Spectroscopic study of Mg(II) ion influence on the autoxidation of gallic acid in weakly alkaline aqueous solutions

Nikolić, Goran; Veselinović, Aleksandar M.; Nikolić, Gordana; Mitić, Snežana S.

doi:10.1134/s0036024411130176

Cited by 7 publications

(4 citation statements)

References 16 publications

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“…Our earlier studies of GA autoxidation in aqueous solutions indicated that autoxidation was achieved at pH 8.5 and higher (21). However, after mixing GA aqueous solution with Zn(II)-acetate buffer at pH 6.5 precipitate formation quickly occurred and we were not able to use UV-Vis spectrophotometry for obtaining reliable spectral data about this system.…”

Section: O R I G I N a L A R T I C L Ementioning

confidence: 89%

Influence of Zn(II) Ion on the Autoxidation of Pyrogallol and Gallic Acid in Weakly Acidic Aqueous Solutions / Uticaj Zn(II) jona na autooksidaciju pirogalola i galne kiseline u slabo kiselim vodenim rastvorima

Veselinović¹,

Nikolić²

2015

Acta Facultatis Medicae Naissensis

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.2 SU M M A RYPyrogallol-type phenolic compounds are widespread in nature and may have significant impact on human health. As Zn(II) ion was proved to be capable of enhancing some biological activities of pyrogallol-type natural phenolic compounds, we decided to study its influence on the autoxidation of pyrogallol and gallic acid in weakly acidic aqueous solutions.UV-Vis spectrophotometric measurements showed that autoxidation of pyrogallol was initiated by the influence of Zn(II) ions at pH 5.5 and pH 6.5. The differences in UV-Vis spectra of the first autoxidation products resolved by the application of multivariate curve resolutionalternating least squares (MCR-ALS) method indicated that pH change also changed the mechanism of autoxidation process. Formation of stable Zn(II) ion spin stabilized free radical obtained during the autoxidation of pyrogallol at pH 6.5 was confirmed by using electron spin resonance (ESR) spectroscopy and its structure was determined. Both UV-Vis spectrophotometric and ESR spectroscopic measurements did not give any evidence that gallic acid autoxidation was initiated by the influence of Zn(II) ions in weakly acidic aqueous solutions.The results of this study may be used for explaining possible differences in the Zn(II) ion influence on various biological activities of pyrogallol-type phenolic compounds containing simple pyrogallol moiety and the ones containing gallate moiety as a part of the molecule. Key words: autoxidation, pyrogallol, zinc, MCR-ALS, ESR O r i g i n a l a r t i c l e I NT ROD U CT I ONPolyphenolic compounds are a class of molecules widespread in nature with significant impact on human health (1). Pyrogallol-type phenolic compounds have three adjacent (vicinal) hydroxyl groups on the same benzene ring which enables their easy oxidation or autoxidation and also allows metal ion chelation, both characteristics contributing significantly to the wide range of biological activities (2).Zinc is an essential biometal, however, contrasting some other cationic micronutrients (for example Fe(II) and Cu(II) ions) Zn(II) ion does not give any redox reactions under physiological conditions (3). However, its importance for the activity of antioxidant enzymes like superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) has been widely recognized (4). There are also numerous reports about physicochemical interactions of Zn(II) ion with various natural phenolic compounds, mostly flavonoids (5-7), and more important, in vitro and animal experiments demonstrated that Zn(II) ion may enhance the biological activities of various phenolic compounds including pyrogallol-type phenolic compounds (8-11). Because literature data about interactions of Zn(II) ion with pyrogallol and pyrogallol-type phenolic compounds are lacking (12), we decided to study the influence of Zn(II) ion on the autoxidation of pyrogallol and gallic acid, a naturally occurring pyrogallol-type simple phenolic acid whose antioxidant properties and health implications are the subjects of very intensive researc...

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Section: O R I G I N a L A R T I C L Ementioning

confidence: 89%

Influence of Zn(II) Ion on the Autoxidation of Pyrogallol and Gallic Acid in Weakly Acidic Aqueous Solutions / Uticaj Zn(II) jona na autooksidaciju pirogalola i galne kiseline u slabo kiselim vodenim rastvorima

Veselinović¹,

Nikolić²

2015

Acta Facultatis Medicae Naissensis

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“…Mg 2+ ion has been shown to exert a great influence on the oxidation of some phenols at slightly basic pH by influencing the general mechanism of catechol (Nikolić et al, 1988) and GA (Nikolić et al, 2011) oxidation. In Figure 9, where the spectra of gallic acid at 100 nM concentration after 60 min of aeration with pure air in NaCl-NaHCO 3 , NaCl-NaHCO 3 -Ca 2+, and NaCl-NaHCO 3 -Mg 2+ are represented, it is observed that with Mg 2+ the signals of benzoquinone and semiquinone are by far the lowest.…”

Section: Discussionmentioning

confidence: 99%

Ocean Acidification Effect on the Iron-Gallic Acid Redox Interaction in Seawater

et al. 2022

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Ocean acidification impacts the iron (Fe) biogeochemistry both by its redox and its complexation reactions. This has a direct effect on the ecosystems due to Fe being an essential micronutrient. Polyphenols exudated by marine microorganisms can complex Fe(III), modifying the Fe(II) oxidation rates as well as promoting the reduction of Fe(III) to Fe(II) in seawater. The effect of the polyphenol gallic acid (GA; 3,4,5-trihydroxy benzoic acid) on the oxidation and reduction of Fe was studied. The Fe(II) oxidation rate constant decreased, increasing the permanence of Fe(II) in solutions at nM levels. At pH = 8.0 and in the absence of gallic acid, 69.3% of the initial Fe(II) was oxidized after 10 min. With 100 nM of gallic acid (ratio 4:1 GA:Fe), and after 30 min, 37.5% of the initial Fe(II) was oxidized. Fe(III) is reduced to Fe(II) by gallic acid in a process that depends on the pH and composition of solution, being faster as pH decreases. At pH > 7.00, the Fe(III) reduction rate constant in seawater was lower than in NaCl solutions, being the difference at pH 8.0 of 1.577 × 10–5 s–1. Moreover, the change of the Fe(III) rate constant with pH, within the studied range, was higher in seawater (slope = 0.91) than in NaCl solutions (slope = 0.46). The Fe(III) reduction rate constant increased with increasing ligand concentration, being the effect higher at pH 7.0 [k′ = 1.078 × 10–4 s–1; (GA) = 250 nM] compared with that at pH 8.0 [k′ = 3.407 × 10–5 s–1; (GA) = 250 nM]. Accordingly, gallic acid reduces Fe(III) to Fe(II) in seawater, making possible the presence of Fe(II) for longer periods and favoring its bioavailability.

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“…Additionally, the partial characterization was accomplished by computer simulation of ESR spectra of formed free radicals during autoxidation of gallic acid at pH 8.5 in the presence of Mg(II) ions. 9 Some of these authors investigated the same process with a different technique -high-performance liquid chromatography with diode array detection (HPLC-DAD). Data obtained in the study proposed the structure of products gained from autoxidation of gallic acid at pH 10, as some form of gallic acid dimer, while among the minor products, the compound with characteristics similar to ellagic acid had been detectable.…”

Section: Oxidative Processes Of Phenolic Compoundsmentioning

confidence: 99%

Application of oxidation processes in the purification of wastewaters from phenolic compounds

Matijević¹,

Stanković²,

KRSTIĆ³

et al. 2020

Rev.Roum.Chim.

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Natural phenolic compounds are significant component of the human diet, as they are present in fruits and vegetables, and they have very important biological activity in the living organisms. Because of their structure, they are subject of numerous oxidation processes, such as autoxidation, but are easily to oxidize in presence of various oxidizing agents and enzymes. Many authors have been investigating phenolic oxidation processes, and have successfully identified their pathways and a significant number of intermediates and products generated by these processes. Also, particular attention has been made to the effects of these processes on food quality and other biological processes in living organisms. Phenols are persistent pollutants of water systems from various agricultural activities and industrial wastewater discharges. It is known that the presence of phenolic compounds in water supplies and industrial effluents directly affects natural processes in the environment due to their toxicity and natural ability to decompose. This property, to easily oxidize and, as a result of it, to mineralize, is practically useful for the treatment of the wastewaters, so it is of global concern to manage the best technology to remove phenols and other organic pollutants, assisted with the oxidation processes. In the aspect of treatment of wastewaters polluted with phenols, we reviewed oxidative processes such as autoxidation, enzyme-catalyzed oxidation, photo-oxidation, electrochemical oxidation and oxidation by Fenton's reagent and, based on the literature data, we presented advantages and disadvantages of these processes compared to each other.

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Spectroscopic study of Mg(II) ion influence on the autoxidation of gallic acid in weakly alkaline aqueous solutions

Cited by 7 publications

References 16 publications

Influence of Zn(II) Ion on the Autoxidation of Pyrogallol and Gallic Acid in Weakly Acidic Aqueous Solutions / Uticaj Zn(II) jona na autooksidaciju pirogalola i galne kiseline u slabo kiselim vodenim rastvorima

Influence of Zn(II) Ion on the Autoxidation of Pyrogallol and Gallic Acid in Weakly Acidic Aqueous Solutions / Uticaj Zn(II) jona na autooksidaciju pirogalola i galne kiseline u slabo kiselim vodenim rastvorima

Ocean Acidification Effect on the Iron-Gallic Acid Redox Interaction in Seawater

Application of oxidation processes in the purification of wastewaters from phenolic compounds

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