Amaryllidaceae alkaloids with anti-Trypanosoma cruzi activity

Abstract

Background: Chagas disease, caused by the protozoan Trypanosoma cruzi, is a neglected disease that affects ~7 million people worldwide. Development of new drugs to treat the infection remains a priority since those currently available have frequent side effects and limited efficacy at the chronic stage. Natural products provide a pool of diversity structures to lead the chemical synthesis of novel molecules for this purpose. Herein we analyzed the anti-T. cruzi activity of nine alkaloids derived from plants of the family Amaryllidaceae.

Methods: The activity of each alkaloid was assessed by means of an anti-T. cruzi phenotypic assay. We further evaluated the compounds that inhibited parasite growth on two distinct cytotoxicity assays to discard those that were toxic to host cells and assure parasite selectivity.

Results: We identified a single compound (hippeastrine) that was selectively active against the parasite yielding selectivity indexes of 12.7 and 35.2 against Vero and HepG2 cells, respectively. Moreover, it showed specific activity against the amastigote stage (IC₅₀ = 3.31 μM).

Conclusions: Results reported here suggest that natural products are an interesting source of new compounds for the development of drugs against Chagas disease.

Keywords: Alkaloids; Amaryllidaceae; Chagas disease; Cytotoxicity; Hippeastrine; Phenotypic assays; Trypanosoma cruzi.

Fig. 1

Chemical structures of the alkaloids evaluated in this study

Fig. 2

Quality controls of the T. cruzi growth inhibition assay (a, b), toxicity assay with Vero cells (c, d) and toxicity assay with HepG2 cells (e, f). Z’-values for each of the rounds launched are represented on the left (a, c, e); dashed line marks the 0.5 threshold. IC₅₀ and TC₅₀ values of the reference drugs BNZ and DTX are represented on the right (b, d, f); continuous lines indicate the average values, whereas the dashed lines indicate ± 3 SD limits

Fig. 3

Anti-T.cruzi phenotypic assay dose-response curves. Graphs represent mean results and SD of at least three biological replicates

Fig. 4

Dose-response curves obtained from the Vero and HepG2 cell toxicity assays. Vero cells toxicity assays are represented by circles and straight lines while HepG2 cell toxicity assays are represented by triangles and dashed lines. Graphs represent mean results and SD of at least three biological replicates

Fig. 5

Anti-amastigote dose response curves of hippeastrine and BNZ. Graphs represent mean results and SD of at least three replicates