Structure of transient radicals from cytostatic-active p-alkoxyphenols by continuous-flow EPR.
Para-alkoxyphenols are of medical significance as futural cytostatic drugs in antimelanoma chemotherapy. They take part in a radical redox-reaction in which the catalytically essential protein-linked tyrosyl radical in the functional subunit R2 of the growth-regulating enzyme ribonucleotide reductase (RR) is quenched. EPR spectroscopy has been employed in conjunction with a continuous-flow system to study the structure of transient radicals from p-alkoxyphenols with different alkyl chain lengths. Radicals of p-alkoxyphenols were generated by oxidation in a Fenton system (Ti3+/H2O2,pH1) after rapid mixing in a novel continuous-flow EPR cavity designed especially for low consumption of substance. Hyperfine structures identified by spectral simulation show that the structure of transient radicals from oxidized para-alkoxyphenols (methyl-, ethyl-, allyl-,propyl-,iso-propyl-, butyl-, iso-butyl-) belong to the type of phenoxyl radicals formed after abstraction of the OH proton. Hyperfine coupling constants are similar and vary only slightly with alkyl substituents.
Lassmann
G
G
Max-Delbrück-Center of Molecular Medicine, Berlin, Germany.
Pötsch
S
S
D000970:Antineoplastic Agents / Q000737:chemistry* / Q000378:metabolism / Q000627:therapeutic use; D001711:Biotransformation; D004578:Electron Spin Resonance Spectroscopy / Q000379:methods; D005609:Free Radicals; D006801:Humans; D008545:Melanoma / Q000188:drug therapy; D010084:Oxidation-Reduction; D010636:Phenols / Q000737:chemistry* / Q000378:metabolism / Q000627:therapeutic use; D013329:Structure-Activity Relationship
D000970:Antineoplastic Agents; D005609:Free Radicals; D010636:Phenols