Traditional medicine and scientific studies have shown that the raw extract of Evanta [Galipea longiflora, Angostura longiflora (Krause) Kallunki] exhibits anti‐leishmanial activity. We hypothesized that the healing observed when using this plant might not only be due to the direct action on the parasite, but possibly to a parallel effect on the host immune response to the parasite involved in the healing process. We show here that an alkaloid extract of Evanta (AEE) directly killed the parasite already at a dose of 10 μg/ml, but at this low concentration, AEE did not have a major effect on viability and proliferation of eukaryotic cells. The whole extract was also found to be stronger than 2‐phenylquinoline, the most prominent alkaloid in AEE. AEE was not directly stimulating B or T cells or J774 macrophages. However, it interfered with the activation of both mouse and human T cells, as revealed by a reduction of in vitro cellular proliferation and interferon‐gamma (IFN‐γ) production. The effect was more evident when the cells were pretreated with AEE and subsequently stimulated with the polyclonal T‐cell activators Concanavalin A and anti‐CD3. Taken together, our results suggest that Evanta have a direct leishmanicidal effect and due to the effect on IFN‐γ production it might contribute to control the chronic inflammatory reaction that characterize Leishmania infection pathology, but in vivo studies are necessary to corroborate this finding.

An antileishmanial activity of quinolinic alkaloids from Galipea longiflora Krause, known as Evanta, has been demonstrated. We have previously shown that, apart from its leishmanicidal effect, in vitro pretreatment of spleen cells with an alkaloid extract of Evanta (AEE) interfered with the proliferation and interferon-c production in lymphocytes polyclonally activated either with concanavalin A or anti-CD3. In the present study, we investigated if AEE could interfere with antigen-specific lymphocyte activation. We found that in vitro and in vivo treatment reduced recall lymphocyte responses, as measured by IFN-c production (55% and 63% reduction compared to untreated cells, respectively). Apart from IFN-c, the production of IL-12 and TNF was also suppressed. No effects were observed for meglumine antimoniate (SbV), the conventional drug used to treat leishmaniasis. When mice infected with Leishmania braziliensis promastigotes in the hind footpad were treated with AEE, the dynamics of the infection changed and the footpath thickness was efficiently controlled. The parasite load was also reduced but to a lesser extent than upon treatment with SbV. Combined treatment efficiently controlled both the thickness and parasite load as smaller lesions during the entire course of the infection were seen in the mice treated with AEE plus SbV compared with AEE or SbV alone. We discuss the benefits of combined administration of AEE plus SbV.