and their in vitro biological activity was evaluated against intracellular amastigotes of Leishmania braziliensis and Trypanosoma cruzi, as well as their cytotoxicity in the U-937 cell line. Compounds (E)-3-(3-(3-ethoxy-4-hydroxyphenyl)acryloyl)-7-methoxy-2H-chromen-2-one (H₂₅) and (E)-7-(diethylamino)-3-(4-(methoxyphenyl)acryloyl)-2H-chromen-2-one (H₁₂) showed the highest antileishmanial activity with EC₅₀ values of 18.6 ± 3.5 and 25.6 ± 0.4 µM, respectively. In general, all 16 compounds exhibited moderate-to-high antitrypanosomal activity. The H₂₅ hybrid also demonstrated the greatest antitrypanosomal activity, with an EC₅₀ value of 13.2 ± 0.4 µM. Notably, the H₂₅ hybrid displayed activity similar to that of benznidazole, which is known for its antiparasitic effects against T. cruzi. The results indicated that all compounds met the drug-like properties criteria. Taking into account the high antiparasitic activity of H₂₅, a molecular docking study with the enzyme trypanothione reductase was performed. The substituent at C7 in the coumarinyl system is an important structural requirement for the antileishmanial and antitrypanosomal activities.