Bismuth complexes involving amino acids provide a model system for probing physiological interactions between bismuth and the abundant thiol-containing proteins in the digestive system, whose direct study would be prohibitively complex. Such interactions may prove beneficial in the improvement of pharmaceutical agents, especially bismuth containing metallodrugs. Interactions of bismuth pharmaceuticals including bismuth subnitrate, bismuth subsalicylate, and bismuth citrate with sulfur-containing biomolecules such as L-cysteine and glutathione were investigated by voltammetry and UV-vis spectroscopy in different pH environments to characterize the complex formation between the bismuth ion and the thiol-containing ligands. Experiments were carried out at pH 1 and 3 to mimic the acidity of stomach contents and pH 7.4, to mimic that of physiological conditions, to identify pH effects on complex formation. Cyclic voltammetry and square wave voltammetry were employed to identify reduction potential shifts that correspond to complex formation. Similarly, UV-vis spectroscopy was used to monitor complexation by a characteristic peak that forms near the 340 nm wavelength. Analysis showed that indeed the pH, the type of thiol-containing compound, and the starting bismuth pharmaceutical had an effect on the complex formation.

Electrochemical and spectroscopic investigations of bismuth ions with sulfur-containing biomolecules

ACS Spring 2022

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