Electrochemical Monitoring and Evaluation of Metallo-Quercetin Complexes’ Antioxidant Activity Toward Electrochemically Generated Superoxide Anion Radical
Bibliographic record
Abstract
The superoxide anion radical, O2˙– (SAR) is a reactive oxygen species (ROS) that is naturally generated within the biological environment via a one electron reduction of molecular oxygen.1-4 Excess production of ROS in the body can lead to undesired reactions that induce cellular death and furthermore, the onset of some pathological diseases.1,3 Antioxidants, such as flavonoids, react with ROS to prevent possible cell damage and development of health issues caused as a result of excess ROS production.2,3 Additionally, flavonoids, such as quercetin (QCR), are known to play a role as metal ion chelators.3,4 Biologically relevant metal ions are also known to influence the activity of ROS via Fenton reactions.3 However, the coordination of metal ions with QCR results in the formation of a metallo-QCR complex that may influence the antioxidant activity and capacity of the flavonoid. The role of metal ions and metallo-QCR complexes as antioxidants toward SAR is not fully understood. Electrochemistry is a valuable analytical tool that can be used to study and assess the reactivity of metal ions and polyphenolic compounds with SAR.1-4 In this work, we monitored and evaluated the ability of QCR and biologically relevant metal ions, Fe(III) and Cu(II) to influence the activity of electrochemically generated SAR. Additionally, we tested and compared the reactivity of metallo-QCR complexes prepared either by sequential addition of metal ion, followed by QCR (in-situ) or by direct addition of a preformed mixture to the electrochemically generated SAR. Specifically, 1:1 and 1:2 molar ratios of metal ion:QCR were explored. The O2˙–/O2 redox couple was generated in-situ using a three-electrode electrochemical cell, with a glassy carbon electrode, a platinum wire counter electrode and a Ag/AgNO3 reference electrode immersed in DMF.1 Using cyclic voltammetry (CV), the current and potential associated with the O2˙–/O2 redox couple was monitored and measured to assess radical scavenging ability of the additives of interest. The data revealed a decrease in SAR associated peak currents for all additives, indicating their role as free radical scavengers. CV data also suggested that the reaction between QCR, metal ions and metallo-QCR complexes is driven by an initial electron transfer mechanism that is followed by a proton transfer.2 Overall, compared to all other variations of additives tested, in-situ prepared 1:2 Cu:QCR complexes exhibited the greatest ability as antioxidants toward SAR. References N. 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). E. Bodini, G. Copia, R. Tapia, F. Leighton, and L. Herrera, Polyhedron, 18, 2233-2239 (1999). 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 | 0.001 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 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 | 0.001 | 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".