## 3 Results and Discussion
### Antioxidant Activity Evaluation and Total Phenolic Determination  
The antioxidant activity evaluation by the DPPH, ABTS, FRAP, and CUPRAC assays and total phenolic content (TPC) of parsley optimized extracts are reported in Table 6.  
There was no statistical difference between optimized extract for apigenin and luteolin on antioxidant activities and total phenolics. On the other hand, the optimized extract for caffeic acid exerted lower antioxidant activities based on DPPH and ABTS assays compared to the optimized extracts for apigenin and luteolin (\(p\) < 0.05). Since the results concern mixtures of different compounds, this effect may be explained by the different composition of each optimized extract in combination with different antioxidant mechanisms for each assay. This is in agreement with reports that refer to synergism between phenolic compounds during the conduct of antioxidant experiments [33]. Both ABTS and DPPH tests measure the ability of compounds to scavenge free radicals. Small differences between the DPPH and ABTS values of the optimized extract indicated that the phenolic compounds contributing to the free radical scavenging activity were compounds with comparable hydrophilicity, as the ABTS assay is applicable to both  
\begin{table}
\begin{tabular}{c c c c} \hline
**1 Independent Factors** & **Predicted Values** & **Experimental Values** & **Desirability** \\ \hline Luteolin (\(\mathrm{\SIUnitSymbolMicro g}\)/\(\mathrm  
hydrophilic and lipophilic antioxidant systems, whereas the DPPH assay is only applicable to hydrophobic antioxidant systems [34]. The FRAP and CUPRAC tests assess the sample's capacity to reduce using ferric and cupric ions, respectively. Non-statistically significant differences between the optimized extracts indicated that the chemicals contained in the optimized extracts may decrease ferric and cupric ions equally. In contrast, the lower DPPH and ABTS values (P0.05) for the optimized caffeic acid extract compared to those for luteolin and apigenin suggest that a fraction of the reductive chemicals in this extract had reduced radical-scavenging capabilities [35; 36]. The results are promising since a higher amount of total phenolic compounds were extracted compared to studies that have been performed in the past. More specifically, the amounts reported were 9.63 \(\pm\) 2.60 for aqueous solutions and 24.77 \(\pm\) 1.2 mg GAE per g of dry parsley for methanolic extracts, but the amount of total phenolic compounds that were extracted with the optimized procedure ranged from 38.8 to 39.9 mg GAE per g of dry parsley. Other studies have reported 42.31 \(\pm\) 0.50 mg GAE per g of dry parsley, but for dichloromethane extracts. Dichloromethane extracts cannot be used in food enrichment Procedures without any sample pretreatment; this study's results are considered satisfactory since they offer an advantage from the green extraction perspective that was employed [37; 38]. Antioxidants are used in foods to delay or prevent the oxidation of molecules. Two types of antioxidants can be used, either natural or synthetic. Butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) are examples of synthetic antioxidants which have been prohibited because of their carcinogenicity. Thus, there is a growing interest in natural antioxidants, such as phenolic compounds, that can be used in food enrichment Procedures. Thus, the development of natural antioxidants from plant matrices for nutritional purposes, along with the improvement of the nutritional profile of the products, is of great interest [39]. More specifically, in view of these results, an adequate quantity of phenolic compounds under evaluation were extracted from _Petroselinum crispum_, especially apigenin and luteolin, while using ultrasound-assisted extraction and green solvents (the ethanol/water mixture was selected as the extracting solution rather than other solvents because both ethanol and water are considered green solvents).