Complexation between γ-L-glutamylhistamine, Zn(II) ions, and molecular oxygen in aqueous solutions of NaClO4 and Zn(NO3)2

The antioxidant properties and mechanism of action of a natural aminoacyl derivative of histamine, namely, γ-L-glutamylhistamine (γ-Glu-HA), were studied in various model redox systems. It was found that γ-Glu-HA, in the presence of zinc salts, exhibits superoxide dismutase activity and that some of its pharmacological properties are enhanced. Labile charge-transfer complexes nZn.O 2 .mL (L = γ-Glu-HA) were detected in 0.1 M NaClO 4 at pH 6 in the presence of the dipeptide using ac voltammetry with a stationary dropping mercury electrode. Spectrophotometric analysis of a solution of 1 mM γ-Glu-HA in the presence of 1 mM Zn(NO 3 ) 2 and atmospheric oxygen revealed an absorption band at λ m a x = 232 nm, which was assigned to the labile oxo complex.