Evaluating the leishmanicidal activity of m-Nitrocinnamic acid containing lipophilic peptide against leishmania donovani

Studies have demonstrated that m-Nitrocinnamic acid containing Lipophilic Peptide (LP) exhibits leishmanicidal activity against Leishmania major promastigotes; however, its efficacy against the amastigote form remains unclear. In this study, we evaluated the activity of LP against Leishmania donovani, the causative agent of Visceral Leishmaniasis (VL), wherein LP demonstrated both anti-promastigote and anti-amastigote activity, as measured by MTS cell viability assay and droplet digital PCR (ddPCR) respectively, the IC₅₀ derived being 22.0 and 6.0 µM respectively, while the CC₅₀ was >500 µM, which translated into a safety index >83. LP induced leishmanicidal activity by triggering a redox imbalance in promastigotes, by enhancing the generation of reactive oxygen species (ROS) and caused lipid peroxidation, but failed to impact on generation of mitochondrial superoxide. Furthermore, as N-acetyl cysteine (NAC) attenuated the parasiticidal properties of LP via scavenging the free radicals, it substantiated that the cytotoxicity of LP was mediated by inducing a redox imbalance. An apoptotic-like cell death was demonstrated in promastigotes, features being an enhanced annexin V positivity, altered mitochondrial membrane potential, and cell cycle arrest at sub G₀/G₁. Collectively, this study confirmed that LP exhibited leishmanicidal activity against L. donovani that was mediated by an apoptotic-like cell death via disruption of redox homeostasis, and could be considered as a compound worthy of further pharmacological consideration.