**5. Conclusions**

The highest total phenolic content 0.84 ± 0.08 mg GAE/mL was found in 50% ethanol extract. This extract also has the highest antioxidant potential as assessed by DPPH and FRAP assays. High correlation coefficients were found between total phenolic contents and antioxidant activities of water-ethanolic extracts from *Sempervivum tectorum* L. The same is valid for the strong relationship between phenolic contents and concentrations of Na and K. Most likely bioavailable species of elements such as Fe, Zn, Ca, and Mg are mostly aqueous

soluble. On the contrary, concentrations of compounds like β-carotene and chlorophyll increase with the increase in ethanol in the extract. The contents of toxic elements, As, Cd, Tl, and Pb, are far below the permissible limits for pharmaceutical products. Results from this study may be used for preliminary prognosis of pharmaceutical applications of extracts from *Sempervivum tectorum* L.

**Author Contributions:** G.G. and I.K. constructed and conceived the project. K.N. and N.P. designed the study. G.G., I.K., K.N., S.M. and N.P. performed the study. V.A. and I.M.-T. analyzed the data and interpreted the results. K.N., G.G. and N.P. wrote the article. All authors have read and agreed to the published version of the manuscript.

**Funding:** The study was funded by MU-Pleven with project code № 13/2018 and the Ministry of Education and Science of Bulgaria under the National Research Program "Healthy Foods for a Strong Bioeconomy and Quality of Life" was approved by DCM № 577/17.08.2018.

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** Datasets from the time of this study are available from the respective authors upon reasonable request.

**Acknowledgments:** Special thanks to the Medical University-Pleven for the financial support provided for the publication of the paper.

**Conflicts of Interest:** The authors declare no conflict of interest.
