AbstractThe interaction between glutathione and the DNA‐binding pyrrolobenzodiazepine (PBD) antitumour antibiotic anthramycin has been studied.A polar adduct has been shown to form as a result of nucleophilic attack of the thiol group of glutathione on the electrophilic C11‐position of the PBD. The kinetics of formation of the adduct have been studied by HPLC and NMR, and its structure has been confirmed by isolation through preparative HPLC, followed by1H NMR and mass spectral analysis.These results suggest a possible role for glutathione conjugation during the metabolism of PBDs such as anthramy