# Phytol-loaded soybean oil nanoemulsion as a promising alternative against Leishmania amazonensis

## TL;DR

A phytol-loaded nanoemulsion shows promise as a safe and effective treatment for leishmaniasis, a tropical disease caused by Leishmania parasites.

## Contribution

The development of a phytol-loaded soybean oil nanoemulsion with enhanced antiparasitic activity and colloidal stability for potential topical therapy.

## Key findings

- The nanoemulsion (PHYT-NE) had a mean droplet size of ~200 nm and high colloidal stability for at least 30 days.
- PHYT-NE exhibited up to 75% parasite death in Leishmania amazonensis promastigotes after 48 hours with significantly lower IC50 values than free phytol.
- The formulation was cytocompatible with 3T3 fibroblasts, suggesting safety for further in vivo studies.

## Abstract

Leishmaniasis, caused by protozoa of the genus Leishmania spp., is a neglected tropical disease that poses a significant challenge to the public health in tropical and subtropical regions, affecting mainly low-income individuals. Current therapies are limited due to severe adverse reactions to currently available drugs, high cost, low patient adherence, and even the emergence of resistant strains. Examining safer and more effective alternatives, natural compounds such as phytol – a diterpene derived from chlorophyll – have attracted attention due to their broad biological activities. To increase their solubility, stability, and cell delivery, nanotechnology-based systems, such as nanoemulsions (NEs), represent a promising approach. In this study, soybean oil nanoemulsions loaded with phytol (PHYT-NE) were developed using the phase inversion composition (PIC) method, and then characterized and evaluated. The PHYT-NE had a mean droplet diameter close to 200 nm, a polydispersity index of less than 0.2, spherical shape, and a pH value compatible with cutaneous application. The formulation showed high colloidal stability for at least 30 days of storage and at least 15 days even under stress conditions, with no signs of macroscopic instability or changes in droplet size. The cytocompatibility of NEs was confirmed in 3T3 fibroblasts at the concentrations tested, indicating potential safety for in vivo trials. Notably, PHYT-NE exhibited significant time-dependent leishmanicidal activity against Leishmania amazonensis promastigotes, with lower IC50 values (up to five times lower at 48 hours) and up to 75% parasite death after 48 hours, showing greater antiparasitic activity compared to that of free phytol. Although the use of promastigotes represents a limitation, this model was used as a proof-of-concept, with promising evidence of the potential of PHYT-NE. Future studies in macrophage models infected with intracellular amastigotes will be essential to confirm the observed efficacy and validate the potential of PHYT-NE as a safe and effective topical therapy for cutaneous leishmaniasis.