Rossi Miriam, Belli Stuart, Velez Paloma, Caruso Alessio, Morresi Camilla, Bacchetti Tiziana, Caruso Francesco
Department of Chemistry, Vassar College, Poughkeepsie, NY 12604, USA.
Department of Chemistry and Chemical Biology, Harvard University, 12 Oxford St., Cambridge, MA 02138, USA.
Molecules. 2025 May 27;30(11):2346. doi: 10.3390/molecules30112346.
In this work, we measured the antioxidant capacity of capers ( L.) and an important component, kaempferol, as scavengers of the superoxide radical anion using hydrodynamic voltammetry with a rotating ring disk electrode (RRDE). Comparing our electrochemical results to other natural products studied using this method, this work demonstrates that kaempferol is a stronger antioxidant than vitamin C, whereas caper extract has weaker antioxidant capability than olive oil. We also investigated the synergistic scavenging relationship between vitamin C and kaempferol and found it to be potent, as all the available superoxide radicals were consumed in the presence of both compounds. Such a dramatic RRDE result was observed for the first time in our laboratory. We then utilized computational Density Functional Theory (DFT) methods to establish a viable mechanism, reminiscent of that exhibited by superoxide dismutase (SOD) enzymes, for the scavenging behavior of kaempferol. In the enzymatic reaction, two molecules of the superoxide radical anion with the assistance of two protons are disproportioned into one molecule of hydrogen peroxide and one oxygen molecule. Our DFT results show kaempferol mimicking superoxide dismutase (SOD) action when one kaempferol molecule reacts with two superoxide radicals and two protons (which can be provided by ascorbic acid); i.e., kaempferol acts as a catalyst that is restored after a cycle of superoxide scavenging. This mechanism is consistent with our experimental RRDE results.
在本研究中，我们使用旋转环盘电极（RRDE）的流体动力学伏安法，测定了刺山柑（L.）及其重要成分山奈酚作为超氧阴离子自由基清除剂的抗氧化能力。将我们的电化学结果与使用该方法研究的其他天然产物进行比较，本研究表明山奈酚是比维生素C更强的抗氧化剂，而刺山柑提取物的抗氧化能力比橄榄油弱。我们还研究了维生素C和山奈酚之间的协同清除关系，发现其作用显著，因为在两种化合物存在的情况下，所有可用的超氧自由基都被消耗了。这种显著的RRDE结果在我们实验室中首次观察到。然后，我们利用计算密度泛函理论（DFT）方法，建立了一种可行的机制，类似于超氧化物歧化酶（SOD）酶所表现出的机制，用于解释山奈酚的清除行为。在酶促反应中，两个超氧阴离子自由基分子在两个质子的协助下歧化为一个过氧化氢分子和一个氧分子。我们的DFT结果表明，当一个山奈酚分子与两个超氧自由基和两个质子（可由抗坏血酸提供）反应时，山奈酚模仿超氧化物歧化酶（SOD）的作用；即，山奈酚作为一种催化剂，在超氧清除循环后恢复原状。该机制与我们的实验RRDE结果一致。
