Antileishmanial activity of the violacein extracted from Chromobacterium violaceum.

Sir, Leishmaniasis is a disfiguring and sometimes fatal protozoan disease, affecting more than 12 million people worldwide. The drugs used to treat the disease were developed more than 50 years ago and are potentially toxic. Leishmania amazonensis is very common in Brazil and is associated with different forms of the disease, including cutaneous, hyperergic mucocutaneous, anergic diffuse cutaneous and visceral leishmaniasis. 1,2 The violacein {3-[1,2-dihydro-5(5-hydroxy-1H-indol-3-yl)-2-oxo-3H-pyrrol-3-ylidene]1,3dihydro-2H-indol-2-1} extracted from Chromobacterium violaceum was obtained as described previously. 3,4 Briefly, C. violaceum (CCT 3496) was cultivated on cotton in modified 1 L Roux bottles, was extracted with commercial ethanol, and was purified by filtration, Soxhlet extraction, crystallization and high-performance liquid chromatography. The violacein was analysed and identified by NMR spectroscopy, thermogravimetric analysis, mass spectrometry, UV-VIS spectroscopy and infrared spectroscopy. An in vitro assay was performed with promastigote forms from L. amazonensis (MHOM/BR/77/LTB0016) in order to determine the ED50. Infective promastigotes containing a high percentage of metacyclic forms were grown at 26� C in Schneider’s Drosophila medium 5 (Gibco, Paisley, UK) supplemented with 10% (v/v) heat-inactivated fetal calf serum. Cells were harvested in the late log phase, resuspended in fresh medium, counted in a Neubauer