Superoxide dismutase activity of macrocyclic polyamine complexes

Copper(II) and nickel(II) complexes of macrocyclic polyamine derivatives possessing partial oligopeptide-like structures are found to suppress the xanthine-xanthine oxidase-mediated reduction of nitroblue tetrazolium and also to suppress formazan formation by potassium superoxide. The activity in the superoxide dismutase assay is dependent on ring size, type and number of donor atoms, metal ion, and substituents on the macrocycles. Some of those are more active than the known O₂^? scavengers such as copper(II)-salicylate and copper(II)-amino acid (or peptide) complexes. Nickel (II)-naphthylmethyl-dioxo-16]ane N₅, 13, 1 : 1 complex (NiH_?2L) is the most active among the 30 chelates examined.