Isopropyl gallate (IPG) is a polyphenol obtained from alterations in the gallic acid molecule via acid catalysis with previously reported leishmanicidal and trypanocidal activities. The present study aims to evaluate in silico binding activity towards some targets for antileishmanial chemotherapy against Leishmania major species, and ADMET parameters for IPG, as well as in vitro antileishmanial and cytotoxic effects. Molecular docking was performed using AutoDockVina and BIOVIA Discovery Studio software, whereas in silico analysis used SwissADME, PreADMET and admetSAR software. In vitro antileishmanial activity on promastigotes and amastigotes of Leishmania major, cytotoxicity and macrophages activation were assessed. IPG exhibited affinity for pteridine reductase (PTR1; −8.2 kcal/mol) and oligopeptidase B (OPB; −8.0 kcal/mol) enzymes. ADMET assays demonstrated good lipophilicity, oral bioavailability, and skin permeability, as well as non-mutagenic, non-carcinogenic properties and low risk of cardiac toxicity for IPG. Moreover, IPG inhibited the in vitro growth of promastigotes (IC50 = 90.813 µM), presented significant activity against amastigotes (IC50 = 13.45 μM), promoted low cytotoxicity in macrophages (CC50 = 1260 μM), and increased phagocytic capacity. These results suggest IPG is more selectively toxic to the parasite than to mammalian cells. IPG demonstrated acceptable in silico pharmacokinetics parameters, and reduced infection and infectivity in parasitized macrophages, possibly involving macrophage activation pathways and inhibition of leishmania enzymes.

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Leishmaniasis is a neglected disease caused by protozoa of the genus Leishmania, endemic in 98 countries, constituting a major public health problem. Conventional treatments cause serious adverse effects, poor tolerance, development of resistant strains, and are costly. Natural products have been investigated in the search for therapeutic alternatives. The cashew nut shell liquid (CNSL) is a natural source of phenolic compounds, showing antioxidant, anti-inflammatory, antimicrobials, antitumors, larvicides and insecticides, with cardanol (CN) being considered one of the most important and promising technical components. This study aimed to evaluate antileishmania, cytotoxic and immunomodulatory activities of CNSL and CN. The substances showed antileishmania potential, with values of mean inhibitory concentration (IC50) of CNSL and CN against Leishmania infantum: 148.12 and 56.74 µg/mL; against Leishmania braziliensis: 85.71 and 64.28 µg/ml; against Leishmania major: 153.56 and 122.31 µg/mL, respectively. The mean cytotoxic concentrations (CC50) of CNSL and CN were 37.51 and 31.44 µg/mL, respectively. CNSL and CN significantly reduced the percentage of infected macrophages, with a selectivity index (SI) > 20 for CN. CNSL and cardanol caused an increase in phagocytic capacity and lysosomal volume, however, they did not exhibit significant induction of nitric oxide synthesis. Survival rates of Zophobas morio larvae at doses of 3; 30 and 300 mg/Kg were: 85%, 75% and 60% in contact with CNSL and 85%, 60% and 40% in contact with CN, respectively. There was a significant difference between the survival curves of larvae when treated with CN, demonstrating a significant acute toxicity for this substance. Additional investigations are needed to evaluate these substances in the in vivo experimental infection model.