title: ESR and UV-Vis studies of semiquinone radical anion and hydroquinone generated by irradiation of 15-deacetyl-13-glycine substituted hypocrellin B.
abstract: 15-Deacetyl-13-glycine substituted hypocrellin B (GDHB) is a new type of hypocrellin derivative with enhanced red absorption longer than 600 nm and water solubility. When an anaerobic DMSO or DMSO-buffer (pH 7.4) solution of GDHB was illuminated with >470 nm light, a strong electron spin resonance (ESR) signal was formed. The ESR signal was assigned to the semiquinone anion radical of GDHB (GDHB*-) based on a series of experiments. GDHB*- was predominantly photoproducted via the self-electron transfer between the excited- and ground-state species. Decay of this species, both in the presence and absence of electron donor, was consistent with second-order kinetics. In aqueous solution, the TEMPO counter-spin experiment indicated the formation of GDHB*- that could not be detected by ESR method directly. The formation of GDHB*- and hydroquinone of GDHB (GDHBH*-) was also confirmed by spectrometric method. These findings suggested that GDHB was at least a favorable type I phototherapeutic agent.
authors.affiliation: Institute of Photographic Chemistry, Academia Sinica, Beijing, China.
authors.forename: S
authors.initials: S
authors.lastname: Yuzhu
authors.forename: A
authors.initials: A
authors.lastname: Jingyi
authors.forename: J
authors.initials: J
authors.lastname: Lijin
mesh_terms: D000693:Anaerobiosis; D000838:Anions; D003497:Cyclic N-Oxides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D005609:Free Radicals / Q000737:chemistry; D005998:Glycine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D006873:Hydroquinones / Q000737:chemistry; D010569:Perylene / Q000031:analogs & derivatives* / Q000737:chemistry / Q000528:radiation effects; D017319:Photosensitizing Agents / Q000737:chemistry*; D011721:Pyrenes / Q000737:chemistry* / Q000528:radiation effects*; D011809:Quinones / Q000737:chemistry* / Q000528:radiation effects*; D012996:Solutions; D013053:Spectrophotometry / Q000379:methods; D013113:Spin Labels; D014466:Ultraviolet Rays; D014867:Water
chemical_list: C404201:15-deacetyl-13-glycylhypocrellin B; D000838:Anions; D003497:Cyclic N-Oxides; D005609:Free Radicals; D006873:Hydroquinones; D017319:Photosensitizing Agents; D011721:Pyrenes; D011809:Quinones; D012996:Solutions; D013113:Spin Labels; D014867:Water; D010569:Perylene; D005998:Glycine; C003959:TEMPO; C064522:hypocrellin B; C031927:hydroquinone