Synthesis of cinnamic acid derivatives and leishmanicidal activity against Leishmania braziliensis.

Leishmania braziliensis is one of the pathogenic agents of cutaneous and mucocutanoeous leishmaniasis. There are no validated vaccines to prevent the infection and the treatment relies on drugs that often present severe side effects, which justify the efforts to find new potential antileishmanial drugs. An alternative to promote the discovery of new drugs would be the association of different chemical groups of bioactive compounds. Here we describe the synthesis and bioactivity evaluation against L. braziliensis of cinnamic acid derivatives possessing isobenzofuranone and 1,2,3-triazole functionalities. We tested 25 compounds at 10 µM concentration against extracellular promastigotes and intracellular amastigotes during macrophage infection. Most compounds were more active against amastigotes than to promastigotes. The derivatives (E)-3-oxo-1,3-dihydroisobenzofuran-5-yl-(3,4,5-trimethoxy) cinnamate (5c), (1-(3,4-difluorobenzyl)-1H-1,2,3-triazol-4-yl)methyl cinnamate (9g), and (1-(2-bromobenzyl)-1H-1,2,3-triazol-4-yl)methyl cinnamate (9l) were the most effective presenting over 80% toxicity on L. braziliensis amastigotes. While compound 5c is a cinnamate with an isobenzofuranone portion, 9g and 9l are triazolic cinnamic acid derivatives. The action of these compounds was comparable to amphotericin B used as positive control. Ultrastructural analysis revealed that 5c-treated parasites showed impaired cytokinesis and apoptosis triggering. Taken together, these results highlight the potential of cinnamic acid derivatives in development of novel anti-leishmanial drugs.

Synthetic analogues of the natural compound cryphonectric acid interfere with photosynthetic machinery through two different mechanisms.

A series of isobenzofuran-1(3H)-ones (phthalides), analogues of the naturally occurring phytotoxin cryphonectric acid, were designed, synthesized, and fully characterized by NMR, IR, and MS analyses. Their synthesis was achieved via condensation, aromatization, and acetylation reactions. The measurement of the electron transport chain in spinach chloroplasts showed that several derivatives are capable of interfering with the photosynthetic apparatus. Few of them were found to inhibit the basal rate, but a significant inhibition was brought about only at concentrations exceeding 50 µM. Some other analogues acted as uncouplers or energy transfer inhibitors, with a remarkably higher effectiveness. Isobenzofuranone addition to the culture medium inhibited the growth of the cyanobacterium Synechococcus elongatus , with patterns consistent with the effects measured in vitro upon isolated chloroplasts. The most active derivatives, being able to completely suppress algal growth at 20 µM, may represent structures to be exploited for the design of new active ingredients for weed control.