Photosensitized formation of ascorbate radicals by riboflavin: an ESR study
| Autor: | Heasook Kim, Ionel Rosenthal, Louis J. Kirschenbaum, Peter Riesz |
|---|---|
| Rok vydání: | 1993 |
| Předmět: |
Antioxidant
Free Radicals Light Photochemistry Radical medicine.medical_treatment Riboflavin chemistry.chemical_element Flavin group Ascorbic Acid Biochemistry Oxygen Superoxide dismutase chemistry.chemical_compound medicine Physical and Theoretical Chemistry biology Superoxide Singlet oxygen Electron Spin Resonance Spectroscopy General Medicine Ascorbic acid Kinetics chemistry biology.protein |
| Zdroj: | Photochemistry and photobiology. 57(5) |
| ISSN: | 0031-8655 |
| Popis: | The riboflavin-sensitized photooxidation of ascorbate ion (HA-) to ascorbate radical (A.-) was followed by electron spin resonance (ESR) spectroscopy in conjunction with oxygen depletion measurements. In air-saturated aqueous media, steady-state amounts of A.- are rapidly established upon irradiation. The ESR signal disappears within a few seconds after the light is extinguished--more slowly under constant irradiation as oxygen is depleted. No photooxidation was observed in deaerated media. Similar results were obtained with other flavins and when ascorbyl palmitate was substituted for HA-. The effect of added superoxide dismutase, catalase, desferrioxamine, and singlet oxygen scavengers (NaN3 and tryptophan) was studied, as was replacement of water by D2O and saturation with O2. The results are indicative of ascorbate free radical production via direct reaction between ascorbate ion and triplet riboflavin in the presence of O2. While the presence of superoxide ion tends to reduce the steady-state concentration of A.-, competition from the reaction of HA- with singlet oxygen is less apparent in this system (at HA- > or = 1 mM) than in the previously studied aluminum phthalocyanine tetrasulfonate-photosensitized reaction. |
| Databáze: | OpenAIRE |
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