Chemical composition, antibiofilm, cytotoxic, and anti-acetylcholinesterase activities of Myrtus communis L. leaves essential oil

Chemical Composition, Antibacterial Properties, and Anti-Enzymatic Effects of Eucalyptus Essential Oils Sourced from Tunisia

This study was conducted to examine the chemical composition of the essential oils (EOs) from six Tunisian Eucalyptus species and to evaluate their anti-enzymatic and antibiofilm activities. The EOs were obtained through hydro-distillation of dried leaves and subsequently analyzed using GC/MS. The main class of compounds was constituted by oxygenated monoterpenes, particularly prominent in E. brevifolia (75.7%), E. lehmannii (72.8%), and E. woollsiana (67%). Anti-enzymatic activities against cholinesterases, α-amylase, and α-glucosidase were evaluated using spectrophotometric methods. Notably, the E. brevifolia, E. extensa, E. leptophylla, E. patellaris, and E. woollsiana EOs displayed potent acetylcholinesterase (AChE) inhibition (IC50: 0.25-0.60 mg/mL), with E. lehmannii exhibiting lower activity (IC50: 1.2 mg/mL). E. leptophylla and E. brevifolia showed remarkable α-amylase inhibition (IC50: 0.88 mg/mL), while E. brevifolia and E. leptophylla significantly hindered α-glucosidase (IC50 < 30 mg/mL), distinguishing them from other EOs with limited effects. Additionally, the EOs were assessed for their anti-biofilm properties of Gram-positive (Staphylococcus aureus and Listeria monocytogenes) and Gram-negative (Acinetobacter baumannii, Pseudomonas aeruginosa and Escherichia coli) bacterial strains. The E. extensa EO demonstrated the main antibiofilm effect against E. coli and L. monocytogenes with an inhibition > 80% at 10 mg/mL. These findings could represent a basis for possible further use of Eucalyptus EOs in the treatment of human microbial infections and/or as a coadjutant in preventing and treating Alzheimer's disease and/or diabetes mellitus.

Unveiling the Chemical Profiling Antioxidant and Anti-Inflammatory Activities of Algerian Myrtus communis L. Essential Oils, and Exploring Molecular Docking to Predict the Inhibitory Compounds against Cyclooxygenase-2

Considering the large spectrum of side effects caused by synthetic drugs and the development of natural alternatives utilizing Algerian flora, this study aimed to place a spotlight on the chemical profile and antioxidant and anti-inflammatory activities of Myrtus communis L. essential oils (MCEOs). In this study, essential oils (EOs) were collected via hydro-distillation of the plant's leaves, and a chemical constituent analysis was performed using gas chromatography-mass spectrophotometry (GC-MS). The in vitro antioxidant activity was evaluated using DPPH, ABTS, and hydroxyl radical scavenging tests. The in vitro anti-inflammatory capacity was estimated by studying the antidenaturation effect using bovine serum albumin (BSA) as a protein model. The in vivo anti-inflammatory activity was carried out by utilizing the classical model of carrageenan-induced paw edema in rats, using diclofenac (DCF) as the reference drug. Moreover, the molecular interaction of the compounds obtained from the GC-MS analysis was studied within the binding site of cyclooxygenase-2 (COX-2) using an in silico approach as the confirmatory tool of the in vitro and in vivo experiments. The GC-MS analysis revealed that MCEOs were mainly composed of oxygenated monoterpenes (70.56%), oxygenated sesquiterpenes (3.1%), sesquiterpenes (4.17%), and monoterpenes (8.75%). Furthermore, 1,8-cineole was the major compound (19.05%), followed by cis-geranyl acetate (11.74%), methyl eugenol (5.58%), α-terpineol (4.62%), and β-myrcene (4.40%). MCEOs exhibited remarkable concentration-dependent free radical scavenging activity, with an IC50 of 15.317 ± 0.340 µg/mL, 18.890 ± 2.190 µg/mL, and 31.877 ± 0.742 µg/mL for DPPH, ABTS, and hydroxyl radical, respectively. The significant in vitro anti-inflammatory activity due to the inhibition of BSA denaturation was proportional to the EO concentration, where the highest value was recorded at 100 μg/mL with an approximately 63.35% percentage inhibition and an IC50 of 60.351 ± 5.832 μg/mL. MCEOs showed a good in vivo anti-inflammatory effect by limiting the development of carrageenan-induced paw thickness. The in silico study indicated that, among the 60 compounds identified by the GC-MS analysis, 9 compounds were observed to have a high binding energy to cyclooxygenase-2 as compared to diclofenac. Our study revealed that EOs from Algerian Myrtus communis L. can be considered to be a promising candidate for alleviating many debilitating health problems and may provide new insights in the fields of drug design, agriculture, and the food industry.

Antimicrobial Effects and Antioxidant Activity of Myrtus communis L. Essential Oil in Beef Stored under Different Packaging Conditions

The aim of this study was to assess the antimicrobial effects of myrtle (Myrtus communis L.) essential oil (EO) on pathogenic (E. coli O157:H7 NCTC 12900; Listeria monocytogenes ATCC BAA-679) and spoilage microbiota in beef and determine its minimum inhibitory concentration (MIC) and antioxidant activity. The behavior of LAB, Enterobacteriaceae, Pseudomonas spp., and fungi, as well as total mesophilic (TM) and total psychotropic (TP) counts, in beef samples, was analyzed during storage at 2 and 8 °C in two different packaging systems (aerobiosis and vacuum). Leaves of myrtle were dried, its EO was extracted by hydrodistillation using a Clevenger-type apparatus, and the chemical composition was determined using chromatographical techniques. The major compounds obtained were myrtenyl acetate (15.5%), β-linalool (12.3%), 1,8-cineole (eucalyptol; 9.9%), geranyl acetate (7.4%), limonene (6.2%), α-pinene (4.4%), linalyl o-aminobenzoate (5.8%), α-terpineol (2.7%), and myrtenol (1.2%). Myrtle EO presented a MIC of 25 µL/mL for E. coli O157:H7 NCTC 12900, E. coli, Listeria monocytogenes ATCC BAA-679, Enterobacteriaceae, and E. coli O157:H7 ATCC 35150 and 50µL/mL for Pseudomonas spp. The samples packed in aerobiosis had higher counts of deteriorative microorganisms than samples packed under vacuum, and samples with myrtle EO presented the lowest microbial contents, indicating good antimicrobial activity in beef samples. Myrtle EO is a viable natural alternative to eliminate or reduce the pathogenic and deteriorative microorganisms of meat, preventing their growth and enhancing meat safety.

Mediterranean Plants with Antimicrobial Activity against Staphylococcus aureus, a Meta-Analysis for Green Veterinary Pharmacology Applications

Antimicrobial resistance (AMR) has emerged as a global health crisis, necessitating the search for innovative strategies to combat infectious diseases. The unique biodiversity of Italian flora offers a treasure trove of plant species and their associated phytochemicals, which hold immense potential as a solution to address AMR. By investigating the antimicrobial properties of Italian flora and their phytochemical constituents, this study aims to shed light on the potential of phyto-complexes as a valuable resource for developing novel or supportive antimicrobial agents useful for animal production.

Antibacterial and Antibiofilm Effects of Different Samples of Five Commercially Available Essential Oils

Essential oils (EOs) have gained economic importance due to their biological activities, and increasing amounts are demanded everywhere. However, substantial differences between the same essential oil samples from different suppliers are reported-concerning their chemical composition and bioactivities-due to numerous companies involved in EOs production and the continuous development of online sales. The present study investigates the antibacterial and antibiofilm activities of two to four samples of five commercially available essential oils (Oregano, Eucalyptus, Rosemary, Clove, and Peppermint oils) produced by autochthonous companies. The manufacturers provided all EOs' chemical compositions determined through GC-MS. The EOs' bioactivities were investigated in vitro against Gram-positive (Staphylococcus aureus) and Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). The antibacterial and antibiofilm effects (ABE% and, respectively, ABfE%) were evaluated spectrophotometrically at 562 and 570 nm using microplate cultivation techniques. The essential oils' calculated parameters were compared with those of three standard broad-spectrum antibiotics: Amoxicillin/Clavulanic acid, Gentamycin, and Streptomycin. The results showed that at the first dilution (D1 = 25 mg/mL), all EOs exhibited antibacterial and antibiofilm activity against all Gram-positive and Gram-negative bacteria tested, and MIC value > 25 mg/mL. Generally, both effects progressively decreased from D1 to D3. Only EOs with a considerable content of highly active metabolites revealed insignificant differences. E. coli showed the lowest susceptibility to all commercially available essential oils-15 EO samples had undetected antibacterial and antibiofilm effects at D2 and D3. Peppermint and Clove oils recorded the most significant differences regarding chemical composition and antibacterial/antibiofilm activities. All registered differences could be due to different places for harvesting the raw plant material, various technological processes through which these essential oils were obtained, the preservation conditions, and complex interactions between constituents.

Flowering phenophases influence the antibacterial and anti-biofilm effects of Thymus vulgaris L. essential oil

BACKGROUND

Essential oils are becoming increasingly popular in medicinal applications because of their antimicrobial effect. Thymus vulgaris L. (Lamiaceae) is a well-known and widely cultivated medicinal plant, which is used as a remedy for cold, cough and gastrointestinal symptoms. Essential oil content of thyme is responsible for its antimicrobial activity, however, it has been reported that the chemical composition of essential oils influences its biological activity. In order to explore flowering phenophases influence on the chemical composition of thyme essential oil and its antibacterial and anti-biofilm activity, plant materials were collected at the beginning of flowering, in full bloom and at the end of flowering periods in 2019.

METHODS

Essential oils from fresh and dried plant materials were distilled and analyzed with gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID). The antibacterial activity was performed by broth microdilution and thin layer chromatography-direct bioautography (TLC-DB) assays and the anti-biofilm effect by crystal violet assay, respectively. Scanning electron microscopy was applied to illustrate the cellular changes of bacterial cells after essential oil treatment.

RESULTS

Thymol (52.33-62.46%) was the main component in the thyme essential oils. Thyme oil distilled from fresh plant material and collected at the beginning of flowering period exerted the highest antibacterial and anti-biofilm activity against Haemophilus influenzae, H. parainfluenzae and Pseudomonas aeruginosa.

CONCLUSION

The different flowering periods of Thymus vulgaris influence the antibacterial and anti-biofilm activity of its essential oils, therefore, the collection time has to be taken into consideration and not only the full bloom, but the beginning of flowering period may provide biological active thyme essential oil.

The Leaf Essential Oil of Myrtus communis subsp. tarentina (L.) Nyman: From Phytochemical Characterization to Cytotoxic and Antimigratory Activity in Human Prostate Cancer Cells

The aim of this study was to investigate the chemical profile and the cytotoxic activity in two castration-resistant prostate cancer (CRPC) cell lines of the leaf essential oil in Myrtus communis subsp. tarentina (L.) Nyman (EO MT), which was cultivated at the Ghirardi Botanical Garden (Toscolano Maderno, Brescia, Italy). The leaves were air-dried and extracted by hydrodistillation with a Clevenger-type apparatus, and the EO profile was characterized by GC/MS. For the cytotoxic activity investigation, we analyzed the cell viability by MTT assay, and the apoptosis induction by Annexin V/propidium iodide assay/Western blot analysis of cleaved caspase 3 and cleaved PARP proteins. Moreover, the cellular migration was analyzed by Boyden's chamber assay and the distribution of actin cytoskeleton filaments by immunofluorescence. We identified 29 total compounds; the main compound classes were oxygenated monoterpenes, monoterpene hydrocarbons, and sesquiterpenes. The main constituents were α-pinene, α-humulene, α-terpineol, durohydroquinon, linalool, geranyl acetate, and β-caryophyllene. We found that EO MT was able to reduce cellular viability, activating an apoptotic process, and to decrease the migratory capacity of CRPC cells. These results suggest that it might be interesting to further investigate the effects of single compounds present in EO MT for their possible use in prostate cancer treatment.

The Influence of Cryogrinding on Essential Oil, Phenolic Compounds and Pigments Extraction from Myrtle (Myrtus communis L.) Leaves

The aim of this study was to investigate the influence of cryogrinding pretreatment on the recovery of essential oil, phenolics and pigments from myrtle leaves. The duration of cryogrinding (3, 6 and 9 min) in combination with the duration of hydrodistillation (30, 60 and 90 min) for the isolation of essential oils and the duration of hydroethanolic extraction (5, 10 and 15 min) for the isolation of phenols and pigments were studied as independent factors in a full factorial design. The major volatile components detected in myrtle leaf essential oil were myrtenyl acetate, 1,8-cineole, α-pinene and linalool. The most abundant phenols detected were myricetin derivatives (myricetin 3-O-galactoside and myricetin 3-O-rhamnoside), galloylquinic acid, myricetin and digalloylquinic acid, while the major pigments were chlorophyll b, pheophytin a and lutein. A 3 min cryogrinding pretreatment significantly increased the yield and concentrations of essential oil volatile compounds and reduced the distillation time to 30 min. A 9 min cryogrinding pretreatment and 15 min extraction resulted in at least 40% higher concentrations of phenolic compounds and pigments in the extracts when compared to the untreated control. According to the results obtained, cryogrinding can significantly increase the yield of myrtle EO and extracts and also modulate their composition.

Inhibitory Effect of Sodium Alginate Nanoemulsion Coating Containing Myrtle Essential Oil (Myrtus communis L.) on Listeria monocytogenes in Kasar Cheese

The present study aimed to characterize the physical properties of nanoemulsion-based sodium alginate edible coatings containing myrtle (Myrtus communis L.) essential oil and to determine its inhibitory effects on Listeria monocytogenes in fresh Kasar cheese during the 24-day storage at 4 °C. The GC-MS analysis showed that the main components of myrtle essential oil were 1,8-cineol (38.64%), α-pinene (30.19%), d-limonene (7.51%), and α-ocimene (6.57%). Myrtle essential oil showed an inhibitory effect on all tested L. monocytogenes strains and this effect significantly increased after ultrasonication. Minimum inhibitory and minimum bactericidal concentrations of myrtle essential oil nanoemulsion were found to be 4.00-4.67 mg/mL and 5.00-7.33 mg/mL, respectively. The antibacterial activity of myrtle essential oil nanoemulsion against L. monocytogenes was confirmed by the membrane integrity and FESEM analyses. Nanoemulsion coatings containing myrtle essential oil showed antibacterial activity against L. monocytogenes with no adverse effects on the physicochemical properties of cheese samples. Nanoemulsion coatings containing 1.0% and 2.0% myrtle essential oil reduced the L. monocytogenes population in cheese during the storage by 0.42 and 0.88 log cfu/g, respectively. These results revealed that nanoemulsion-based alginate edible coatings containing myrtle essential oil have the potential to be used as a natural food preservative.

An Overview of Biofilm Formation-Combating Strategies and Mechanisms of Action of Antibiofilm Agents

Biofilm formation on surfaces via microbial colonization causes infections and has become a major health issue globally. The biofilm lifestyle provides resistance to environmental stresses and antimicrobial therapies. Biofilms can cause several chronic conditions, and effective treatment has become a challenge due to increased antimicrobial resistance. Antibiotics available for treating biofilm-associated infections are generally not very effective and require high doses that may cause toxicity in the host. Therefore, it is essential to study and develop efficient anti-biofilm strategies that can significantly reduce the rate of biofilm-associated healthcare problems. In this context, some effective combating strategies with potential anti-biofilm agents, including plant extracts, peptides, enzymes, lantibiotics, chelating agents, biosurfactants, polysaccharides, organic, inorganic, and metal nanoparticles, etc., have been reviewed to overcome biofilm-associated healthcare problems. From their extensive literature survey, it can be concluded that these molecules with considerable structural alterations might be applied to the treatment of biofilm-associated infections, by evaluating their significant delivery to the target site of the host. To design effective anti-biofilm molecules, it must be assured that the minimum inhibitory concentrations of these anti-biofilm compounds can eradicate biofilm-associated infections without causing toxic effects at a significant rate.