Antioxidant, Volatile Compounds; Antimicrobial, Anti-Inflammatory, and Dermatoprotective Properties of Cedrus atlantica (Endl.) Manetti Ex Carriere Essential Oil: In Vitro and In Silico Investigations

Cedrus atlantica extract inhibits melanoma progression by suppressing epithelial-mesenchymal transition and inducing mitochondria-mediated apoptosis

Melanoma has a low incidence, accounting for less than 5% of skin cancers; however, it is the most lethal cancer, primarily because of its high potential for metastasis and resistance to different treatments. Natural products can sensitize melanoma to chemotherapy and overcome drug resistance. Previous studies have reported Cedrus atlantica extract has various pharmacological benefits such as anti-inflammatory, antioxidant, antibacterial, and analgesic properties. This study aimed to explore the effects of C. atlantica extract (CAt) against melanoma in vitro and in vivo. The effects of CAt on B16F10 cell viability, proliferation, migration, invasion, and apoptosis were detected using MTT, colony formation, wound-healing, Boyden chamber, and TUNEL assays. Semi-quantitative RT-PCR and western blotting were used to measure mRNA and protein expression, respectively. Results revealed that CAt selectively decreased the viability of B16F10 cells and inhibited colony formation in a dose-dependent manner. CAt reduces cell migration and invasion by regulating epithelial-mesenchymal transition-associated proteins (Snail, E-cadherin, and vimentin). Moreover, CAt enhanced the Bax/Bcl-2 ratio and the expression of cleaved-caspase-9, caspase-3, and PARP1, resulting in the activation of mitochondria-mediated apoptosis. In an in vivo study, CAt significantly inhibited tumor growth and prolonged the lifespan of mice at a well-tolerated dose. Importantly, the combination of CAt and 5-fluorouracil (5-FU) exhibited synergistic growth suppression and attenuated the development of 5-FU resistance. Overall, the findings suggest that CAt holds promise as a potential drug or adjuvant to improve melanoma treatment.

Methods for Determination of Antimicrobial Activity of Essential Oils In Vitro-A Review

Essential oils (EOs) have been gaining popularity in the past decades among researchers due to their potential to replace conventional chemicals used in the fight against pests, pathogenic and spoilage microbes, and oxidation processes. EOs are complex mixtures with many chemical components, the content of which depends on many factors-not just the plant genus, species, or subspecies, but also chemotype, locality, climatic conditions, phase of vegetation, method of extraction, and others. Due to this fact, there is still much to study, with antimicrobial effect being one of the key properties of EOs. There are many methods that have been frequently used by researchers for in vitro evaluation; however, although the research has been going on for decades, an internationally accepted standard is still missing. Most of methods are based on time-proven standards used for the testing of antibiotics. Due to the specific properties of EOs and their components, such as volatility and hydrophobicity, many modifications of these standard procedures have been adopted. The aim of this review is to describe the most common methods and their modifications for the testing of antimicrobial properties of EOs and to point out the most controversial variables which can potentially affect results of the assays.

Inactivation mechanism of phenyllactic acid against Bacillus cereus spores and its application in milk beverage

Phenyllactic acid (PLA) as a natural phenolic acid exhibits antibacterial activity against non-spore-forming bacteria, while the inhibitory effect against bacterial spore remained unknown. Herein, this study investigated the inactivation effect of PLA against Bacillus cereus spores. The results revealed that the minimum inhibitory concentration of PLA was 1.25 mg/mL. PLA inhibited the outgrowth of germinated spores into vegetative cells rather than germination of spores. PLA disrupted the spore coat, and damaged the permeability and integrity of inner membrane. Moreover, PLA disturbed the establishment of membrane potential due to the inhibition of oxidative metabolism. SEM observations further visualized the morphological changes and structural disruption caused by PLA. Besides, PLA caused the degradation of DNA of germinated spores. Finally, PLA was applied in milk beverage, and showed promising inhibitory effect against B. cereus spores. This finding could provide scientific basis for the application of PLA against spore-forming bacteria in food industry.

Characterization of Volatile Organic Compounds and Essential Oil Profile of Pittosporum tobira (Thunb.) W.T. Aiton Cultivated in Tunisia

The chemical compositions of the essential oils (EOs) of roots, young and old leaves and stems, and flowers of Pittosporum tobira (Thunb.) W.T. Aiton cultivated in Tunisia and of the volatile organic compounds (VOCs) emitted by the powder of each organ were identified. The EOs are extracted from fresh material by hydrodistillation, whereas the VOCs are obtained by head space solid-phase microextraction (HS-SPME) from the powdered dry tissues. Fifty-eight VOCs are identified, while, 105 components are detected for the EOs. The main EOs compounds are α-neoclovene, β-caryophyllene and limonene in roots (22.56, 12.52, and 8.59 %, respectively), viridiflorol in young stems, flowers and young leaves (34.90, 31.60, and 24.60 %, respectively), α-cadinol in young stems and leaves, and flowers (13.80, 10.40, and 9.10 %, respectively), (E)-nerolidol in flowers (13.30 %), and germacrene D in old stems (9.06 %). The major detected VOCs are n-undecane, mainly in young and old leaves (71.40 and 40.90 %, respectively), n-nonane in young leaves and flowers (31.80 and 27.10 %, respectively), α-cubebene in old stems and flowers (22.60 and 15.50 %, respectively), and α-gurjunene and β-gurjunene in roots (14.20 and 12.20 %, respectively). Principal Component Analysis (PCA) carried out on the 26 main volatile compounds (relative content exceeding 6 %) identified both by HS and in the EOs allowed their classification into two groups; compounds specific to roots and those specific to aerial parts. The later are subdivided in to two subgroups; old leaves and stems compounds subgroup, and young leaves and stems, and flowers one. We can notice that the two methods used to extract P. tobira volatile compounds and identify them are complementary. This study defines and differentiates, for the first time, the specific aroma profile of P. tobira from Tunisia. In addition to its ornamental value, all the organs of this species, could be valued as a source of volatile compounds useful in perfume, cosmetics and as food flavoring products.

Phytochemical characterization, antimicrobial properties and in silico modeling perspectives of Anacyclus pyrethrum essential oil

Medicinal plants are used widely in the treatment of various infectious diseases. One of these medical plants is Moroccan plants such as Anacyclus pyrethrum. In this study, the essential oil isolated from the leaves of Anacyclus pyrethrum (APEO) by the hydrodistillation method was analyzed using (GC/MS) analysis. A total of forty-four compounds were identified form the oil and the oxygenated monoterpenes were the most abundant class of compounds. The major identified compound is santolina alcohol (40.7 %), followed by germacrene-D (8.9 %). The in-vitro assessment of the antimicrobial efficacy of APEO encompassed an investigation involving six microbial strains, including two Gram-positive bacteria, four Gram-negative bacteria, and three fungal strains. The findings revealed noteworthy antibacterial and antifungal properties against all examined microorganisms, with inhibitory zone diameters ranging from 25.67 ± 0.06 mm to 25.19 ± 0.03 mm for Gram-positive bacteria and from 22.34 ± 0.01 mm to 14.43 ± 0.02 mm for Gram-negative bacteria, as determined through the disc-diffusion assay. In the case of antifungal activity, inhibitory zones ranged from 24.57 ± 0.04 mm to 18.37 ± 0.06 mm. Further evaluation revealed that the MIC values of Gram-positive bacteria were at the concentration 0.25 % v/v, while MBC values ranged from 0.25 % to 1.0 % v/v. The Gram-negative bacteria exhibited MIC values spanning from 0.5 % to 2.0 % v/v, with MBC values in the range of 0.5 %-2.0 % v/v. For the fungal strains, MIC values ranged from 0.5 % to 1.0 % v/v, while the MFC consistently remained at 1.0 % for all tested fungal strains. The assessment of the MBC/MIC and MFC/MIC ratios collectively indicates that A. pyrethrum EO possesses bactericidal and fungicidal attributes. The in silico study of bioavailability predictions for compounds in APEO based on six physicochemical properties show optimal physiochemical properties including size, lipophilicity, solubility, flexibility, and saturation. α-Pinene, limonene, germacrene D, and (E)-β-farnesene are non-polar due to their lack of polar groups, and the ADME profile indicates desirable properties for considering these compounds in drug development. Molecular docking investigation indicates that all the compounds of APEO reside well into the binding site of the DNA gyrase B enzyme of Staphylococcus aureus by mediating a number of significant interactions with the binding site residues. The ADME analysis suggested that the major compounds APEO possess desirable properties for further consideration in drug development. In light of these findings, APEO could serve as a natural source for the elaboration of new and active antimicrobial drugs.

Exploring the antidiabetic and anti-inflammatory potential of Lavandula officinalis essential oil: In vitro and in silico insights

Medicinal plants have been utilized for centuries in traditional medicine systems worldwide, providing a rich source of bioactive compounds with diverse biological activities. Lavandula officinalis, a member of the Lamiaceae family, has been recognized for its multifaceted pharmacological activities. In this current investigation, our primary objective was to scrutinize the in vitro inhibitory potential of L. officinalis essential oil (LOEO) against alpha-amylase and alpha-glucosidase, with the aim of understanding its antidiabetic effects. Additionally, the assay encompassed tyrosinase and lipoxygenase (LOX) to assess its anti-inflammatory attributes. Unraveling the underlying molecular mechanisms of these activities prompted an in-silico study. The purpose was to establish correlations between in-vitro observations and computational insights derived from molecular docking, which forecasts the interaction of LOEO molecules with their respective targets, alongside ADMET prediction. The Gas Chromatography-Mass Spectrometry (GC-MS) analysis allow to identify eighteen compounds, with the dominance of L-camphor (43.12 %), 1,8-cineole (34.27 %) and borneol (8.60 %) in LOEO. The antidiabetic evaluation revealed that LOEO exhibited noteworthy inhibitory activity against both α-amylase and α-glucosidase, displaying IC50 values of 3.14 ± 0.05 mg/mL and 2.07 ± 0.03 mg/mL, respectively. The subsequent in-silico study highlighted the particularly strong binding affinity of (E)-Farnesene, with a binding score of -7.4 kcal/mol for alpha-glucosidase, while Germacrene D displayed the highest affinity among the ligands (-7.9 kcal/mol) for the alpha-amylase target. Furthermore, the investigation into in vitro anti-inflammatory activity unveiled LOEO efficacy against tyrosinase (IC50 = 42.74 μg/mL) and LOX (IC50 = 11.58 ± 0.07 μg/mL). The in-silico analysis echoed these findings, indicating α-Cadinene's notable binding affinity of 6 kcal/mol with tyrosinase and α-Cedrene's binding score of -6.5 kcal/mol for LOX. Impressively, for both COX-1 and COX-2, α-Cedrene exhibited significant binding affinities of -7.6 and -7.3 kcal/mol, respectively. The convergence between the in vitro and in silico outcomes underscores the potential of LOEO and its constituent compounds as potent inhibitors targeting both diabetes and the inflammatory processes.

QbD Approach in Cosmetic Cleansers Research: The Development of a Moisturizing Cleansing Foam Focusing on Thickener, Surfactants, and Polyols Content

Cleansing products, particularly innovative cosmetic foams, must efficiently remove impurities with minimal impact on the skin barrier and have a favorable sensory profile. The choice of product ingredients is crucial to ensure the optimal characteristics. The current study aims to provide a comprehensive framework for understanding the variability in the characteristics of a cleansing foam to achieve desired properties. The novelty of this study lies in the combination of ingredients for their potential synergistic and complementary effects in cleansing dry skin, as well as the application of Quality by Design (QbD) elements to develop and optimize the formulation of cleansing foam. The effects of varying the concentration of mild surfactants, polyols, and gel-forming agents on the properties of the gels and of the generated foams were studied. Significant influences of the formulation factors were observed: an increased ratio of xanthan gum positively impacted the texture properties of the gel, whereas higher concentrations of surfactants had a negative impact on these parameters. Additionally, increasing the polyols ratio was found to negatively influence the foaming property and stability of the foam. The study established an optimal formulation of a cleansing foam with a ratio of 0.45% xanthan gum, 26.19% surfactants and 2.16% polyols to be used for dry skin hygiene.

Abuelizz H, Lafdil FZ, Er-rahmani S, Lyoussi B, Derwich E. Coriandrum sativum L., essential oil as a promising source of bioactive compounds with GC/MS, antioxidant, antimicrobial activities: in vitro and in silico predictions

Introduction: Coriandrum sativum L. essential oil (CS-EO) is being evaluated in vitro for its antioxidant and antimicrobial properties, and its volatile compounds are to be identified as part of this exploratory study. Methods: The processes underlying the in vitro biological properties were explained using in silico simulations, including drug-likeness prediction, molecular docking, and pharmacokinetics (absorption, distribution, metabolism, excretion, and toxicity-ADMET). Chemical screening of CS-EO was conducted using gas chromatography-mass spectrometry (GC-MS). Five in vitro complementary techniques were used to assess the antioxidant activity of CS-EO: reducing power (RP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging activity, β-Carotene bleaching test (BCBT), and phosphomolybdenum assay (TAC). Results: According to GC-MS analysis, linalool (59.04%), γ-Terpinene (13.02%), and α-Pinene (6.83%) are the main constituents of CS-EO. Based on the in vitro antioxidant assay results, CS-EO has been found to have a superior antioxidant profile. Its estimated scavenging rates for ABTS+ are 0.51 ± 0.04 mg/mL, BCBT is 9.02 ± 0.01 mg/mL, and CS-EO is 1.52 ± 0.14 mg/mL. C. sativum demonstrated 6.13 ± 0.00 μg/mL for reducing power and 213.44 ± 0.45 mg AAE/mL for total antioxidant activity. The in vitro antimicrobial activity of CS-EO was assessed against five strains, including two gram-positive bacteria, two gram-negative bacteria, and one fungal strain (Candida albicans). Significant antibacterial and antifungal activities against all strains were found using the disc-diffusion assay, with zones of inhibition larger than 15 mm. The microdilution test highlighted the lowest MIC and MBC values with gram-positive bacteria, ranging from 0.0612 to 0.125% v/v for MIC and 0.125% v/v for MBC. The fungal strain's MFC was 1.0% v/v and its MIC was measured at 0.5%. Based on the MBC/MIC and MFC/MIC ratios, CS-EO exhibits bactericidal and fungicidal activity. The ADMET study indicates that the primary CS-EO compounds are good candidates for the development of pharmaceutical drugs due to their favorable pharmacokinetic properties. Conclusion: These results point to a potential application of this plant as a natural remedy and offer empirical backing for its traditional uses. It is a promising environmentally friendly preservative that can be used extensively in the food and agricultural industries to prevent aflatoxin contamination and fungal growth in stored goods.

Unlocking the combined action of Mentha pulegium L. essential oil and Thym honey: In vitro pharmacological activities, molecular docking, and in vivo anti-inflammatory effect

Mentha pulegium L., a plant widely embraced for its therapeutic properties by populations worldwide, including Morocco, has long been recognized for its potential in treating various ailments. This study aims to comprehensively evaluate the antioxidant, anti-inflammatory, and dermatoprotective properties of essential oil derived from M. pulegium, and thyme honey as well as their combined effects. To unravel the chemical composition, a rigorous GC-MS analysis was conducted. Subsequently, we examined their antioxidant potential through three distinct assays: DPPH●, hydrogen peroxide assay, and xanthine oxidase assay. The anti-inflammatory properties were scrutinized through both in vitro and in vivo experiments. Simultaneously, the dermatoprotective efficacy was investigated in vitro by evaluating tyrosinase inhibition. Our findings revealed that pulegone constitutes the predominant compound in M. pulegium essential oil (MPEO), constituting a remarkable 74.82 % of the composition. Significantly, when the essential oil was combined with thym honey, it exhibited superior anti-inflammatory and dermatoprotective effects across all in vivo and in vitro tests. Moreover, our in silico molecular docking analysis hinted at the potential role of cyclohexanone, 3-methyl, an element found in the MPEO, in contributing to the observed outcomes. While this study has unveiled promising results regarding the combined in vitro, in vivo and in silico biological activities of the essential oil and honey, it is imperative to delve further into the underlying mechanisms through additional experimentation and alternative experimental methods. Understanding these mechanisms in greater detail will not only enhance our comprehension of the therapeutic potential but also pave the way for the development of innovative treatments and applications rooted in the synergy of these natural compounds. Furthermore, it would be advantageous to test different possible combinations using experimental design model. Moreover, it would be better to test the effect of single compounds of MPEO to clearly elucidate their efficiency. MPEO alone or combined with thyme honey may be a useful for the development of novel biopharmaceuticals.

Petroselinum crispum L., essential oil as promising source of bioactive compounds, antioxidant, antimicrobial activities: In vitro and in silico predictions

This exploratory study aims to identify the volatile compounds in PC-Eo (Petroselinum crispum L. essential oil) and evaluate its antioxidant and antimicrobial properties in vitro. Molecular docking, drug-likeness prediction, and pharmacokinetics (absorption, distribution, metabolism, excretion, and toxicity-ADMET) were among the in silico simulations that were used to explain the biological properties observed in vitro. For PC-Eo's chemical screening, gas chromatography-mass spectrophotometry (GC-MS) was employed. The antioxidant activity of PC-Eo was evaluated using five in vitro complementary techniques, including 2,2-diphenyl-1-picrylhydrazyl (DPPH), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) radical scavenging activity, β-Carotene bleaching test (BCBT), reducing power (RP), and phosphomolybdenum assay (TAC). GC-MS analysis revealed that the primary components of PC-Eo are apiol (49.05 %), Myristicin (21.01 %), and 1-allyl-2,3,4,5-tetramethoxybenzene (13.14 %). The results of the in vitro antioxidant assays indicate that PC-Eo exhibits a superior antioxidant profile. The in vitro antimicrobial activity of PC-Eo was assessed against five strains, including 2 g-positive bacteria, 2 g-negative bacteria, and one fungal strain (Candida albicans). The disc-diffusion assay revealed significant antibacterial and antifungal activities against all strains, with zones of inhibition exceeding 15 mm. The microdilution test highlighted the lowest MIC and MBC values with gram-positive bacteria, ranging from 0.25 to 0.5 % v/v for MIC and 0.5-1.0 % v/v for MBC. For the fungal strain, MIC was recorded at 1.25 % and MFC at 2.5 % v/v. PC-Eo demonstrates bactericidal and fungicidal activity based on the MBC/MIC and MFC/MIC ratios. According to the ADMET study, the primary PC-Eo compounds have advantageous pharmacokinetic characteristics. These findings provide empirical support for the traditional uses of this plant and indicate its possible use as a natural remedy.

Chemical profiling of volatile compounds of the essential oil of grey-leaved rockrose (Cistus albidus L.) and its antioxidant, anti-inflammatory, antibacterial, antifungal, and anticancer activity in vitro and in silico

Cistus albidus: L., also known as Grey-leaved rockrose and locally addressed as šṭab or tûzzâla lbîḍa, is a plant species with a well-established reputation for its health-promoting properties and traditional use for the treatment of various diseases. This research delves into exploring the essential oil extracted from the aerial components of Cistus albidus (referred to as CAEO), aiming to comprehend its properties concerning antioxidation, anti-inflammation, antimicrobial efficacy, and cytotoxicity. Firstly, a comprehensive analysis of CAEO's chemical composition was performed through Gas Chromatography-Mass Spectrometry (GC-MS). Subsequently, four complementary assays were conducted to assess its antioxidant potential, including DPPH scavenging, β-carotene bleaching, ABTS scavenging, and total antioxidant capacity assays. The investigation delved into the anti-inflammatory properties via the 5-lipoxygenase assay and the antimicrobial effects of CAEO against various bacterial and fungal strains. Additionally, the research investigated the cytotoxic effects of CAEO on two human breast cancer subtypes, namely, MCF-7 and MDA-MB-231. Chemical analysis revealed camphene as the major compound, comprising 39.21% of the composition, followed by α-pinene (19.01%), bornyl acetate (18.32%), tricyclene (6.86%), and melonal (5.44%). Notably, CAEO exhibited robust antioxidant activity, as demonstrated by the low IC50 values in DPPH (153.92 ± 4.30 μg/mL) and β-carotene (95.25 ± 3.75 μg/mL) assays, indicating its ability to counteract oxidative damage. The ABTS assay and the total antioxidant capacity assay also confirmed the potent antioxidant potential with IC50 values of 120.51 ± 3.33 TE μmol/mL and 458.25 ± 3.67 µg AAE/mg, respectively. In terms of anti-inflammatory activity, CAEO displayed a substantial lipoxygenase inhibition at 0.5 mg/mL. Its antimicrobial properties were broad-spectrum, although some resistance was observed in the case of Escherichia coli and Staphylococcus aureus. CAEO exhibited significant dose-dependent inhibitory effects on tumor cell lines in vitro. Additionally, computational analyses were carried out to appraise the physicochemical characteristics, drug-likeness, and pharmacokinetic properties of CAEO's constituent molecules, while the toxicity was assessed using the Protox II web server.

Tetraclinis articulata (Vahl) Mast. essential oil as a promising source of bioactive compounds with antimicrobial, antioxidant, anti-inflammatory and dermatoprotective properties: In vitro and in silico evidence

Tetraclinis articulata is a known traditional medicinal plant used to manage various ailments, such as diabetes, rheumatism and infectious diseases. This study aims to determine the chemical constituents of T. articulata essential oil (EO) and to evaluate its in vitro antibacterial, anti-candidal, antioxidant, anti-inflammatory and dermatoprotective properties. In addition, a computational docking approach was used to predict the potential antioxidant, antibacterial, antifungal, anti-inflammatory, and cytotoxic properties of the identified compounds. The volatile oil obtained by hydrodistillation was characterized using gas chromatography-mass spectrometry (GC-MS). The antioxidant activity of T. articulata EO was investigated using three complementary assays: DPPH, ABTS and FRAP. Lipoxygenase (5-LOX) and tyrosinase enzymes were used to assess the anti-inflammatory and dermatoprotective effects of this oil. Moreover, disc-diffusion technique, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) assays were employed for the antimicrobial screening. The GC-MS analysis revealed that bornyl acetate (41.80 %), α-pinene (17.97 %) and camphor (15.97 %) are the major components of the studied EO. Moreover, T. articulata EO has exhibited promising antioxidant effect on FRAP, DPPH, and ABTS experiments. It also significantly inhibited 5-LOX (IC50 = 67.82 ± 0.03 μg/mL) and tyrosinase (IC50 = 211.93 ± 0.02 μg/mL). The results of MIC and MBC assays indicated that T. articulata EO is able to inhibit the growth of all tested bacteria (Gram + and Gram -) and Candida species. The ratio of tolerance level indicated that the tested oil was bactericidal against the Gram + bacteria and Candida species, whereas it has a bacteriostatic behavior against the Gram- bacteria. In light of these findings, T. articulata EO may be suggested as a potential pharmaceutical agent to prevent inflammation and skin problems and may serve as a natural antimicrobial and antioxidant alternative for sustainable application in food products.

GC/MS Profiling, In Vitro Antidiabetic Efficacy of Origanum compactum Benth. Essential Oil and In Silico Molecular Docking of Its Major Bioactive Compounds

Diabetes is a global health concern with significant implications for individuals and healthcare systems. Finding effective and safe antidiabetic agents is crucial for the management of this chronic disease. Natural products have emerged as potential alternatives to allopathic drugs, offering a vast source of bioactive compounds. In this study, we conducted an assessment of the antidiabetic potential of Origanum compactum essential oil, employing a two-pronged approach, i.e., experimental investigation and computational docking analysis. The results of gas chromatography–mass spectrometry (GC-MS) showed that thymol (54.6%), carvacrol (23.18%), and p-cymene (7.12%) were the major compounds. Experimental assessments revealed higher IC50 values (150 µg/mL for α-amylase; 120 µg/mL for α-glucosidase) of O. compactum oil, compared to the control drug acarbose. In silico analysis revealed the best binding affinity of the oil components (carvacrol and thymol) with human NADPH oxidase, while the lysosomal acid-α-glucosidase and salivary amylase also demonstrated good binding affinity towards carvacrol and thymol. Our findings highlight the translational potential of O. compactum oil-based treatment for diabetes mellitus and provide a basis for further studies on the modulation of NADPH oxidase, amylase inhibition, and α-glucosidase by antidiabetic natural products. However, further in vivo investigations are strongly required to confirm the results of in vitro antidiabetic effect of O. compactum EO.

Abdallah E, Assaggaf H, Qasem A, S. Rajab B, Lee LH, Bouyahya A, Goh KW, Ming LC, Mrabti HN. Combination of sweet orange, lentisk and lemon eucalyptus essential oils: Optimization of a new complete antimicrobial formulation using a mixture design methodology

Sweet orange (Citrus × sinensis (L.) Osbeck), lentisk (Pistacia lentiscus L.) and lemon eucalyptus (Eucalyptus citriodora Hook) are medicinal plants known by its culinary virtues. Their volatile oils have demonstrated promising antimicrobial activity against a panel of microbial strains, including those implicated in food deterioration. In this exploratory investigation, we aimed to determine the antimicrobial formulation of sweet orange, lentisk and lemon eucalyptus essential oils (EOs) using the simplex-centroid mixture design approach coupled with a broth microdilution method. EOs were first extracted by hydrodistillation, and then their phytochemical profile was characterized using Gas chromatography-mass spectrometry (GC-MS). GC-MS analysis identified d-limonene (14.27%), careen-3 (14.11%), β-myrcene (12.53%) as main components of lentisk EOs, while lemon eucalyptus was dominated by citronellal (39.40%), β-citronellol (16.39%) and 1,8-cineole (9.22%). For sweet orange EOs, d-limonene (87.22%) was the principal compound. The three EOs exhibited promising antimicrobial potential against various microorganisms. Lemon eucalyptus and sweet orange EO showed high activity against most tested microorganisms, while lentisk EO exerted important effect against some microbes but only moderate activity against others. The optimization formulations of antimicrobial potential showed interesting synergistic effects between three EOs. The best combinations predicted on C. albicans, S. aureus, E. coli, S. enterica and B. cereus correspond to 44%/55%/0%, 54%/16%/28%, 43%/22%/33%, 45%/17%/36% and 36%/30%/32% of Citrus sinensis, Pistacia lentiscus and Eucalyptus citriodora EOs, respectively. These findings suggest that the combination of EOs could be used as natural food preservatives and antimicrobial agents. However, further studies are needed to determine the mechanisms of action and efficacy of these EOs against different microorganisms.