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Free radical formation from the antineoplastic agent VP 16-213
J M Van Maanen1, C De Ruiter, P R Kootstra
1Department of Oncology, Free University Hospital, Amsterdam, The Netherlands.
Free Radical Research Communications
|January 1, 1986
Summary
Free radical formation from VP 16-213 was detected using ESR spectroscopy. This study identifies a specific free radical generated by VP 16-213 under oxidative conditions.
Area of Science:
- Biochemistry
- Chemical Biology
- Spectroscopy
Background:
- VP 16-213 is a compound with potential biological activity.
- Understanding its metabolic pathways and reactive intermediates is crucial for assessing its safety and efficacy.
- Free radical formation can be a key mechanism in drug metabolism and toxicity.
Purpose of the Study:
- To investigate the formation of free radicals from VP 16-213.
- To characterize the nature and stability of these radicals.
- To explore the role of enzymatic and electrochemical oxidation in VP 16-213 radical generation.
Main Methods:
- Electron Spin Resonance (ESR) spectroscopy was employed to detect and study free radicals.
- VP 16-213 was incubated with one-electron oxidants: persulphate-ferrous, myeloperoxidase (MPO)/hydrogen peroxide, and horseradish peroxidase (HRP)/hydrogen peroxide.
- Electrochemical oxidation of VP 16-213 was performed at +550 mV for spectral comparison.
- Radical stability was assessed by measuring half-life in a Tris buffer.
- Interactions with rat liver microsomes and microsomal protein were investigated.
Main Results:
- Incubation of VP 16-213 with persulphate-ferrous, MPO/H2O2, and HRP/H2O2 readily generated a free radical.
- ESR spectra from MPO/H2O2 and HRP/H2O2 incubations matched the spectrum of electrochemically oxidized VP 16-213.
- The generated free radical exhibited a half-life of 257 +/- 4 seconds under specified buffer conditions.
- The radical signal persisted upon addition of microsomal protein.
- No ESR signals were detected from incubations with rat liver microsomes and NADPH.
Conclusions:
- VP 16-213 can form a detectable free radical when exposed to specific one-electron oxidants.
- The radical species generated by enzymatic oxidation (MPO/H2O2, HRP/H2O2) is consistent with electrochemical oxidation products.
- The free radical is relatively stable and its formation is not inhibited by microsomal proteins.
- Metabolism of VP 16-213 by rat liver microsomes in the presence of NADPH does not appear to generate detectable free radicals via ESR.