Emodin derivatives with multi-factor anti-AD activities: AChE inhibitor, anti-oxidant and metal chelator

Four new emodin derivatives which inhibit Alzheimer's disease were designed and the related activities such as cholinesterase inhibitor, anti-oxidant and metal chelator were evaluated. Among them, compounds a and b had comparable inhibitory activities of acetylcholinesterase to control drug tacrine. In particular, compound a had the strongest inhibitory effect on acetylcholinesterase with IC 50 value of 0.067 μM. Kinetic analysis of a and b indicated the mixed-type inhibition. Molecular simulation studies showed that they could bind both the catalytically active site and the peripheral anion site of acetylcholinesterase. The antioxidant activities were determined using the superoxide radical ( . O 2 – ) and hydroxyl radical ( . OH) assays. All derivatives showed high anti-oxidative activities. The mechanisms of electrochemical oxidation of emodin and its derivations were studied by cyclic voltammetry. In addition, compounds a-d exhibited obvious chelating abilities with Cu 2+ , Fe 3+ , Zn 2+ and Al 3+ ions. Interestingly, complexes chelated with Cu 2+ and Zn 2+ showed better acetylcholinesterase inhibitory activities and antioxidative activities. Taken together, emodin derivatives have multi-factor anti-Alzheimer's disease activities, and they are worthy of further study as potential candidate drugs for Alzheimer's disease.