Affiliations: Department of Medicine and Therapeutics, Chinese University of Hong Kong, Shatin, Hong Kong
Correspondence:
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Corresponding author: Larry Baum, Department of Medicine and Therapeutics, Chinese University of Hong Kong, Shatin, Hong Kong. Tel.: +852 2632 3487; Fax: +852 2637 3852; E-mail: lwbaum@cuhk.edu.hk.
Note: [] Communicated by Craig S. Atwood
Abstract: Curcumin is a polyphenolic diketone from turmeric. Because of its anti-oxidant and anti-inflammatory effects, it was tested in animal models of Alzheimer's disease, reducing levels of amyloid and oxidized proteins and preventing cognitive deficits. An alternative mechanism of these effects is metal chelation, which may reduce amyloid aggregation or oxidative neurotoxicity. Metals can induce Aβ aggregation and toxicity, and are concentrated in AD brain. Chelators desferrioxamine and clioquinol have exhibited anti-AD effects. Using spectrophotometry, we quantified curcumin affinity for copper, zinc, and iron ions. Zn2+ showed little binding, but each Cu2+ or Fe2+ ion appeared to bind at least two curcumin molecules. The interaction of curcumin with copper reached half-maximum at ∼3–12 μM copper and exhibited positive cooperativity, with Kd1∼10–60 μM and Kd2∼1.3 μM (for binding of the first and second curcumin molecules, respectively). Curcumin-iron interaction reached half-maximum at ∼2.5–5 μM iron and exhibited negative cooperativity, with Kd1∼0.5–1.6 μM and Kd2∼50–100 μM. Curcumin and its metabolites can attain these levels in vivo, suggesting physiological relevance. Since curcumin more readily binds the redox-active metals iron and copper than redox-inactive zinc, curcumin might exert a net protective effect against Aβ toxicity or might suppress inflammatory damage by preventing metal induction of NF-κB.
