Laser Access to Quercetin Radicals and Their Repair by Co-antioxidants
| العنوان: | Laser Access to Quercetin Radicals and Their Repair by Co-antioxidants |
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| المؤلفون: | Tim Kohlmann, Martin Goez |
| المصدر: | Chemistry (Weinheim an Der Bergstrasse, Germany) |
| سنة النشر: | 2020 |
| مصطلحات موضوعية: | Full Paper, Radical, Lasers, Organic Chemistry, Kinetics, Protonation, General Chemistry, Photoionization, Ascorbic Acid, Full Papers, Photochemistry, Bond-dissociation energy, Laser Chemistry, Catalysis, chemistry.chemical_compound, Reaction rate constant, antioxidants, chemistry, Kinetic isotope effect, Quercetin, photoionization |
| الوصف: | We have demonstrated the feasibility and ease of producing quercetin radicals by photoionization with a pulsed 355 nm laser. A conversion efficiency into radicals of 0.4 is routinely achieved throughout the pH range investigated (pH 2–9), and the radical generation is completed within a few ns. No precursor other than the parent compound is needed, and the ionization by‐products do not interfere with the further fate of the radicals. With this generation method, we have characterized the quercetin radicals and studied the kinetics of their repairs by co‐antioxidants such as ascorbate and 4‐aminophenol. Bell‐shaped pH dependences of the observed rate constants reflect opposite trends in the availability of the reacting protonation forms of radical and co‐antioxidant and even at their maxima mask the much higher true rate constants. Kinetic isotope effects identify the repairs as proton‐coupled electron transfers. An examination of which co‐antioxidants are capable of repairing the quercetin radicals and which are not confines the bond dissociation energies of quercetin and its monoanion experimentally to 75–77 kcal mol−1 and 72–75 kcal mol−1, a much narrower interval in the case of the former than previously estimated by theoretical calculations. Make ‘n’ Break: The repairs of quercetin H2Q by co‐antioxidants, such as ascorbate HAsc−, were investigated; and for this, ns laser pulses were used to generate high concentrations of the radicals HQ. by near‐UV photoionization of H2Q. |
| تدمد: | 1521-3765 |
| URL الوصول: | https://explore.openaire.eu/search/publication?articleId=doi_dedup___::5511bef645b7cae3a08a092ab638e406 https://pubmed.ncbi.nlm.nih.gov/32776362 |
| حقوق: | OPEN |
| رقم الأكسشن: | edsair.doi.dedup.....5511bef645b7cae3a08a092ab638e406 |
| قاعدة البيانات: | OpenAIRE |
| تدمد: | 15213765 |
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