Design, synthesis, antimicrobial and antioxidant activity of 3-formyl chromone hydrazone and their metal (II) complexes

In search of a new antimicrobial and antioxidant with improved potency, we designed and synthesized a pair of chromone hydrazones and their transition metal complexes. The characterization and elucidation of the structure of the prepared compounds were performed by elemental analysis, IR, electronic, EPR and thermo gravimetric analyzes, as well as conductivity and magnetic susceptibility measurements. The EPR spin Hamiltonian parameters of copper complexes were calculated. The spectroscopic data showed that the ligands act as a monobasic tridentate. The coordination sites with the metal (II) ion are pyrone oxygen, azomethine nitrogen and hydrazonic oxygen. Hydrazones and their metal complexes have shown antimicrobial activity against Gram-positive bacteria (S. aureus and B. subtilis); Gram-negative bacteria (P. aeruginosa and E. coli) and fungus (C. albicans) and also the synthesized ligands were tested for their antioxidant activity in vitro by DPPH scanning and the ABTS radical method. The substitution requirements for favorable antioxidant activity were investigated. Compounds containing a phenolic hydroxyl group at the imine (azomethine) position as well as an additional electron donor group exhibited lower IC50 values and the result shows that all hydrazones have a significant antioxidant activity compared to the standard antioxidants Trolox. (C) 2017 Elsevier B.V. All rights reserved.