Department of Chemistry, University of Warsaw, Warsaw, Poland.
Biometals. 2011 Feb;24(1):41-9. doi: 10.1007/s10534-010-9372-7. Epub 2010 Sep 11.
Quercetin, one of the most common dietary flavonols, was investigated in the presence of Cu(II) ions in methanolic solution in order to obtain some explanation on the mechanism interaction and its action against free radical-mediated damage. The spectroscopic studies (UV-VIS, IR, ESI-MS) were used to assess the extent to which it undergo complex formation through chelation or modification through oxidation. The reaction of quercetin with Cu(II) resulted in the formation of 1:1 metal-ligand complex (λ(max) = 436 nm) through the carbonyl oxygen and 3-OH group in C ring. Then quercetin is oxidized to the benzoquinone type products. The addition of EDTA destroyed the complex but did not regenerate the whole original spectrum of quercetin. From the other hand, the presence of EDTA inhibits formation of copper-quercetin complex and quercetin oxidation. The antioxidant activity of the Q + Cu solutions was evaluated by using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH∙) radical scavenging method and from an electrochemical point of view. The complex is much more effective as free radical scaveninger than the free flavonoid.
槲皮素是最常见的膳食类黄酮之一，在甲醇溶液中研究了其与 Cu(II)离子的相互作用，以了解其对自由基介导的损伤的作用机制。光谱研究（UV-VIS、IR、ESI-MS）用于评估其通过螯合或通过氧化修饰形成配合物的程度。槲皮素与 Cu(II)反应通过 C 环上的羰基氧和 3-OH 基团形成 1:1 金属配体络合物（λ(max) = 436nm）。然后，槲皮素被氧化为苯醌型产物。EDTA 的加入破坏了配合物，但没有再生槲皮素的整个原始光谱。另一方面，EDTA 的存在抑制了铜-槲皮素配合物的形成和槲皮素的氧化。通过 2,2-二苯基-1-苦基肼自由基（DPPH•）清除法和电化学观点评估了 Q + Cu 溶液的抗氧化活性。与游离黄酮类化合物相比，该配合物作为自由基清除剂的效果要好得多。
