## 4 Discussion
GPx has a higher degree of affinity for H\({}_{2}\)O\({}_{2}\) and it also reduces lipidperoxides, meaning it is more resistant as compared with CAT. This could be a possible explanation regarding the differences between these two enzymes, when exposed to CPA. It is worth mentioning the fact that the GPx-CAT cooperativity was noticed by other scientists, who discovered that GPx protects CAT from H\({}_{2}\)O\({}_{2}\) toxicity [41]. In order to elucidate the CAT/GPx enigma during CPA exposure, further studies with different concentrations of CPA are required. However, _P. sempervirens_ pretreatment, in particular in CPA + P3 group, significant changes have been registered as compared to CPA group, irrespective to CAT/GPx abnormalities. Regarding SH concentration, the highest dose (P3) of the extract reestablished the equilibria of the endogenous non-enzymatic antioxidant species to greater values than the control group. The dose-dependent suppression was also observed in the nitric oxide levels, comparable with 3-NT levels, after pretreatment with all three doses of _P. sempervirens_ extract, as seen in the results section. Our observations support the idea that CPA significantly increased RNS species, while _P. sempervirens_ extract turned out to be a great scavenger for RNS, rather than for oxygen-based species. NO and 3-NT are well known as nitrosative stress markers, but these parameters are essential indicators in inflammatory processes, also common during CPA treatments [42; 43]. Therefore, we can argue the anti-inflammatory effect of the extract in the present experimental model. This observation aligns with our previous research regarding _P. sempervirens_ anti-inflammatory potential [15]. Cyclophosphamide is the first chemotherapeutic agent that was demonstrated to induce ovarian toxicity in mouse models and nowadays CPA is used as an experimental model for studying the physiology of the ovaries devoid of follicles [44]. 200 mg/kg BW CPA was proved to suppress half of the ovarian follicle pool [9]. Our experiment was performed with a 200 mg/kg CPA for a mild level of toxicity and still preserving the ovarian function. Thus, the E2 concentrations are slightly decreased in CPA group, as seen in Figure 3b, while FSH were similarly lowered, but with a greater significance. In rodents, several studies have shown a reduction in E2 and an increase in FSH levels, during chemotherapy [45; 46]. This unusual change must be because we used a single unique dose with a mild amount of CPA that aimed to reduce, not to destroy, the ovarian cycle. Hence, 200 mg of CPA, one single time, may induce negative feedback on the pituitary gland with a consequence of reduction in its serum level. _P. sempervirens_ extract has shown a dose-dependent increase in FSH and E2 levels, near normal control values. In this situation, our hypothesis is that the chemical composition of the extract is rich in flavonoids, which are well-known for their estrogen-like activity, interacting with endogenous estrogen receptors (ER\(\alpha\),\(\beta\)). In addition, our study provides data on folliculogenesis dynamics. From the 15 th day of the experiment, when animals received the CPA injection, the oestrus cycles remained in the metaoestrus stage, at least until the end of the experiment, which was the 21 st day. This observation confirms the fact that folliculogenesis could have been blocked for a few days, with an inhibition of the pituitary-gonadal axis. More studies need to be done for clarifying the exact mechanisms and hormonal changes with a focus on their dynamics in time. _P. sempervirens_ extract managed to place back the oestrus cycles in a normal dynamic, which increases its therapeutic potential and consideration for pharmaceutical formulations in this field. There is a significant lack of information in the literature concerning the transmission electron microscopy of the ovaries after chemotherapy.