## 3 Results and Discussion
### Antioxidant Activity of Essential Oils

Table 4: Antioxidant activity of essential oils determined by F-C assay—experimental data compared to the published data. two radical scavenging assays. The results obtained in this study did not agree with this statement for all essential oils. This suggests that other compounds present in the essential oils influence antioxidant activity. The phenolic content is often used as an indicator of antioxidant activity, as some essential oils contain significant amounts of phenolic compounds such as thymol, carvacrol or eugenol, which show high antioxidant activity in radical scavenging assays. While essential oils with a high phenolic content often exhibit strong antioxidant activity, this is not always a direct or exclusive correlation. The overall antioxidant capacity of essential oils is influenced by several factors, including the presence of non-phenolic antioxidants (e.g., terpenes, carotenoids, vitamins, metals), synergistic effects, the structure and reactivity of the phenols, and the variability in assay methods. Therefore, essential oils with a lower phenolic content may still exhibit strong antioxidant activity. In addition, other non-phenolic reducing agents in the sample may inflate the antioxidant activity, resulting in discrepancies with the antioxidant activity measured by DPPH or ABTS assays, as the Folin-Ciocalteu reagent reacts with any reducing compound. Previous investigations have indicated that terpenes also contribute to the antioxidant potential of essential oils. Moreover, the presence of conjugated double bonds in the terpene structure (\(\alpha\)-terpinene, farnesene, \(\alpha\)-phellandrene, citral, ocimene) contributes to the free radical scavenging activity. Investigators also showed antioxidant synergistic and antagonistic interactions between terpenes, which can significantly affect the antioxidant potential of essential oils, regardless of the phenolic component proportion [82]. Since antioxidant activity is often expressed by IC\({}_{50}\) values, these values were evaluated based on the dependence of radical scavenging inhibition for both assays. The results obtained were compared with the literature data and are reported in Tables 5 and 6. The IC\({}_{50}\) values obtained with the ABTS assay were higher than those obtained with the DPPH assay for all essential oils except OEO. [PERSON] et al. [89] also obtained a higher antioxidant activity of clove oil with the ABTS assay and explained the differences in antioxidant activity with different reaction mechanisms. It was also reported that significant differences were obtained by different methods [77]. Similar antioxidant activity is also found in the published articles [19], where high antioxidant activity was attributed to high phenolic content. The correlation between antioxidant activity determined by F-C assay \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Essential Oil** & **IC\({}_{50}\) (exp), mg/mL** & **IC\({}_{50}\) (lit) 1, mg/mL** & **Ref.** \\ \hline Lemon peel & 29.9995 \(\pm\) 1.5516 & 3 & [20] \\ Bay leaf & 3.9897 \(\pm\) 0.0064 & 0.0448–0.0998 & [85; 86] \\ Clove buds & 0.1954 \(\pm\) 0.0012 & 0.0083–0.0789 & [19; 29] \\ Star anise & 306.4840 \(\pm\) 3.4531 & - & - \\ Oregano & 0.2681 \(\pm\) 0.0101 & 0.08–2.14 & [77; 87] \\ Nutmeg & 27.9003 \(\pm\) 2.0015 & 0.1 & [88] \\ \hline \hline \end{tabular} \({}^{\dagger}\) The literature IC\({}_{50}\) are given for the lowest and highest reported values.  
\end{table} 
Table 6: IC\({}_{50}\) values of essential oils in ABTS assay—experimental data compared to the published data.