Stability Constants of Some Metal Complexes Formed by Mimosine and Related Compounds

Abstract

Complex formation of the biologically active amino acid L-mimosine [α-amino-β-(3-hydroxy-4-oxo-1,4-dihydropyridin-1-yl)propanoic acid (1)], mimosinic acid (2), mimosine methyl ether (9) and 3-hydroxy-1-methylpyridin-4(1H)-one (4) with Cu²⁺, Zn²⁺, Cd²⁺ and Pb²⁺ was studied. Stability constants were determined by potentiometric titration in 0.15_M KNOB₃ as inert electrolyte at 37º. In the monomeric complexes formed by the mimosine derivatives, metal binding by the hydroxypyridone moiety was favoured relative to the amino acid group. With mimosine, dimeric complexes were major species. Under physiological conditions, mimosine binds copper and zinc ions more strongly than do simpler amino acids.