Synthesis and antiradical activity of novel copper(II) complexes of long chain reduced Schiff base ligands

Abstract

Oxidative stress is the cause of many diseases and at the heart of it is the overproduction of reactive oxygen species (ROS). There are several protective enzymes, e.g., superoxide dismutases (SOD), able to decrease the level of ROS in the cell; however, a therapeutic use of these enzymes is problematic. Small molecule compounds and complexes able to scavenge free radicals such as superoxide anion radicals could be used instead. These compounds are often called SOD-mimics and various researches are interested in synthesis and study of these compounds. In our study, a series of Cu(II) complexes were synthesized, containing reduced Schiff base ligands prepared from salicylaldehyde and amino acids with longer chain length (5-aminopentanoic acid, 6-aminohexanoic acid, 8-aminooctanoic acid, 11-aminoundecanoic acid, and 12-aminododecanoic acid). Complexes prepared from these ligands are novel and were prepared using three different methods. An assay based on the ability to inhibit reduction of iodonitrotetrazolium dye by superoxide anion radicals was used to determine antiradical activity of the prepared complex. Most of the prepared complexes proved to be good antiradical agents compared to cystamine and the copper(II) complex with Schiff base type ligand N-salicylidene-β-alanine. The best IC50 values of the radical transfer of the prepared compounds were two complexes of N-(2-hydroxybenzyl)-11-aminoundecanoic acid: 97.0 ± 1.9 and 45.1 ± 0.5 μM.