## 4 Discussion
hortensis_ L. oil showed that the oil from this plant and its main component--carvacrol (which accounts for about 80% of volatile compounds in the F2 vegetation phase when polyphenols rutin and rosmarinic acid content was highest) was highly cytotoxic for human breast cancer cells--MDA MB231 and therefore it has been suggested that this compound may have potential therapeutic significance in the treatment of cancer [42]. However, so far, the cytotoxicity of this monoterpene for epidermal cells (both normal and neoplastic) has not yet been analyzed. The obtained results indicate that F2 extract from _S. hortensis_ L. may have a differentiating effect on the response of normal and cancer cells because this extract is cytotoxic to melanoma already at a concentration of 12.5 \(\upmu\)g/mL, in the absence of cytotoxicity to melanocytes. Therefore, this extract may be a potential therapeutic element in relation to skin melanoma. Regardless of the effect of the _S. hortensis_ L. extract on cell survival, its antioxidant activity has been demonstrated, associated with the polyphenols contained in this extract. The antioxidant properties of _S. hortensis_ L. extracts have been directly assessed, one of the most used methods for assessing the antioxidant activity of natural oils/extracts with the ability to scavenge DPPH radicals. It has been shown that radicals most effectively capture antioxidants contained in _S. hortensis_ L. extract from the V2 phase of vegetation. At the same time, in this phase of vegetation, _S. hortensis_ L. contains the largest number of polyphenols, including flavonoids. Literature data confirm that there is a direct relationship between the content of polyphenolic compounds and the antioxidant activity of most plant extracts/components [43]. The antioxidant activity of polyphenols is associated with hydroxyl groups associated with the aromatic ring, which are able donate hydrogen atoms with electrons and stabilize free radicals [44]. The antioxidant activity of these compounds is also associated with the ability to chelate transition metal ions and quench singlet oxygen. The consequence of polyphenol antioxidant activity is also their participation in lipid stabilization by preventing their peroxidation [45; 46]. Therefore, due to the different mechanisms of possible antioxidant activity, polyphenols can effectively inhibit phospholipid metabolism particularly lipid peroxidation that occurs on enzymatic and non-enzymatic ways following cells exposure to UV radiation contained e.g., in sunlight. Despite of the multiple pathways of UV radiation action, dependent to a large extent on its wavelength, exposure to it usually leads to the intracellular pro-oxidative pathways induction and oxidative stress occurring, which results in the lipid oxidation upon lipid radical formation [47]. Oxidative chain reactions are initiated by non-enzymatic lipid peroxidation initiators such as hydroxyl and hydroperoxyl radicals. Membrane phospholipids containing polyunsaturated fatty acids (PUFAs), namely arachidonic, linoleic, linoleic, eicosapentaenoic, and docosahexaenoicenoic acids mostly suffer from UV-induced peroxidation. Due to the action of reactive oxygen species on membrane phospholipids, fragmentation produces unsaturated short chain, reactive aldehydes, such as MDA, while cyclic prostaglandin derivatives result from oxidative cyclization [48]. In addition, endocannabinoids and eicosanoids are generated as a result of enzymatic metabolism with the participation of cyclooxygenase and lipoxygenase (COXs/LOXs) [49]. The production of these biologically active compounds can disrupt cellular metabolism, but above all, through the metabolism of membrane PUFAs, it affects the modification of the structure and function of biological membranes. Therefore, most studies on the effects of polyphenic antioxidants focus on their effects on biological membranes, including preventing changes in their structure as a result of the peroxidation process. The results of this work show that the higher level of polyphenols in the _S.