## 3 Results and Discussion
### TPC, Antioxidant and Antimicrobial Activity of Licorice Extracts  
#### 3.2.1 TPC and Antioxidant Activity  
The TPC of licorice extracts (mg GAE/g), together with their antioxidant (DPPH test) and antimicrobial activities (IC\({}_{50}\) values), are reported in Table 3. The extracts with the higher content of TPC were obtained with ethanol (ELe25 and ELe50), followed by methanol (MLe25 and MLe50), ethanol:water (EWLe25 and EWLe50) and methanol:water (MWLe25 and MWLe50), with values in the range 60-160 mg GAE/g extract. Figure 1 shows that the TPC values of the extracts obtained at 25 \({}^{\circ}\)C decreased when the dielectric constant of the solvent increased. Similar results were obtained at the extraction temperature of 50 \({}^{\circ}\)C. Then, it can be established that the addition of water to the organic solvents (methanol or ethanol) enhanced the extraction yields, while the TPC concentration decreased, maybe due to the extraction of other polar compounds, as suggested by [PERSON] et al. (2015). For example, the glycyrrhizic acid (GA) molecule has several hydroxyl groups and thus, it is easily soluble when extracted with polar solvents ([PERSON] et al., 2016). Then, higher concentrations of GA were obtained in the extracts produced using ethanol:water (EWLe25 and EWLe50) and methanol:water (MWLe25 and MWLe50). \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sample** & **Liquiritin** & **Glabridin** & **Glycyrrhizin** & **Isoliquiritigenin** & **Liquiritigenin** \\ \hline ELe25 & 0.60 \(\pm\) 0.01 \({}^{\text{a}}\) & 55.80 \(\pm\) 5.03 \({}^{\text{a}}\) & 17.30 \(\pm\) 1.56 \({}^{\text{c}}\) & 0.87 \(\pm\)0.03 \({}^{\text{a}}\) & 0.95 \(\pm\) 0.10 \({}^{\text{c}}\) \\ MLE25 & 0.60 \(\pm\) 0.01 \({}^{\text{a}}\) & 21.35 \(\pm\) 0.72 \({}^{\text{b}}\) & 53.45 \(\pm\) 0.85 \({}^{\text{b,c}}\) & 0.60 \(\pm\) 0.01 \({}^{\text{a}}\) & 2.00 \(\pm\) 0.01 \({}^{\text{b}}\) \\ EWLe25 & 0.70 \(\pm\) 0.07 \({}^{\text{a}}\) & 2.73 \(\pm\) 0.12 \({}^{\text{c}}\) & 159.50 \(\pm\) 12.51 \({}^{\text{a}}\) & 0.40 \(\pm\) 0.01 \({}^{\text{a}}\) & 3.95 \(\pm\) 0.30 \({}^{\text{a}}\) \\ MWLe25 & 0.80 \(\pm\) 0.01 \({}^{\text{a}}\) & 1.00 \(\pm\) 0.02 \({}^{\text{c}}\) & 123.85 \(\pm\) 10.11 \({}^{\text{a,b}}\) & 0.40 \(\pm\) 0.01 \({}^{\text{a}}\) & 3.30 \(\pm\) 0.35 \({}^{\text{a,b}}\) \\ ELe50 & 1.10 \(\pm\) 0.12 \({}^{\text{a}}\) & 55.13 \(\pm\) 2.77 \({}^{\text{a}}\) & 13.60 \(\pm\) 0.23 \({}^{\text{c}}\) & 0.60 \(\pm\) 0.01 \({}^{\text{a}}\) & 1.00 \(\pm\) 0.01 \({}^{\text{c}}\) \\ MLE50 & 1.00 \(\pm\) 0.06 \({}^{\text{a}}\) & 24.40 \(\pm\) 0.90 \({}^{\text{b}}\) & 96.80 \(\pm\) 4.27 \({}^{\text{b,c}}\) & 1.60 \(\pm\) 0.09 \({}^{\text{a}}\) & 2.60 \(\pm\) 0.22 \({}^{\text{b}}\) \\ EWLe50 & 0.60 \(\pm\) 0.01 \({}^{\text{a}}\) & 2.45 \(\pm\) 0.03 \({}^{\text{c}}\) & 145.10 \(\pm\) 10.23 \({}^{\text{a}}\) & 0.40 \(\pm\) 0.01 \({}^{\text{a}}\) & 3.45 \(\pm\) 0.30 \({}^{\text{a}}\) \\ MWLe50 & 0.80 \(\pm\) 0.01 \({}^{\text{a}}\) & 0.80 \(\pm\) 0.07 \({}^{\text{c}}\) & 133.40 \(\pm\) 15.24 \({}^{\text{a,b}}\) & 0.40 \(\pm\) 0.00 \({}^{\text{a}}\) & 3.60 \(\pm\) 0.46 \({}^{\text{a,b}}\) \\ \hline \hline \end{tabular}  
* Values with different letters (\({}^{\text{a-c}}\)) in the column and row differ significantly (\(p<0.05\)).  
\end{table} 
Table 2: Concentration (mg/g extract) of bioactive compounds identified in licorice UAE extracts (High Performance Liquid Chromatography—HPLC analysis). Figure 1: Concentration of glabridin (\(\square\)), glycyrrhizin (\(\blacksquare\)) and (\(\times\)) total phenolic compounds (TPC) in UAE licorice extracts as a function of the estimated dielectric constant of the solvent (extraction temperature 25 \({}^{\circ}\)C); (—) trend line. Concerning the effect of temperature, an increase of the extraction temperature (25 to 50 \({}^{\circ}\)C) increases the TPC content, showing significant differences (\(p<0.05\)). A similar positive effect of temperature on total polyphenols recovery has been previously reported, for example in the extraction of olive leaves [47].