Stability constants for metal complexation by isomers of mimosine and related compounds

Abstract

Stability constants for the Mg²⁺, Ca²⁺, Cu²⁺ and Zn²⁺ complexes of two isomers (2) and (3) of the defleecing agent mimosine (1) have been sought from potentiometric titrations in aqueous solution, 0.15 M KNO₃, at 37°. For the interpretation of the results, complex formation of the simpler ligands 3-hydroxypyridin-4(1H)-one (4), its 2-oxo isomer (5) and DL-α-amino-β-(6-oxo-1,6-dihydropyridin-2-yl)propanoic acid (6) was studied. The results with ligand (2) are very similar to those with mimosine, for which a computer blood-plasma model indicates metal chelation under physiological conditions. Ligand (3) is a much weaker complexing agent.