Bifunctional antioxidant enzyme mimics of albumin-binding salphen Schiff-base metal complexes

Abstract

New kinds of bifunctional antioxidant enzyme mimics were prepared, and their superoxide anion radical (O2•–) and hydroxyl radical (•OH) scavenging activity was investigated. These conjugates were prepared by binding insoluble salphen [N,N-(phenylene)salicylidene] Schiff-base metal complexes (HO-salphen-M, M = Co, Mn, Cu) with bovine serum albumin (BSA). They were characterized by UV–vis spectra, circular dichroism (CD), and native polyacrylamide gel electrophoresis (PAGE). It showed that the binding mode was an axial coordination between HO-salphen-Co and amino acid residue of BSA. The structure of BSA was maintained when the binding amount of HO-salphen-Co was less than 10. After combining HO-salphen-Co into BSA, the low solubility of HO-salphen-Co was overcome, and the O2•– and •OH scavenging activity of BSA was improved two orders of magnitude. In similar inhibitory value, the scavenging rate of salphen-Co20@BSA was far higher than -others. The scavenging activity of different proportion salphen-Co@BSA was salphen-Co20@BSA > salphen-Co10@BSA > salphen-Co5@BSA > salphen-Co2@BSA. But salphen-Cu@BSA and salphen-Mn@BSA did not show •OH scavenging activity.