Analysis of two new degradation products of arsenic triglutathione in aqueous solution

Inorganic arsenicals, including arsenite (As^III) and arsenate (As^V), are well-known human carcinogens. Recently, studies have indicated that arsenic triglutathione (As(GS)₃) is unstable in an aqueous solution. The present study was designed to evaluate the degradation mechanism of As(GS)₃ in an aqueous solution using high-performance liquid chromatography-electrospray ionisation mass spectrometry (HPLC-ESI-MS). Based on the fragments obtained from MS² and MS³, we identified two new compounds: one was an isomer of glutathione (GSH), and the other was a product from the cleavage of the glutamyl of oxidised glutathione (GSSG). The isomerization of GSH resulted in the loss of its function such as detoxification of many reactive metabolites. The formation of the two new compounds affected the ratio of GSH/GSSG, and thus may affect the antioxidant and detoxification of GSH/GSSG in mammalian cells.