In vitro anti-Leishmania activity of 8-hydroxyquinoline and its synergistic effect with amphotericin B deoxycholate against Leishmania martiniquensis

Leishmania (Mundinia) martiniquensis is responsible for visceral leishmaniasis in patients with no known underlying immunodeficiency, and visceral or disseminated cutaneous leishmaniasis in HIV-infected patients. The available anti-Leishmania drugs for treatment have limitations such as high toxicity and variable efficacy. To improve the therapeutic index of anti-Leishmania drugs, the search for a new drug or a new natural compound in combination therapy instead of using monotherapy to reduce drug side effect and have high efficacy is required. In this study, anti-Leishmania activity of 8-hydroxyquinoline (8HQN) and its synergistic effect with amphotericin B (AmB) against L. martiniquensis were evaluated in vitro for the first time. These results showed that 8HQN presented anti-Leishmania activity against L. martiniquensis with IC(50) 1.60 ± 0.28 and 1.56 ± 0.02 µg/mL for promastigotes and intracellular amastigotes, respectively. The selectivity index (SI) value of 8HQN was 79.84 for promastigotes and 82.40 for intracellular amastigotes, which highlight promising results for the use of 8HQN in the treatment of L. martiniquensis-infected host cells. Interestingly, four combinations of 8HQN and AmB provided synergistic effects for intracellular amastigotes and showed no toxic effects to host cells. These results provided information of using a combination therapy in treating this Leishmania species leads to further development of therapy and can be considered as an alternative treatment for leishmaniasis.