Optical Properties and Antioxidant Activity of Water-Ethanolic Extracts from Sempervivum tectorum L. from Bulgaria

Abstract

Sempervivum tectorum L. is an evergreen plant belonging to a large family of the Crassulaceae. The fresh juice of the plant is used as a folk remedy almost exclusively for external purposes. The combination of several instrumental methods—transmission and fluorescence spectroscopy, ICP-MS spectrometry, and assays for the assessment of antioxidant activities were used for the characterization of water-ethanolic extracts from the leaves of Sempervivum tectorum L. with different polarities (ethanol content in the extracts varied between 10% and 95%). The highest total phenolic content was found in the 50% ethanol extract—0.84 ± 0.08 mg GAE/mL. Furthermore, this extract also possessed the highest antioxidant potential evaluated by DPPH and FRAP assays—7.02 ± 0.71 mM TE/mL and 6.15 ± 0.25 mM TE/mL, respectively. High correlation coefficients were found between the total phenolic contents and the antioxidant activities of water-ethanolic extracts from Sempervivum tectorum L. The same is true for the strong relationship between the phenolic contents and the concentrations of Na and K. Most likely, the bioavailable species of elements such as Fe, Zn, Ca, and Mg are mostly aqueous soluble. For all the studied extracts, the toxic element (As, Cd, Pb, Tl, Hg) contents are very much below the permissible limits for pharmaceutical products. On the contrary, the concentrations of compounds such as β-carotene and chlorophyll increase with the increase in ethanol in the extract. Results from this study may be used for the preliminary prognosis of pharmaceutical applications of extracts from Sempervivum tectorum L.