Differential Reactivity of Flavonoids with Molecular Oxygen and the Superoxide Anion Radical
Bibliographic record
Abstract
Phenolic compounds, such as flavonoids have strong antioxidant properties against reactive oxygen species (ROS), such as the superoxide anion radical (O2˙–, SAR). In the biological environment, SAR is naturally generated via a single electron reduction of molecular oxygen.1-3 The production of excess ROS in the body leads to some undesired reactions, resulting in cellular death and subsequently, the onset of some pathological diseases.1 The activity of antioxidants is directly related to their ability to donate an electron to the ROS. Generally, phenolic compounds act as scavengers of ROS in their reactions with the free radicals to prevent possible cell damage and the resulting health complications induced by ROS production.2 Flavonoids also play a role as metal ion chelators, by which their coordination with specific metal ions results in the formation of a metallo-flavonoid complex.4 Biologically relevant metal ions are known to regulate the ROS activity via Fenton reactions, and as, such may also influence the antioxidant activity and capacity of the flavonoid upon complex formation. The role of metal ions and metallo-flavonoid complexes as antioxidants toward SAR is not fully understood. Additionally, reactions with molecular oxygen within the body is also important, thus further evaluation of flavonoids’ and metallo-flavonoids’ reactivity with molecular oxygen is needed. Herein, we evaluated the activity of a flavonoid, Quercetin (QCR) and its complexes with biologically relevant metal ions, Fe(III) and Cu(II) in their reactions with molecular oxygen and SAR. Using cyclic voltammetry (CV), the current and potential associated with an in-situ generated O2˙–/O2 redox couple was used to monitor the quenching abilities of the additives. CV data indicated a decrease in anodic and cathodic peak currents, but differential reactivity and quenching of molecular oxygen and SAR. Data also suggested that the reactions with QCR, metal ions and their metallo-QCR complexes is driven by an electron transfer mechanism. L. Zabik, S. Anwar, I. Ziu, and S. Martic-Milne, Electrochim. Acta, 296, 174-180 (2019). Ahmed, F. Shakeel, Czech J. Food Sci., 30, 153-163 (2012). M. Kasprzak, A. Erxleben, J. Ochocki, RSC Adv., 5, 45853-45877 (2015).
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".