Altered sterol profile induced in Leishmania amazonensis by a natural dihydroxymethoxylated chalcone

The effects of the antileishmanial chalcone 2',6'-dihydroxy-4'-methoxychalcone (DMC) on Leishmania amazonensis sterol composition and biosynthesis were investigated to obtain information about the mechanism of growth inhibition by DMC on this parasite. The interference of sterol biosynthesis by DMC was studied in drug-treated promastigotes by two different methods. (i) Newly synthesized sterols from parasites grown in the presence of [H-3]mevalonate were analysed by thin layer chromatography (TLC)/fluorography. (ii) Total sterols extracted from the parasites grown with or without DMC were characterized by gas chromatography coupled to mass spectroscopy (GC/MS). TLC and GC/MS analyses of sterols extracted from DMC-treated promastigotes revealed the accumulation of early precursors and a reduction in the levels of C-14 demethylated and C-24 alkylated sterols, as well as a reduction in exogenous cholesterol uptake. This study demonstrates that the natural chalcone DMC alters the sterol composition of L. amazonensis and suggests that the parasite target is different from other known sterol inhibitors.