## 4 Discussion  
In this study, the secondary metabolites content (including total polyphenol, flavonoid, and tannin) of the EEs of five Tunisian plants--_Pistacia lentiscus_, _Rosmarinus officinalis_, _Erica multiflora_, _Calcitome villosa_, and _Phillyrea ltifolia_ were measured. Moreover, the antioxidant and antimicrobial activities of these five EEs were evaluated, and finally, the mechanisms of action were studied. The studied plants were a great reservoir of phenolic compounds (Table 5). They were among the most versatile herbs that have been studied for their pharmacological and therapeutic effects. Tested plants were characterized by their high content of total polyphenols, tannins, and flavonoids [35]. The highest values of these biomolecules were demonstrated in _P. lentiscus_, followed by _R. officinalis_. However, _E. multiflora_ and _C. villosa_ showed the highest values of tannins. Similarly, previous research had found a similar richness in phenolic compounds [36; 37; 38]. Phenolic compounds are important biomolecules in plants due to their capacity to eliminate free radicals [39]. The most important total activity antioxidant was shown higher in _C. villosa_ (15.33 \(\pm\) 0.39 mg GAE/gDW) and _P. ltifolia_ (20.16 \(\pm\) 0.32 mg GAE/gDW). Additionally, the antioxidant activities of the EEs of the studied plants were evaluated by two different assay methods, which were DPPH and FRAP assays. The EEs of _P. lentiscus_ and _E. multiflora_ showed the highest DPPH inhibition capacity. Similarly, the latter plants showed the highest iron-reducing capacity. These results were in accordance with previous data indicating a pronounced antioxidant effect of the studied plants [40]. This potentiality is mainly correlated with their richness in phenolic compounds known for their important reactivity as hydrogen or electron donors [41; 42; 43; 44]. The antibacterial activity of EEs from the leaves of _Rosmarinus officinalis_, _Erica multiflora_, _Pistacia lentiscus_, _Calcitome villosa_, and _Phillyrea ltifolia_ was determined by measuring the zone of inhibition made against important pathogens (_Escherichia coli_, _Salmonella typhimurium_, _Listeria monocytogenes_ and _Staphylococcus aureus_). The intensity of antibacterial activity was estimated by the double serial dilution method to determine the minimum inhibitory concentration (MIC) of the ethanolic extracts, whereas the bactericidal activity was determined by the in vitro killing time test, salt tolerance, and bacteriolysis. The results demonstrated that EEs had good antibacterial activity at different concentrations against Gram-positive and Gram-negative bacteria (Table 2). The agar diffusion assay revealed that the bacteria were inhibited by the ethanolic extract to produce concentration-dependent zones of inhibition. At the MIC utilized, all bacteria strains were inhibited. The zones of inhibition produced by 0.04 to 3.84 mg/mL of EEs ranged from \begin{table}
\begin{tabular}{c l c c} \hline \hline
**Species** & **Major Compound** & **Concentrations** & **References** \\ \hline \multirow{3}{*}{_Pistacia lentiscus_} & Chlorogenic acid & 17.4 \(\pm\) 1.9 & \multirow{3}{*}{[10,11]} \\  & 3,4,5 Tri-O-galloyquinic acid & 15.9 \(\pm\) 0.2 & \\  & Rutin & 13.6 \(\pm\) 1.5 & \\ \hline \multirow{3}{*}{_Phillyrea ltifolia_} & Tyrosol & 78.2 \(\pm\) 18.4 & \multirow{3}{*}{[11]} \\  & Quercetin-7-O-rutinoside & 42.5 \(\pm\) 5.1 & \\  & Oleuropein & 167.0 \(\pm\) 7.7 & \\ \hline \multirow{3}{*}{_Erica multiflora_} & Quercetin & 43.57 \(\pm\) 0.18 & \multirow{3}{*}{[9]} \\  & Rutin & 42.05 \(\pm\) 2.67 & \\  & Catechin & 27.29 \(\pm\) 2.73 & \\ \hline \multirow{3}{*}{_Rosmarinus officinalis_} & Rosmarinic acid & 38.5 \(\pm\) 0.04 & \multirow{3}{*}{[12,34]} \\  & Carnosic acid & 26.4 \(\pm\) 0.15 & \\ \cline{1-1}  & Chlorogenic acid & 11.2 \(\pm\) 0.17 & \\ \hline \multirow{3}{*}{_Calcitome villosa_} & vanillic acid & 1.4 & \multirow{3}{*}{[33]} \\  & 4-hydroxybenzoic acid & 0.39 & \\ \cline{1-1}  & chlorogenic acid & 0.39 & \\ \hline \hline \end{tabular}
\end{table}