Ionic quasi-splet mechanism of the interaction of some organic antioxidant acids with the radicals ABTS•+ and DPPH•
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2023-03-04 20:11
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547.2/.5 (1)
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GORBACHEV, Mikhail, GORINCHOY, Natalia, BALAN, Iolanta. Ionic quasi-splet mechanism of the interaction of some organic antioxidant acids with the radicals ABTS•+ and DPPH• . In: Ecological and environmental chemistry : - 2022, Ed. 7, 3-4 martie 2022, Chișinău. Chisinau: Centrul Editorial-Poligrafic al USM, 2022, Ediția 7, Vol.1, pp. 50-51. ISBN 978-9975-159-07-4.. 10.19261/eec.2022.v1
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Ecological and environmental chemistry
Ediția 7, Vol.1, 2022
Conferința "Ecological and environmental chemistry 2022"
7, Chișinău, Moldova, 3-4 martie 2022

Ionic quasi-splet mechanism of the interaction of some organic antioxidant acids with the radicals ABTS•+ and DPPH•

CZU: 547.2/.5

Pag. 50-51

Gorbachev Mikhail, Gorinchoy Natalia, Balan Iolanta
 
Institute of Chemistry
 
Proiecte:
 
Disponibil în IBN: 3 martie 2022


Rezumat

The classical SPLET mechanism of antioxidants‘ action of chemical compounds is based on the supposition that the proton transfer from an antioxidant molecule to an oxidant free radical particle is its first stage. The second stage of the given mechanism includes the following electron transfer which occurs between two the newly formed ions (the former antioxidant and oxidant molecules). Thus, the presence of active hydrogen atoms, which can abandon (at experimental conditions) the studied antioxidant molecules in the form of the corresponding protons, can indicate on possibility of the SPLET mechanism. However, it was shown in our recent [1] and previous [2] works that in the reactions of the certain antioxidant food acids with the radical ABTS•+ along with the reaction of dihydroxyfumaric acid with the radical DPPH• (see [2]) there is not any direct transfer of protons from molecules of the given acids to the above radicals. In both these cases the corresponding redox reactions begin from the dissociation of these acids in the ethanol–water medium (see [1,2]) and the formation of their anions in the studied solutions. Their former protons are bonded with solvents‘ molecules. Then, for the food acids their anions form charge transfer complexes with the radical cation ABTS•+ and transform it in its diamagnetic derivative. In the case of dihydroxyfumaric acid the protonation of the radical DPPH• occurs due to the passing of needed protons from protonated molecules of the solvents (ethanol and water) to the given radical [2]. Thus, in both cases considered, the primary proton transfer proceeds from neutral antioxidant acids molecules to solvent ones. At the same time the second stages of the studied redox reeactions include the formation of the corresponding charge transfer (electron transfer) complexes with the participation of the anions arising during their first stages. In this connection it seems to us reasonable that one can call the such type of antioxidant mechanism as „quasi-SPLET‖ one. I.e. the quasi-SPLET mechanism can be characterized by the following particularities: firstly, the absence of the direct transfer of protons from antioxidant molecules of the acids to the studied radicals; secondly, the active participation of solvents‘ molecules in both the processes: the passing of protons to the studied radicals (their protonation) and the formation of acids‘anions, which, in their turn, take part (via the formation of the charge teransfer complexes) in the process of donating of their electrons to the protonated (DPPH•) or positively charged (ABTS•+) radicals and, therefore, transform these radicals in their diamagnetic derivatives.