Novel 1,4-Naphthoquinone-Zidovudine Hybrid: Design, Synthesis, and In Vitro Evaluation of Its Anti-Trypanosomatid and Cytotoxic Activities

This work reports the synthesis and characterization of a new molecular hybrid 4, created by combining 1,4-naphthoquinone with the drug zidovudine (AZT) through an azide-alkyne cycloaddition reaction catalyzed by Cu1+. In vitro studies assessed the anti-trypanosomatid activity of hybrid 4, along with its precursors and synthetic intermediates (1, 2, and 3), against Trypanosoma cruzi (T. cruzi Tulahuen C2C4 LacZ), Trypanosoma brucei (T. b. brucei 427), and Leishmania infantum, as well as cytotoxicity in RAW 264.7 macrophages and LLC-MK2 cells. The biological results confirm the molecular design, showing that the new hybrid is effective against both epimastigotes and amastigotes of T. cruzi (IC50 = 22.26 ± 5.78 μM and 143.10 ± 5.79 μM, respectively), with approximately 4.5-fold better capacity than AZT to inhibit the epimastigote form. Additionally, the hybrid was also active against bloodstream T. b. brucei (IC50 = 54.47 ± 6.70 μM), with approximately 2.2-fold better capacity than AZT to inhibit this parasite. It also shows low toxicity in RAW 264.7 macrophages (CC50 > 200 μM) and LLC-MK2 cells (CC50 > 200 μM). For example, hybrid 4 exhibited approximately a 6.6-fold higher SI than 1,4-naphthoquinone 1 against T. cruzi amastigotes. In this context, the work contributes to the broader knowledge base guiding the design of hybrid molecules for antiparasitic chemotherapy. It provides a rational foundation for preparing subsequent, more potent analogues.