Zinc nanoparticles coated with peppermint (Mentha piperita) essential oil: a nanoformulated compound with anti-leishmanial activity.

Currently, cutaneous leishmaniasis (CL) treatment is facing a problem due to the increase in drug resistance. Nanoparticles, due to their characteristics, are suitable candidates for disease treatment. The aim of this study is the in vitro evaluation of zinc nanoparticles coated with peppermint (Mentha piperita) essential oil on Leishmania major. The effects of different concentrations of Zn-Mp and meglumine antimoniate (MA; as a positive control) were studied on the promastigote and amastigote of Leishmania major, and their selectivity index (SI) was evaluated. The peaks at 2361.02 cm^-1 (C-N stretching), 1213.78 cm^-1 (CO-NH stretching), and 1110.83 cm^-1 (C=O stretching) were attributed to Zn-Mp. The inhibitory concentration 50 (IC₅₀) was 17.48 μg/mL for Zn-Mp and 19.09 μg/mL for MA on promastigote (P = 0.47). It was 11.3 μg/mL for Zn-Mp and 14.1 μg/mL for MA on amastigote (P = 0.79). Lower IC₅₀ on amastigote for Zn-Mp indicated better effectiveness on L. major compared to MA, but higher SI for MA (37.55) as compared to Zn-Mp (18.9) (P = 0.0002), highlighting more safety for MA. Compared to MA, the anti-leishmanial effect of Zn-Mp and its nontoxic effects on macrophages (SI > 10) show that Zn-Mp can be a candidate for the treatment of CL and it should be further studied on animal models.