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Dependence of the Fe(II)-Gallic Acid Coordination Compound Formation Constant on the pH.

Authors :
Frešer, Franjo
Hostnik, Gregor
Tošović, Jelena
Bren, Urban
Source :
Foods; Nov2021, Vol. 10 Issue 11, p2689, 1p
Publication Year :
2021

Abstract

One important property of tannins involves their ability to form coordination compounds with metal ions, which is vital for the bioavailability of these ions, as well as for the antibacterial and antioxidative activities of tannins. In this study, the pH dependence of interactions between gallic acid, one of the basic building blocks of tannins, and Fe(II) ions, was investigated using UV/Vis spectroscopy, in conjunction with density functional theory (DFT) calculations. Moreover, two models were developed to explain the processes taking place in the solution. The first model treated the reaction as a simple bimolecular process while the second also considered the protolytic equilibrium, which was proven very successful in discerning the pH dependence of formation constants, and whose assumptions were well supported by DFT calculations. We showed that the two-time deprotonated gallic acid species forms the coordination compound with Fe(II) ions in a 1:1 molar ratio. To gain better insight into the process, the coordination compound formation was also studied using various DFT functionals, which further supported the model results. Furthermore, due to the relatively low sample amounts needed, the methodology developed here will be useful to study compounds that are more difficult to isolate. [ABSTRACT FROM AUTHOR]

Details

Language :
English
ISSN :
23048158
Volume :
10
Issue :
11
Database :
Complementary Index
Journal :
Foods
Publication Type :
Academic Journal
Accession number :
153876464
Full Text :
https://doi.org/10.3390/foods10112689