Background: Leishmaniasis is a neglected public health problem caused by several protozoanspecies
of the genus Leishmania. The therapeutic arsenal for treating leishmaniasis is quite limited,
raising concerns about the occurrence of resistant strains. Furthermore, most of these drugs were developed
more than 70 years ago and suffer from poor efficacy and safety and are not well adapted to the
needs of patients. Therefore, research on novel natural or synthetic compounds with antiparasitic activity
is urgently needed. In this paper, we evaluated the effect and the mechanism of action of
naphthotriazolyl-4-oxoquinolines on promastigotes and intracellular amastigotes of Leishmania amazonensis.
Materials and Methods: The naphthotriazolyl-4-oxoquinoline derivatives were obtained in good to
moderate yields via the [3+2] cycloaddition reaction between 1,4-naphtoquinone and azido-4-
oxoquinoline derivatives. HMPA at 100°C was established as the best solvent and temperature condition
for this reaction. The structures of the compounds were confirmed by spectral analyses (infrared spectroscopy,
one- and two-dimensional ¹H and ¹³C NMR spectroscopy, and high-resolution mass spectrometry).
The compounds exhibited promising activities with IC50 values ranging from 0.7 to 2.0 µM
against intracellular amastigotes of Leishmania amazonensis. The most selective compound was the Npentyl-
substituted derivative, which showed a Selectivity Index (SI) of 8.6, making it less toxic than
pentamidine (SI 4.5).
Results: Our results demonstrated that all compounds, except the N-propyl-substituted derivative, induce
ROS production by parasites early in the culture. As a proof of concept, we demonstrated that the
most selective compound was able to interfere with sterol biosynthesis in L. amazonensis.
Conclusion: The naphthotriazolyl-4-oxoquinoline derivatives were obtained in good to moderate yields.
These conjugates have potent in vitro antileishmanial activity involving at least two different mechanisms
of action, making them promising lead compounds for the development of new therapeutic alternatives