Caffeic acid and related natural compounds were previously described as Leishmania amazonensis arginase (L-ARG) inhibitors, and against the whole parasite in vitro. In this study, we tested cinnamides that were previously synthesized to target human arginase. The compound caffeic acid phenethyl amide (CAPA), a weak inhibitor of human arginase (IC50 = 60.3 ± 7.8 μM) was found to have 9-fold more potency against L-ARG (IC50 = 6.9 ± 0.7 μM). The other compounds that did not inhibit human arginase were characterized as L-ARG, showing an IC50 between 1.3–17.8 μM, and where the most active was compound 15 (IC50 = 1.3 ± 0.1 μM). All compounds were also tested against L. amazonensis promastigotes, and only the compound CAPA showed an inhibitory activity (IC50 = 80 μM). In addition, in an attempt to gain an insight into the mechanism of competitive L-ARG inhibitors, and their selectivity over mammalian enzymes, we performed an extensive computational investigation, to provide the basis for the selective inhibition of L-ARG for this series of compounds. In conclusion, our results indicated that the compounds based on cinnamoyl or 3,4-hydroxy cinnamoyl moiety could be a promising starting point for the design of potential antileishmanial drugs based on selective L-ARG inhibitors.

Arginase is a metalloenzyme that plays a central role in Leishmania infections. Previously, rosmarinic and caffeic acids were described as antileishmanial agents and as Leishmania amazonensis arginase inhibitors. Here, we describe the inhibition of arginase in L. amazonensis by rosmarinic acid analogs (1–7) and new caffeic acid-derived amides (8–10). Caffeic acid esters and amides were produced by means of an engineered synthesis in E. coli and tested against L. amazonensis arginase. New amides (8–10) were biosynthesized in E. coli cultured with 2 mM of different combinations of feeding substrates. The most potent arginase inhibitors showed Ki(s) ranging from 2 to 5.7 μM. Compounds 2–4 and 7 inhibited L. amazonensis arginase (L-ARG) through a noncompetitive mechanism whilst compound 9 showed a competitive inhibition. By applying an in silico protocol, we determined the binding mode of compound 9. The competitive inhibitor of L-ARG targeted the key residues within the binding site of the enzyme, establishing a metal coordination bond with the metal ions and a series of hydrophobic and polar contacts supporting its micromolar inhibition of L-ARG. These results highlight that dihydroxycinnamic-derived compounds can be used as the basis for developing new drugs using a powerful tool based on the biosynthesis of arginase inhibitors.

Arginase is a metalloenzyme that plays a central role in Leishmania infection. Previously, rosmarinic and caffeic acids were described as antileishmanial and as a Leishmania amazonensis arginase inhibitor and now, we describe the inhibition of arginase in L. amazonensis by rosmarinic acid analogs (1-7) and new caffeic acids derived amides (8-10). Caffeic acid esters and amides were produced by means of the engineered synthesis in E. coli and tested against L. amazonensis arginase. New amides (8-10) were biosynthesized in E. coli cultured with 2 mM of different combinations of feeding substrates. The most potent arginase inhibitors showed Ki(s) between 2 - 5.7 μM. Compounds 2-4 and 7 inhibited L-ARG through a noncompetitive mechanism, and 9 showed a competitive inhibition. By applying an in silico protocol we determined the binding mode of compound 9. The competitive inhibitor of L-ARG targets key residues within the binding site of the enzyme establishing a metal coordination bond with the metal ions as well as a series of hydrophobic and polar contacts supporting its micromolar inhibition of L-ARG. These results highlight that the dihydroxycinnamic-derived compounds can be used as the basis for the development of new drugs using a powerful tool based on the biosynthesis of arginase inhibitors.

As leishmanioses constituem um complexo de doenças causadas por protozoários do gênero Leishmania. São transmitidas pela picada de fêmeas parasitadas do gênero Phlebotomus e/ou Lutzomyia. A leishmaniose é uma doença zoonótica que afeta mais de 12 milhões de pessoas no mundo, e constituem uma preocupação para a saúde pública. A arginase de Leishmania é a primeira enzima da via das poliaminas e constitui um importante alvo terapêutico devido ao seu papel ativo na sobrevivência do parasita no hospedeiro. Neste trabalho, 78 moléculas sintéticas e naturais de diferentes grupos químicos foram testadas com objetivo de determinar a sua capacidade de inibição da enzima arginase recombinante de Leishmania (L.) amazonensis (ARG-LA). Foram considerados inibidores da ARG-LA os compostos que apresentaram uma inibição ≥ 70% a 100 µM. Os resultados revelaram 28,2 % de compostos com elevado potencial de inibição da ARG-LA, exibindo valores de IC50 na faixa micromolar. A cinética de inibição foi determinada pelo método de Dixon e Cornish-Bowden e revelou diferentes mecanismos de inibição enzimática. As moléculas sintéticas com potencial inibitório da ARG-LA correspondem aos ésteres e cinamidas biosintéticos, cinamidas derivados do ácido cafeico e pirazolopirimidinas. Além disso, foram testados 4 compostos naturais estruturalmente relacionados ao ácido caféico: piceatannol e 3 ácidos salvianólicos (A, B e D). Os resultados poderão servir de ponto de partida para o planejamento e síntese de novos fármacos para tratamento da leishmaniose, baseado na inibição da ARG-LA.