High- and low-spin Fe(III) complexes of various AGE inhibitors.

Density functional theory calculations [CPCM/UM06/6-31+G(d,p)] were used to elucidate the structures and relative stability of Fe(III) complexes with various ligands that inhibit the formation of advanced glycation end products (AGEs) or iron overloaded disease (viz. aminoguanidine, pyridoxamine, LR-74, Amadori compounds, and ascorbic acid). EDTA was used as the free energy reference ligand. The distorted neutral octahedral complex containing one iron atom and three molecules of pyridoxamine [Fe(PM)(3)] was found to be the most stable. The stability of the complexes decreases in the following chelate sequence: pyridoxamine, Amadori complex, aminoguanidine, LR inhibitor, and ascorbic acid.