Malaria is a disease caused by protozoa of the genus Plasmodium. The treatment of
malaria is becoming increasingly difficult with the expansion of the cases of parasites
resistant to drugs used in therapy. In this context, products isolated from plants have give
an important contribution, representing an important source for obtaining new antimalarial
drugs. Antiplasmodial activity of alkaloids of plant origin has been widely reported in the
literature. Plants of the Apocynaceae family, rich in indole alkaloids have medicinal
properties and some large species of the genus Aspidosperma have demonstrated
antimalarial potential. Thus, this study aimed to perform a phytochemical approach,
evaluate the antiplasmodial activity and toxicity in vitro preliminary of the hydroethanolic
extract from the bark of A. excelsum, native of the Amazon region, where it is traditionally
used to treat various diseases, including malaria. Antiplasmodial activity in vitro of different
concentrations of the extract and alkaloidal and methanolic fractions was evaluated in
cultures of P. falciparum W2 by the percentage of inhibition of parasitaemia and the mean
inhibitory concentration (IC50) was determined at intervals of 24, 48 and 72 h. The
cytotoxicity assay of the extract and alkaloidal fraction was carried out on L929 mouse
fibroblasts by MTT method and the testing of acute oral toxicity of the extract was carried
out according to the Fixed Dose Procedure adopted by the OECD with small modifications.
The phytochemical approach revealed the presence of saponins, reducing sugars, phenols
and tannins and alkaloids, and these were confirmed in significant amounts in the
alkaloidal fraction with chloroform fraction (C2). Through thin layer chromatography and
high performance liquid chromatography of the extract characterized the presence of the
indole alkaloid yohimbine. The extract and fractions showed antiplasmodial activity in vitro.
The extract showed the best activity in 24 h (IC50 = 5.2 ± 4.1 μg / mL), indicating a good
activity schizonticide. Only C2 alkaloidal fraction showed a small but significant cytotoxicity
(concentrations higher than 800 μg/mL). The extract not only cytotoxicity but also did not
showed any obvious sign of toxicity in acute oral dose of 5000 mg/mL. The results indicate
that the extract of Aspidosperma excelsum Benth presents promising potential antimalarial
and deserves more detailed studies on antiplasmodial activity, aiming the isolation of
active compounds and elucidation of their mechanisms of action.
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