Reactions of the Antiarthritic Drug Aurothiomalate With Phenylmercury(II) Compounds: NMR Studies

Clinical formulations of the antiarthritic drug aurothiomalate sometimes contain phenylmercury(ll) compounds as antimicrobial preservative agents and, in the presence of para-chloromercuri-benzoate, aurothiomalate is a potent inhibitor of collagenase. By (1)H NMR spectroscopy, para-hydroxymercuribenzoate and para-hydroxymercuriphenylsulphonate were shown to react with aurothiomalate by complexing only with the terminal thiomalate of aurothiomalate oligomers, thereby converting them to ring complexes. The reaction was also detected by UV spectroscopy. The arylmercury complexes produced no change in the bulk of the thiomalate residues of aurothiomalate indicating considerable stability of the polymeric structure of aurothiomalate in which each gold is bound to two thiolate residues. The potent inhibition of the mercurial induced collagenase activity may be due either to aurothiomalate or to a complex formed between the terminal thiomalate residues with the arylmercurial. The arylmercury complexes may be unsuitable as antimicrobials in solutions of aurothiomalate because of complexation with the terminal thiomalate residues.