3rd International Conference on Chemo and BioInformatics, Kragujevac, September 25-26, 2025. (pp. 53-57)
AUTOR(I) / AUTHOR(S): Gregor Hostnik, Sara Štumpf, Anja Petek, Franjo Frešer, Veronika Furlan, Jelena Tošović, Matja Zalar, Urban Bren
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DOI: 10.46793/ICCBIKG25.053H
SAŽETAK / ABSTRACT:
Tannins are a wide group of natural polyphenols that are traditionally used for leather tanning. Nowadays, these compounds are also being researched for their antioxidative, anticarcinogenic and other health-beneficial properties. Among them is also their antibacterial activity. This is to a large extent ascribed to their ability to chelate metal ions and therefore deplete growth media of metal ions. However, studies that would enable a better understanding of these interactions are still relatively rare, mostly due to the difficulty of obtaining the pure compounds.
Initially, the four compounds, namely vescalin, castalin, vescalagin and castalagin, were isolated using preparative reverse-phase C18 HPLC. Finally, the metal chelating ability of isolated compounds was examined using UV/Vis spectroscopy in conjunction with a Job plot. Because the interactions of tannins with metal ions are closely connected to the deprotonation of ellagitannins, the microscopic protolytic equilibrium of ellagitannins was examined. During the work, the DFT computations were used to get better elucidation of the obtained results on the molecular level, either for the explanation of the obtained chemical shifts or to search for the most probable binding positions of metal ions.
KLJUČNE REČI / KEYWORDS:
ellagitannins, isolation, Fe(II) ions chelation, pKa, DFT
PROJEKAT / ACKNOWLEDGEMENT:
The authors thank the Slovenian NMR centre at the National Institute of Chemistry for the opportunity to perform NMR experiments. The authors acknowledge the use of research procured within the project “Upgrading national research infrastructures – RIUM”, which was co-financed by the Republic of Slovenia, the Ministry of Higher Education, Science and Innovation and the European Union from the European Regional Development Fund . Chemicalize was used for the prediction of methyl gallate p values, October 2024, https://chemicalize.com/, developed by ChemAxon. Marvin was used for drawing, displaying and characterising chemical structures, substructures, and reactions, Marvin 17.21.0, ChemAxon (https://www.chemaxon.com) This work was supported by the Slovenian Research and Innovation Agency (ARIS) through programme and project grants J4-4633, J1-2471, P2-0046, L2-3175, J1-4398, L2-4430, J3- 4498, J7-4638, J1-4414, J3-4497, P2-0438, I0-E015, J1-50034, and J7-50043
LITERATURA / REFERENCES:
- F. Frešer, G. Hostnik, J. Tošović, U. Bren, Dependence of the Fe(II)-Gallic Acid Coordination Compound Formation Constant on the pH, Foods, 10, 2689
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- S. Štumpf, G. Hostnik, M. Primožič, M. Leitgeb, J-P. Salminen, U. Bren, The Effect of Growth Medium Strength on Minimum Inhibitory Concentrations of Tannins and Tannin Extracts against E. coli, Molecules, 25 (2020) 2947.