Antileishmanial activity of some Brazilian plants, with particular reference to Casearia sylvestris.

Leishmaniasis is a complex of diseases caused by Leishmania protozoa which treatment is restricted to a limited number of drugs that exhibit high toxicity, collateral effects and are often costly. There are a variety of tropical plants distributed in Brazil, and for many poor people the therapy for several diseases is based mainly on the use of traditional herbal remedies. In this work, the cytotoxic activity of 17 plant methanol extracts was evaluated on several Leishmania species and murine macrophages. Among them, the extract of Casearia sylvestris, Piptocarpha macropoda, Trembleya parviflora, Samanea tubulosa and Plectranthus neochilus showed a promissing leishmanicidal activity, exhibiting IC50 values below of 20 µg/mL against at least one species of Leishmania. Casearia sylvestris showed the most expressive activity against all promastigote forms of Leishmania species (IC50 values of 5.4 µg/mL, 5.0 µg/mL, 8.5 µg/mL and 7.7 µg/mL for L. amazonensis, L. braziliensis, L. chagasi and L. major, respectively), being more effective than the reference drug miltefosine. In spite of the cytotoxic effect on macrophages (CC50 value of 5.2 µg/mL), C. sylvestris exhibited a strong inhibition against intracellular amastigotes of L. braziliensis (IC50 value of 1.3 µg/mL). Further studies, including bio-guided fractionation will be conducted to identify the active compounds.