title: Photochemical generation of superoxide radical and the cytotoxicity of phthalocyanines.
abstract: The effect of the central metal atom on the photodynamic activity of phthalocyanine dyes has been estimated by cytotoxicity to cultured Chinese hamster cells. Chloroaluminium phthalocyanine,, followed by the Zn- derivate, were found to be the only active dyes. In parallel it was found that visible light (615 +/- 10 nm) excitation of phthalocyanines dissolved in dimethylsulphoxide in the presence of oxygen generates superoxide radical anion. O2- radicals were spin--trapped with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and identified by electron spin resonance. The quantum yields for O2- generation range from 10(-5) (Zn-phthalocyanine) to 4.2 X 10(-4) (Ga-phthalocyanine). The efficiency of generating O2- was apparently uncorrelated with the phototoxicity of the same dyes. Furthermore, the biological photodamage could not be inhibited by the addition of superoxide dismutase. It is concluded that O2- is involved very little, if at all, in the phthalocyanine-induced photo-killing of mammalian cells.
mesh_terms: D000818:Animals; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D006224:Cricetinae; D003412:Cricetulus; D003497:Cyclic N-Oxides; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals; D007211:Indoles / Q000494:pharmacology*; D054833:Isoindoles; D010777:Photochemistry; D010778:Photochemotherapy; D013482:Superoxide Dismutase / Q000494:pharmacology; D013481:Superoxides
chemical_list: D003497:Cyclic N-Oxides; D005609:Free Radicals; D007211:Indoles; D054833:Isoindoles; D013481:Superoxides; C017245:5,5-dimethyl-1-pyrroline-1-oxide; D013482:Superoxide Dismutase; C013647:phthalocyanine