## 3 Results and Discussion
### Antioxidant Activity of Essential Oils  
Medicinal aromatic plants, which contain essential oils, are rich sources of antioxidants with beneficial properties for human health. When the overproduction of ROS occurs, it may lead to the damage of cellular structures and biomolecules such as lipids, proteins and DNA. Essential oils are the source of numerous compounds with the potential to interfere with ROS through different molecular mechanisms. Their diverse phytochemical composition provides them with pharmacological properties that make them useful in the prevention of oxidative stress-associated diseases [3]. Since the phenolic compounds act as antioxidants, the antioxidant activity, AA, of the extracted essential oils was determined experimentally. Antioxidants reduce the anionic derivatives of phosphotungstic and phosphomolybdic acids, resulting in a visible colorimetric transition from yellow (FC reagent) to blue. The final intensity of the blue color is directly proportional to the antioxidant capacity of the essential oil. The Folin-Ciocalteu method is based on reducing the power of phenolic antioxidants and can be used as a measurement of total phenolic content, but non-phenolic reducing agents can contribute to the reduction in the FC reagent [69]. The results obtained were compared with the published data in Table 4. The AA of lemon peel, bay laurel and star anise essential oils are within the published data. Clove buds, nutmeg and oregano essential oils have a higher AA. These differences are attributed to factors such as plant origin, harvest time, extraction methods and environmental conditions. The antioxidant activity of the essential oils was evaluated using two radical scavenging assays (DPPH and ABTS). In both assays, the antioxidants from essential oils reduce the radical (dark blue ABTS*+ and dark purple DPPH*) into colorless ABTS or yellow DPPH. The higher the amount of antioxidant in an essential oil, the higher the degree of decolorization will be achieved. The effects of essential oil concentration in the methanolic solutions on the inhibition of ABTS** and DPPH* radicals are shown in Figure S1 (Supplemental Data). Increasing the concentration of the essential oil concentration led to a corresponding increase in scavenging activity in both assays. The highest scavenging activities achieved for each essential oil and referent compound (BHT) are as follows:  
* DPPH assay: BLEO (90.28% at 5.00 mg/mL) > BHT (90.22 at 0.31 mg/mL) > OEO (89.29% at 10.00 mg/mL) > NEO (88.17% at 40.00 mg/mL) > CEO (89.14% at 0.63 mg/mL) > SAEO (79.80% at 160.00 mg/mL) > LEO (77.64% at 160.00 mg/mL);
* ABTS assay: BHT (100% at 1.61 mg/mL) > OEO (100% at 7.37 mg/mL) > LEO (98.97% at 170.47 mg/mL) > CEO (97.4% at 0.68 mg/mL) > NEO (67.46% at 41.41 mg/mL) > BLEO (63.26% at 5.10 mg/mL) > SAEO (53.92% at 548.28 mg/mL). The different scavenging activities observed with the DPPH and ABTS assays is due to the different affinities of ABTS** and DPPH* radicals towards the compounds contained in the essential oils. While both assays are used to evaluate antioxidant activity, the ABTS assay is more versatile and suitable for a wider range of compounds [79; 80]. Although phenolic compounds are strong antioxidants [41; 75; 81], the results from this study do not fully support the correlation between results obtained by F-C assay and \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Essential Oil** & **AA (exp)**, & **AA (lit) 1,** & **Ref.** \\  & **mg GAE/g EO** & **mg GAE/g EO** & **Ref.** \\ \hline Lemon peel & 18.29 \(\pm\) 1.16 & 0.0032–94.95 & [70; 71] \\ Bay leaf & 59.74 \(\pm\) 6.64 & 0.1686–49.86 & [72; 73] \\ Clove buds & 739.38 \(\pm\) 25.36 & 1.136–653.29 & [19; 74] \\ Star anise & 26.73 \(\pm\) 3.31 & 0.0334–59.60 & [75; 76] \\ Oregano & 328.77 \(\pm\) 3.43 & 0.1718–47.54 & [35; 77] \\ Nutmeg & 24.27 \(\pm\) 2.15 & 4.04–7.49 & [32; 78] \\ \hline \hline \end{tabular} \({}^{\dagger}\) The literature AA are given for the lowest and highest reported values.  
\end{table}