## 2 Results and Discussion
### Antioxidant Potential of Egyptian Dukkah and Syrian Za'atar  
There are various in vitro chemical models to evaluate the antioxidant potential of the tested mixtures and that are likely to be mediated via phenolic compositions of these herbal blends. The results are shown in Table 4. Radical scavenging capabilities were revealed using DPPH, ABTS, and ORAC and expressed as Trolox equivalent (\(\upmu\)M T eq/mg). The DPPH radical scavenging activities of herbal blend extracts varied from 59.93 to 104.10 \(\upmu\)M T eq/mg (Table 4). All tested herbal mixtures exerted scavenging activity, indicating that the components of the herbal mixtures have proton donating ability as well as free radical scavenging ability. STZ showed the highest antioxidant capacity (104.10 \(\upmu\)M T eq/mg), followed by SZS (86.79 \(\upmu\)M T eq/mg), while EDN showed the lowest antioxidant capacity (26.92 \(\upmu\)M T eq/mg). The high concentration of phenolic compounds in SZT (catechin, vanillic acid, rosmarinic acid, and quercetin) may account for its strong DPPH scavenging activity [46]. Regarding the ABTS assay, values varied from 125.15 to 337.26 \(\upmu\)M T eq/mg (Table 4). SZT possessed the highest antioxidant capacity (337.26 \(\upmu\)M T eq/mg) followed by EDT (225.32 \(\upmu\)M T eq/mg). In accordance with the DPPH assay, EDN showed the lowest antioxidant capacity (125.15 \(\upmu\)M T eq/mg). Catechin and rosmarinic acids are the major constituents in SZT, detected at 14.8 and 149.6 \(\upmu\)g/g, respectively, suggesting that they play a significant role in the antioxidant activity in various assays [47; 48]. Figure 1: Heatmap showing the vapor-phase antibacterial activity of the tested herbal mixtures and their major individuals. The antibacterial activity is represented by means of vapor-phase minimum inhibitory concentration (VP-MIC). Dark red and yellow represent the lowest and highest VP-MIC (mg/mL), respectively. Symbol “X” means that there was no antibacterial activity detected within the tested concentrations. ORAC values varied from 1138.11 to 1577.86 uM T eq/mg (Table 4). The herbal blend that showed the highest antioxidant capacity was EDT (1577.86 uM T eq/mg) followed by SZT (1479.09 uM T eq/mg). The ORAC assay also confirmed the presence of polyphenols in various blends with significant antioxidant activity [49]. EDT encompassed high levels of caffe acid, ferulic acid, rutin, and rosmarinic acid (194.4, 325.8, 302.1, and 338.3 ug/g, respectively), demonstrating the strongest antioxidant effect and ROS scavenging activity [48; 50]. In this assay, SZS (1138.11 uM T eq/mg) showed the lowest antioxidant potential compared to other tested herbal mixtures. To confirm the antioxidant potential of herbal blends, ferric reducing antioxidant power (FRAP) was also performed considering its slightly different action mechanism targeting metal chelation and likely mediated via flavonoids found in abundance using HPLC analysis (Table 2). The results did not show much differences from DPPH and ABTS scavenging activities. Similar to the results attained for radical scavenging assays, SZT (212.75 uM T eq/mg) exhibited the highest ferric ion reducing potential versus the lowest, which was exhibited by EDN (59.89 uM T eq/mg). The ferrozine iron metal chelation power assay was performed to determine the chelation ability of the four herbal blends. Unlike the other assays, the varieties of dukkah exhibited the highest capacities to chelate ferrous ions in comparison to za'atar varieties. EDT (51.69 uM EDTA eq/mg) showed the highest chelation capacity followed by EDN (22.26 uM EDTA eq/mg). The observed iron chelating activity of dukkah's varieties may be explained by the chelating activity of nut components (hazelnuts, almonds, peanuts, and walnuts) [51]. The chelating activity is attributed to the fact that transition metal ions contribute to oxidative damage in neurodegenerative disorders such as Parkinson's and Alzheimer's [52].