## 4 Discussion
After 24 h of treatment, both extracts induced comparable cytotoxic effects on the tumor cells, except for the HeLa cell line, where the extract of in vitro cultivated plants showed a much better effect than the extract from wild plants, decreasing significantly the cell viability of the cervical carcinoma cells at 500 \(\upmu\)g/mL, confirmed also by the lower IC\({}_{50}\) for the in vitro plants. The decrease in the tumor cell viability determined at 48 h was more pronounced for the extracts obtained from in vitro cultivated plants for all cell lines used. Moreover, a time-dependent increase in the cytotoxicity was found for all types of cancer cells treated with the in vitro plant extracts, while after 48 h treatment of HeLa and MCF-7 cells with the wild plant extract, a slight decrease in the cytotoxic effect compared to the 24 th h was observed. Regarding the effect of the extract of in vitro cultivated plants at the 48 th h, the most pronounced was the influence on the HepG-2 cell line, followed by HeLa, which at 500 \(\upmu\)g/mL reached a 54% and 37% decrease in cell viability, respectively (the effect at 1000 \(\upmu\)g/mL, although strongest, is disregarded as at this concentration a significant decrease in the cell viability of non-tumor cell lines was also observed). Comparing the effects of the extracts on the different types of tumor cells, it was found that MCF-7 mammary carcinoma cells were the least sensitive. The lowest IC\({}_{50}\) value corresponding to the highest cytotoxicity at the 24 th and 48 th h was established for HeLa and HepG-2 cells, respectively. In contrast to the other cancer cell lines, in HT-29 colorectal carcinoma cells, a statistically significant decrease in cell viability compared to controls was found for all concentrations of the tested extracts at both treatment time intervals studied. To assess the selectivity of the cytotoxic effects induced by the tested _C. vulgaris_ extracts toward cancer cells, the human non-tumor cell line HaCaT was included as a control in the panel of human cancer cell lines. The normal cells demonstrated lower sensitivity to the cytotoxic effects of the tested plant extracts compared to the tumor cells. Statistically significant differences between the effects of the wild and in vitro plant extracts were found only after 48 h of treatment and at the highest concentration (1000 \(\upmu\)g/mL). Interestingly, in contrast to all other cell lines used in the present study, the effect of the wild plant extract on HaCaT cells was more pronounced than that of the extract of in vitro cultured _C. vulgaris_ plants, pointing to a less detrimental influence on normal, non-tumor cells of the extract of in vitro cultured plants compared to wild plants. Our results are consistent with previously published data demonstrating the selective anticancer effects of different types of _C. vulgare_ extracts against various cancer cell types. Aqueous extracts of _C. vulgare_ have been shown to exhibit high cytotoxic activity against HEp-2 human larynx epidermoid carcinoma, A2058 human metastatic melanoma and L5178Y mouse lymphoma cells, while FL human normal amniotic cells and 3T3 murine embryonic fibroblast cells were significantly less affected [24]. Another study examined the antitumor activity of acidified, alkalized and neutral water extracts, as well as lipophilic _C. vulgare_ extracts, on HeLa cervical carcinoma, HT-29 colorectal carcinoma and CaOV testicular cystadenocarcinoma [8]. The results of this study demonstrated the highest activity for the acidified and lipophilic extracts. Both extracts showed concentration-dependent cytotoxic effects on cancer cells and a lack of cytotoxicity toward the FL human amniotic cells used in the study as a non-tumor control cell line [8]. The in vitro antitumor activity of methanolic _C. vulgare_ extracts against A549 lung carcinoma, HepG-2 hepatocellular carcinoma, CaCo colorectal carcinoma and MCF-7 mammary carcinoma has also been reported [25; 35].