Structure–activity relationship of (−) mammea A/BB derivatives against Leishmania amazonensis

To study the structure–activity relationship of coumarin (−) mammea A/BB isolated from the CH2Cl2 extract of Calophyllum brasiliense leaves, we evaluated the antileishmanial activity of natural, synthetic and derivatives of this coumarin, against promastigote and intracellular amastigote forms of Leishmania amazonensis, and their cytotoxicity to J774G8 murine macrophages. The derivatives were obtained by hydrogenation and methoxylation reactions. The compound structures were elucidated on the basis of spectroscopic data. The compounds 5,7-dihydroxy-8-(2-methylbutanoyl)-6-(3-methylbutyl)-4-phenyl-chroman-2-one (3), 7-hydroxy-5-methoxy-8-(2-methylbutanoyl)-6-(3-methylbut-2-en-1-yl)-4-phenylcoumarin (4) and 5,7-dimethoxy-8-(1-methoxy-2-methylbutyl)-6-(3-methylbut-2-en-1-yl)-4 phenylcoumarin (6) were more biologically active than the compound (−) mammea A/BB (1) (7.4 μM), with IC50 values from 0.9, 2.4 and 1.9 μM respectively; compound (3) displayed the highest activity. The compounds mammea B/BB (2), 5,7-dimethoxy-8-(2-methylbutanoyl)-6-(3-methylbut-2-en-1-yl)-4-phenylcoumarin (5) and 5,7-dihydroxy-4-phenylcoumarin (7) were less active than (−) mammea A/BB (1), with IC50 of 30.1, 15.1 and 60.2 μM respectively; compound (7) showed the lowest antileishmanial activity of all. Compounds (1), (3), (4) and (6) were active not only against promastigote forms of L. amazonensis, but also against intracellular amastigote forms with IC50 of 14.3, 0.6, 34.0 and 22.2 μM, respectively. Interestingly, compound (3) showed the most antileishmanial activity of all. This study demonstrated that several aspects of the structure were important for antileishmanial activity.