## 3 Results and Discussion
### Phenolic Acid Profile of the Tested Plant Extracts  
The results of phenolic acid identification using HPLC are presented in Table 6 and Figures S2 and S3. In the extract of the sideritis aerial parts obtained using acetone as a solvent, three compounds were identified, including chlorogenic acid with a retention \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Compound/AAC**} & \multicolumn{4}{c}{**Extract**} \\ \cline{3-6}  & **ACT** & **MET** & **EtOH-H\({}_{2}\)O** & **EtOAc** \\ \hline \multirow{4}{*}{TFC} & TPAC & \(-0.998190\) * & \(0.975796\) * & \(-0.968122\) * & \(-0.999104\) * \\  & AAC–DPPH & \(-0.999250\) * & \(-0.995786\) * & \(0.982767\) * & \(-0.999258\) * \\  & AAC–FRAP & \(-0.686423\) & \(0.984452\) * & \(-0.935777\) * & \(0.961422\) * \\  & TPC & \(-0.939186\) * & \(0.890216\) * & \(0.820933\) * & \(-0.970955\) * \\ \hline \multirow{4}{*}{TPAC} & AAC–DPPH & \(0.999538\) * & \(-0.991446\) * & \(-0.993789\) * & \(0.999815\) * \\  & AAC–FRAP & \(0.658483\) & \(0.935648\) * & \(0.988061\) * & \(-0.961763\) * \\  & TPC & \(0.956980\) * & \(0.808368\) & \(-0.723206\) & \(0.970589\) * \\ \hline \multirow{4}{*}{AAC–DPPH} & AAC–FRAP & \(0.664808\) & \(-0.967907\) * & \(-0.968210\) * & \(-0.965447\) * \\  & TPC & \(0.948541\) * & \(-0.865067\) * & \(0.729254\) & \(0.970166\) * \\ \cline{1-1}  & AAC–FRAP & TPC & \(0.878578\) * & \(-0.714550\) & \(-0.933343\) * & \(0.503842\) \\ \hline \hline \end{tabular}  
* AAC—antioxidant activity; ACT—acetone; MET—methanol; EtOH–H\({}_{2}\)O—ethanol 70%; EtOAc—ethyl acetate; TPC—total flavonoids content; TPAC—total phenolic acids content; TPC—total polyphenols content;
* significant at \(p<0.05\).  
\end{table} 
Table 5: [PERSON]’s correlation coefficients of antioxidant activities, phenolic compounds, and type of extract. time of 3.15 min, protocatechuic acid (RT--6.99 min), and ferulic acid (RT--10.27 min) (Figure S2). In the MeOH extract of sideritis, three phenolic acids were also identified, including chlorogenic acid, caffeic acid, and ferulic acid, with retention times of 3.2 min, 5.04 min, and 11.2 min, respectively (Figure S2). In the EtOH-H\({}_{2}\)O and EtOAc extracts, only chlorogenic acid was identified, with retention times of 3.33 min EtOH and 3.63 min EtOAc, respectively. The HPLC analysis of extracts obtained from the sideritis aerial parts allowed for the identification of four compounds belonging to the phenolic acid group, including chlorogenic, protocatechuic, ferulic, and caffeic acid. The ACT extract allowed for the identification of three of the four phenolic acids, i.e., chlorogenic, pro-tocatechuic, and ferulic acid, similarly to the MeOH extract, where, in this case, chlorogenic, caffeic, and ferulic acid were identified. [PERSON] et al. [19] determined only chlorogenic acid (RT-3.15) using LC-MS/MS-QTOF in sideritis hydroalcoholic extracts (70:30 MeOH/H\({}_{2}\)O mixture), which was confirmed by our studies (in the ethanol extract, which was a mixture of alcohol and water, the presence of chlorogenic acid was also detected: RT-3.33). The present study showed that most of the detected phenolic acids were detected in the ACT extract obtained from _S. scardia_'s aerial parts, including chlorogenic, protocatechuic, and ferulic acids; the presence of these was also confirmed in the aqueous extract in the study conducted by [PERSON] et al. [20] using the UHPLC-HRMS method. In the case of the analysis of extracts obtained from thyme aerial parts, three compounds were identified (Figure S3). In the ACT extract, three phenolic acids were identified: caffeic acid (RT--4.88 min), ferulic acid (RT--9.87 min), and m-coumaric acid (RT--15.65 min). In the MeOH thyme extract, the presence of caffeic acid and ferulic acid was detected, with retention times of RT--5.01 min and RT--10.21 min, respectively. In the EtOH-H\({}_{2}\)O extract, ferulic acid was identified (RT--9.49 min), while in the EtOAc extract, caffeic acid (RT--5.04 min) was identified (Figure S3).