In the course of selection of novel drug candidates for Chaga's disease from Brazilian
flora, we undertook the study of stem bark from Calophyllum brasiliense (Clusiaceae)1,2. After extraction, the MeOH extract was partitioned between MeOH:H2O and EtOAc. The organic phase displaying anti-Trypanosoma cruzi activity and was subjected to Sephadex LH-20 (MeOH), to yield nine fractions (A –
I). Through bio-guided fractionation, the activity was detected at fraction C, which
was subjected to silica gel column (hexane-EtOAc) resulting in four fractions (C1
– C4). Since the activity was detected in fraction C2, this material was purified
using preparative TLC to afford soulamarin (Figure 1), a previously isolated coumarin
from C. soulatrii
3. The structure of this compound was established on the basis of spectroscopic data,
mainly NMR and MS. Soulamarin showed activity against trypomastigotes of T. cruzi with an IC50 value of 85.3 µg/mL and a similar IC50 value to benznidazole (114.6 µg/mL). No hemolytic activity could be detected up to
150 µg/mL. By using the fluorimetric vital dye SYTOX Green, soulamarin induced permeabilization
of plasma membrane when compared to untreated group. Spectrofluorimetric data using
MitoTracker Red, demonstrated that soulamarin also induced a strong depolarization
of the mitochondrial membrane potential, reducing the fluorescence intensity by 97%
when compared to untreated group. These data suggest that the lethal effects of soulamarin
in T. cruzi involve damages to plasma membrane of the parasite, which may have contributed
to the mitochondrial disturbance and cell death. Considering the unique mitochondrion
of T. cruzi, secondary metabolites of plants as soulamarin may contribute as scaffolds for the
design of novel and selective drug candidates for neglected diseases. Support: FAPESP
and CNPq.
References:
[1] ABE F et al. Biol. Pharm. Bull. 2004, 27,141 – 143.
[2] NOLDIN VF et al. Quím. Nova 2006, 29, 3, 549 – 554.
[3] EE GCL et al. Molecules 2011, 16, 9721 – 9727.
