Issue 17, 2011
From the journal:

Dalton Transactions

Comparative spectroscopic and mechanistic study of chelation properties of fisetin with iron in aqueous buffered solutions. Implications on in vitroantioxidant activity†

Jasmina M. Dimitrić Marković,*a   Zoran S. Marković,b   Tanja P. Brdarićc  and  Nenad D. Filipovićde  

* Corresponding authors

a Faculty of Physical Chemistry University of Belgrade, Studentski trg 12-16, Belgrade, Republic of Serbia
E-mail: markovich@ffh.bg.ac.rs

b Department of Bio-chemical and Medical Sciences, State University of Novi Pazar, Vuka Karadžića bb, Novi Pazar, Republic of Serbia

c Kirilo Savić Institute, Vojvode Stepe 51, Belgrade, Republic of Serbia

d Harvard School of Public Health, Harvard University, Boston, MA, USA

e Bioengineering Research and Development Center, Kragujevac, Republic of Serbia

Abstract

Fisetin (3,3′,4′,7-tetrahydroxyflavone) has been investigated for its ability to bind iron in a wide range of pH values of acetate and phosphate buffered solutions. To assess the relevant interactions of iron with fisetin, combined spectroscopic (UV/visible, Raman, MS) and theoretical approaches were used. The chelation sites, stoichiometry, stability and the dependence of the complexes structures on pH were defined. The results pointed to the formation of two iron–fisetin complexes with stoichiometries of 1 : 1 and 1 : 2, depending on the pH. Results of vibrational analysis and theoretical calculations implicated the 3-hydroxyl-4-carbonyl group as a chelating site in acidic media while catechol (3′-hydroxyl-4′-hydroxyl) group was identified as the chelating group in neutral and alkaline media. Determined relative, conditional, stability constants with iron–fisetin were in the range from 6 × 104 dm3 mol−1 to 7 × 109 dm6 mol−2. Competition experiments demonstrated that fisetin bound iron less strongly than EDTA and citric acid under the investigated experimental conditions. Rate constant values calculated for the fast step of the DPPH reduction for fisetin and the iron–fisetin complex are k1 = 225.75 dm3 mol−1s−1 and k1 = 658.00 dm3 mol−1s−1. These values fit within the interval of the rate constant values which are typical for antioxidants which have a single polyphenolic nucleus. The equilibrium geometries, optimized at the B3LYP/6-311 + G(d,p) and M06/6-311 + G(d,p) levels of theory, predicted structural modifications between the ligand molecule in the free state and in the complex structure. The theoretical model has been validated by both vibrational and electronic spectroscopies.

Graphical abstract: Comparative spectroscopic and mechanistic study of chelation properties of fisetin with iron in aqueous buffered solutions. Implications on in vitroantioxidant activity

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Article information

DOI
https://doi.org/10.1039/C0DT01834A
Article type
Paper
Submitted
27 Dec 2010
Accepted
21 Feb 2011
First published
23 Mar 2011

Dalton Trans., 2011,40, 4560-4571

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Comparative spectroscopic and mechanistic study of chelation properties of fisetin with iron in aqueous buffered solutions. Implications on in vitroantioxidant activity

J. M. Dimitrić Marković, Z. S. Marković, T. P. Brdarić and N. D. Filipović, Dalton Trans., 2011, 40, 4560 DOI: 10.1039/C0DT01834A

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