Synthesis, structure and SOD activity of Mn complexes with symmetric Schiff base ligands derived from pyridoxal

Abstract

This study describes the synthesis, crystal structure and antioxidant activity of manganese(III) complexes with Schiff-base ligands obtained from condensation of pyridoxal with alkyl diamines: [Mn(pyr2en) (H2O)2]Cl 4H2O, [Mn(pyr2en)(H2O)(CH3OH)]Cl, [Mn(pyr2pn)(H2O)2]ClO4 and [Mn2(pyr2bn)3] 4H2O, where H2pyr2en = 1,2-bis(pyridoxylidenamino)ethane, H2pyr2pn = 1,3-bis(pyridoxylidenamino)propane and H2pyr2bn = 1,4-bis(pyridoxylidenamino)butane. The four complexes catalyze the dismutation of superoxide efficiently with IC50 values in the range of 1.22?2.15 lM, evaluated through the nitro blue tetrazolium photoreduction inhibition superoxide dismutase assay, in aqueous solution of pH 7.8. The length of the alkyl spacer in the diamine fragment plays a key role in the antioxidant activity of these complexes, with [Mn(pyr2pn)(H2O)2]ClO4 showing the lowest IC50 value.