Diketopiperazine alkaloids produced by the endophytic fungus Penicillium citrinum and evaluation of their antileishmanial activity

Chromatographic fractionation of the antileishmanial extract obtained from fermentation of the endophytic fungus Penicillium citrinum, isolated from leaves of Ageratum myriadenia, yielded three diketopiperazine alkaloids; cyclo(L-Pro-L-Leu) (1), cyclo-(L-Pro-L-Phe) (2) and tryprostatin B (3). The structures of these compounds were established on the basis of spectroscopic methods and comparison with the literature. Compounds 1 and 2 were active against both amastigote-like forms of Leishmania (Leishmania) amazonensis and intracelular amastigotes of L. (Leishmania) infantum with approximately 50% of parasite growth inhibition at 100 μM. None of the compounds were considered toxic against human leukemia monocyte cell line (THP-1) at 100 μM. It is the first report about isolation of these diketopiperazines from P. citrinum and their antileishmanial potential against L. (L.) infantum.   Key words: Microfungi, natural products, in vitro, Leishmania, amphotericin B, cytotoxic activity.