# Chemical Composition and Biological Activities of Oregon and Lavender Essential Oils
## 4 Discussion
[PERSON] et al. [50] and [PERSON] et al. [45] reported that the biological activities of the essential oils depend on their chemical composition. It is noteworthy that the tested essential oils show remarkable antibacterial activity against antibiotic-resistant bacterial strains. As for \(O\). _glandulosum_, which is the more active, our antibacterial results are in agreement with those reported by [PERSON] et al. [21], who noted in their study that the \(O\). _glandulosum_ essential oils exhibited an antimicrobial activity against 10 Gram-negative bacteria. Similarly [PERSON] et al. [22] noted that \(O\). _glandulosum_ essential oils were very active against the Gram-negative and Gram-positive strains tested (_P. aeruginosa, K. pneumoniae, Enterobacteriaceae cloacae, Salmonella typhi, Proteus mirabilis, E. coli, Citrobacter freundii; Listeria monocytogenes_, and _Staphylococcus aureus_) some of which also ATCC. Among these _K. pneumoniae_, both obtained from clinical isolates and the ATCC strain, was inhibited by the essential oil of oregano, while _P. aeruginosa_ was resistant, as often happens for this bacterium. [PERSON] et al. [2] also reported that the essential oils from \(O\). _glandulosum_ showed good antibacterial activity againstopathogenic multiresistant strains of \(E\). _coli_, while [PERSON], et al. [21] and [PERSON] et al. [22] reported that the essential oil of oregano was active precisely on _K. pneumoniae_ as our data also showed. The antimicrobial activity of \(O\). _glandulosum_ essential oils was possibly related to its phenolic components, such as thymol, carvacrol, but also to their biosynthetic intermediates \(p\)-cymene and c-terpinene. It has been suggested that phenolic derivatives may cause membrane-disrupting activities [21]. In fact, [PERSON] et al. [48] reported that phenolic components and their precursors contained in essential oils are responsible for high antifungal activity. [PERSON] et al. [2] found that carvacrol and thymol were the most active components and showed good antibacterial activity (MIC and MBC ranging from 0.25 to 0.5 mg/mL), p-cymene was less active, and \(\gamma\)-terpinene was totally inactive against all the strains tested. There are reports in the literature that oregano essential oils have the ability to sensitize the cell membrane phospholipid bilayer, causing increased permeability and leakage of vital intracellular constituents or alteration of the enzyme systems in Gram-positive and Gram-negative bacteria [48, 51]. [PERSON] et al. [52] in their study attributed the antimicrobial capacity of oregano essential oil to thymol and carvacrol, capable of disintegrating the outer membrane of the microorganism, causing cell death. The results on \(L\). _dentata_ antibacterial activity are according to literature data on lavender species [27, 28, 53]. [PERSON] et al. [54] found remarkable antibacterial activity in the essential oils of _Lavandula angustifolia_ against multidrug-resistant (MDR) _K. pneumoniae_ strains and also highlight the probable mechanism of action. In contrast, [PERSON] and [PERSON] [43] found that \(L\). _dentata_ essential oils had very low antibacterial activity against antibiotic-resistant strains of _K. pneumoniae_, which was however evaluated only by the disc diffusion method. Our data do not agree with this last statement as we have obtained interesting MIC values. The antibacterial activity of Moroccan \(L\). _dentata_ essential oilsis quite different from the Algerian oils and different results have been found in other studies [28]. The above reported differences in the antibacterial activity could be related to the bacterial species tested and the previously discussed differences in the chemical composition of the oils. As for the ways of action of the essential oils on the bacterial cells, the antimicrobial activity could result from the joint association of several mechanisms on different cellular targets, like plasma membrane, cell wall, or bacterial DNA [27; 54].