## 3 Results and Discussion
### Effects of Telekia speciosa Essential Oils Melanoma Cells  
The strongest cytotoxic activity was noticed for the flower EO. However, the leaf and root Eos' biological activities were of little importance to that of the flower EO; thus, the further explanation and results discussion on the effect on melanoma cells were based on the flower EO. These are the first studies focused on the cytotoxic effect of _Telekia_'s oils. The effect of _T. speciosa_ EOs on the viability of malignant melanoma (A375) and amelonic melanoma (C32), skin keratinocytes HaCaT, and dermal fibroblasts was evaluated using the MTT assay. Cells were treated with a series of EO concentrations (1.5, 3.1, 6.2, 12.5, and 25 \(\mathrm{\SIUnitSymbolMicro m}\)/mL) for 24, 48, and 72 h. Cisplatin was used as a reference compound. IC\({}_{50}\) values were calculated and are presented in Table 2. The inhibitory effect of _T. speciosa_ EOs on cell viability was time-dependent in all cell lines tested. The strongest cytotoxic activity was noticed for flower EO. However, the biological activity of the leaf and root EOs was similar to that of flower EO; thus, the further explanation of the effect on melanoma cells was based on the flower EO. A375 cells were the most susceptible to the cytotoxic activity of _T. speciosa_ EO at all time points, and its IC\({}_{50}\) values were 7.2, 5.1, and 3.4 \(\mathrm{\SIUnitSymbolMicro m}\)/mL for 24, 48, and 72 h of treatment, respectively. The IC\({}_{50}\) values in other cell lines were around 50% higher in keratinocytes, 2 times higher in C32 cells, and 3 times higher in fibroblasts compared with those obtained in A375 cells. Cisplatin also strongly and time-dependently reduced the viability of all cell lines. The IC\({}_{50}\) values of A375 cells were 7.4, 3.7, and 2.0 \(\mathrm{\SIUnitSymbolMicro m}\)/mL for 24, 48, and 72 h of treatment, respectively. The IC\({}_{50}\) values of cisplatin in C32 cells and keratinocytes were similar to those obtained in A375 cells, whereas fibroblasts were a few times more resistant than these cells. The presented MTT assay data show that _T. speciosa_ EO effectively reduced the viability of the A375 cell line, but the viability of both normal cell lines was significantly less affected than that of the A375 cells. The above experiments are the first, focused on _T. speciosa_ EOs. In a similar study, 20 non-volatile compounds were identified in the polar extract of _T. speciosa_[7]. Calenduladiol esters and asperirlin were the major constituents of the extract. Their cytotoxic effect on human normal prostate epithelial cells, human prostate carcinoma cell lines, human skin fibroblasts, and human melanoma cell lines was examined in vitro. The above-mentioned triterpene esters, which, because of their molecular structure, cannot be constituents of EOs, showed no cytotoxicity against nearly all cell lines tested, except for prostate carcinoma cells (IC\({}_{50}\)--62.0 \(\mathrm{\SIUnitSymbolMicro m}\)/M). Further, asperirlin displayed anticancer activity against the melanomas cell lines, including A375 (IC\({}_{50}\)--17.6 \(\mathrm{\SIUnitSymbolMicro m}\)/M), WM793 (IC\({}_{50}\)--28.2 \(\mathrm{\SIUnitSymbolMicro m}\)/M), and Hs 294T (IC\({}_{50}\)--29.5 \(\mathrm{\SIUnitSymbolMicro m}\)/M) [7].