Antileishmanial potential of a total phenolic fraction rich in hydroxytyrosol and tyrosol and its additive interaction with miltefosine against Leishmania

Leishmaniasis is a major public health problem, caused by protozoa of the genus Leishmania, with a wide spectrum of clinical manifestations. Chemotherapies include old drugs with drawbacks such as toxicity, high cost and emerging resistance [1]. Thus, the development of new therapeutics is focused on combination therapies and new formulations. Previous studies demonstrated that total phenolic fraction (TPF) derived from extra virgin olive oil, exhibits antileishmanial activity. Present study aims to evaluate the leishmanicidal activity of a TPF extract, especially rich in hydroxytyrosol (HT) and tyrosol (Tyr) biophenols, in combination with miltefosine, the standard antileishmanial drug, against L. infantum and L. major extracellular promastigotes and intracellular amastigotes. Its qualitative and quantitative analysis revealed a content of 7 and 42 mg/g of extract for HT and Tyr, respectively. TPF caused a concentration-dependent inhibition on promastigote and amastigote viability, at 72 h after treatment, for both strains. The half maximal inhibitory and cytotoxic concentrations (IC50 and CC50 values) of TPF and miltefosine were estimated using the resazurin cell viability assay ([Table 1]). TPF (IC50) inhibited parasite proliferation and triggered a significant enhancement of intracellular ROS levels in L. infantum and L. major promastigotes after incubation for 72 h, as it was demonstrated by increased fluorescence intensity compared to untreated parasites. Its antileishmanial effect in combination with miltefosine, was determined on promastigotes of both strains and isobolograms revealed additive effects. Our overall results strongly suggest that TPF rich in HT and Tyr active molecules, is a powerful inhibitory factor against viscerotropic and dermotropic Leishmania strains.