LUMINESCENT SPECTROSCOPY AND CHROMATOGRAPHY OF MILK THISTLE OIL OF DIFFERENT STORAGE PERIODS

The luminescence spectral properties of milk thistle oil obtained by cold pressing were studied over a storage period of up to two years. A high sensitivity of luminescence-active components of the oil (tocopherols, polyunsaturated fatty acids, vitamins, pigments, and oxidation products) to storage time under household conditions (in a refrigerator at +4 °C) was observed. It was established that storage for more than six months leads to oxidation and degradation of phenols, tocopherols, polyunsaturated (linoleic and linolenic) and monounsaturated (oleic) fatty acids, vitamins (B₂, E), the precursor of vitamin A (carotene), and the chlorophyll pigments. These processes are accompanied by a decrease in the intensity of luminescence bands of tocopherol-phenol group, polyunsaturated (linoleic, linolenic) and monounsaturated (oleic) fatty acids, vitamins (B₂, E), and chlorophyll pigment with characteristic peaks at λmax = 332, 390, 415, 515, 525, and 678 nm, along with changes in intensity and structure of the excitation spectra of these fluorophores. The decomposition and oxidation of phenols, tocopherols, polyunsaturated fatty acids, vitamins (B₂, E), carotene, and chlorophyll pigments are reflected by the appearance of luminescence bands with peaks at λmax = 370, 440, and 470 nm. The fatty acid composition of milk thistle oil of different storage durations was determined using gas chromatography. The results are consistent with those reported by other authors. Chromatographic analysis revealed a significant decrease in polyunsaturated linolenic acid (ω-3) and monounsaturated oleic acid (ω-9), indicating their effective oxidation during storage.