Anticancer agent 3-bromopyruvic acid forms a conjugate with glutathione

Background 3-Bromopyruvic acid (3-BP), a glycolytic inhibitor and a promising anticancer compound, induces oxidative stress and depletes cells of glutathione (GSH). The causes of GSH loss remain unclear. The aim of this study was to ascertain whether 3-BP forms a conjugate with glutathione. Methods GSH was incubated with various amounts of 3-BP and the extent of reaction was titrated with ¹H NMR and ¹H-¹H NMR. The reaction outcome was identified by MS/MS. Intracellular formation of the conjugate was assessed in cells treated with 3-BP and 3-BP(¹³C) and analyzed using the targeted LC-MS/MS method in negative ionization MRM mode. Results 3-BP was found to react with GSH in a 1:1 ratio forming an S-conjugate. The same conjugate was formed intracellularly in erythrocytes and MCF-7 cells. Conclusions 3-BP reacts with GSH in the absence of cells and intracellularly. This reaction appears to be the main cause of GSH loss in 3-BP treated cells.