Abstract
It is known that flavonoids can react with toxic carbonyl compounds in the process of the storage, aging, and digestion of flavonoid-rich foods and beverages. However, the effect of these reactions on the antioxidant properties of the polyphenolic fraction and the properties of the resulting products remain poorly studied. The aim of the present work was to study the antioxidant activity of quercetin, taxifolin, catechin, eriodictyol, hesperetin, naringenin and a product of the condensation of taxifolin with glyoxylic acid, as well as to reveal the structure–activity relationship of these polyphenols. It was found that flavonoids containing the catechol moiety exhibited higher antioxidant activity than hesperetin and naringenin. The product showed the highest hydrogen peroxide scavenging activity, a lower metal-reducing and a higher iron-binding ability than catechol-containing flavonoids, and a lipid peroxidation inhibitory activity comparable with that of taxifolin. Thus, the condensation of flavonoids with toxic carbonyl compounds might lead to the formation of products exhibiting high antioxidant activity. Meanwhile, the conditions under which parent flavonoids and their products exhibit the maximal antioxidant activity may differ. The data suggest that the antioxidant profile of the polyphenolic fraction and bioavailability of polyphenols, carbonyl compounds, and metal ions may change when these reactions occur.
Highlights
More than 8000 polyphenols have been identified; of these, more than 4000 compounds belong to the group of flavonoids [1]
We have found earlier that DfTf is capable of binding iron (II) ions [31]
It is significant that the concentration of iron (II) ions in the presence of DfTf depends only insignificantly on its concentration in the system, which we have shown earlier at pH 5.4 [31]
Summary
Polyphenols are the most numerous and widely distributed compounds of plant origin [1]. They are involved in various processes of the growth and development of plants [2], and their protection against unfavorable environmental factors [3,4,5]. They enter the body of humans and animals with plant food. More than 8000 polyphenols have been identified; of these, more than 4000 compounds belong to the group of flavonoids [1]
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