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

Content Provider	World Health Organization (WHO)-Global Index Medicus
Author	Brdaric, Tanja P. Markovic, Zoran S. Dimitric Markovic, Jasmina M. Filipovic, Nenad D.
Description	Author Affiliation: Dimitric Markovic JM ( Faculty of Physical Chemistry, University of Belgrade, Studentski trg 12-16, 11000, Belgrade, Republic of Serbia. markovich@ffh.bg.ac.rs)
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 × $10^{4}$ $dm^{3}$ $mol^{−1}$ to 7 × $10^{9}$ $dm^{6}$ $mol^{−2}.$ 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 $k_{1}$ = 225.75 $dm^{3}$ $mol^{−1}s^{−1}$ and $k_{1}$ = 658.00 $dm^{3}$ $mol^{−1}s^{−1}.$ 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.
ISSN	14779226
Issue Number	17
Volume Number	40
e-ISSN	13645447
Journal	Dalton Trans.
Language	English
Publisher	Royal Society of Chemistry
Publisher Date	2011-05-07
Publisher Place	Great Britain (UK)
Access Restriction	Subscribed
Subject Keyword	Antioxidants Chemistry Chelating Agents Flavonoids Iron Biphenyl Compounds Buffers Hydrogen-Ion Concentration Picrates Quantum Theory Solutions Water Journal Article Research Support, Non-U.S. Gov't
Content Type	Text
Resource Type	Article
Subject	Inorganic Chemistry

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