title: Free radical formation from the antineoplastic agent VP 16-213.
abstract: Free radical formation from VP 16-213 was studied by ESR spectroscopy. Incubation of VP 16-213 with the one-electron oxidators persulphate-ferrous, myeloperoxidase (MPO)/hydrogen peroxide and horseradish peroxidase (HRP)/hydrogen peroxide readily led to the formation of a free radical. The ESR spectra obtained in the last two cases, were in perfect accord with that of a product obtained by electrochemical oxidation of VP 16-213 at +550 mV. The half-life of the free radical in 1 mM Tris (pH 7.4), 0.1 M NaCl at 20 degrees C, was 257 +/- 4 s. The signal recorded on incubation with HRP/H2O2 or MPO/H2O2 did not disappear on addition of 0.3 - 1.2 mg/ml microsomal protein. From incubations with rat liver microsomes in the presence of NADPH, no ESR signals were obtained.
authors.affiliation: Department of Oncology, Free University Hospital, Amsterdam, The Netherlands.
authors.forename: J M
authors.initials: JM
authors.lastname: Van Maanen
authors.forename: C
authors.initials: C
authors.lastname: De Ruiter
authors.forename: P R
authors.initials: PR
authors.lastname: Kootstra
authors.forename: J
authors.initials: J
authors.lastname: De Vries
authors.forename: H M
authors.initials: HM
authors.lastname: Pinedo
mesh_terms: D000818:Animals; D004578:Electron Spin Resonance Spectroscopy; D005047:Etoposide; D005609:Free Radicals; D066298:In Vitro Techniques; D008297:Male; D008862:Microsomes, Liver; D051381:Rats
chemical_list: D005609:Free Radicals; D005047:Etoposide