The Antimicrobial and Antibiofilm Potential of Citrus Aurantium and Artemisia Annua Essential Oils Nanoemulsions.

Acinetobacter baumannii has been identified as a critical pathogen, and new antibiotics are urgently needed. Volatile oils, which function as natural antibacterial agents, may provide an effective means of inhibiting A. baumannii. However, the antibacterial activity and mechanism of the volatile oil derived from the dried bark of Cinnamomum cassia (CBV), as well as its additive effect when combined with imipenem (IPM) against A. baumannii, remain unclear. CBV was extracted using the hydrodistillation method and characterized by gas chromatography-mass spectrometry (GC-MS) analysis. The minimum inhibitory concentrations (MICs) of CBV and IPM against A. baumannii were determined using the microdilution method. A checkerboard assay was performed to evaluate the additive effect of CBV (concentration range: 0-1 μL/mL) and IPM (concentration range: 0-256 μg/mL) against A. baumannii, with the fractional inhibitory concentration index (FICI) calculated. A time-kill curve analysis was performed to assess the additive effect of CBV (0.125 μL/mL) and IPM (4 μg/mL) against A. baumannii. Antibiofilm activity was evaluated using a crystal violet staining assay. Cell membrane integrity was assessed using SYTO 9/PI staining based on fluorescence color. Intracellular protein levels were quantified using a BCA kit according to the manufacturer's instructions. Scanning electron microscopy (SEM) was used to observe morphological changes in A. baumannii. Additionally, the antibacterial mechanism was elucidated through a combination of transcriptomic and proteomic analyses. An additive effect (FICI = 0.53) was observed when CBV and IPM were combined against A. baumannii, reducing the MIC of IPM from 256 μg/mL to 4 μg/mL. CBV and IPM inhibited biofilm formation, damaged the cell membrane, and induced intracellular protein leakage in A. baumannii. Compared to CBV or IPM alone, the combination group (at the dosage showing an additive effect) caused significantly greater damage to the cell membrane of A. baumannii. CBV and IPM also induced significant changes at both the transcriptomic and proteomic levels in A. baumannii. Functional analysis revealed that the differentially expressed genes (DEGs) and proteins (DEPs) were involved in multiple pathways. Both CBV and IPM contributed to the observed antibacterial activity. CBV primarily influenced the ribosome pathway, while IPM mainly influenced oxidative phosphorylation. In the combination treatment, the simultaneous targeting of the ribosome and oxidative phosphorylation pathways was identified as the key antibacterial mechanism. This study demonstrated that the combination of CBV and IPM exhibits promising antimicrobial activity against A. baumannii, suggesting that CBV could serve as a potential natural candidate for the development of novel antibiotic agents. While the current findings establish a mechanistic foundation for CBV's antimicrobial effects, further research is necessary to facilitate its clinical translation. Specifically, formulation optimization studies are necessary to enhance the therapeutic viability of the CBV/IPM combination, and comprehensive in vivo investigations are crucial to validate the antibacterial efficacy and safety profile of CBV/IPM prior to clinical application.

Objective: The genus Phrynium has medicinal value and is effective in relieving sore throat and mouth ulcers. However, the extraction and chemical analysis of essential oils from Phrynium tonkinense Gagnep, have not yet been reported. The present study aimed to extract, chemically characterize, and evaluate the antimicrobial properties of volatile oils from Phrynium tonkinense Gagnep ( P. tonkinense). Methods: In the present study, essential oil was extracted from the leaves of P. tonkinense for the first time by the hydrodistillation method, and its chemical composition was determined by gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). The area normalization method was used to calculate the relative percentage content of each chemical constituent in the essential oil. Additionally, the antibacterial efficacy of the essential oil was tested against six pathogenic microorganisms by the agar diffusion method and the microdilution method. Result: The yield of essential oil obtained by hydrodistillation was 0.499%. Ninety volatile components were identified from the essential oil, with fatty acid compounds (47.36%) accounting for the largest proportion of these components. The main compounds were hexadecanoic acid (25.20%), ( Z)-3-hexen-1-ol (10.31%), pentadecanoic acid (8.09%), and myristic acid (3.99%). The results of the in vitro antimicrobial assay showed that essential oils from P. tonkinense had a good inhibitory effect on the six selected pathogenic microorganisms and showed good bactericidal activity, with the minimum inhibitory concentration (MIC) value ranging from 31.3 to 250 μg/mL and the minimum bactericidal concentration (MBC) value ranging from 62.5 to 500 μg/mL. Notably, the essential oil exhibited the highest antibacterial activity against Staphylococcus aureus, with the MIC of 31.3 μg/mL and the MBC of 62.5 μg/mL. Conclusion: The findings of this study provided new insights into the medicinal functions of P. tonkinense and offered a scientific basis for the development and utilization of P. tonkinense as a natural antibacterial agent.

BackgroundIdentification of natural antibacterial agents from various sources that can act effectively against disease causing foodborne bacteria is one of the major concerns throughout the world. However, the natural antibacterial agents identified to date are primarily effective against Gram positive bacteria, but less effective against Gram negative bacteria. In the present study, Enteromorpha linza L. essential oil (EEO) was evaluated for antibacterial activity against Escherichia coli and Salmonella Typhimurium along with the mode of their antibacterial action.ResultsThe chemical composition of EEO revealed high amounts of acids (54.6 %) and alkenes (21.1 %). EEO was effective against both E. coli and S. Typhimurium. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of EEO for both pathogens were 12.5 mg/ml and 25.0 mg/mL, respectively. EEO at the MIC acted on the loss in viability of E. coli ATCC 43890, which was used as the model system for evaluation of the antibacterial mode of action of EEO against Gram negative bacteria. Significant increase in relative electrical conductivity and K+ concentration were recorded with respect to time, indicating the disruption of tested E. coli cells owing to the controlling effect of EEO. Alternation of the morphology of the cell surface, increase in the release of 260 nm absorbing materials and loss of high salt tolerance were observed.ConclusionsThe results suggest that EEO induced a bactericidal effect via structural membrane damage caused by deposition of EEO in the cytosol or through enzymatic degradation of bacterial intracellular enzymes that resulted in cellular lysis. Accordingly, EEO can be used as a strong natural antibacterial agent against Gram negative foodborne pathogens such as E. coli and S. Typhimurium.Electronic supplementary materialThe online version of this article (doi:10.1186/s40529-015-0093-7) contains supplementary material, which is available to authorized users.

Physicochemical properties, GC–MS profiling, and antibacterial potential of Allium sativum essential oil: In vitro and in silico approaches

Achillea sintenisii Hub-Mor is an endemic species in Türkiye, characterized by 1–10 capitula and ray flowers, and it thrives on calcareous rocks or gypsum-rich soils. This study aimed to determine the chemical composition and assess the antibacterial and antibiofilm activity of the essential oil of A. sintenisii (AS-EO). The essential oil compounds of the flowering aerial part of A. sintenisii were extracted using both hydrodistillation and solid-phase microextraction (SPME) techniques and identified by gas chromatography-mass spectrometry (GC-MS). Two different adsorbents were employed in the SPME approach. The yield of the essential oil of flowering aerial parts of A. sintenisii was 0,.4% h/h. A total of 74, 112, and 78 compounds were identified from the samples obtained by hydrodistillation (S1) and SPME extraction using the CAR-PDMS (S2) and PDMS-DVB (S3) adsorbents, respectively. The AS-EO exhibited the highest antibacterial activity against Staphylococcus aureus ATCC 25923 and S. aureus ATCC 43300 (MRSA), with a minimum inhibitory concentration (MIC) of <1/512 for each bacterium. This strong antibacterial effect may be attributed to the high content of 1,8-cineole and l-borneol. However, AS-EO did not exhibit any antibiofilm activity. These findings suggest that the essential oil of A. sintenisii has potential as a natural antibacterial agent, warranting further research to uncover its full potential.

Allium tenuissimum L. as a kind of food condiment in northern China, is popular among more and more consumers owning to its special flavor from the flower. However, its composition has not been widely studied. Hence, the aim of this study was to investigate the chemical composition and antimicrobial and antioxidant activity of essential oil from Allium tenuissimum L. flowers. Gas chromatography−mass spectrometry (GC-MS) was applied to detect the chemical composition. The antimicrobial activity against foodborne pathogens was evaluated by measuring the zones of inhibition (ZOI), the minimal inhibitory concentration (MIC), and the minimal bactericidal concentration (MBC). The antioxidant effect was tested by the scavenging capacity on DPPH, ABTS+•, and •OH. The results of GC-MS showed that 72 volatile components were isolated and the structures 68 of them were identified, which comprised about 91.92% of the total composition of the oil. Among these compounds, terpenoid compounds and sulfurous compounds had the highest contents, especially dimethyl trisulfide. Our investigation demonstrated that the essential oil has better antimicrobial efficiency to Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Aspergillus flavus, and Saccharomyces cerevisiae. In addition, the essential oil had a strong stability to UV. Furthermore, the essential oil exhibited a high radical-scavenging effect on DPPH, ABTS+•, and •OH, which is significant for application in the food industry. In conclusion, the essential oil could be used as an inexpensive and natural antibacterial and antioxidant agent in food.

Antibacterial characteristics of allyl methyl disulfide and dimethyl trisulfide of Allium tenuissimum flower essential oil against Escherichia coli O157:H7

Chemical composition and biological activity of essential oil of the Moroccan endemic Origanum grosii

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.

Antioxidant and antibacterial activities of essential oil from Atractylodes lancea rhizomes

Piper nigrum or black pepper, is renowned for its medicinal properties and widespread use as a spice. Its essential oil, rich in active compounds, holds promise for combating bacterial contamination, particularly in food and beverages. This study analyzed the antibacterial potential of black pepper essential oil through active compound profiling and computational assessment. Gas chromatography-mass spectrometry (GCMS) analysis was conducted to identify compounds in black pepper essential oil. Toxicity analysis of the identified compounds was performed using ProTox 3.0, while molecular docking and molecular dynamics simulations were employed to assess their interactions with bacterial proteins. GCMS analysis revealed the presence of eleven secondary metabolite compounds in black pepper essential oil, predominantly piperine derivatives. Toxicity analysis indicated low toxicity levels for these compounds. Molecular docking simulations showed strong binding affinity of certain compounds to bacterial proteins, including FtsZ, GyrB, murA, and PTP. Molecular dynamics simulations further confirmed stable interactions between the compounds and their target proteins. Black pepper essential oil, enriched with piperine derivatives, exhibits promising antibacterial activity by targeting FtsZ, GyrB, murA, and PTP proteins. These findings suggest the potential utility of black pepper essential oil as a natural antibacterial agent.

Despite recent scientific advances, the global load of bacterial disease remains high and has been established against a backdrop of increasing antimicrobial resistance. Therefore, there is a pressing need for highly effective and natural antibacterial agents. In the present work, the antibiofilm effect provided by essential oils was evaluated. Of these, cinnamon oil extract showed potent antibacterial and antibiofilm activities against Staphylococcus aureus at an MBEC of 75.0 µg/mL. It was revealed that benzyl alcohol, 2-propenal-3-phenyl, hexadecenoic acid, and oleic acid were the major components of the tested cinnamon oil extract. In addition, the interaction between the cinnamon oil and colistin showed a synergistic effect against S. aureus. Cinnamon oil that had been combined with colistin was encapsulated by liposomes to enhance the essential oil's chemical stability, demonstrating a particle size of 91.67 nm, a PDI of 0.143, a zeta potential of -0.129 mV, and an MBEC of 50.0 µg/mL against Staphylococcus aureus. Scanning electron microscopy was employed to observe the morphological changes in the Staphylococcus aureus biofilm that was treated with the encapsulated cinnamon oil extract/colistin. As a natural and safe option, cinnamon oil exhibited satisfactory antibacterial and antibiofilm performance. The application of liposomes further improved the stability of the antibacterial agents and extended the essential oil release profile.

Identifying its bioactive compounds is essential for understanding its therapeutic potential. The increasing prevalence of antibiotic resistance, inflammation-related diseases, and diabetes underscores the need for effective natural alternatives. Ixora duffii, a medicinal plant from the Rubiaceae family commonly used in traditional Vietnamese medicine, has not been evaluated its biological activities. Therefore, this study was conducted to investigate the antibacterial, antioxidant, anti-inflammatory, and antidiabetic activity of the ethanol, n-hexane, dichloromethane, ethyl acetate, and water extracts of I. duffii leaves. The antioxidant activity was assessed by methods of ABTSŸ+, DPPH, RP, FRAP, and TAC. Anti-inflammatory effect was assessed by assays of protecting red blood cell membranes (RBCs), inhibiting denaturation of bovine serum albumin (BSA), inhibiting nitric oxide (NOŸ). Antidiabetic efficacy was assessed by the inhibitory assays on 2 enzymes of α-amylase, α-glucosidase. Antibacterial activity was determined based on the diameter of the inhibition zone, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC) against 4 strains of Gram-negative, Gram-positive bacteria (Listeria innocua, Staphylococcus aureus, Psedomonas aeruginosa, and Escherichia coli). The results showed that I. duffii leaf extracts had good activity in all tests. The ethyl acetate fraction (EF) exhibited the lowest IC50 values in antioxidant, antidiabetic, and anti-inflammatory tests, ranging from 5.15 ± 0.06 to 66.22 ± 0.40 µg/mL. EF inhibited Gram-positive bacteria more effectively than Gram-negative bacteria, with antibacterial zone diameters ranging from 9.13 ± 0.31 to 26.83 ± 0.76 mm, MIC and MBC values ranging from 8 to 32 and 16 to 64 µg/mL. The I. duffii leaves extracts’ effects were linked to their polyphenol, flavonoid, alkaloid, tannin contents. These findings point to the possible use of I. duffii leaves as a natural antioxidant, antidiabetic, anti-inflammatory, and antibacterial agents. HIGHLIGHTS The chemical composition and biological activity of Ixora duffii, a medicinal plant that is frequently employed in folk medicine of Vietnam, have not been the subject of any specific research. The preliminary examination of the chemical composition of Ixora duffii leaves, as well as their antibacterial, antioxidant, anti-inflammatory, and antidiabetic effects in vitro. The leaves of Ixora duffii have significant antibacterial, antioxidant, anti-inflammatory, and antidiabetic qualities in vitro because to the presence of alkaloids, tannins, polyphenols, flavonoids. The research findings indicated that extracts exhibit strong antibacterial, antioxidant, anti-inflammatory, and antidiabetic effects. The findings suggest that Ixora duffii possesses potential as a natural antibacterial, antioxidant, anti-inflammatory and antidiabetic agent. GRAPHICAL ABSTRACT

Comparison of chemometric assisted targeted and untargeted approaches for the prediction of radical scavenging activity of ylang-ylang essential oils

Background: The essential oils of aromatic plants have wide range of biological applications. Natural food preservatives have been always a demanding for food industries in both developed and developing countries to prevent bacterial growth in food stuffs. Therefore, focused on Cinnamon leaves essential oils components against food pathogens have been investigated to confirm its potential use in food products. Methods: The antimicrobial activity of two Cinnamon leaves oils and extracts (T-2 and T-19) were examined by disc diffusion assay and the minimum inhibitory concentration by two-fold serial dilution method against foodborn pathogenic microorganisms i.e. E.coli (MTCC 723), B. Cereus (MTCC 430), S. aureus (MTCC 3381), S. typhi (MTCC 734) and C. perfringens (MTCC 1349). The antioxidant activity of both essential oils and extract was determined by DPPH assay. The chemical profiling of Cinnamon essential oils were determined by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS). Result: The antimicrobial activity of both Cinnamon leaves oils and extract were evaluated by disc diffusion assay and it showed that in essential oils and extracts exhibited the highest zone of inhibition (ZOI) against S. aureus and E.coli. Minimum inhibitory concentration (MIC) of both oils and extracts ranged from 0.156 mg/ml to 5mg/ml and the antioxidant properties of oils and extract of cinnamaldehyde type Cinnamon possessed the highest antioxidant activity than linalool type. The chemical constituent of Cinnamon oil was analyzed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC-MS) revealed that T-2 contains cinnamaldehyde (75%) and T-19 contains Linalool (63.77%) were found as major constituents. Therefore the results shows that essential oil of cinnamaldehyde type Cinnamon could be a potential rich source of natural antioxidants and also more effective against food borne pathogens than linalool type and could be used as natural antibacterial agents in food preservation.