## 4 Discussion  
The choice of _Schizosaccharomyces pombe_ as a model organism in our study has extended previous knowledge about the response of the eukaryotic organism to _Cornus mas_ L. treatment and thus adds novelty to the existing studies on its effects [19; 20; 21; 37; 38; 39]. The results of this study provide evidence of complex cellular responses and response to oxidative stress in _S. pombe_ cells supplemented with the _Cornus mass_ L. fruit ethanol extract. Several recent studies investigated the composition and effect of the _Cornus mass_ L. ethanolic extract on different model systems, and they revealed that the ethanol extraction retained biologically active compounds of the fruit, resulting in its significant effect on tested model systems [13; 40; 41]. Thus, the use of ethanol for extraction was considered suitable for our study. Various aspects of the cell response were investigated, including growth intensity, ROS generation, MDA content, respiratory activity, antioxidant enzyme activity, and gene expression determination. The results of our study revealed that the effect of the extract on the cellular response is largely dependent on the used dose. Cell supplementation with 2% extract, unlike 0.5%, resulted in cell growth repression and oxidative stress, demonstrated by the increased ROS formation and elevated MDA content, along with a decrease in respiratory activity. Altered respiratory activity might be associated with a potential disruption of mitochondrial functions, resulting in ROS overproduction. Although many studies examining the effect of _Cornus mas_ L. on living organisms revealed its antioxidant properties [20; 42; 43], in the study conducted by [PERSON] et. al. [38], it was evident that a lower concentration (50 \(\mathrm{\SIUnitSymbolMicro m^{-1}}\)) of _Cornus mas_ leaves extract exhibited antioxidant properties, whereas a higher concentration (100 \(\mathrm{\SIUnitSymbolMicro m^{-1}}\)) exhibited a slight pro-oxidative effect during longer incubation periods (2-3 h), resulting in an increase in intracellular ROS. This study confirms the dose- and time-dependent effect of _Cornus mas_ L. extract, which is in line with our findings. The pro-oxidative effect observed at higher concentrations of the extract may be attributed to the elevated levels of antioxidants, as certain antioxidants can exhibit pro-oxidative behavior under specific conditions, influenced by factors such as the presence of metal ions, the antioxidant concentration in matrix environments, and its redox  
Figure 6: Matrix of Pearson’s correlation coefficients (\(\mathrm{r_{P}}\)) of growth, biochemical traits, and gene expression level parameters in _S. pombe_ cells affected by _Cornus mas_ L. extract. The \(\mathrm{r_{P}}\) values are reported, and the asterisk indicates statistically significant correlations with \(p<0.05\) *, 0.01 **, and 0.001 ***. GL—growth intensity; gt—generation time; RA—respiration activity. potential [44]. Compounds known for their pro-oxidative effects include vitamin C [45], alpha-tocopherol, beta-carotene [46], and certain flavonoids like quercetin and kaempfer, as well as phenols [47] that are highly abundant in the fruit of the Correlian cherry [15; 16]. It has been demonstrated that quercetin-mediated depletion of antioxidant systems of the cell is associated with the formation of quinoid forms of quercetin, which may exhibit cytotoxic effects by promoting ROS generation, inducing the formation of covalent bonds with proteins, or inhibiting the cellular respiratory chain [48]. Importantly, quercetin ranks as the third most prevalent flavonoid in the Correlian cherry in terms of quantity [49]. In addition, the strong antimicrobial activity of the Correlian cherry has been reported by [PERSON] et al. [18]. This effect was associated with the specific composition of the _Cornus mas_ L. extract rather than the TPC (total phenolic content), as it contained iri-doids and ellagitannins that were not detected in other tested fruits, such as _A. melanogaster_ or _C. superba_ extracts.