## 3 Results and Discussion
### Antioxidant/Pro-Oxidative Effect of Mountain Germander Extract on Human Cell Lines
Furthermore, no statistically significant (\(p>0.05\)) dependence of ROS generation on the reduction of cell viability was observed in the tested cell lines compared to the control. On the other hand, it should be noted that a statistically significant (\(p<0.05\)) reduction in reactive radical induction was observed in HepG2 cells at all concentrations, and partially in CAL 27 and Caco-2, while the percentage of cell survival (%) remained relatively unchanged. A similar trend was observed in the study by [PERSON] et al. (2011) [27], in which the correlation between the increased formation of superoxide (O\({}^{2-}\)) and nitrite (NO\({}^{2-}\)) radicals and the decrease in proliferation of HCT-116 colon tumor cells in the presence of a methanolic extract of MG extract (\(0.050^{-1}\) mg mL\({}^{-1}\)) was investigated. The results did not indicate a statistically significant increase in generated radicals, while an increase in viable cells was observed at lower concentrations during the same treatment (72 h), which implies that the proliferative effect is independent of the ROS presence. On the other hand, [PERSON] et al. (2016) [53] investigated the migration potential of MG extract (1-100 \(\upmu\)g mL\({}^{-1}\)) on human colon cancer cell lines, SW-480 and breast cancer MDA-MB-231, depending on the change in redox status measured by the concentrations of reduced glutathione (GSH), superoxide, and nitrite radicals after 24 and 72 h of treatment. Generally, the migration potential is the first step in cancer metastasis. By penetrating into the surrounding tissue and bloodstream, it creates the conditions for the formation of secondary tumors. The results showed that only the lowest concentration of the extract (1 \(\upmu\)g mL\({}^{-1}\) for SW-480; 10 \(\upmu\)g mL\({}^{-1}\) for MDA-MB-231) reduced the migration potential, while a further increase in concentration had the opposite effect. Additionally, no correlation was found between the reduction in migration potential and the pro-oxidant effect of the extract due to the increased formation of the tested radicals, indicating a possible modulation of tumor cell migration by mechanisms independent of the redox status. It is known that polyphenols have the ability to have a very selective pro-oxidant effect on cancer cells by inducing the formation of free radicals, leading to a toxic effect and cell death, while not damaging normal cells [30]. On the other hand, their antioxidant role is based on the elimination and reduction of free radical formation, which is the main role in the regulation of oxidative stress and the prevention of cancer. The lack of a positive correlation between the ROS induction and the cytotoxic effect during treatment with MG extract can be partly explained by the extract's pronounced antioxidant properties after 24 h of treatment, such as the ability to chelate metals in a cancer environment, activate the defense system, and regenerate cells [27]. In this context, it can be partially concluded that the polyphenolic compounds of MG extract play a role in the prevention of pathogenesis, which can be used for chemopre purposes [54]. In contrast to some phenolic acids (gallic acid, ellagic acid) and flavonoids (epigallocatechin gallate, rutin, myristic acid, resveratrol), for which both antioxidant and pro-oxidant roles have been demonstrated, the available research on various phenylethanolamine glycosides, such as echinacoside and salidroside, points to their preventive, antioxidant role by reducing lipid peroxidation, improving mitochondrial functions, inhibiting oxidative stress, improving intercellular communication, regulating the MAPK signaling pathway (mitogen-activated protein kinase/extracellular signal-regulated kinase), as one of the fundamental cascade reactions in the proliferation, differentiation, survival, and apoptosis of inflammatory cells and others [55; 56].