The Chemical Composition and Antibacterial and Antioxidant Activities of Five Citrus Essential Oils

Increasing concerns over the use of antimicrobial growth promoters in animal production has prompted the need to explore the use of natural alternatives such as phytogenic compounds and probiotics. Citrus EOs have the potential to be used as an alternative to antibiotics in animals. The purpose of this research was to study the antibacterial and antioxidant activities of five citrus EOs, grapefruit essential oil (GEO), sweet orange EO (SEO), bergamot EO (BEO), lemon EO (LEO) and their active component d-limonene EO (DLEO). The chemical composition of EOs was analyzed by gas chromatography–mass spectrometry (GC-MS). The antibacterial activities of the EOs on three bacteria (Escherichia coli, Salmonella and Lactobacillus acidophilus) were tested by measuring the minimum inhibitory concentration (MIC), minimal bactericidal concentration (MBC) and inhibition zone diameter (IZD). The antioxidant activities of EOs were evaluated by measuring the free radical scavenging activities of DPPH and ABTS. We found that the active components of the five citrus EOs were mainly terpenes, and the content of d-limonene was the highest. The antibacterial test showed that citrus EOs had selective antibacterial activity, and the LEO had the best selective antibacterial activity. Similarly, the LEO had the best scavenging ability for DPPH radicals, and DLEO had the best scavenging ability for ABTS. Although the main compound of the five citrus EOs was d-limonene, the selective antibacterial and antioxidant activity of them might not be primarily attributed to the d-limonene, but some other compounds’ combined action.     

The Chemical Compositions,and Antibacterial and Antioxidant Activities of Four Types of Citrus Essential Oils

Nanfeng mandarins (Citrus reticulata Blanco cv. Kinokuni), Xunwu mandarins (Citrus reticulata Blanco), Yangshuo kumquats (Citrus japonica Thunb) and physiologically dropped navel oranges (Citrus sinensis Osbeck cv. Newhall) were used as materials to extract peel essential oils (EOs) via hydrodistillation. The chemical composition, and antibacterial and antioxidant activities of the EOs were investigated. GC-MS analysis showed that monoterpene hydrocarbons were the major components and limonene was the predominate compound for all citrus EOs. The antibacterial testing of EOs against five different bacteria (Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium) was carried out using the filter paper method and the broth microdilution method. Kumquat EO had the best inhibitory effect on B. subtilis, E. coli and S. typhimurium with MIC (minimum inhibitory concentration) values of 1.56, 1.56 and 6.25 µL/mL, respectively. All citrus EOs showed the antioxidant activity of scavenging DPPH and ABTS free radicals in a dose-dependent manner. Nanfeng mandarin EO presented the best antioxidant activity, with IC₅₀ values of 15.20 mg/mL for the DPPH assay and 0.80 mg/mL for the ABTS assay. The results also showed that the antibacterial activities of EOs might not be related to their antioxidant activities.     

Chemical Composition,Antioxidant, Antibacterial,and Antibiofilm Activities of Backhousia citriodora Essential Oil

The essential oil of Backhousia citriodora, commonly known as lemon myrtle oil, possesses various beneficial properties due to its richness in bioactive compounds. This study aimed to characterize the chemical profile of the essential oil isolated from leaves of Backhousia citriodora (BCEO) and its biological properties, including antioxidant, antibacterial, and antibiofilm activities. Using gas chromatography–mass spectrometry, 21 compounds were identified in BCEO, representing 98.50% of the total oil content. The isomers of citral, geranial (52.13%), and neral (37.65%) were detected as the main constituents. The evaluation of DPPH radical scavenging activity and ferric reducing antioxidant power showed that BCEO exhibited strong antioxidant activity at IC₅₀ of 42.57 μg/mL and EC₅₀ of 20.03 μg/mL, respectively. The antibacterial activity results showed that BCEO exhibited stronger antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis) than against Gram-negative bacteria (Escherichia coli and Klebsiella pneumoniae). For the agar disk diffusion method, S. epidermidis was the most sensitive to BCEO with an inhibition zone diameter of 50.17 mm, followed by S. aureus (31.13 mm), E. coli (20.33 mm), and K. pneumoniae (12.67 mm). The results from the microdilution method showed that BCEO exhibited the highest activity against S. epidermidis and S. aureus, with the minimal inhibitory concentration (MIC) value of 6.25 μL/mL. BCEO acts as a potent antibiofilm agent with dual actions, inhibiting (85.10% to 96.44%) and eradicating (70.92% to 90.73%) of the biofilms formed by the four tested bacteria strains, compared with streptomycin (biofilm inhibition, 67.65% to 94.29% and biofilm eradication, 49.97% to 89.73%). This study highlights that BCEO can potentially be a natural antioxidant agent, antibacterial agent, and antibiofilm agent that could be applied in the pharmaceutical and food industries. To the best of the authors’ knowledge, this is the first report, on the antibiofilm activity of BCEO against four common nosocomial pathogens.     

Eucalyptus gunnii and Eucalyptus pulverulenta ‘Baby Blue’ Essential Oils as Potential Natural Herbicides

The phytotoxicity and eco-compatibility of essential oils (EOs) from Eucalyptus gunnii (EG) and E. pulverulenta ‘Baby Blue’ (EP), cultivated in Italy for their cut foliage, were investigated. Leaf micromorphology, EOs phytochemical characterization, and phytotoxicity were analysed. EP revealed a significantly higher oil gland density and a higher EO yield with respect to EG. In both EOs, 1,8-cineole was the major compound (~75%), followed by α-pinene in EG (13.1%) and eugenol in EP (7.5%). EO phytotoxicity was tested on both weeds (Lolium multiflorum, Portulaca oleracea) and crops (Raphanus sativus, Lactuca sativa, Lepidium sativum, Solanum lycopersicum, Pisum sativum, Cucumis sativus). EG EO inhibited germination of P. oleracea, R. sativus, and S. lycopersicum seeds (ranging from 61.5 to 94.6% for the higher dose used), while affecting only radical elongation in S. lycopersicum (ranging from 66.7 to 82.6%). EP EO inhibited germination of P. oleracea and R. sativus (ranging from 41.3 to 74.7%) and affected radical elongation of L. sativum and L. multiflorum (ranging from 57.4 to 76.0%). None of the EOs affected the germination and radical growing of L. sativa, P. sativum, and C. sativus. Moreover, EP EO was more active than EG EO in inhibiting α-amylase, a key enzyme for seed growth regulation. Brine shrimp lethality assay showed that both EOs are safe for aquatic organisms, suggesting their high eco-compatibility. The data collected provide useful information for future applications of these EOs in agriculture as safe and selective bioherbicides.     

Buffalo Yogurt Fortified with Eucalyptus (Eucalyptus camaldulensis) and Myrrh (Commiphora Myrrha) Essential Oils: New Insights into the Functional Properties and Extended Shelf Life

Eucalyptus (Eucalyptus camaldulensis) and Myrrh (Commiphora Myrrha) essential oils (EOs) stand out for their benefits in terms of health and functionality. Buffalo set yogurt enriched with different concentrations of EOs (0.3, 0.6, and 0.9%) were investigated. The effects of addition on sensory, syneresis, antibacterial activity, and bioactive properties (total phenol content and antioxidant activity) of yogurt were studied. The most acceptable organoleptic properties of treated yogurt were those samples treated with Eucalyptus oil. The levels of syneresis were decreased by increasing the concentration of EOs. Moreover, the antioxidant activity, antibacterial activity, and total phenolic content were enhanced by increasing the concentration of EOs. Yogurt with 0.9% Eucalyptus oil showed the highest antioxidant activity and total phenolic content. The same concentration of Eucalyptus oil showed the highest antibacterial activity against S. typhimurium (the inhibition zone was 20.63 mm) then E. coli (the inhibition zone was 19.43 mm). On the other hand, the highest antibacterial effect against L. monocytogene was for Myrrh oil-enriched yogurt by 0.9% and the inhibition zone was 19.21 mm. The obtained results showed that Eucalyptus and Myrrh oils can be applied to yogurt to improve its beneficial properties in terms of physical characteristics and for human health due to their antioxidant activity and phenolic materials.     

Chemical Composition,Antioxidant, Anti-Bacterial,and Anti-Cancer Activities of Essential Oils Extracted from Citrus limetta Risso Peel Waste Remains after Commercial Use

Citrus plants are widely utilized for edible purposes and medicinal utility throughout the world. However, because of the higher abundance of the antimicrobial compound D-Limonene, the peel waste cannot be disposed of by biogas production. Therefore, after the extraction of D-Limonene from the peel wastes, it can be easily disposed of. The D-Limonene rich essential oil from the Citrus limetta risso (CLEO) was extracted and evaluated its radical quenching, bactericidal, and cytotoxic properties. The radical quenching properties were DPPH radical scavenging (11.35 ± 0.51 µg/mL) and ABTS scavenging (10.36 ± 0.55 µg/mL). There, we observed a dose-dependent antibacterial potential for the essential oil against pathogenic bacteria. Apart from that, the essential oil also inhibited the biofilm-forming properties of E. coli, P. aeruginosa, S. enterica, and S. aureus. Further, cytotoxicity was also exhibited against estrogen receptor-positive (MCF7) cells (IC₅₀: 47.31 ± 3.11 µg/mL) and a triple-negative (MDA-MB-237) cell (IC₅₀: 55.11 ± 4.62 µg/mL). Upon evaluation of the mechanism of action, the toxicity was mediated through an increased level of reactive radicals of oxygen and the subsequent release of cytochrome C, indicative of mitotoxicity. Hence, the D-Limonene rich essential oil of C. limetta is useful as a strong antibacterial and cytotoxic agent; the antioxidant properties exhibited also increase its utility value.     

Chemical Composition and Antioxidant and Antibacterial Potencies of the Artemisia ordosica Aerial Parts Essential Oil during the Vegetative Period

As one of the vital shrubs growing in crusted areas in China, Artemisia ordosica (belonging to the Asteraceae family) is abundant in essential oil, and its aerial part’s essential oil has been reported to have some biological activities during the flowering and fruit set stage, and has been used in folk medicine. However, little is known about the biological activities of its aerial part’s essential oil during the vegetative period. Thus, the purpose of this work was to determine the chemical composition and evaluate the antioxidant and antibacterial potencies of the essential oil extracted from A. ordosica aerial parts during the vegetative stage. Gas chromatography coupled with mass spectrometry (GC-MS) revealed that spathulenol (9.93%) and α-curcumene (9.24%), both sesquiterpenes, were the most abundant of the 74 chemical constituents detected in the essential oil of A. ordosica. The antioxidant activity of the essential oil was found to be relatively moderate against 2,2-diphenylhydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl radical (OH^●) radicals. The essential oil exhibited strong antibacterial activity against Staphylococcus aureus, Salmonella abony and Escherichia coli, with minimum inhibitory concentrations (MICs) of 2.5, 5, and 10 μL/mL, respectively. The results indicate that the essential oil of A. ordosica possesses notable antibacterial properties as well as antioxidant capability and can thus be employed as a natural ingredient which can be used as a substitute for antibiotics in the animal feed industry. However, in vivo toxicological studies are still required to determine the safety level and beneficial outcomes of the A. ordosica essential oil for future utilization.     

Phytochemical Compositions and Antioxidant Activities of Essential Oils Extracted from the Flowers of Paeonia delavayi Using Supercritical Carbon Dioxide Fluid

Essential oils were extracted from dark-purple, red and yellow petals of Paeonia delavayi using Supercritical Carbon Dioxide method. The compositions of essential oils were analyzed using gas chromatography-mass spectrometry (GC-MS). Antioxidant activity assays were carried out using DPPH, ABTS- and FRAP methods. Total polyphenols and total flavonoids were measured to evaluate the in vitro antioxidant activity in addition to the volatile compounds contained in the essential oils extracted from the flower petals of P. delavayi with the three flower colors. A total of 194 compounds were detected from essential oils of P. delavayi flowers, including 83 in dark-purple petals, 90 in red petals and 80 in yellow petals. These compounds mainly include alcohols, aldehydes, ketones, alkenes, alkanes, esters and polyphenols. The results showed that the volatile compounds accumulated differentially among the essential oils from the different colors of flower petals. Principal component analysis (PCA) indicated that essential oils derived from dark-purple and red petals were more closely clustered while the yellow petal essential oil was very different with both the purple-red and red. Antioxidant assays suggested that the radical scavenging activity and the iron reduction antioxidant activity in the essential oils were highly correlated with the flower petal colors. These results suggest P. delavayi flower petals are potentially good resources for high quality essential oils and natural antioxidants.     

Adulteration of Essential Oils: A Multitask Issue for Quality Control. Three Case Studies: Lavandula angustifolia Mill., Citrus limon (L.) Osbeck and Melaleuca alternifolia (Maiden & Betche) Cheel

The quality control of essential oils (EO) principally aims at revealing the presence of adulterations and at quantifying compounds that are limited by law by evaluating EO chemical compositions, usually in terms of the normalised relative abundance of selected markers, for comparison to reference values reported in pharmacopoeias and/or international norms. Common adulterations of EO consist of the addition of cheaper EO or synthetic materials. This adulteration can be detected by calculating the percent normalised areas of selected markers or the enantiomeric composition of chiral components. The dilution of the EO with vegetable oils is another type of adulteration. This adulteration is quite devious, as it modifies neither the qualitative composition of the resulting EO nor the marker’s normalised percentage abundance, which is no longer diagnostic, and an absolute quantitative analysis is required. This study aims at verifying the application of the two above approaches (i.e., normalised relative abundance and absolute quantitation) to detect EO adulterations, with examples involving selected commercial EO (lavender, bergamot and tea tree) adulterated with synthetic components, EO of different origin and lower economical values and heavy vegetable oils. The results show that absolute quantitation is necessary to highlight adulteration with heavy vegetable oils, providing that a reference quantitative profile is available.     

Bioassay-Guided Isolation of New Flavonoid Glycosides from Platanus × acerifolia Leaves and Their Staphylococcus aureus Inhibitory Effects

Despite the rapid advances in drug R&D, there is still a huge need for antibacterial medications, specifically for the methicillin-resistant Staphylococcus aureus (MRSA). Inspired by the research where a viable class of MRSA inhibitors was found in the species Platanus occidentalis, a S. aureus inhibition screening-guided phytochemical reinvestigation on Platanus × acerifolia (London plane tree) leaves were performed with four flavonoid glycosides garnered, including two new compounds, quercetin-3-O-α-l-(2″-E-p-coumaroyl-3″-Z-p-coumaroyl)-rhamnopyranoside (E,Z-3′-hydroxyplatanoside, 1) and quercetin-3-O-α-l-(2″-Z-p-coumaroyl-3″-E-p-coumaroyl)-rhamnopyranoside (Z,E-3′-hydroxyplatanoside, 2). All of the isolates showed significant S. aureus ATCC 25904 inhibitory activity with MICs ranging from 4 to 64 μg/mL, suggesting the potential of discovering drug leads for the control of S. aureus from such a rich, urban landscaping plant in the Platanus genus.     

Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum essential oils against four insect species, Sitophilus oryzae, Lasioderma serricorne, Necrobia rufipes, and Rhyzoperta dominica, which are common pests of stored products. The composition of both oils, extracted by hydrodistillation from the aerial parts of the two plants, was evaluated by GC×GC-MS. Calendula incana subsp. maritima essential oil was rich in oxygenated sesquiterpenoids, such as cubebol (35.39%), 4-epi-cubebol (22.99%), and cubenol (12.77%), while the Laserpitium siler subsp. siculum essential oil was composed mainly of monoterpene hydrocarbons, such as β-phellandrene (42.16%), limonene (23.87%), and β-terpinene (11.80%). The toxicity Petri dish bioassays indicated that C. maritima oil killed a mean of 65.50% of S. oryzae and 44.00% of R. dominica adults, indicating a higher biocidal activity in comparison with L. siculum oil, while toward the other species, no significant differences in mortality were recorded. Calendula maritima oil could be, then, considered a promising candidate for further tests as an alternative biocide toward S. oryzae and R. dominica. The possibility that the relatively high content of oxygenated sesquiterpenoids in C. maritima essential oil determines its higher biocidal activity is discussed.     

Chemical Compositions and Antioxidant Activities of Essential Oils,and Their Combinations,Obtained from Flavedo By-Product of Seven Cultivars of Sicilian Citrus aurantium L.

In this work, seven Citrus aurantium essential oils (EOs) derived from flavedo of cultivars ‘Canaliculata’, ‘Consolei’, ‘Crispifolia’, ‘Fasciata’, ‘Foetifera’, ‘Listata’, and ‘Bizzaria’ were investigated. EOs were also combined in 1:1 (v/v) ratio to identify possible synergism or antagonism of actions. GC-MS analysis was done to investigate Eos’ phytochemical profiles. The antioxidant activity was studied by using a multi-target approach based on FRAP, DPPH, ABTS, and β-carotene bleaching tests. A great difference was observed in EOs’ phytochemical profiles. d-limonene (33.35–89.17%) was the main monoterpene hydrocarbon, and α-Pinene, β-myrcene, and β-linalool were identified in almost all samples. Among EOs, only C3 showed high quantitative and qualitative variability in its chemical composition. The chemical diversity of EOs was also demonstrated by PCA and HCA statistical analysis. Samples C2, C4, C5, C6, and C7 were statistically similar to each other, while C1 and C3 were characterized as having a different amount of other compounds and oxygenated monoterpenes, respectively, with respect to the other EOs mentioned. The global antioxidant score (GAS) revealed that among the tested EOs, C. aurantium ‘Fasciata’ EO had the highest antioxidant potential, with a GAS value of −0.47, whereas among combinations, the EO obtained by mixing ‘Canaliculata’ + ‘Bizzaria’ was the most active. Comparison by theoretical and real data on inhibitory concentration (IC₅₀) and FRAP values did not reveal any significant effect of synergism or antagonism of actions to be valid in all biological applied tests. These findings, considered together, represent an important starting point to understand which compounds are responsible for the activities and their future possible industrial application.     

Chemical Diversity and Potential Target Network of Woody Peony Flower Essential Oil from Eleven Representative Cultivars (Paeonia × suffruticosa Andr.)

Woody peony (Paeonia × suffruticosa Andr.) has many cultivars with genetic variances. The flower essential oil is valued in cosmetics and fragrances. This study was to investigate the chemical diversity of essential oils of eleven representative cultivars and their potential target network. Hydro-distillation afforded yields of 0.11–0.25%. Essential oils were analyzed by GC-MS and GC-FID which identified 105 compounds. Three clusters emerged from multivariate analysis, representative of phloroglucinol trimethyl ether (‘Caihui’), citronellol (‘Jingyu’, ‘Zhaofen’ and ‘Baiyuan Zhenghui’) and mixed (the rest of the cultivars) chemotypes. ‘Zhaofen’ and ‘Jingyu’ also exhibited low levels of other rose-related compounds. The main components were subjected to a target network approach. Drug-likeness screening gave 20 compounds with predictive blood–brain barrier permeation. Compound target network identified six key compounds, namely nerol, citronellol, geraniol, geranic acid, cis-3-hexen-1-ol and 1-hexanol. Top enriched terms in GO, KEGG and DisGeNET were mostly related to the central nervous system (CNS). Protein—protein interactions revealed a core network of 14 targets, 11 of which were CNS-related (targets for antidepressants, analgesics, antipsychotics, anti-Alzheimer’s and anti-Parkinson’s agents). This work provides useful information on the production of woody peony essential oils with specific chemotypes and reveals their potential importance in aromatherapy for alternative treatment of CNS disorders.     

Antioxidant and Toxic Activity of Helichrysum arenarium (L.) Moench and Helichrysum italicum (Roth) G. Don Essential Oils and Extracts

Helichrysum arenarium (L.) Moench (sandy everlasting) is the only species from genus Helichrysum Mill that grows spontaneously in Lithuania. The chemical composition of the essential oils (EOs) from inflorescences and leaves of H. arenarium wild plants was analysed by GC-MS. Palmitic (≤23.8%), myristic (≤14.9%) and lauric (6.1%) acids, n-nonanal (10.4%), and trans-β-caryophyllene (≤6.5%) were the major constituents in the EOs. For comparison, the main components in EO from flowers (commercial herb material) of H. italicum were γ-curcumene (21.5%), β-selinene (13.6%), α-selinene (8.1%), β-eudesmol (8.3%), and α-pinene (6.5%). Composition of H. arenarium methanolic extracts was investigated by HPLC-DAD-TOF. The main compounds were the following: luteolin-7-O-glucoside, naringenin and its glucoside, apigenin, chlorogenic acid, arenol, and arzanol. Antioxidant activity of EOs and extracts was tested by DPPH^● and ABTS^●+ assays. Sandy everlasting extracts exhibited significantly higher radical scavenging activities (for leaves 11.18 to 19.13 and for inflorescences 1.96 to 6.13 mmol/L TROLOX equivalent) compared to those of all tested EOs (0.25 to 0.46 mmol/L TROLOX equivalent). Antioxidant activity, assayed electrochemically by cyclic and square wave voltammetry correlated with total polyphenolic content in extracts and radical scavenging properties of EOs and extracts. The toxic activity of EOs of both Helichrysum species was evaluated using a brine shrimp (Artemia salina) bioassay. H. italicum inflorescence EO was found to be toxic (LC₅₀ = 15.99 µg/mL) as well as that of H. arenarium (LC₅₀ ≤ 23.42 µg/mL) oils.     

Phytochemical Characterization of Rhus coriaria L. Extracts by Headspace Solid-Phase Micro Extraction Gas Chromatography,Comprehensive Two-Dimensional Liquid Chromatography,and Antioxidant Activity Evaluation

Rhus coriaria L. (Anacardiaceae), commonly known as sumac, has been used since ancient times for many different applications, and nowadays is used mostly as a spice obtained from its in the Mediterranean and the Middle ground fruits and employed for flavoring and garnishing food, predominantly Eastern regions. Traditionally, sumac has been also used in popular medicine for the treatment of many ailments including hemorrhoids, wound healing, diarrhea, ulcers, and eye inflammation. Sumac drupes are indeed rich in various classes of phytochemicals including organic acids, flavonoids, tannins, and others, which are responsible of their powerful antioxidant capacity, from which treatment of many common diseases such as cardiovascular disease, diabetes, and cancer could benefit. In this work we evaluated the influence of fruit ripeness, conservation, and processing. To this aim, a phytochemical characterization of six different samples of Rhus coriaria L. was carried out. Specifically, headspace solid-phase micro extraction gas chromatography coupled to mass spectrometry and comprehensive two-dimensional liquid chromatography coupled to photodiode array and mass spectrometry detection, were employed. A total of 263 volatile compounds, including terpene hydrocarbons, acids, and aldehydes, as well as 83 polyphenolic compounds, mainly gallic acid derivatives, were positively identified. All samples showed a significant antioxidant activity by means of oxygen radical absorbance capacity, in line with their polyphenolic content and composition. Such findings set a solid ground to support the utilization of this plant as an attractive target for novel nutraceutical approaches and for drug discovery.     

Antimicrobial,Antioxidant, Anti-Acetylcholinesterase,Antidiabetic, and Pharmacokinetic Properties of Carum carvi L. and Coriandrum sativum L. Essential Oils Alone and in Combination

Herbs and spices have been used since antiquity for their nutritional and health properties, as well as in traditional remedies for the prevention and treatment of many diseases. Therefore, this study aims to perform a chemical analysis of both essential oils (EOs) from the seeds of Carum carvi (C. carvi) and Coriandrum sativum (C. sativum) and evaluate their antioxidant, antimicrobial, anti-acetylcholinesterase, and antidiabetic activities alone and in combination. Results showed that the EOs mainly constitute monoterpenes with γ-terpinene (31.03%), β-pinene (18.77%), p-cymene (17.16%), and carvone (12.20%) being the major components present in C. carvi EO and linalool (76.41%), γ-terpinene (5.35%), and α-pinene (4.44%) in C. sativum EO. In comparison to standards, statistical analysis revealed that C. carvi EO showed high and significantly different (p < 0.05) antioxidant activity than C. sativum EO, but lower than the mixture. Moreover, the mixture exhibited two-times greater ferric ion reducing antioxidant power (FRAP) (IC₅₀ = 11.33 ± 1.53 mg/mL) and equipotent chelating power (IC₅₀ = 31.33 ± 0.47 mg/mL) than the corresponding references, and also potent activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) (IC₅₀ = 19.00 ± 1.00 mg/mL), β-carotene (IC₅₀ = 11.16 ± 0.84 mg/mL), and superoxide anion (IC₅₀ = 10.33 ± 0.58 mg/mL) assays. Antimicrobial data revealed that single and mixture EOs were active against a panel of pathogenic microorganisms, and the mixture had the ability to kill more bacterial strains than each EO alone. Additionally, the anti-acetylcholinesterase and α-glucosidase inhibitory effect have been studied for the first time, highlighting the high inhibition effect of AChE by C. carvi (IC₅₀ = 0.82 ± 0.05 mg/mL), and especially by C. sativum (IC₅₀ = 0.68 ± 0.03 mg/mL), as well as the mixture (IC₅₀ = 0.63 ± 0.02 mg/mL) compared to the reference drug, which are insignificantly different (p > 0.05). A high and equipotent antidiabetic activity was observed for the mixture (IC₅₀ = 0.75 ± 0.15 mg/mL) when compared to the standard drug, acarbose, which is about nine times higher than each EO alone. Furthermore, pharmacokinetic analysis provides some useful insights into designing new drugs with favorable drug likeness and safety profiles based on a C. carvi and C. sativum EO mixture. In summary, the results of this study revealed that the combination of these EOs may be recommended for further food, therapeutic, and pharmaceutical applications, and can be utilized as medicine to inhibit several diseases.     

Characterization of Primary Action Mode of Eight Essential Oils and Evaluation of Their Antibacterial Effect against Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli Inoculated in Turkey Meat

The current study aims to evaluate the antimicrobial activity of eight essential oils (EOs) against multidrug-resistant Escherichia coli strains, producing extended-spectrum β-lactamase (ESBL) enzymes and isolated from foods. Disc-diffusion assay showed that the inhibition diameters generated by EOs varied significantly among the tested EOs and strains. In fact, EOs extracted from Thymus capitaus, Eucalyptus camaldulensis, Trachyspermum ammi and Mentha pulegium exerted an important antimicrobial effect against tested strains, with the diameters of inhibition zones varied between 20 and 27 mm. Moreover, minimal inhibition and bactericidal concentration (MIC and MBC) values demonstrated that T. capitatus EOs generate the most important inhibitory effect against E. coli strains, with MIC values ranging from 0.02 to 0.78%. Concerning the mode of action of T. capitatus EO, the obtained data showed that treatment with this EO at its MIC reduced the viability of E. coli strains, their tolerance to NaCl and promoted the loss of 260-nm-absorbing material. In addition, in the presence of T. capitatus EO, cells became disproportionately sensitive to subsequent autolysis. Moreover, the inhibitory effect of T. capitatus was evaluated against two E. coli strains, experimentally inoculated (10⁵ CFU/g) in minced turkey meat, in the presence of two different concentrations of EO (MIC and 2 × MIC), and stored for 15 days. In both samples, EO exerted a bacteriostatic effect in the presence of concentrations equal to MIC. Interestingly, at 2 × CMI concentration, the bactericidal activity was pronounced after 15 days of storage. Our results highlighted that the use of essential oils, specially of T. capitatus, to inhibit or prevent the growth of extended-spectrum β-lactamase (ESBL)-producing E. coli in food, may be a promising alternative to chemicals.     

GC/MS Analysis of Essential Oil and Enzyme Inhibitory Activities of Syzygium cumini (Pamposia) Grown in Egypt: Chemical Characterization and Molecular Docking Studies

Syzygium cumini (Pomposia) is a well-known aromatic plant belonging to the family Myrtaceae, and has been reported for its various traditional and pharmacological potentials, such as its antioxidant, antimicrobial, anti-inflammatory, and antidiarrheal properties. The chemical composition of the leaf essential oil via gas chromatography–mass spectrometry (GC/MS) analysis revealed the identification of fifty-three compounds representing about 91.22% of the total oil. The identified oil was predominated by α-pinene (21.09%), followed by β-(E)-ocimene (11.80%), D-limonene (8.08%), β-pinene (7.33%), and α-terpineol (5.38%). The tested oil revealed a moderate cytotoxic effect against human liver cancer cells (HepG2) with an IC₅₀ value of 38.15 ± 2.09 µg/mL. In addition, it effectively inhibited acetylcholinesterase with an IC₅₀ value of 32.9 ± 2.1 µg/mL. Furthermore, it showed inhibitory properties against α-amylase and α-glucosidase with IC₅₀ values of 57.80 ± 3.30 and 274.03 ± 12.37 µg/mL, respectively. The molecular docking studies revealed that (E)-β-caryophyllene, one of the major compounds, achieved the best docking scores of −6.75, −5.61, and −7.75 for acetylcholinesterase, α-amylase, and α-glucosidase, respectively. Thus, it is concluded that S. cumini oil should be considered as a food supplement for the elderly to enhance memory performance and for diabetic patients to control blood glucose.     

Variability of the Chemical Composition and Bioactivity between the Essential Oils Isolated from Male and Female Specimens of Hedyosmum racemosum (Ruiz & Pav.) G. Don

Hedyosmum racemosum (Ruiz & Pav.) G. is a native species of Ecuador used in traditional medicine for treatment of rheumatism, bronchitis, cold, cough, asthma, bone pain, and stomach pain. In this study, fresh H. racemosum leaves of male and female specimens were collected and subjected to hydrodistillation for the extraction of the essential oil. The chemical composition of male and female essential oil was determined by gas chromatography–gas chromatography equipped with a flame ionization detector and coupled to a mass spectrometer using a non-polar and a polar chromatographic column. The antibacterial activity was assayed against five Gram-positive and two Gram-negative bacteria, and two dermatophytes fungi. The scavenging radical properties of the essential oil were evaluated by DPPH and ABTS assays. The chemical analysis allowed us to identify forty-three compounds that represent more than 98% of the total composition. In the non-polar and polar column, α-phellandrene was the principal constituent in male (28.24 and 25.90%) and female (26.47 and 23.90%) essential oil. Other main compounds were methyl chavicol, germacrene D, methyl eugenol, and α-pinene. Female essential oil presented a strong activity against Klebsiella pneumoniae (ATCC 9997) with an minimum inhibitory concentration (MIC) of 500 μg/mL and a scavenging capacity SC₅₀ of 800 µg/mL.     

Comparative Studies on Essential Oil and Phenolic Content with In Vitro Antioxidant,Anticholinesterase, Antimicrobial Activities of Achillea biebersteinii Afan. and A. millefolium subsp. millefolium Afan. L. Growing in Eastern Turkey

The potential applications of Achillea species in various industries have encouraged the examination of their phytochemical components along with their biological potential. In the present study, phenolic contents and essential oil compositions together with the in vitro biological activities of the aerial parts from Achillea biebersteinii Afan. and Achillea millefolium subsp. millefolium Afan. collected from Turkey were evaluated. Different solvent extracts (n-hexane, chloroform, methanol, water) were prepared and their antimicrobial, anticholinesterase, and antioxidant activities were studied. The LC-MS/MS results revealed the presence of 16 different phenolic compounds, including chlorogenic acid, rutin, quercetin, and luteolin glycosides, in methanolic extracts. According to GC-FID and GC/MS results, the primary components of the oils were identified as 1,8-cineole (32.5%), piperitone (14.4%), and camphor (13.7%) in A. biebersteinii and 1,8-cineole (12.3%) and β-eudesmol (8.9%) in A. millefolium subsp. millefolium. The infusion and methanolic extracts of both species were found to be rich in their total phenolic content as well as their antioxidant and anticholinesterase activity. In contrast, the n-hexane and chloroform extracts of both species showed strong antimicrobial activity with MIC values ranging from 15 to 2000 μg/mL. Our findings suggest that the investigated Achillea species could be evaluated as potent natural agents, and further studies into the promising extracts are needed.