Desenvolvimento e avaliação da atividade antileishmania de microemulsão contendo fração resinosa refugada na extração do óleo essencial de Copaíba por hidrodestilação.

Abstract

The Amazon biome stands out for its remarkable biodiversity, including plant species of pharmaceutical interest, such as the copaiba tree (Copaifera sp.). The oleoresin extracted from this plant exhibits well-documented therapeutic properties, including analgesic, anti-inflammatory, antimicrobial, and antileishmanial activities. This oleoresin comprises two main fractions: a volatile one, rich in sesquiterpene essential oils, and a resinous one, rich in terpenic compounds. The extraction of the essential oil, which has commercial value, is performed by hydrodistillation or steam distillation, while the resinous fraction is often discarded by the industry.The aim of this study was to repurpose the resinous fraction as the oil phase in microemulsion systems and to evaluate the in vitro activity of these formulations against promastigote forms of Leishmania amazonensis, one of the most prevalent species in Brazil. Characterization of the formulations showed that bicontinuous and O/W-type microemulsions were obtained, containing 10% and 20% of the resinous fraction of copaiba oleoresin, respectively. All formulations tested were able to inhibit the in vitro proliferation of L. amazonensis promastigotes, presenting IC₅₀ values below 6.9 µg·mL⁻¹ after 48 hours of incubation, indicating higher efficacy than the standard drug used for leishmaniasis treatment, Glucantime®, whose IC₅₀ exceeded 100 µg·mL⁻¹.The placebo formulations also inhibited parasite growth, since Tween 20 (the surfactant used) is known to have activity against parasite cell proliferation, thereby enhancing the oleoresin’s effect. Furthermore, the microemulsion with the lower oleoresin content (10%) but higher water content (20%) exhibited the lowest IC₅₀ after 24 hours of incubation (2.7 µg·mL⁻¹), demonstrating that the water content of the formulation plays an important role in improving the cellular permeation of active compounds and enhancing pharmacological efficacy.