Photosensitization by antitumor agents 2: Anthrapyrazole-photosensitized oxidation of ascorbic acid and 3,4-dihydroxyphenylalanine

A novel anthrapyrazole anticancer agent has been examined for photosensitizing properties. Illumination of the anthrapyrazole and ascorbic acid with blue light in aerated aqueous solutions causes SOD and catalasesensitive oxygen consumption, indicating involvement of both Superoxide radical and hydrogen peroxide in this process. Electron paramagnetic resonance showed that the ascorbyl radical is also produced during the photooxidation. When 3,4-dihydroxyphenylalanine (Dopa) is used as a substrate, production of hydrogen peroxide is evidenced by catalase-sensitive oxygen consumption. Generation of hydroxyl radicals during illumination of the drug and ascorbic acid (or Dopa) in the presence of catalytic amounts of the Fe(III)/EDTA complex is demonstrated using EPR and spin-trapping techniques.