Chemical Composition and Antibacterial Activities of Eight Plant Essential Oils from Morocco against Escherichia coli Strains Isolated from Different Turkey Organs

Assessing the Optimal Antibacterial Action of Lavandula stoechas L., Thymus zygis L., and Eucalyptus camaldulensis Dehnh Essential Oils

The use of combined essential oils (EOs) is a new technique that can improve their preservative effects while minimizing their sensory impact in foods. The aim of this study was to determine the chemical profile of three essential oils (EOs) extracted from Lavandula stoechas L. (Ls), Thymus zygis L. (Tz), and Eucalyptus camaldulensis Dehnh (Ec) and to evaluate their synergistic antibacterial activity for optimal inhibition against Bacillus subtilis, Escherichia coli, and Staphylococcus aureus using an augmented Simplex centroid mixing scheme. The essential oils were extracted by hydrodistillation and analyzed via gas chromatography-mass spectrometry. Anti-bacterial potency was evaluated by disk diffusion. Chemical analysis revealed the main compounds in Lavandula stoechas (Ls) essential oil: camphor (36.15%), followed by fenchone (16.57%) and Z-8-hydroxy linalool (8.28%). The Thymus zygis (Tz) essential oil is dominated by δ-terpineol (27.64%), δ-3-carene (15.7%), and thymol (14.17%). In contrast, the Eucalyptus camaldulensis (Ec) essential oil contains mainly 1,8-cineole (43.61%), γ-terpinene (11.71%), and α-terpineol (10.58%). The optimal mixture is the binary association of 40% E. camaldulensis EO and 60% T. zygis EO, which provides an effective inhibition diameter (ID) of 13.37 mm to inhibit S. aureus. Furthermore, the formulation of 27% and 73% EOs of E. camaldulensis and T. zygis, respectively, corresponds to the mixture required to achieve the optimum inhibition diameter (ID = 11.55 mm) against E. coli. In addition, the mixture of 29% EO of E. camaldulensis and 71% EO of T. zygis is the optimum mixture to inhibit B. subtilis, with an inhibition diameter of 12.31 mm. These findings highlight the potency of antibacterial formulations of these essential oils and suggest that they might be used as substitutes for conventional drugs to prevent the development of bacteria responsible for serious infections and food spoilage.

Antibacterial, bacteriolytic, and antibiofilm activities of the essential oil of temu giring (Curcuma heyneana Val.) against foodborne pathogens

Foodborne pathogens may cause foodborne illness, which is among the major health problems worldwide. Since the therapeutic options for the treatment of the disease are becoming limited as a result of antibacterial resistance, there is an increasing interest to search for new alternatives of antibacterial. Bioactive essential oils from Curcuma sp become potential sources of novel antibacterial substances. The antibacterial activity of Curcuma heyneana essential oil (CHEO) was evaluated against Escherichia coli, Salmonella typhi, Shigella sonnei, and Bacillus cereus. The principal constituents of CHEO are ar-turmerone, β-turmerone, α-zingiberene, α-terpinolene, 1,8-cineole, and camphor. CHEO exhibited the strongest antibacterial activity against E. coli with a MIC of 3.9 µg/mL, which is comparable to that of tetracycline. The combination of CHEO (0.97 µg/mL) and tetracycline (0.48 µg/mL) produced a synergistic effect with a FICI of 0.37. Time-kill assay confirmed that CHEO enhanced the activity of tetracycline. The mixture disrupted membrane permeability of E. coli and induced cell death. CHEO at MIC of 3.9 and 6.8 µg/mL significantly reduced the formation of biofilm in E. coli. The findings suggest that CHEO has the potential to be an alternative source of antibacterial agents against foodborne pathogens, particularly E. coli.

Unveiling the Antimicrobial, Anti-Biofilm, and Anti-Quorum-Sensing Potential of Paederia foetida Linn. Leaf Extract against Staphylococcus aureus: An Integrated In Vitro-In Silico Investigation

Antimicrobial resistance poses a global health threat, with Staphylococcus aureus emerging as a notorious pathogen capable of forming stubborn biofilms and regulating virulence through quorum sensing (QS). In the quest for novel therapeutic strategies, this groundbreaking study unveils the therapeutic potential of Paederia foetida Linn., an Asian medicinal plant containing various bioactive compounds, contributing to its antimicrobial activities, in the battle against S. aureus. Through a comprehensive approach, we investigated the effect of ethanolic P. foetida leaf extract on S. aureus biofilms, QS, and antimicrobial activity. The extract exhibited promising inhibitory effects against S. aureus including the biofilm-forming strain and MRSA. Real-time PCR analysis revealed significant downregulation of key virulence and biofilm genes, suggesting interference with QS. Biofilm assays quantified the extract's ability to disrupt and prevent biofilm formation. LC-MS/MS analysis identified quercetin and kaempferol glycosides as potential bioactive constituents, while molecular docking studies explored their binding to the QS transcriptional regulator SarA. Computational ADMET predictions highlighted favorable intestinal absorption but potential P-glycoprotein interactions limiting oral bioavailability. While promising anti-virulence effects were demonstrated, the high molecular weights and excessive hydrogen bond donors/acceptors of the flavonoid glycosides raise concerns regarding drug-likeness and permeability. This integrated study offers valuable insights for developing novel anti-virulence strategies to combat antimicrobial resistance.

Biological Activity and Phytochemical Characteristics of Star Anise (Illicium verum) Essential Oil and Its Anti-Salmonella Activity on Sous Vide Pumpkin Model

Illicium verum, commonly known as star anise, represents one of the notable botanical species and is recognized for its rich reservoir of diverse bioactive compounds. Beyond its culinary application as a spice, this plant has been extensively utilized in traditional medicine. Given the contemporary emphasis on incorporating natural resources into food production, particularly essential oils, to enhance sensory attributes and extend shelf life, our study seeks to elucidate the chemical composition and evaluate the antibacterial (in vitro, in situ) and insecticidal properties of Illicium verum essential oil (IVEO). Also, microbiological analyses of pumpkin sous vide treated with IVEO after inoculation of Salmonella enterica were evaluated after 1 and 7 days of study. GC/MS analysis revealed a significantly high amount of (E)-anethole (88.4%) in the investigated EO. The disc diffusion method shows that the antibacterial activity of the IVEO ranged from 5.33 (Streptococcus constellatus) to 10.33 mm (Citrobacter freundii). The lowest minimal inhibition concentration was found against E. coli and the minimum biofilm inhibition concertation was found against S. enterica. In the vapor phase, the best antimicrobial activity was found against E. coli in the pears model and against S. sonei in the beetroot model. The application of the sous vide method in combination with IVEO application decreased the number of microbial counts and eliminated the growth of S. enterica. The most isolated microbiota identified from the sous vide pumpkin were Bacillus amyloliquefaciens, B. cereus, B. licheniformis, and Ralstonia picketii. Modifications to the protein composition of biofilm-forming bacteria S. enterica were suggested by the MALDI TOF MS instigations. The IVEO showed insecticidal potential against Harmonia axyridis. Thanks to the properties of IVEO, our results suggest it can be used in the food industry as a natural supplement to extend the shelf life of foods and as a natural insecticide.

Determination of Chemical Composition and Investigation of Biological Activities of Ocimum basilicum L

This study aimed to determine the chemical composition of the essential oils (EOs) of Ocimum basilicum L., as well as to evaluate the antibacterial, antidiabetic, dermatoprotective, and anti-inflammatory properties, and the EOs and aqueous extracts of O. basilicum. The antibacterial activity was evaluated against bacterial strains, Gram-positive and Gram-negative, using the well diffusion and microdilution methods, whereas the antidiabetic activity was assessed in vitro using two enzymes involved in carbohydrate digestion, α-amylase and α-glucosidase. On the other hand, the dermatoprotective and anti-inflammatory activities were studied by testing tyrosinase and lipoxygenase inhibition activity, respectively. The results showed that the chemical composition of O. basilicum EO (OBEO) is dominated by methyl chavicol (86%) and trans-anethol (8%). OBEO exhibited significant antibacterial effects against Gram-negative and Gram-positive strains, demonstrated by considerable diameters of the inhibition zones and lower MIC and MBC values. In addition, OBEO exhibited significant inhibition of α-amylase (IC50 = 50.51 ± 0.32 μg/mL) and α-glucosidase (IC50 = 39.84 ± 1.2 μg/mL). Concerning the anti-inflammatory activity, OBEO significantly inhibited lipoxygenase activity (IC50 = 18.28 ± 0.03 μg/mL) compared to the aqueous extract (IC50 = 24.8 ± 0.01 μg/mL). Moreover, tyrosinase was considerably inhibited by OBEO (IC50 = 68.58 ± 0.03 μg/mL) compared to the aqueous extract (IC50 = 118.37 ± 0.05 μg/mL). The toxicological investigations revealed the safety of O. basilicum in acute and chronic toxicity. The finding of in silico analysis showed that methyl chavicol and trans-anethole (main compounds of OBEO) validate the pharmacokinetics of these compounds and decipher some antibacterial targets.

Agar Plate Methods for Assessing the Antibacterial Activity of Thyme and Oregano Essential Oils against S. epidermidis and E. coli

The resistance to antimicrobials (AMR), especially antibiotics, represents a serious problem and, at the same time, a challenge. In the last decade, a growing interest in the use of essential oils (EOs) as antimicrobial substances was observed. Commercial thyme and oregano EOs are reported to be the main responsible of the oil antimicrobial efficacy against both Gram-positive and Gram-negative pathogenic bacteria. The aim of the present work was to study the efficacy of EOs against Staphylococcus epidermidis and Escherichia coli in long-time treatments. In a preliminary microdilution test, a MIC value was obtained for thyme EO against S. epidermidis and E. coli. After that, disk diffusion and disk volatilization tests were set up to study the influence of main cultural parameters on EO activity in liquid or vapor phase. Both bacteria were inhibited by thyme and oregano EOs when applied pure (100% v/v) or diluted (75% and 50% v/v): a higher inhibition was observed in a disk diffusion test in which the antimicrobial effect was due to both liquid and vapor phase components. Finally, a comparison with literature data was carried out even if it was not so easy because standard methods are usually modified and adapted to specific case study. For this reason, the results have to be interpreted in relation to the analytical method applied.

Phytochemical Analysis and Study of Antioxidant and Antimicrobial Activities of Two Parts of Cupressus arizonica Essential Oils

The present work aimed to determine the difference in the chemical composition of essential oils isolated from two parts of Cupressus arizonica and to evaluate their in vitro antimicrobial and antioxidant effects. The yields of the essential oil obtained by hydrodistillation from the leaves and cones were 0.85% and 1.29%, respectively. The chemical analysis of the constituents of the two essential oils of Cupressus arizonica was carried out by using the GC and GC/MS techniques. The results of this analysis show that the leaves are dominated by cis-muurola-4 (14), 5-diene (21.27%), umbellulone (19.88%), α-pinene (9.39%), and α-muurolene (7.87%7); on the other hand, the cones are rich in α-pinene (51.07%) accompanied by other variable content constituents, myrcene (17.92%), limonene (9.66%), β-pinene (4.92%), meta-cymenene (2.6%), and α-terpineol (2.38%). The antimicrobial activity against four bacterial strains, four wood decay fungi, and three mould strains were determined using the agar-agar dispersion method. The studied essential oils exhibited moderate antimicrobial properties, which demonstrates the sensibility of all strains tested with the exception of wood rot fungi to which they do not have activity against all concentrations tested. The dosage of antioxidant activity was evaluated using DPPH scavenging and ferric ion reducing power (FRAP). The results indicate that the essential oils from cones of Cupressus arizonica possess a strong antioxidant activity (lower IC50) IC50 = 0.098 ± 0.008/EC50 = 0.646 ± 0.02) in comparison with those from the leaves (IC50 = 5.297 ± 0.09/EC50 = 2.335 ± 0.36). The results suggest that both essential oils could be used as a source of treatment for bacterial infections and also as natural antioxidant substances.

Medicinal Uses, Phytochemistry, Pharmacology, and Toxicology of Mentha spicata

Mentha spicata, also called Mentha viridis, is a medicinal plant of the Lamiaceae family characterized by its potency to synthesize and secret secondary metabolites, essentially essential oils. Different populations use the aerial parts of this plant for tea preparation, and this tisane has shown several effects, according to ethnopharmacological surveys carried out in different areas around the world. These effects are attributed to different compounds of M. spicata, in which their biological effects were recently proved experimentally. Pharmacological properties of M. spicata extracts and essential oils were investigated for different health benefits such as antioxidant, anticancer, antiparasitic, antimicrobial, and antidiabetic effects. In vitro and in vivo studies showed positives effects that could be certainly related to different bioactive compounds identified in M. spicata. Indeed, volatile compounds seem to be efficient in inhibiting different microbial agents such as bacteria, fungi, and parasites through several mechanisms. Moreover, M. spicata exhibited, according to some studies, promising antioxidant, antidiabetic, anti-inflammatory, and anticancer effects, which show its potential to be used as a source for identifying natural drugs against cellular oxidative stress and its related diseases. Importantly, toxicological investigations of M. spicata show the safety of this species at different doses and several periods of use which justify its use in traditional medicines as tisane with tea. Here, we report, explore, and highlight the data published on M. spicata concerning its botanical description and geographical distribution, its phytochemical compounds, its pharmacological properties, and its toxicological investigations of M. spicata.