12th International Conference of Pharmaceutical Sciences

Tegumentary Leishmaniasis (TL) is an anthropozoonosis caused by protozoa of the genus Leishmania spp. The disease has a wide clinical spectrum, affecting the skin and mucosa of the host, thereby causing pain and social stigmatization. The current treatment presents a variable effectiveness, high cost, parasite resistance and high toxicity (BRASIL, 2017). It is estimated that about 1 billion people live in areas at risk of infection and from 0.6 to 1 million new cases of TL occur annually (WHO, 2019). Essential oils are promising candidates for an alternative or complementary treatment of TL because they present chemical diversity and several biological activities in the literature. In this study, a random screening of essential oils in promastigotes forms of Leishmania amazonensis revealed one of the essential oils coded as OE11 as a potential leishmanicide candidate. This essential oil is already recommended by the Brazilian Pharmacopoeia for the treatment of other diseases. However, there are no reports of scientific literature on activity against parasites of the genus Leishmania Therefore, the aim of this work was to investigate the anti-Leishmania amazonensis activity of OE11. For this, the OE11 was subjected to analysis by gas chromatography and mass spectrometry (GC-MS) for phytochemical profile evaluation. For biological assays, the L. amazonensis promastigotes forms were incubated with different OE11 concentration for 72h at 28°C. After treatment, a viability was determined with resazurin. Then, the cells were reincubated in fresh medium to evaluate the leishmanicidal effect. Cytotoxicity was evaluated in VERO, J774, RAW 264.7 cells and peritoneal macrophages from BALB/c mice (MOp) and red blood cells. The MOp was infected with L. amazonensis and treated with different concentrations of OE11. Amastigotes load and percentage of infected MOp were evaluated by direct counting under the optical microscope. Nitric oxide (NO) production by the infected and treated MOp was evaluated by Griess reaction. Phytochemical analysis revealed the major presence of organo-sulfur compounds. OE11 presented a 50% inhibitory concentration of parasites (IC50) of 1.76 ± 0.37 and 3.1 μg/mL for promastigote and amastigote forms of L. amazonensis, respectively. However, OE11 was not able to alter NO levels in infected MOp. The OE11 presented a cytotoxic concentration of 50% (CC50) for MOp of 50 μg/mL. Thus, selectivity index of 28.4 and 16 were observed for promastigote and amastigote forms, respectively. In addition, OE11 showed no cytotoxicity to VERO cells and red blood cells at the highest concentration tested (2 mg/mL). Therefore, OE11 has a promising source of substances with anti-L. amazonensis. The next steps of this study are the development of OE11 microemulsions (M-OE11) and the evaluation of the effect of OE11 and M-OE11 in in vivo infection model.