Antitrypanosomal Alkaloids from the Marine Bacterium Bacillus pumilus

Fractionation of the ethyl acetate extract of the marine bacterium Bacillus pumilus isolated from the black coral Antipathes sp. led to the isolation of five compounds: cyclo-(L-Leu-L-Pro) (1), 3-hydroxyacetylindole (2), N-acetyl-beta-oxotryptamine (3), cyclo-(L-Phe-L-Pro) (4), and 3-formylindole (5). The structures of compounds 1-5 were established by spectroscopic analyses, including HRESITOF-MS and NMR (H-1, C-13, HSQC, HMBC and COSY). Compounds 2, 3 and 5 caused the inhibition on the growth of Trypanosoma cruzi (T. cruzi), with IC50 values of 20.6, 19.4 and 26.9 mu M, respectively, with moderate cytotoxicity against Vero cells. Compounds 1-5 were found to be inactive when tested against Plasmodium falciparum and Leishmania donovani, therefore showing selectivity against T. cruzi parasites.