## 4 Discussion
Extract-induced oxidative stress in _S. pombe_ cells was confirmed via determination of the increased activity of antioxidant enzymes SOD and CAT, revealing a dynamic response of the cell to extract supplementation. The activity of these enzymes significantly increased upon the addition of the 2% extract, indicating that the cell was experiencing oxidative stress and that the system to counteract free radicals had been activated. The complexity of the regulatory network in the cell was manifested by the detected disparity between increased enzyme activity and the reduced expression of genes encoding the antioxidant enzymes SOD and CAT. The results of our study show that a 2% extract of _Cornus mas_ L. reduces the expression of genes encoding the antioxidant enzymes _sod1_, _sod2_, and _ctt1_, but not _pgr_, while at the same time, it increases activities of SOD and CAT, suggesting that the cell response is being fine-tuned at the cellular and molecular levels. We suspect that the extract-induced decrease in the expression of antioxidant enzymes leads to increased activity in these enzymes to protect cells from enhanced ROS generation that results from the extract-mediated alteration of mitochondrial function. Supporting our findings, mutual correlations, positive and negative, between gene expression and enzyme activities under starvation stress that lead to increased ROS formation in _Arabidopsis_ seedlings, have been described by [PERSON] et al. [50]. In their study, it is shown that depending on the conditions, the correlation between the expression of genes and enzyme activities may vary. Similarly, in a study by [PERSON] et al. [51], the authors reported no significant correlation between gene expression and enzyme activity in zebrafish treated with varying amounts of royal jelly. In accordance with this, diverse relations between enzyme activities and the expression of genes encoding these enzymes have been reported by [PERSON] et al. [52] in their study of the impact of cadmium on _Pleurotus eryngii_ mycelia. All of these data infer that increased enzyme activity is not necessarily the result of increased expression of the gene encoding the corresponding enzyme and vice versa. The way the cell responds to stress on cellular and molecular levels largely depends on the stress inducer, its dose, and time of exposure. Studies uncovering such processes are thus required to better understand the biological pathways of living organisms under certain conditions that help cells deal with stress. In addition, such studies might help to discover new antimicrobial or antitumor substances. Supporting this notion, findings from various studies on cell cultures have shown that bioactive substances such as quercetin, when present in concentrations exceeding 100 uM and subjected to prolonged incubation, can lead to a reduction in the activity of intracellular antioxidant enzymes such as SOD and CAT [53]. By contrast, in our study, we observed an increase in the activity of these enzymes; however, it is crucial to note that these changes in enzyme activity were not associated with the expression of the corresponding genes. The expression of genes encoding SOD, CAT, and PGR were either unchanged or reduced, indicating the inhibitory effect of the extract toward the antioxidant defense system of the yeast cell. Importantly, different experimental conditions and the use of different model systems might also account for the differences in results obtained from various studies. Taken together, the results of our study and those from other authors show that the extract of _Cornus mas_ L. under a dose- and time-dependent manner possesses prooxidative properties, resulting in the cytotoxic effect of the extract that could be of interest for antimicrobial treatment or anti-tumor therapy. Due to the prooxidant effect of a higher concentration of the extract, the dosage of the extract used for therapy must always be considered.