## 3 Results
### Antioxidant Effect of G. hederaca Extracts  
Plants are a rich source of natural antioxidants, mainly phenolic compounds, that may delay, inhibit, or prevent oxidative processes that contribute to the deterioration of food quality or to the onset and development of degenerative diseases in the body [58]. Generally, antioxidant activity is primarily based on two chemical mechanisms: single-electron transfer and hydrogen atom transfer. However, due to the various mechanisms, reaction characteristics and variable phase localizations that are typically involved in the process, there is currently no single standardized method for determining antioxidant activity. It is worth noting that the DPPH radical is a stable free radical that is commonly used to assess antioxidants' free radical scavenging capacities [23]. In this study, the antioxidant activity of _G. hederaca_ extracts obtained using SC-CO\({}_{2}\) with methanol as a co-solvent was analyzed spectrophotometrically using three different assays (DPPH, ABTS and FRAP). The findings showed that the antioxidant activity of the _G. hederacea_ extracts was significantly different at \(p\) < 0.05 between the extraction temperatures. However, any of these assays could be used for the analysis of the antioxidant activity of _Gleduma_ because all tested assays confirmed 40 \({}^{\circ}\)C/250 bar to be the best conditions for the extraction of antioxidants in this study. The results are summarized in Table 2. Compared with \begin{table}
\begin{tabular}{c c} \hline
**Extraction Conditions** & **TPC (mg GAE/g Extract)** \\ \hline
40 \({}^{\circ}\)C & 138.33 \({}^{\text{a}}\)\(\pm\) 5.00 \\
50 \({}^{\circ}\)C & 43.00 \({}^{\text{b}}\)\(\pm\) 3.04 \\
60 \({}^{\circ}\)C & 46.00 \({}^{\text{b}}\)\(\pm\) 9.26 \\ \hline \end{tabular} Values are mean \(\pm\) standard deviation, n = 3, values with the same lowercase letters in the same column indicating no significant difference at the level of 5\(\%\) (_p_ < 0.05).  
\end{table} 
Table 1: Total phenolic content of _G. hederaca_ extracts obtained from different extraction variants. other authors, [PERSON] et al. (2012) [18] reported that the antioxidant activities of the hot water extract of _G. hederacea_ (HWG) were significantly higher than those of vitamin C and Trolox in terms of superoxide anion radical-scavenging activity and Fe\({}^{2+}\)-chelating ability (\(p<0.05\)). Similarly, [PERSON] et al. (2021) [29] investigated the antioxidant activity of methanolic, ethanolic and aqueous extracts of _Glechoma hederacea_, _Hyssopus officinalis_, _Lavandula angustifolia_, _Leonurus cardiaca_, _Marrubium vulgare_ and _Sideritis scardica_ (_Lamiaceae_) using several experimental models. Their findings revealed that the ethanolic extract of _G. hederacea_ had the highest DPPH scavenging activity among the investigated extracts, which was comparable to that of the positive control, 2-tert-butyl-4-hydroxyanisole (BHA) [29]. Furthermore, [PERSON] (2008) [59] examined the antioxidant capacity of extracts and various solvent fractions of _Glechoma hederacea_ L. and _Orthosiphon stamineus_ (Benth.) [PERSON]. The results demonstrated that the methanolic extracts of _O. stamineus_ exhibited much higher activity than those of _G. hederacea_[59]. The correlation of total phenolic content with FRAP, ABTS and DPPH scavenging activities is shown in Figure 1a-c, respectively. The analysis revealed that the results of all three assays best correlated with the gallic acid equivalent values, estimated using the Folin\(-\)Ciocalteu method. The Pearson's correlation coefficient (r) and coefficient of determination (R\({}^{2}\)) were the highest (r = 0.9983, R\({}^{2}\) = 0.9967) between total phenolic content and FRAP activity than those of total phenolic content and ABTS activity (r = 0.9938, R\({}^{2}\) = 0.9877), followed by total phenolic content and DPPH activity (r = 0.9926, R\({}^{2}\) = 0.9853). These results suggest that the total phenols in the _G.