## 3 Results and Discussion
### Antioxidant Activity  
The antioxidant activity of \(C\). _sativa_ leaf methanolic extracts was assessed using five in vitro methods, such as scavenging activity ABTS**+** radicals (ABTS), the ability to copper ion reduction (CUPRAC), iron ion chelation (ChA) and scavenging reactive oxygen species (ROS), namely superoxide radicals (O\({}_{2}\)*-) and hydroxyl radicals (OH**+**). The obtained results are presented in Table 3.  
In the assessment of the antioxidant potential using the ABTS and CUPRAC methods for \(C\). _sativa_ leaf methanolic extract, the obtained values were 11.52 and 1.96 mmol TE/g, respectively. In turn, for the remaining three methods, chelating iron ions and scavenging O\({}_{2}\)*- and OH**+** radicals, the activity was 0.310, 0.067 and 0.207 mg/mL, respectively.  
There are very few reports on the antioxidant potential of \(C\). _sativa_ leaves. To date, the analysis of ABTS activity expressed in Trolox equivalents has only been performed by [PERSON] et al. (2020), where the obtained value was lower than in this work (5.81 mmol TE/g) [37]. Higher activity was demonstrated by [PERSON] et al. (2005) and [PERSON] et al. (2008) in the analysis of O\({}_{2}\)*- radical scavenging (0.0016-0.014 mg/mL) and OH**+** radical scavenging (0.160-0.216 mg/mL) [1, 39]. No reports have been published yet for the remaining two methods--CUPRAC and ChA.  
With respect to the remaining morphological parts of the \(C\). _sativa_ tree, the ABTS activity of the tested leaves was 3.2 times higher than the bur activity [40], 2.4 times higher than the shell activity [41], including 3.3 and 57.6 times higher than the inner and outer shell activity, respectively [37]. On the other hand, the O\({}_{2}\)*- radical scavenging capacity was 5.1 times lower than the activity of the shell extract [42]. The indicated differences in the measurement of antioxidant activity compared to the cited works assessing the activity of leaves and other morphological parts of the \(C\). _sativa_ tree may result from the date of harvesting the raw material, location and extraction method. [PERSON] et al. (2012), in the analysis of extraction conditions using the Box-Wilson experimental design (CCC), showed that the highest antioxidant activity of the leaf extract is provided by the use of ethanol as a solvent while maintaining the extraction time and temperature of \(>\)90 min and 50 \({}^{\circ}\)C, respectively [12]. In turn, [PERSON] et al. (2005), in the analysis of \(C\). _sativa_ leaves, proved that the radical scavenging activity in the DPPH method increases with the TPC, and the ability to scavenge O\({}_{2}\)*- and OH**+** radicals depends on the ratio of tannins to other phenolic compounds [1]. Our own analyzes showed a strong correlation between the CUPRAC method and the sum of phenol compounds (r = 0.999, \(p\) < 0.05), the ABTS method and TPC (r = 0.994, \(p\) < 0.05).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{4}{c}{**Antioxidant Activities**} \\ \hline  & ABTS & CUPRAC & ChA & O\({}_{2}\)*- & OH\({}^{-}\) \\ \hline  & \multicolumn{4}{c}{mmol TE/g} & IC\({}_{50}\) (mg/mL) \\ \cline{2-5} _C. _sativa_ leaf & 11.52 \(\pm\) 0.16 & 1.96 \(\pm\) 0.01 & 0.31 \(\pm\) 0.08 & 0.067 \(\pm\) 0.09 & 0.207 \(\pm\) 0.02 \\ methanolic extract & & & & & \\ \hline \end{tabular} Values are expressed as mean \(\pm\) SD.  
\end{table}
Table 3: Antioxidant activities of \(C\). _sativa_ leaf methanolic extract.