## 3 Results and Discussion
### Physical-Chemical Parameters of the Essential Oils
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Essential Oils**} & \multicolumn{2}{c}{**Femnel EO**} & \multicolumn{1}{c}{**Sage EO**} & \multicolumn{1}{c}{**Eucalyptus EO**} & \multicolumn{1}{c}{**Thyme EO**} & \multicolumn{1}{c}{**Pine EO**} \\  & **(FEN)** & **(SV)** & **(EUC)** & **(CI)** & **(PIN)** \\ \hline \(\text{Relative density [g/cm^{3}]}\) & 0.96 & 0.89 & 0.90 & 0.91 & 0.85 \\ \hline \(\text{Refractive index},\lambda\) [nm] & 1.528 & 1.456 & 1.458 & 1.495 & 1.465 \\ \hline \multicolumn{2}{c}{**Antioxidant activity**} & \multirow{2}{*}{6.09} & \multirow{2}{*}{6.54} & \multirow{2}{*}{7.09} & \multirow{2}{*}{6.79} & \multirow{2}{*}{6.49} \\ \(\text{(mg equivalent to Fe}_{2}\text{SO}_{4}\text{x}\text{7H}_{2}\text{O}/\text{g for sample})\) & & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Physical-chemical properties of obtained essential oils. The essential oils of eucalyptus, sage, pine, and thyme are especially characterized by the presence of monoterenes (monoterpenic hydrocarbons and oxygenated monoterenes), while the fennel EO contains phenylpropanoids as the main constituents (compounds that can be classified as phenylpropenes or allylbenzenes). Sesquiterpenes are found to a lesser extent in pine, thyme, and sage essential oils. In eucalyptus EO, eucalypt was identified from the total constituents as the main compound (82.10%), followed by D-limonel (8.82%) and p-cymen (4.59%). From the total constituents identified in the case of thyme EO, carvacrol (58.52%) was the main compound detected followed by p-cymen (35.10%) and other by-products such as pinocarvone, \(\beta\)-caryophyllene. \(\beta\)-pinene, carene, and D-limonene are the main compounds identified in pine EO in a concentration of 30.21%, 29.08%, and 18.92% respectively. In sage EO, 18 compounds were identified, of which thujone and (+)-2-bornanone as majority products in a proportion of 38.92% and 21.32%, respectively. For fennel EO, 4 compounds anenthole (majority compound, 79.46%), fenchone, \(\alpha\)-phellandrene, and estragole were highlighted. Thyme EO contains predominantly phenolic terpenoids, such as carvacrol, which explain why exhibited antioxidant activity. The antioxidant activity of eucalyptus EO is due to the presence of the monoterene compounds 1,8-Cineole (Eucalypt) and \(\gamma\)-Terpinene while the antioxidant activity of sage EO is attributed to the presence in the composition of the following compounds 1,8-Cineole (Eucalypt), \(\gamma\)-Terpinene, and linalool. \(\beta\)-caryophyllene and terpionlene are compounds that cause the antioxidant activity of pine EO while \(\alpha\)-phellandrene and anethole influence the antioxidant activity of fennel EO. The results are sustained by other studies [67; 92] that have demonstrated that thymol and carvacrol, are responsible for the antioxidant activity of the essential oils obtained from _Thymus seryllus_ and _Mentha longifolia_. The antioxidant activity of 1,8-Cineole (Eucalypt), \(\gamma\)-terpinene, linalool, \(\beta\)-caryophyllene, terpionlene, \(\alpha\)-phellandrene, and anethole was demonstrated in many studies carried out on a wide range of essential oils [93; 94; 95; 96].