Metal-chelating properties and antiviral activity of some 2-hydroxyphenyl amides

Influenza virus is an hot topic in medicinal chemistry and great efforts are ongoing for the discover of new antivirals able to overcome problems related to resistant strains and adverse side effects of current drugs. Influenza virus endonuclease is an attractive target for antiviral drug development and in particular the strategy to chelate the metal ion(s) within the active site proved to be an efficient mode to inhibit enzymatic activity. Our previous findings revealed that 2-hydroxyamide derivatives are able to chelate Mg2+ ions, forming complexes with different stoichiometric ratios. Here we report on the activity of the three ligands N-(4-fluorobenzyl)-2-hydroxybenzamide, N-(4-fluorobenzyl)-2,3-dihydroxybenzamide, and N1,N3-bis(4-fluorobenzyl)-2-hydroxyisophthalamide, containing the salicylic group, and their Mg2+ complexes (7)–(9), evaluated by means of virus yield assay in influenza virus-infected MDCK cells and vRNP reconstitution assay in HEK293T cells. In some cases, promising anti-influenza activities with EC50 values in the low micromolar range were found. As a contribute to clarify the activity in cells of the ligands, here we also present a study on the their coordinating properties towards the other essential metal ion Cu(II), carried out by potentiometric and calorimetric measurements.