Tehran University of Medical Sciences Iranian Journal of Parasitology 1735-7020 21 2 2026 07 12 217 226 Sahar Gheisari Infectious Diseases Research Center, Kashan University of Medical Sciences, Kashan, Iran Mahdi Delavari Infectious Diseases Research Center, Kashan University of Medical Sciences, Kashan, Iran Iraj Salimikia Department of Pharmacognosy, Faculty of Pharmacy, Lorestan University of Medical Sciences, Khorramabad, Iran Ali Sobhani Nasab Physiology Research Center, Institute for Basic Sciences, Kashan University of Medical Sciences, Kashan, Iran 2026 01 22 2026 07 12 Background: Cutaneous leishmaniasis is a neglected parasitic disease prevalent in tropical and subtropical regions, caused by different species of the genus Leishmania. Current therapeutic options are limited due to toxicity, prolonged treatment regimens, and emerging drug resistance. Methods: This study was conducted at Kashan University of Medical Sciences, Kashan, Iran in 2024. The antileishmanial activity of quercetin and a synthesized quercetin–ZnMgFe₂O₄ nanostructure was evaluated against L. major promastigotes in vitro conditions. The nanostructure was synthesized and characterized using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). The antileishmanial activity was assessed by determining the mortality rate of promastigotes at different concentrations (150, 300, 450, and 600 μg/mL) of quercetin and also quercetin–ZnMgFe₂O₄ nanostructure. In addition, ultrastructural and nuclear alterations were examined following exposure to 150 and 600 μg/mL of both quercetin and the nanostructure. Results: The quercetin–ZnMgFe₂O₄ nanostructure exhibited significantly higher inhibitory activity compared with quercetin. The mortality rates for the nanostructure were 73% and 85.9% at 150 and 600 μg/mL, respectively, compared with 42% and 81% for quercetin. Microscopic analysis revealed pronounced morphological alterations, including damage to the cell body and flagella, as well as destruction of the nucleus and kinetoplast. Conclusion: The Quercetin_ZnMgFe₂O₄ nanostructure exhibited considerable antileishmanial activity against L.major promastigotes in vitro. Considering the obtained results, this nanostructure can be considered in anti-leishmanial studies and further in vitro and in vivo investigations are required to evaluate its safety and efficacy. https://ijpa.tums.ac.ir/index.php/ijpa/article/view/4871 https://ijpa.tums.ac.ir/index.php/ijpa/article/download/4871/1496