mgr inż. Oskar Sitarz
ORCID: 0009-0008-7325-8199
The topic of my dissertation is: „Characteristics of the oxidation process of anthocyanins and anthocyanidins”
Anthocyanins belong to polyphenolic organic compounds – flavonoids, characterized by a C6-C3-C6 carbon skeleton. All anthocyanin pigments are derivatives of the flavyl cation – 2-phenylbenzopyryl, which occurs in the form of carbonyl or the more common oxonium form. The basic structure of anthocyanins is anthocyanidin (aglycone part) consisting of an aromatic ring A connected to a heterocyclic ring C containing oxygen. This ring is in turn connected by a carbon-carbon bond to another aromatic ring, designated as B. In natural products, anthocyanins are found in the form of mono-, di- or triglycosides. In the form of monoglycosides, they occur as glucose, galactose, rhamnose, arabinose, and xylose. Diglycosides may contain two molecules of the same monosaccharides (soforose) or different ones (rutinose, sambubioside). Anthocyanin triglycosides are rare and may contain branched trisaccharides or mono- and disaccharides substituted at two hydrocarboxyl groups. Several hundred natural anthocyanin pigments and over 100 synthetically obtained pigments are known. Among the approximately 20 anthocyanidins, only pelargonidin, cyanidin, peonidin, delphinidin, petunidin, and malvidin are found in pigments commonly found in plant-based foods. Individual types of fruit or vegetables contain several to a dozen or so anthocyanins, which are characterized by a variety of colors, from orange through various shades of red and purple to blue, depending on their structure. They determine the shade and stability of the product's color. For example, in strawberries, the dominant pigment is 3-glucoside pelargonidin, and in grapes, it is 3-glucoside malvidin. Anthocyanins are very good agents for quenching oxygen free radicals, including singlet oxygen, superoxide anion radical, and hydroxyl radical. This effect is related to their chemical structure, namely the presence of hydroxyl groups at position 3 of the C ring and at positions 3', 4', and 5' positions in ring B. Thanks to these properties, anthocyanins have a protective effect in cancer, as well as anti-atherosclerotic properties and a positive effect on eyesight.
The aim of the research is to characterize the oxidation process of anthocyanidins and anthocyanins under the influence of various physical and chemical factors (kinetics, dependence on concentration/intensity), the influence of other antioxidants and the matrix on the oxidation processes of these compounds. The physical factors taken into account in the research are: temperature, pH, light, UV radiation, and ionizing radiation, while the chemical factors are biologically relevant oxidants such as hydrogen peroxide, other peroxides, reactive oxygen species and the factors that generate them, peroxynitrite, hypochlorite, and transition metal ions. The effect of antioxidants such as glutathione, ascorbate, trolox, tocopherols, and polyphenols on the oxidation of anthocyanidins and anthocyanins is also being studied.
The research focuses on both anthocyanidins and selected anthocyanins, as well as plant concentrates rich in anthocyanins (concentrates of black carrot, red cabbage, elderberry, blueberry, and chokeberry juices).
Testing techniques include Spectrophotometry, Fluorimetry, and (in cooperation) High Performance Liquid Chromatography (HPLC), Mass Spectrometry (MS), Electron Paramagnetic Resonance (EPR), and Nuclear Magnetic Resonance (NMR) spectroscopy.
Publication:
- Rak M., Mendys D., Płatek A, Sitarz O., Stefaniuk I., Bartosz G., Sadowska-Bartosz I. 2025. Generation of Hydrogen Peroxide in Beer and Selected Strong Alcoholic Beverages. Processes, 13(1), 227. DOI: 10.3390/pr13010277