Carnosine and Related Compounds Protect Against Copper-Induced Damage of Biomolecules

At concentrations of 1 mM, the protective effects of carnosine and related compounds including anserine, homocarnosine, histidine, ${\beta}$-alanine were investigated against copper-catalyzed oxidative damage to deoxyribose, ascorbic acid, human serum albumin, liposome, and erythrocytes. Carnosine and anserine reduced Cu (II) to bathocuproine-reactive Cu (I) in a time- a and a dose-dependent manner while the others did not. Carnosine reduced 86% of $100\;{\mu}M$ Cu (II) in 60 min. Carnosine, homocarnosine, anserine, and histidine inhibited copper-catalyzed deoxyribose degradation by 75, 66, 65, and 45%, respectively. In the presence of $1\;{\mu}M$ Cu (II), carnosine and related compounds inhibited ascorbic acid oxidation by 55-85% after incubation for 20 min. In the presence of 0.15 mM ascorbic acid and 0.8 mM $H_2O_2$, carnosine, anserine, homocarnosine, and histidine inhibited copper-catalyzed oxidation of human serum albumin by 41, 21, 29, and 24%, respectively, as determined by carbonyl formation. These compounds also significantly inhibited copper-catalyzed liposomal lipid peroxidation as measured by malondialehyde and lipid hydroperoxides. Carnosine, anserine, homocarnosine, and histidine inhibited hemolysis of bovine erythrocytes induced by 0.1 mM Cu (II). These results suggest that histidine-containing dipeptides may play an important role in protecting against free radical-mediated tissue damage.