Hydrosoluble formazan XTT: its application to natural products drug discovery for Leishmania

• DOI: 10.1016/j.mimet.2003.08.013
• Publication Date: 2003-10-22T12:20:53Z
• Authors: C Williams
• Keywords: Formazan; Miltefosine; Colorimetry; Amastigote; Nitroblue tetrazolium

A colorimetric method for measuring the viability of Leishmania promastigotes is described that is based on the reduction of the tetrazolium salt, XTT, to a water-soluble formazan. Values obtained by the XTT method correlated well with parasite number (r=0.965) and with methods that rely upon the reduction of MTT or MTS (r=0.96 and 0.97, respectively). The IC(50) values obtained by XTT method with amphotericin-B, miltefosine and ketoconazole were similar to those previously reported by other methods. The XTT method proved to be a reliable and convenient method for the screening of methanolic extracts from 1059 plants and was used for the bioassay-guided fractionation of the alkaloid aegeline from Sarcorhachis naranjoana.