Toward the prediction of the activity of antioxidants: experimental and theoretical study of the gas-phase acidities of flavonoids
| Autor: | M. Natália D. S. Cordeiro, Victor H. C. Lopes, M. Tereza Fernandez, Hugo Martins, J. Paulo Leal |
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| Jazyk: | angličtina |
| Předmět: |
Naringenin
chemistry.chemical_classification Flavonoids Models Molecular Spectrometry Mass Electrospray Ionization Flavonoid Molecular Conformation Catechin Hydrogen-Ion Concentration Medicinal chemistry Flavones Antioxidants chemistry.chemical_compound Deprotonation chemistry Structural Biology Organic chemistry Taxifolin Thermodynamics Myricetin Gases Kaempferol Spectroscopy |
| Zdroj: | Journal of the American Society for Mass Spectrometry. (6):848-861 |
| ISSN: | 1044-0305 |
| DOI: | 10.1016/j.jasms.2004.02.007 |
| Popis: | The relative gas-phase acidities were determined for eight flavonoids, applying the kinetic method, by means of electrospray-ion trap mass spectrometry. The experimental acidity order, myricetin > luteolin > quercetin > (±)-taxifolin > kaempferol > apigenin > (+)-catechin > (±)-naringenin shows good agreement with the order obtained by theoretical calculations at the B3LYP/6-311 + G(2d,2p)//HF/6-31G(d) level. Moreover, these calculations provide the gas-phase acidities of the different OH groups for each flavonoid. The calculated acidity values (ΔacH), corresponding to the most favorable deprotonation, cover a narrow range, 314.8–330.1 kcal/mol, but the experimental method is sensitive enough to differentiate the acidity of the various flavonoids. For all the flavones and the flavanol, catechin, the 4′-hydroxyl group is the most favored deprotonation site whereas for the flavanones studied, taxifolin and naringenin, the most acidic site is the 7-hydroxyl group. On the other hand, the 5-hydroxyl, in flavones and naringenin, and the 3-hydroxyl, in taxifolin and catechin, are always the less acidic positions. The acidity pattern observed for this family of compounds mainly depends on the following structural features: The ortho-catechol group, the 2,3 double bond and the 4-keto group. |
| Databáze: | OpenAIRE |
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