title: Active oxygen species generated from photoexcited fullerene (C60) as potential medicines: O2-* versus 1O2.
abstract: To characterize fullerenes (C(60) and C(70)) as photosensitizers in biological systems, the generation of active oxygen species, through energy transfer (singlet oxygen (1)O(2)) and electron transfer (reduced active oxygen radicals such as superoxide anion radical O(2)(-)* and hydroxyl radical *OH), was studied by a combination of methods, including biochemical (DNA-cleavage assay in the presence of various scavengers of active oxygen species), physicochemical (EPR radical trapping and near-infrared spectrometry), and chemical methods (nitro blue tetrazolium (NBT) method). Whereas (1)O(2) was generated effectively by photoexcited C(60) in nonpolar solvents such as benzene and benzonitrile, we found that O(2)(-)* and *OH were produced instead of (1)O(2) in polar solvents such as water, especially in the presence of a physiological concentration of reductants including NADH. The above results, together with those of a DNA cleavage assay in the presence of various scavengers of specific active oxygen species, indicate that the active oxygen species primarily responsible for photoinduced DNA cleavage by C(60) under physiological conditions are reduced species such as O(2)(-)* and *OH.
authors.affiliation: Division of Organic Chemistry, National Institute of Health Sciences, 1-18-1 Kamiyoga, Setagaya, Tokyo 158-8501, Japan. yamakosh@nihs.go.jp
authors.forename: Yoko
authors.initials: Y
authors.lastname: Yamakoshi
authors.forename: Naoki
authors.initials: N
authors.lastname: Umezawa
authors.forename: Akemi
authors.initials: A
authors.lastname: Ryu
authors.forename: Kumi
authors.initials: K
authors.lastname: Arakane
authors.forename: Naoki
authors.initials: N
authors.lastname: Miyata
authors.forename: Yukihiro
authors.initials: Y
authors.lastname: Goda
authors.forename: Toshiki
authors.initials: T
authors.lastname: Masumizu
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Nagano
mesh_terms: D004278:DNA, Superhelical / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004578:Electron Spin Resonance Spectroscopy; D037741:Fullerenes / Q000737:chemistry* / Q000494:pharmacology; D017665:Hydroxyl Radical / Q000737:chemistry; D009243:NAD / Q000737:chemistry / Q000378:metabolism; D009580:Nitroblue Tetrazolium / Q000737:chemistry; D010777:Photochemistry; D017319:Photosensitizing Agents / Q000737:chemistry* / Q000494:pharmacology; D026082:Singlet Oxygen / Q000737:chemistry* / Q000494:pharmacology; D019265:Spectroscopy, Near-Infrared; D013481:Superoxides / Q000737:chemistry* / Q000494:pharmacology; D014867:Water / Q000737:chemistry
chemical_list: D004278:DNA, Superhelical; D037741:Fullerenes; D017319:Photosensitizing Agents; D014867:Water; D009243:NAD; D013481:Superoxides; D026082:Singlet Oxygen; D009580:Nitroblue Tetrazolium; D017665:Hydroxyl Radical; C069837:fullerene C60