**3. Results**

The results for the total phenolic contents and antioxidant activities of the obtained plant extracts are summarized in Table 1. Two methods evaluated the antioxidant activities of extracts: DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability assay based on mixed hydrogen atom transfer (HAT) and FRAP (ferric reducing antioxidant power) assay based only on a single electron transfer mechanism.

**Table 1.** Total phenolic content (mg GAE/mL) and in vitro antioxidant activities (mM TE/mL) in extracts.


The color coordinates were obtained in two different colorimetric systems XYZ and CIELab. The results are presented in Table 2.


**Table 2.** Color parameters in two different colorimetric systems.

The chromaticity and color tone angle were determined by using the data in Table 2. The brightness L decreases and the chromaticity increases when the ethanol concentration is high. The values for the color tone angle of 10% and 50% water-ethanolic extracts are between 88–90 degrees, but the value is −75 degrees for the 95% ethanol concentration.

Transmission spectra for the investigated samples have been obtained (Figure 1). Chlorophyll and β-carotene are computed based on the transmission spectrum of the sample, and the color characteristics are obtained using the specially developed soft wear application Lovibond ™ PFX/PFXi Software Upgrade for Chlorophyll and Beta-Carotene. The average results and standard deviations are shown in Table 3.

**Figure 1.** Transmission spectra for ethanol extracts of *Sempervivum tectorum* L.

**Table 3.** Content of pigments in ethanol extracts.


\* Detection limit (DL) 0.01 ppm.

The linear dependencies between the color parameters, obtained in Table 2, and the contents of β-carotene from Table 3 were obtained. They are presented in Figure 2.

**Figure 2.** Linear dependances between contents of pigments and color characteristics. (**a**) β-carotene related to brightness; (**b**) Transmission coefficient at 655 nm related to chlorophyll; Cab related to: (**c**) β-carotene and (**d**) color parameter.

The fluorescence spectra of ethanolic extracts from *Sempervivum tectorum* L. with excitation light of 395 nm, 405 nm, 410 nm, 425 nm, 435 nm, and 450 nm were obtained. The results are presented in Figure 3. In addition, for better fluorescence visualization, excitation-emission matrices of ethanol extracts are shown in Figure 4.

For better visualization, in addition to the individual fluorescence spectra shown in Figure 3a–c, the three-dimensional emission matrices and two-dimensional contours with isolines are presented, representing a universal profile of the so-called fingerprints for selected samples extracts. The matrices presented were obtained after averaging the fluorescence spectra of the samples from a given concentration.

The contents of essential and toxic elements in three extracts were determined by ICP-MS. Results are presented in Table 4.

**Figure 3.** Fluorescence spectra in the visible region for water ethanol extracts from *Sempervivum tectorum* L.: (**a**) 10%; (**b**) 50%; (**c**) 95%.

(**a**) 10% ethanolic extracts (**b**) 50% ethanolic extracts

(**c**) 95% ethanolic extracts

**Figure 4.** Excitation-emission matrices of ethanolic extracts of *Sempervivum tectorum* L. (**a**) 10%; (**b**) 50%; (**c**) 95%.



Tl, As, Cd, and Hg concentrations are below detection limit (0.02 mg kg−1) for all extracts.
