Properties of dihydroasparagusic acid and its use as an antidote against mercury(II) poisoning

Dihydroasparagusic acid is the first naturally occurring dimercaptanic compound that was isolated in 1948 from Asparagus concentrate. Although several synthetic procedures were proposed in the past decades for this natural substance, most of its chemical properties remain unstudied. In this work the capacity of the acid to act as an antidote against mercury(II) toxicity was evaluated in a simple biological model system, Saccharomyces cerevisiae, and is explained by the formation of a precipitate between mercury(II) and dihydroasparagusic acid. The precipitate was analyzed and studied. The solubility was determined by measuring in equilibrated solutions either the concentration of the total mercury(II) present in solution or the free concentration of hydrogen ions. The protonation constants were determined at 25 C and in 1.00 M NaCl, as constant ionic medium, by means of potential difference measurements of a galvanic cell with a glass electrode. The experimental data are explained by proposing the chemical composition of the precipitate and the value of its solubility product. As the solubility of the precipitate increases by increasing the concentration of dihydroasparagusic acid, the further formation of a complex between mercury(II) and dihydroasparagusic acid is assumed. Graphical abstract: [Figure not available: see fulltext.] © 2013 Springer-Verlag Wien.