Antileishmanial activity of Hesperetin on Leishmania donovani, in vitro and in silico inhibition of acetylcholinesterase and investigation of the targets sterol C-24 reductase and N-myristoyltransferase.

Abstract

The current treatment of leishmaniasis is confronted with significant challenges, including limited efficacy, adverse effects, and parasite resistance to drugs. The search for alternative therapeutic options, including the utilization of natural products, has demonstrated considerable promise. In this study, the antileishmanial activity of the flavonoid hesperetin against Leishmania donovani, the causative agent of visceral leishmaniasis, was reported for the first time. Hesperetin was obtained through the hydrolysis of hesperidin and subsequently subjected to chemical characterisation via Infrared and NMR spectroscopy. The antileishmanial activity and cytotoxicity against RAW 264.7 macrophages were evaluated using the MTT colorimetric assay. In order to investigate the potential mechanisms of action, in vitro acetylcholinesterase inhibition assays and molecular docking analyses were conducted. Hesperetin showed an antipromastigote effect (IC₅₀: 62.89 μM) with no evidence of cytotoxicity (CC₅₀: 612.8 μM), with a selectivity index (SI) of 9.74, being 5.4 times more effective than trivalent antimony. In comparison, antimony showed an IC₅₀ of 80.16 μM, a CC₅₀ of 145.04 μM and a SI of 1.8, indicating a limited safety margin. The compound was observed to inhibit acetylcholinesterase (IC₅₀ of 18.44 μg/mL), present in mitochondrial and plasma membrane of the parasite. Molecular docking and dynamic simulations indicated that hesperetin inhibit sterol C-24 reductase, essential for ergosterol biosynthesis and membrane integrity of L. donovani and shows activity against N-myristoyl transferase, responsible for parasite proliferation cycle. These findings open promising avenues for the development of effective antileishmanial therapies.