GREEN-SYNTHESIZED SILVER NANOPARTICLES FROM MORINGA OLEIFERA FOR THE TREATMENT OF LEISHMANIA MAJOR: ANTILEISHMANIAL ACTIVITY, CYTOTOXICITY, AND MECHANISTIC INSIGHTS

Abstract

Treatment of CL (caused by L. major) presents a serious challenge due to the toxicity, long-term use, inconsistent efficacy and resistance of available drugs. Silver nanoparticles (AgNPs) which are synthesized using green methods are a promising alternative because of their antimicrobial properties and the bioactive compounds of medicinal plants. In this study, antileishmanial activity, cytotoxicity, and the possible mechanisms of action of Moringa oleifera-mediated AgNPs against L. major were evaluated. Various process parameters such as precursor concentration, extract concentration, pH, temperature, and reaction time were optimized to produce AgNPs with the leaf extract of M. oleifera. The obtained nanoparticles were characterized by the various techniques like UV-Visible spectroscopy, FTIR, XRD, SEM/TEM, EDX, DLS and zeta potential. The antileishmanial activity was measured against promastigotes and intracellular amastigotes, and the mammalian-cell cytotoxicity and hemocompatibility were evaluated to determine selectivity. The effects of oxidative stress, mitochondrial dysfunction, integrity of membranes, ultrastructural changes, apoptosis-like responses and expression of selected stress and cell death-associated genes were examined. The optimized AgNPs exhibited a characteristic SPR peak at 420 nm, mostly spherical shape, mean TEM particle size of 18.6 ± 6.4 nm, hydrodynamic diameter of 22.8 nm, PDI of 0.184 and zeta potential of −28.7 mV. AgNPs were found to inhibit the promastigote stage of L. major at an IC₅₀ of 44.7 µg/mL and the intracellular amastigote stage at an IC₅₀ of 12.1 µg/mL. The mammalian-cell CC₅₀ was 231.8µg/mL with selectivity indices of 5.2 and 19.2 (CC₅₀ / IC₅₀). Accumulation of ROS, depletion of antioxidants, mitochondrial depolarization, ATP reduction, membrane disruption, ultrastructural damage, and apoptosis-like responses were induced by treatment. AgNPs formulation by M. oleifera was found to have promising and selective antileishmanial activity, which is suggested to have antioxidant and mitochondrial dysfunction action. Additional in vivo evaluation is needed.