, Volume 24, Issue 1, pp 41–49 | Cite as

Interaction of quercetin with copper ions: complexation, oxidation and reactivity towards radicals

  • Anna Pękal
  • Magdalena Biesaga
  • Krystyna PyrzynskaEmail author


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 (λmax = 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.


Flavonoid Quercetin Copper complexation Antioxidant properties 



The authors would like to thank the Structural Research Laboratory at the Department of Chemistry, University of Warsaw for using HPLC–MS. SRL has been established with financial support from European Regional Development Found in the Sectorial Operational Programme “Improvement of the competitiveness of Enterprises” project No. WPK-1/1.4.3./1/2004/72/72/165/2005/U.


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Copyright information

© Springer Science+Business Media, LLC. 2010

Authors and Affiliations

  • Anna Pękal
    • 1
  • Magdalena Biesaga
    • 1
  • Krystyna Pyrzynska
    • 1
    Email author
  1. 1.Department of ChemistryUniversity of WarsawWarsawPoland

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