Cinnamide Derivatives as Mammalian Arginase Inhibitors: Synthesis, Biological Evaluation and Molecular Docking

Arginases are enzymes that are involved in many human diseases and have been targeted for new treatments. Here a series of cinnamides was designed, synthesized and evaluated in vitro and in silico for their inhibitory activity against mammalian arginase. Using a microassay on purified liver bovine arginase (b-ARG I), (E)-N-(2-phenylethyl)-3,4-dihydroxycinnamide, also named caffeic acid phenylamide (CAPA), was shown to be slightly more active than our natural reference inhibitor, chlorogenic acid (IC50 = 6.9 +/- 1.3 and 10.6 +/- 1.6 mu M, respectively) but it remained less active that the synthetic reference inhibitor N-omega-hydroxy-nor-L-arginine nor-NOHA (IC50 = 1.7 +/- 0.2 mu M). Enzyme kinetic studies showed that CAPA was a competitive inhibitor of arginase with Ki = 5.5 +/- 1 mu M. Whereas the activity of nor-NOHA was retained (IC50 = 5.7 +/- 0.6 mu M) using a human recombinant arginase I (h-ARG I), CAPA showed poorer activity (IC50 = 60.3 +/- 7.8 mu M). However, our study revealed that the cinnamoyl moiety and catechol function were important for inhibitory activity. Docking results on h-ARG I demonstrated that the caffeoyl moiety could penetrate into the active-site pocket of the enzyme, and the catechol function might interact with the cofactor Mn2+ and several crucial amino acid residues involved in the hydrolysis mechanism of arginase. The results of this study suggest that 3,4-dihydroxycinnamides are worth being considered as potential mammalian arginase inhibitors, and could be useful for further research on the development of new arginase inhibitors.