Interaction of curcumin with Al(III) and its complex structures based on experiments and theoretical calculations

Curcumin has been recognized as a potential natural drug to treat the Alzheimer’s disease (AD) by chelating baleful metal ions, scavenging radicals and preventing the amyloid β (Aβ) peptides from the aggregation. In this paper, Al(III)–curcumin complexes with Al(III) were synthesized and characterized by liquid-state 1H, 13C and 27Al nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet spectroscopy (UV) and generalized 2D UV–UV correlation spectroscopy. In addition, the density functional theory (DFT)-based UV and chemical shift calculations were also performed to view insight into the structures and properties of curcumin and its complexes. It was revealed that curcumin could interact strongly with Al(III) ion, and form three types of complexes under different molar ratios of [Al(III)]/[curcumin], which would restrain the interaction of Al(III) with the Aβ peptide, reducing the toxicity effect of Al(III) on the peptide.