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.

Cobalamin is an essential nutrient required for the normal functioning of cells. Its deficiency can lead to various pathological states. Hydroxocobalamin (HOCbl) and cyanocobalamin (CNCbl) are the forms of vitamin B12 that are most commonly used for supplementation. There is substantial evidence indicating that cobalamins can both suppress and promote oxidative stress; however, the mechanisms underlying these effects are poorly understood. Here, it was shown that the oxidation of thiols catalyzed by HOCbl and CNCbl is accompanied by reactive oxygen species (ROS) production and induces, under certain conditions, oxidative stress and cell death. The form of vitamin B12 and the structure of thiol play a decisive role in these processes. It was found that the mechanisms and kinetics of thiol oxidation catalyzed by HOCbl and CNCbl differ substantially. HOCbl increased the rate of oxidation of thiols to a greater extent than CNCbl, but quenched ROS in combination with certain thiols. Oxidation catalyzed by CNCbl was generally slower. Yet, the absence of ROS quenching resulted in their higher accumulation. The aforementioned results might explain a more pronounced cytotoxicity induced by combinations of thiols with CNCbl. On the whole, the data obtained provide a new insight into the redox processes in which cobalamins are involved. Our results might also be helpful in developing new approaches to the treatment of some cobalamin-responsive disorders in which oxidative stress is an important component.

The aim of this work was to study the effect of taxifolin, a conjugate of taxifolin with glyoxalic acid, and naringenin on the phagocytosis of latex beads by neutrophils and the adhesive properties of these cells. It has been shown that taxifolin did not affect the phagocytic activity and adhesive properties of neutrophils. The conjugate of taxifolin with glyoxylic acid significantly inhibited the phagocytic activity of neutrophils. The conjugate also significantly enhanced the adhesion of these cells. Naringenin reduced the phagocytic activity of neutrophils, however, to a lesser extent than the conjugate. Naringenin also inhibited the adhesion of neutrophils. The data obtained indicate that polyphenols can affect the functional activity of neutrophils; this effect can play an important role in modulating the inflammatory process, in particular when prolonged activation of neutrophils leads to damage of the body’s own cells and tissues.

One of the urgent tasks of tissue engineering is the development of stable non-toxic materials that support cell migration during tissue regeneration. This study was aimed at obtaining new gel materials based on collagen and derivatives of taxifolin, taxifolin pentaglutarate and a conjugate of taxifolin with glyoxylic acid and investigating their properties. It was shown that an increase in the proportion of polyphenols in the gel led to a decrease in the rate of degradation of the material. The obtained materials did not negatively affect the viability of NIH/3T3 mouse fibroblasts. The cells were attached to the surface of the materials and spread out on the surface of the material containing taxifolin pentaglutarate. It was also found that fibroblasts migrated through the obtained materials. An increase in the proportion of the conjugate of taxifolin with glyoxylic acid in the material led to inhibition of migration through the material, whereas an increase in the proportion of taxifolin pentaglutarate in the material, on the contrary, led to a significant increase in cell migration through the material. The results obtained indicated the possibility of modulating cell adhesion and migration in biomaterials by including various taxifolin derivatives in their composition. Thus, materials obtained on the basis of collagen and taxifolin derivatives may be of interest for regenerative medicine.

The interaction of two structurally close flavanones: taxifolin and naringenin with copper(I) ions and its effect on the distribution of flavonoids and the corresponding ions in a biphasic system octanol–water have been studied. It has been shown that these polyphenols form complexes with copper ions of different stoichiometric ratio depending on the pH of medium (5.4, 7.4, and 9.0). The interaction of the flavonoids with copper ions leads to an increase in the fraction of polyphenols in the water phase at all pH values examined. The fraction of metal ions in octanol in the presence of both taxifolin and naringenin is maximal in the range of neutral pH values. The parameters obtained in the study, such as the partition coefficient and the coefficient of distribution in a biphasic system octanol–water (logP and logD) form the physicochemical basis necessary for the estimation of the bioavailability of flavonoids and the corresponding metal ions upon their combined consumption.