Effects of pH and Ligands on the Metals-Catalyzed Hydrolysis of Clioquinol Conjugates

概要

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Metals-catalyzed hydrolysis of clioquinol (C) conjugates, namely C-glucuronide (CG) and C-sulfate (CS), was examined to investigate the effects of pH and ligands on the activities. The initial rates of hydrolysis (V_o) of CG and CS were measured as a function of pH in systems containing various metals. The profiles of V_o of CG varied from metal to metal, but the order of V_o in the acidic pH region was Cu (II) > Fe (III) > Ni (II) > Zn (II) > Mn (II), Mg (II), Ca (II). Acid hydrolysis of CG in the absence of metals was negligible down to pH 1. The profiles of V_o of CS were similar to that of acid hydrolysis in the absence of metals, except for the Cu (II) system, which gave a higher V_o. Under the condition [substrate] : [Cu (II)] : [ligand]=1 : 10 : 10,the hydrolysis in the presence of various ligands was a pseudo-first order reaction (rate constant=k'). All ligands which coordinate to Cu (II) reduced the value of k'. Such metals-catalyzed hydrolysis may be one of the mechanism of hydrolysis of C conjugates to produce C-metal chelates in vivo.
社団法人日本薬学会の論文
1984-08-25