Oxidative stress protection by manganese complexes of tail-tied aza-scorpiand ligands

Abstract

The Mn²⁺ coordination chemistry of double scorpiand ligands in which two polyazacyclophane macrocycles have been connected by pyridine, phenanthroline and bipyridine spacers has been studied by potentiometry, paramagnetic NMR and electrochemistry. All ligands show high stability with Mn²⁺ and the complexes were formed in a wide pH range. DFT calculations support the structures and coordination geometries derived from the study. A remarkable antioxidant activity was evidenced for these systems by the McCord-Fridovich assay and in Escherichiacoli sodAsodB deficient bacterial cells. The three systems were tested as anti-inflammatory drugs in human macrophages measuring the accumulation of cytokines upon lipopolysaccharide (LPS) pro-inflammatory effect. All complexes showed anti-inflammatory effect, being [Mn₂L1]⁴⁺ the most efficient one.

Keywords: Anti-inflammatory activity; Antioxidant activity; Bacteria; Double polyazamacrocyclic scorpiands; Mn(2+) complexes.