A Complete Physicochemical Identity Card of S-nitrosoglutathione

S-nitrosoglutathione (GSNO) is one of low molecular weight S-nitrosothiols occuring in humans. Nowadays, it is widely used as a nitric oxide donor for in vitro, ex vivo and in vivo experiments related to the investigation of its pathophysiological role as well as in clinical trials, aimed at its potential therapeutic use. Despite numerous reports on this physiological molecule, its quality control does not match the criteria required by competent pharmaceutical authorities. Hereby, an extensive physicochemical characterisation of synthesised and purified GSNO is provided for the first time. Indeed, structural identification including spectrometric, thermal and elemental analyses was consistent with the GSNO structure. An ion-pairing reversed phase HPLC system was developed to assess (i) GSNO content with UV detection at 334 nm, and (ii) fingerprint of its impurities coming from synthesis process and/or storage conditions, at 220 nm. The assynthesised product showed a content of 102.5 %, with respect to a commercially available standard. The identified impurities, i.e. chloride, nitrite, nitrate, reduced glutathione and glutathione disulfide, were also quantified basing on pharmaceutical requirements. Main products released during various storage conditions (pH, temperature, dioxygen, …) were disulfide glutathione and nitrite ion. Recommendations are given for the safe use of GSNO in biological and pharmacological experiments.