INTRODUCTION:

Phytotherapy is a form of alternative and complementary medicine using plants and their extracts for healthcare ¹. Essential oils are well-known in traditional medicine due to their different beneficial uses. Some of the essential oils are used in the food industry, cosmetics, and pharmaceutical preparations. Essential oils can be obtained from pharmacies, drug stores, and markets ². Due to the increased number of oil suppliers, the demand for efficient analysis and quality control has increased. The offer available on the essential oils market is consequently very diverse in terms of quality for two main reasons: The first one is that nature is not a factory: it cannot produce the same standard product twice ³. Each plant is a living organism whose fruit will depend on the genetics of the plant, its growing conditions, the weather, and its growing soil ⁴. For essential oils, this natural variation in quality is increased by using a concentrated extract of the plant's active ingredients. The fraud is the second cause of this high diversity of qualities. Oils are particularly affected by the risk of fraud. They are expensive and sometimes come from other countries, with many intermediaries. Fraud cases are challenging to trace and often go unnoticed by the final consumer. It can be a question of dilution with simple raw materials (water, alcohol, fat...), of a mixture with a close and less expensive essential oil, or of a modification of the essential oil either by adding synthetic compounds or by physical processes. Medicinal herbs can be easily contaminated with heavy environmental metals from: soil, water, or air, during growth and the manufacturing processes when ready-made products are manufactured ^5,6. Additional sources of heavy metal contamination are rainfall, atmospheric dust, plant protective agents, and fertilizers ^7,8,9. The level of essential elements in plants is conditional. Their content is affected by the soil's geochemical characteristics and by plants' ability to selectively accumulate some of these elements ^10,11. Considering the complexity of these aromatic medicinal herbs and their inherent biological variation, it becomes necessary to evaluate their safety, efficiency, and quality ¹². The regulations on essential oils tend to control their use to limit the risks. Only respecting quality, criteria will guarantee the authenticity of essential oils, and their therapeutic effectiveness and reduce the risk of toxicity. The European Pharmacopoeia (EP) ¹² has developed a general monograph applied to all essential oils to define the EO and verify its identification and purity. In March 2021, the European Pharmacopoeia Commission adopted the revised version of the General Monograph Essential Oils and the new chapter Essential Oil Monographs (informative chapter) ¹³. The general monograph for Essential Oils has been completely revised. It contains requirements for Heavy Metals ¹⁴ Pesticide Residues, and Microbiological Quality ¹³. In this work, we present the results of a survey focusing on the quality control of five essential oils marketed in Morocco and referred to the Agency of Medicines by making a series of analyses. The analysis was carried out according to the general monograph of the pharmacopeia of EO as well as their monograph in force: Eucalyptus ¹⁵, Cinnamon, Lemon ¹⁶, Lavender ¹⁷ and tea tree.

Therefore, the present study aimed to conduct a comparative evaluation of the quality of essential oils and heavy metals content Eos.

MATERIAL AND METHODS:

1. Sourcing of essential oils:

The studied five essential oils Cinnamon (Cinnamomum zeylanicum); Eucalyptus (Eucalyptus globulus); Lavender (Lavandula latifolia); Tea tree (Camellia sinensis) and Lemon (Citrus limon), were provided by a reliable supplier.

2. Sourcing of bacterial strains:

The antimicrobial activity of the studied essential oils was conducted on three reference bacteria. One Gram-positive: Staphylococcus aureus ATCC 29213, and two Gram-negative: Escherichia coli ATCC 25922 and Pseudomonas aeruginosa ATCC 27853. The strains were all acquired from the National Institute of Hygiene (INH) -Rabat-Morocco.

3. Preparation of bacteria suspension:

A bacteria colony from each strain was inoculated into 10 mL of the pre-prepared suspension. Then, it was adjusted to match the turbidity standard 0.5 Mac Farland. The final inoculum concentration is approximately 10⁷- 10⁸ CFU/mL ^{18, 19}.

4. Disc-diffusion method:

The antimicrobial test was performed according to the work of Balouiri et al., 2016, Sbayou et al., 2014, Khribch et al., 2018 and Kandikonda et al., 2021 ^20,21,22,23. 1 mL of standardized inoculum from selected bacterial strains was added to each pre-prepared tube that contained 20 mL of Mueller–Hinton Agar (MHA) culture medium. Then, each inoculated tube was agitated, poured into Petri dishes, and kept for a few minutes until solidification. Sterile discs of 6 mm in diameter were soaked with 10 μL of the selected essential oil. Then placed in the center of the treated plates. On the other hand, standard antibiotics as shown in Table 1 conducted positive control of each bacteria strain.

Table 1. The Antibiotic used as a positive control

Bacteria Strain	Antibiotic
Staphylococcus aureus	Kanamycin
Escherichia coli	Chloramphenicol
Pseudomonas aeruginosa	Vancomycin

Likewise, the growth of the inoculums was tested by launching some inoculated plates without discs. Afterward, the Petri dishes are left for one hour at room temperature and then incubated in a dry incubator at 37°C for 16 to 24 hours. The analysis was conducted in triplicate. A graduated ruler measured the inhibition zones in millimeters (mm). Consistent with the work issued by Liasi, S. A. et al., 2009 and Wanja et al., 2020, the potential of inhibition was interpreted as shown in Table 2 ^24,25.

Table 2. The interpretation of diameter inhibition Zone

Diameter Inhibition Zone (mm)	Action
0 – 10	Inactive (No inhibition)
11 – 18	Moderately active
19 - 28	Strong activity
>= 29	very strong inhibition

5. Determination of Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC)

The minimum Inhibitory Concentration (MIC) test was conducted based on the broth macro-dilution method ²⁶. 21g of Mueller-Hinton Broth (MHB) with 0,15% Agar was added to 1000 mL of distilled water, then poured into a series of eight test tubes, of which tube number one, contained 10 mL and others held 5 mL each. Then, the culture medium was autoclaved at 121^oC for 15min. Each essential oil was prepared with half dilutions ranging from 20 μL/mL concentration to 0.156 μL/mL. Afterward, 10 μL of the standardized bacterial suspension was added to each test tube and then incubated at 37^oC for 16-48h. The lowest concentration that showed no growth of organisms was considered the MIC.

To determine the MBC, 5 μL of the negative MIC test samples of each bacterium were deposited on the surface of a Petri dish containing MHA and incubated at 37°C for 16-24 hours. The lowest concentration for which no obvious growth was observed on the MHA medium was considered the MBC. Bacterial growth controls without essential oil were also prepared. All tests were repeated three times.

The ratio (MBC/MIC) was calculated and interpreted according to the criteria established by Pankey et al., 2004 ²⁷, Which aimed to determine whether the EO exerted significant bactericidal (MBC/MIC ≈ 1) or bacteriostatic action (MBC/MIC ≥ 4).

6. Chemical Composition:

The composition and characterization of essential oils are determined by GC/MS (HP 6890 series). A single HP DB-5 capillary column (30 m ×0.25 mm i.d.; film thickness, 0,32 µm) was used. The carrier gas used is nitrogen with a flow rate of 1 mL/min. Samples of essential oils were diluted in CHCl3 (1:5), the volume injected is 0.1 µL. The column temperature is programmed from 50°C to 250°C at a rate of 4°C/min, then maintained at 250°C for 20 min. The injector temperature was 260°C, and a split ratio of 10:1 was applied. An electronic impact for a field of 70 eV is adopted for fragmentation. The identification method is based on the comparison of the mass spectrum obtained for each compound of the essential oil, with a spectrum bank of reference products. The relative proportions of the essential oil constituents were expressed as percentages obtained by peak area normalization, all relative response factors being taken as one ²⁸.

7. The organoleptic examination (OE):

The organoleptic examination consists of evaluating the aspect, viscosity, color, and smell of the analysed essential oil. An essential oil that ages oxidize, especially if it has not been properly stored in a well-sealed bottle, away from air, heat, and light.

8. The density (D):

The European Pharmacopoeia specifies that essential oil density should be determined using a densimeter or pycnometer. The relative density at 20°C of an essential oil is the ratio of the mass of a certain volume of essential oil at 20°C to the equal mass of the volume of distilled water at 20°C. we used the pycnometer for the relative density at 20°C.

m₂– m₀

d= ------------

m₁– m₀

m_{0 =}mass of the pycnometer

m₁₌mass of the pycnometer and water

m₂₌mass of the pycnometer and essential oil

9. The refractive index (RI)²⁹

The refractive index was measured with a refractometer (CONVEX 8200.0000). The refractive index allows us to check the quality of the distillation. Indeed, a distillation too fast, at too high temperature, or too slow, drops the refractive index of the essential oil obtained. Each essential oil has a specific RI. Thus, the closer the refractive index of a product is to the expected value, the greater its purity.

10. The Optical Rotation (OR) ³⁰

The specific rotation is the optical rotation was measured using a polarimeter (ADP440+) noted [α]²⁰_D.The concentration of the solution was 1g/mL in a 1 cm polarimeter tube at20°C and wavelength (sodium D line, 589 nm).

[α] ²⁰D= --------

- α: the measured optical rotation

- d: the light path in (dm)

- c: the concentration (g/ml)

11. Determination of heavy metals content ¹⁴^{, 31 , 32}

The heavy metals content of EOs was analysed using an atomic absorption spectrometer (Perkin Elmer 900H). The Winlab32 software controls the instrument. The Standard solutions are prepared by diluting the stock solutions to 1000 mg/L (brand: Merck). 0.50g of essential oil is introduced into a mineralization vial. 4 mL of hydrochloric acid and 6 mL of nitric acid-free of heavy metals were added. The vials are placed in a microwave oven. We carried out the mineralization in 3 stages, according to the following program: 7 vials each containing the oil to be examined: 80 percent power for 15 min, 100 percent power for 5 min, 80 percent power for 20 min. After cooling, the clear and colourless solution obtained is poured into a 50 mL volumetric flask. Each mineralization flask is rinsed with twice 15 mL of diluted nitric acid (65%) free of heavy metals. The rinsing liquids are poured into a volumetric flask and then made up to 50.0 mL of deionized water.

12. Statistical analysis:

The results obtained from all the experiments were subjected to statistical analysis using RStudio software, where we performed the Multiple Factor Analysis (MFA) and Ascending Hierarchical Classification (AHC). The results were presented as the mean ± standard deviation (SD) based on three independent replicates (n=3)

RESULTS:

1. The antimicrobial activity:

The results of the antimicrobial susceptibility of the tested essential oils against the three referential bacterial strains were expressed as the inhibition zone as shown in Table 3.

We noticed that the diameter of inhibition zones varied from 0 to 49.83 ± 7.97 mm. Our results showed that Lemon essential oil was unsuccessful in inhibiting the growth of all examined microorganisms. Consequently, this oil has not been examined for the following tests.

More detailed analyses were conducted on the antimicrobial properties through the estimating of the MIC, MBC, and the ratio of MBC/MIC. The results are illustrated in Table 4.

According to found results, Cinnamon essential exhibited very strong activity for all tested bacteria and the lowest MIC and MBC as well as a bactericidal potential. The maximum inhibition zone diameter for this essential oil was observed on Gram-positive bacteria S. aureus (49,83 mm), followed by Gram-negative bacteria: E. coli (38 mm) and P. aeruginosa (32,33 mm).

On the other hand, besides the great activity of Cinnamon oil, E. coli was conferred to be the most resistant strain among the two tested Gram-negative bacteria. It showed a diameter zone inferior to 10 mm, while treated with Eucalyptus and Lavender essential oils. The MIC registered were 5 and 15 μL/mL respectively. We note that a double concentration of Eucalyptus was needed to cause a lethal action on this bacterium (10 μL/mL). while the same concentration of Lavender oil (15 μL/mL) has a bactericidal effect on E. coli.

Table 3: Inhibitory activity of the five essential oils against the three referential bacterial strains

EOs	Bacterial Strains	Average ZI (mm)	Inhibition Potential
Cinnamon	*E. coli*	38 ± 6.00	Very strong activity
	*P. aeruginosa*	32.33 ± 4.93	Very strong activity
	*S. aureus*	49.83 ±7.97	Very strong activity
Eucalyptus	*E. coli*	9.67 ±1.52	Inactive
	*P. aeruginosa*	12.33 ±1.53	Moderately active
	*S. aureus*	9.67 ±1.15	Inactive
Lavender	*E. coli*	10 ± 1.00	Inactive
	*P. aeruginosa*	15 ±1.73	Moderately active
	*S. aureus*	12 ± 2.00	Moderately active
Tea tree	*E. coli*	13.33 ± 0.58	Moderately active
	*P. aeruginosa*	16.33 ± 2.52	Moderately active
	*S. aureus*	10 ± 1.41	Inactive
Lemon	*E. coli*	0 ± 0.00	Inactive
	*P. aeruginosa*	0 ± 0.00	Inactive
	*S. aureus*	0 ± 0.00	Inactive

However, in the present study, P. aeruginosa was found to be the most resistant bacterial strain. Even though tea tree oil has a low MIC of 2.5 μL/mL, its required MBC was six times higher (15 μL/mL).

In addition, the MIC of Lavender oil was 7,5μL/mL. However, this oil was not bactericidal for P. aeruginosa even with a concentration of 20 μL/mL. Consequently, Lavender and tea tree oils were acting in a bacteriostatic manner against P. aeruginosa.

Table 4: Minimal inhibitory concentration (MIC) and Minimal bactericide concentration (MBC) of the five EOs.

EOs	Bacterial Strains	MIC Average μL/mL	MBC Average μL/mL	MBC/MIC	Antimicrobial Potential
Cinnamon	*E. coli*	0.31± 0.00	0.31 ± 0.00	1.00	Bactericidal
	*P. aeruginosa*	0.26 ± 0.09	0.31 ± 0.00	1.20	Bactericidal
	*S. aureus*	0.42 ± 0.18	0.42 ± 0.18	1.00	Bactericidal
Eucalyptus	*E. coli*	5.00 ± 0.00	10.00 ± 0.00	2.00	Bactericidal
	*P. aeruginosa*	10.00 ± 0.00	10.00 ± 0.00	1.00	Bactericidal
	*S. aureus*	10.00 ± 0.00	10.00 ± 0.00	1.00	Bactericidal
Lavender	*E. coli*	15.00 ± 8.66	15.00 ±8.66	1.00	Bactericidal
	*P. aeruginosa*	7.50 ± 4.33	>20	>2	Bacteriostatic
	*S. aureus*	2.50 ± 0.00	5.00 ±0 .00	2.00	Bactericidal
Tea tree	*E. coli*	7.50 ± 4.33	7.50 ± 4.33	1.00	Bactericidal
	*P. aeruginosa*	2.50 ± 0.00	15.00 ± 8.66	6.00	Bacteriostatic
	*S. aureus*	7.50 ± 4.33	8.33 ± 2.89	1.11	Bactericidal

Table 5: Physical analyses and organoleptic examinations of the five essential oils according to the monographs of the pharmacopeia

	Quality indices
	Specification				Results
EOs	RI ^20°C	D ^20°C	[α⁰]²⁰_D	E.O	RI ^20°C	D ^20°C	[α⁰]²⁰_D	E.O
Eucalyptus (Eucalyptus globulus)	1.458 to 1.470	0.906 to 0.927	0° to +10°	Colorless or pale-yellow liquid	1.459 ± 0.001	0.908 ± 0.001	0.26° ± 0.001	yellow liquid
Cinnamon (Cinnamomum verum)	1.572 to 1.591	1.000 to 1.030	-2° to +1°	Clear, light-yellow liquid becoming reddish with age	1.585 ± 0.001	1.003 ± 0.001	-0.95° ± 0.001	clear liquid
Lemon (Citrus limon)	1.473 to 1.476	0.850 to 0.858	+5.7° to +7.0	Light yellow or yellow-green clear liquid	1.473 ± 0.002	0.851 ± 0.001	6.02° ± 0.001	Green clear liquid
Lavender (Lavandula angustifolia)	1.455 to 1.466	0.878 to 0.892	-12.5° to -6.0°	Clear colorless or yellow liquid	1.457 ± 0.004	0.882 ± 0.001	-9.78° ± 0.001	Liquid colorless
Tea tree (Camellia sinensis)	1.475 to 1.482	0.885 to 0.906	+5° to + 15°	Clear, mobile, colorless, or pale-yellow liquid characteristic odor	1.475 ± 0.010	0.883 ± 0.001	12.9° ± 0.001	Liquid clear with characteristic odor

Results are shown as mean ± S.D, n = 3.

Table 6: Concentration (ppm) of heavy metals in the five essential oils

Heavy metals (ppm)	Specifications				Results
EOs	Cu	Pb	Zn	Hg	Cu	Pb	Zn	Hg
Eucalyptus (Eucalyptus globulus)	NA	Max 5.0	NA	Max 0.1	10.600*10^-3 ± 0.01	4.459*10^-3 ± 0.04	0.051 ± 0.24	0.700*10^-3 ± 0.01
Cinnamon (Cinnamomum zeylanicum)	NA	Max 5.0	NA	Max 0.1	11,300*10^-3 ± 0.150	5.669*10^-3 ± 0.01	0.076 ± 0.24	1.450*10^-3 ± 0.01
Lemon (Citrus limon)	NA	Max 5.0	NA	Max 0.1	10.200*10^-3 ± 0.01	9.205 *10^-3 ± 0.01	0.095 ± 0.02	0.241*10^-3
Lavender (Lavandula angustifolia)	NA	Max 5.0	NA	Max 0.1	15.629*10^-3 ± 0.13	3.418*10^-3 ± 0.01	0.05 ± 0.01	0.313*10^-3 ± 0.01
Tea tree (Camellia sinensis)	NA	Max 5.0	NA	Max 0.1	11.440*10^-3 ± 0.12	5.723*10^-3 ± 0.02	0.065 ± 0.03	57.23*10^-3 ± 0.01

*NA: Not applicated

Table 7: The chemical composition of the five EOs

	Composition %
Compounds	*Eucalyptus:* *(Eucalyptus globulus)*	*Cinnamon:* *(Cinnamomum verum)*	*Lemon* *(Citrus limon)*	*Lavender* *(Lavandula angustifolia)*	*Tea tree* *(Camellia sinensis)*
α-Pinene	4.55	-	3.72	-	-
3-Octen-5-yne, 2,7-dimethyl	-	-	13.51	-	-
α-Thujene	0.87	-	-	-	-
β-Pinene	0.68	-	-	0.08	-
Camphene	-	-	-	0.08	0.34
β-Myrcene	-	-	2.09	1.37	-
Benzaldehyde	-	0.75	-	-	-
Salicylaldehyde	-	0.11	-	-	-
Phenylacetaldehyde	-	0.18	-	-	-
Phenethyl alcohol	-	0.28	-	-	-
Benzenepropanal	-	0.45	-	-	-
Cinnamaldehyde	-	82.26	-	-	-
α-Terpinene	5.55	-	-	-	-
α-Terpineol	-	-	-	-	5.32
α-Copaene	-	0.45	-	-	-
Coumarin	-	2.69	-	-	-
Caryophyllene	-	-	-	2.56	-
Humulene	-	-	-	0.24	-
trans-Cinnamic acid	-	1.97	-	-	-
3-(2-Phenylethyl) benzonitrile	-	0.66	-	-	-
D-Limonene	-	-	59.55	-	11.10
Terpinen-4-ol	-	-	-	1.34	40.28
4-Carene	-	-	0.73	-	-
3-Carene	-	-	-	-	2.34
p-Mentha-2,4(8)-diene	-	-	-	-	6.50
p-Mentha-1,4(8)-diene	-	-	-	-	2.37
Camphor	-	-	-	1.18	-
Isoborneol	-	-	-	1.6	-
trans-.beta.-Ocimene	-	-	0.79	-	-
trans-.alpha.-Bergamotene	-	-	0.91	-	-
Linalool	-	-	-	43.17	-
Linalyl isobutyrate	-	-	-	40.18	-
β-Phellandrene	-	-	-	-	0.33
β-Citral	-	-	3.1	-	-
γ-Terpinene	-	-	12.51	-	16.95
Aromadendrene	-	-	-	-	3.05
Eucalyptol	86.25	-	-	2.12	-

DISCUSSION:

As described in the results section above, Cinnamomum zeylanicum was revealed as the most efficient essential oil. Our results corroborate with other studies that reported the highly effective antimicrobial activity of Cinnamon EO against S. aureus than E.coli and the minimum zone diameter was witnessed on P. aeruginosa ^33,34,35.

Moreover, in the present study, Tea tree and Lavender essential oil showed a bactericidal potential on E.coli and S. aureus while they demonstrated a bacteriostatic effect on P. aeruginosa. Our reported results are in good agreement with previous findings, where the authors noted an effective antimicrobial activity of tea tree essential oil against various microorganisms, except for P. aeruginosa ^36,37,38. However, EricW et al., 2011 didn’t report any antimicrobial activity against P. aeruginosa and E.coli ³⁹. The antimicrobial activity of essential oil could be attributed to the plant varieties, various environmental, and genetic differences, and the experimental procedure. These different conditions make a reliable comparison with published results practically difficult.

Nevertheless, P. aeruginosa has become an important cause of fatal infections and is well known for increased antibiotic resistance. To this end, considerable interest has been focused on providing an alternative bioactive substance against this multidrug-resistant strain ⁴⁰. Thus, our results seem to be remarkable, as Cinnamon and Eucalyptus essential oils showed effective bactericidal activity against this bacterial strain.

Indeed, from the present findings, each essential oil exhibits distinct effects against particular bacterial strains. These results could be due either to the difference in the structure of the bacteria walls or to the difference in the chemical composition of the essential oils ^{35, 39,40}.

Several studies have explained the antimicrobial activity of essential oils by the predominance of their major components ^41,42,43, including Cinnamaldehyde (82.26%) in Cinnamon EO, Eucalyptol (86.25%) in Eucalyptus globulus, Linalool and Linalyl isobutyrate (43.17% - 40.18%) in Lavandula angustifolia, Limonene (59.55%) in Citrus limon, and Terpinene-4-ol (40.28%) in Camellia sinensis.

However, the antimicrobial activity might also be advanced by the presence of low amounts of components other than the main constituent. For instance, trans-cinnamic acid (1,97%), d-Terpinene (12,29%), α pinene (4,39%), and β pinene (0,68%) present in Cinnamon oil are in like manner known for their good antimicrobial properties ^44,45.

On the other hand, the five essential oils were characterized by parameters that were distributed into three groups. The quality indices group, the heavy metal group, and the antibacterial activity group. To analyse this type of data and identify information relating to the characterizations of the 5 oils, we opted for multiple factor analysis (MFA) which is a method well suited to this type of data. The MFA method is considered a weighted Principal component analysis (PCA). We found that the foreground explains about 80% of the information, meaning there is significant variability in the data.

Figure 1: Graph of Multiple Factor Analysis (MFA)

The graph of Figure 1 shows the importance of the effect of each group. Indeed, according to axis 1 which represents 48% of variability, the two groups of parameters of the quality indices and the antibacterial activity (bioactivity) give diversification characteristics between the five analyzed oils. However, according to axis 2, we observe that the group of heavy metals gives a significant effect of distinction.

We can therefore give more information on this dispersion between oils through the graph of individuals (Figure 2-A) and correlation (Figure 2-B). It indicates clearly that the properties of Citrus -Limon are different from Cinnamon according to axis 1. This variance is explained by the fact that Cinnamon is characterized by very high values in antibacterial activity and by the quality indices (D et RI and α). On the other hand, Citrus- Limon has a low activity but it is distinguished by a high rotational power. This study allows us to conclude that there is a significant difference between the five essentials oils, according to the 3 groups’ studied parameters.

Figure 2-A: Graph of Individual parameters

Figure 2-B: Graph of Correlation parameters

We also carried out an Ascending Hierarchical Classification (AHC) (Figure 3-A) to consolidate the findings drawn from Figure 2. The dendrogram (Figure 3-B) indicates that three classes of oils are obtained. The first group corresponds to Lemon and tea tree, the second to Eucalyptus and Lavandula, and the third one corresponds to cinnamon. This classification can be explained by the chemical composition of essential oils.

The major products of eucalyptus and lavender are eucalyptol and linalool respectively which are monoterpenes, this is why they are in the same classification. The second classification concerns the essential oil of cinnamon, we find no correspondence between the majority product cinnamaldehyde and the majority products of other oils and this can be explained by the nature of the structure of cinnamaldehyde ⁴⁶, which is an organic compound of the phenylpropanoids family. The third class which includes Tea tree and Citrus, might be due to the presence of unique chemical compounds such as D-Limonene and γ-Terpinene.

Figure 3-A: Factor Map

Figure 3-B: Dendrogram

CONCLUSION:

The present study evaluated the chemical composition, Physical analyses, the content of heavy metals: Cu, Pd, Zn, and Hg, and the antimicrobial activity of five essential oils. The results showed that most quality indices (refractive index, Optical Rotation, density) and concentrations of heavy metals of oils are aligned with the European Pharmacopoeia monographs. In addition, Cinnamon, Eucalyptus, Lavender, and Tea tree essential oils demonstrated varying levels of inhibition against the tested organisms. On the other hand, P. aeruginosa was considered the most resistant bacterial strain and showed a bacteriostatic effect when treated with Lavender or Tea tree oils. However, Cinnamon oil revealed the most efficient antimicrobial activity.

The statistical treatment by Multiple Factor Analysis (MFA) of all the results obtained for the 5 essential oils showed a significant correlation between the chemical and biological tests carried out. The study was able to classify the 5 oils into three classes, according to their content of the main compounds and their anti-bacterial activity in relation to the strains tested.

The results of this study show that the 5 essential oils are of very high quality and can be sold in pharmacies. Sales staff must be fully trained in their use and safety, and have technical data sheets (analysis bulletins) proving their quality.

Also, our preliminary results on anti-bacterial activity may also be useful for more in-depth studies into the use of these essential oils to control certain pathogens that are becoming multi-resistant to antibiotics.

ACKNOWLEDGMENT:

The authors express their gratitude to Mrs. Zineb Ouazzani for graciously supplying the essential oils intended for commercialization. Additionally, they extend their appreciation to Dr. Aziz Razkaoui, the CEO of the pharmaceutical laboratory Soludia Maghreb, for generously providing the necessary equipment and chemical substances for the meticulous quality assessment of the essential oils.

CONFLICT OF INTEREST:

The authors declare that there are no conflicts of interest.

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Received on 28.05.2024 Revised on 11.09.2024

Accepted on 17.12.2024 Published on 27.03.2025

Available online from March 27, 2025

Research J. Pharmacy and Technology. 2025;18(3):1200-1208.

DOI: 10.52711/0974-360X.2025.00174

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