RESUMEN
Leishmaniases are neglected tropical diseases caused by obligate intracellular protozoa of the genus Leishmania. The drugs used in treatment have a high financial cost, a long treatment time, high toxicity, and variable efficacy. 3-Carene (3CR) is a hydrocarbon monoterpene that has shown in vitro activity against some Leishmania species; however, it has low water solubility and high volatility. This study aimed to develop Poloxamer 407 micelles capable of delivering 3CR (P407-3CR) to improve antileishmanial activity. The micelles formulated presented nanometric size, medium or low polydispersity, and Newtonian fluid rheological behavior. 3CR and P407-3CR inhibited the growth of L. (L.) amazonensis promastigote with IC50/48h of 488.1 ± 3.7 and 419.9 ±1.5 mM, respectively. Transmission electron microscopy analysis showed that 3CR induces multiple nuclei and kinetoplast phenotypes and the formation of numerous cytosolic invaginations. Additionally, the micelles were not cytotoxic to L929 cells or murine peritoneal macrophages, presenting activity on intracellular amastigotes. P407-3CR micelles (IC50/72 h = 0.7 ± 0.1 mM) increased the monoterpene activity by at least twice (3CR: IC50/72 h >1.5 mM). These results showed that P407 micelles are an effective nanosystem for delivering 3CR and potentiating antileishmanial activity. More studies are needed to evaluate this system as a potential therapeutic option for leishmaniases.
RESUMEN
The drugs used in the treatment of leishmaniasis show problems concerning side effects and toxicity. As a result, the search for new actives is necessary, and natural products like carvacrol - 5-isopropyl-2-methylphenol, become a relevant alternative. To enable the use of carvacrol as an antileishmanial agent, thermosensitive hydrogels were developed from poloxamer triblock copolymers 407 (P407) and 188 (P188). Carvacrol-free and carvacrol-containing hydrogels were obtained from P407 alone and from the mixture of P407 and P188. The hydrogels were subjected to Differential scanning calorimetry, Small-angle X-ray scattering, Scanning electron microscopy, and Rheology analysis. The activity of hydrogels and carvacrol isolated against promastigotes and intracellular amastigotes of Leishmania amazonensis and their cytotoxicity in mammalian cells was determined. The sol-gel transition temperature for the binary hydrogel containing carvacrol (HG407/188CA) was 37.04 ± 1.35 °C. HG407/188CA presented lamellar structure at temperatures of 25 °C and 37 °C. HG407/188CA and carvacrol presented IC50 against Leishmania amazonensis promastigotes of 18.68 ± 1.43 µg/mL and 23.83 ± 3.32 µg/mL, respectively, and IC50 against Leishmania amazonensis amastigotes of 35.08 ± 0.75 µg/mL and 29.32 ± 0.21 µg/mL, respectively. HG407/188CA reduced the toxicity of carvacrol in all mammalian cells evaluated, raising the CC50 in murine peritoneal macrophages from 40.23 ± 0.21 µg/mL to 332.6 ± 4.89 µg/mL, obtaining a Selectivity Index (SI) of 9.5 against 1.37 of the isolated carvacrol. HG407/188CA provided higher selectivity of carvacrol for the parasite. Thus, the binary hydrogel obtained may enable the use of carvacrol as a potential antileishmanial agent.