Antiparasitic effect of Farnesol against Leishmania major: A rationale from in vitro and in silico investigations

Leishmaniasis is a vector-borne parasitic infection caused by the infective bite of female Phlebotomine sandflies. Treatment of leishmaniasis by conventional synthetic compounds is met by challenges pertaining to adverse effects which call for the discovery of newer anti-leishmanial molecules. This study was performed to evaluate the effect and modes of action of a sesquiterpene alcoholic molecule Farnesol on Leishmania major, the causative agent of Zoonotic CL. The cytotoxic effect of Farnesol against L.major promastigotes, amastigotes and macrophages was assessed by MTT test and counting. The IC50 on promastigotes by Farnesol on L.major was also evaluated by flow cytometry. In the findings, promastigotes were reduced at 167μM. The mean numbers of L.major amastigotes in macrophages were significantly decreased on exposure to Farnesol at 172μM. In addition, Farnesol induced significant apoptosis dose-dependent on L.major promastigotes. In silico protein-ligand_binding analyses indicated the effect of Farnesol in perturbation of the ergosterol synthesis pathway of Leishmania with attributes suggesting inhibition of Lanosterol-α-demethylase, the terminal enzyme of ergosterol synthesis machinery. Findings from flow cytometry reveal the role of Farnesol in apoptosis-induced killing in promastigotes. Farnesol was effective at very lower concentrations when compared to Paromomycin. Further studies are crucial to evaluate the therapeutic potential of Farnesol alone or in combination with other conventional drugs in animal models.

Optimization of Orally Bioavailable Antileishmanial 2,4,5-Trisubstituted Benzamides

Leishmaniasis, a neglected tropical disease caused by Leishmania species parasites, annually affects over 1 million individuals worldwide. Treatment options for leishmaniasis are limited due to high cost, severe adverse effects, poor efficacy, difficulty of use, and emerging drug resistance to all approved therapies. We discovered 2,4,5-trisubstituted benzamides (4) that possess potent antileishmanial activity but poor aqueous solubility. Herein, we disclose our optimization of the physicochemical and metabolic properties of 2,4,5-trisubstituted benzamide that retains potency. Extensive structure-activity and structure-property relationship studies allowed selection of early leads with suitable potency, microsomal stability, and improved solubility for progression. Early lead 79 exhibited an 80% oral bioavailability and potently blocked proliferation of Leishmania in murine models. These benzamide early leads are suitable for development as orally available antileishmanial drugs.