Natural phenolic antioxidants electrochemistry: Towards a new food science methodology

Abstract

Natural phenolic compounds are abundant in the vegetable kingdom, occurring mainly as secondary metabolites in a wide variety of chemical structures. Around 10,000 different plant phenolic derivatives have been isolated and identified. This review provides an exhaustive overview concerning the electron transfer reactions in natural polyphenols, from the point of view of their in vitro antioxidant and/or pro‐oxidant mode of action, as well as their identification in highly complex matrixes, for example, fruits, vegetables, wine, food supplements, relevant for food quality control, nutrition, and health research. The accurate assessment of polyphenols’ redox behavior is essential, and the application of the electrochemical methods in routine quality control of natural products and foods, where the polyphenols antioxidant activity needs to be quantified in vitro, is of the utmost importance. The phenol moiety oxidation pathways and the effect of substituents and experimental conditions on their electrochemical behavior will be reviewed. The fundamental principles concerning the redox behavior of natural polyphenols, specifically flavonoids and other benzopyran derivatives, phenolic acids and ester derivatives, quinones, lignins, tannins, lignans, essential oils, stilbenes, curcuminoids, and chalcones, will be described. The final sections will focus on the electroanalysis of phenolic antioxidants in natural products and the electroanalytical evaluation of in vitro total antioxidant capacity.

Effects of the Reactive Moiety of Phenolipids on Their Antioxidant Efficiency in Model Emulsified Systems

“…Whatever is the predominant mechanism, it results in the production of a phenoxy radical. It is currently accepted that the electrochemical oxidation occurring at the –OH groups, is largely influenced by the number and position of the substituents linked to the aromatic ring [ 36 ]. In addition, environmental parameters such as the acidity also affect the phenols’ antiradical scavenging activity, redox behavior and oxidation product formation [ 37 ].…”

“…Mono-phenols have been described as oxidizing in a one-electron, one-proton irreversible step, to a phenoxy radical [ 32 ]. On the other hand, the oxidation mechanism of AOs bearing the catecholic moiety involves a two-electron and two-proton reversible process [ 36 ] that appears at less positive potentials due to the higher stability of the radical formed, when compared to that of the mono-phenol. In the case of esters of dihydrocaffeic acid, E pa values have a significantly lower valor than those of caffeic acid, suggesting that the extension of the resonance over the alkyl side chain removes electronic density at the aromatic hydroxyl groups, decreasing their ability to donate H-atoms.…”

DNA Electrochemical Biosensors for In Situ Probing of Pharmaceutical Drug Oxidative DNA Damage

“…Natural phenolic compounds are abundant in the vegetable kingdom, occurring mainly as secondary metabolites in a wide variety of chemical structures, and many of them present antibiotic, antiviral, antifungal, antiparasitic, anti-inflammatory, antiproliferative, and cytotoxic activities [110].…”

Tyrosinase Inhibitory Activity of Soybeans Fermented with Bacillus subtilis Capable of Producing a Phenolic Glycoside, Arbutin

“…Therefore, it seems likely that for arbutin production, precursors other than hydroquinone are present in soybeans. A recent review described the formation of hydroquinone from polyphenols via the phenol moiety oxidation pathways [49]. As polyphenols are abundantly present in soybeans [29,30], the phenolic compounds might be utilized as precursors of arbutin during the fermentation of soybeans.…”