Value Of Essential Oils Research Articles

The Essential Oil of Rocket Seeds Maintains Its Antibacterial Effects After Encapsulation in Nanoliposomes

IntroductionIt has been demonstrated that the essential oil (EO) of Eruca sativa seeds could be potentially used as an antiseptic agent. However, the application of EOs is restricted because of their chemical instability and volatility. Encapsulation in liposomes is an efficient technique for the protection of the oils. MethodsThe EO of the seeds was obtained using the hydro-distillation method. Liposomal formulation of the oil was prepared using thin layer method. ResultsGC/MS analysis indicated that erucin (1-isothiocyanato-4-methylsulfanylbutane) was the main compound of the oil, accounting for 88.86%. The prepared oil-loaded liposomes had more negative zeta potential (−17.13 mV) compared with the empty liposomes (−9.26 mV), indicating the higher stability of the liposomal oil. SEM imaging confirmed that the encapsulation of the oil does not cause any distortion in the structure of the liposomes, in comparison to the oil-free liposomes. The seed oil showed antimicrobial activities at 20 μg/ml (against Staphylococcus aureus, Enterobacter aerogenes, and Escherichia coli) and 80 μg/ml (against Enterococcus faecalis, Pseudomonas aeruginosa, and Klebsiella pneumonia), while the minimum inhibitory concentration values of the liposomal EO were 160 μg/ml against E faecalis, 80 μg/ml against P aeruginosa and K pneumonia, and 20 μg/ml against S aureus, E aerogenes, and E coli. ConclusionsAntibacterial experiments revealed that the EO of Eruca sativa seeds maintained its antibacterial effect after loading into the liposomes. Moreover, encapsulation in liposomes could improve the sustainability of the oil and increased the bioavailability of its active chemical compounds.

Advanced analytical techniques for authenticity identification and quality evaluation in Essential oils: A review

Essential oils (EO), secondary metabolites of plants are fragrant oily liquids with antibacterial, antiviral, anti-inflammatory, anti-allergic, and antioxidant effects. They are widely applied in food, medicine, cosmetics, and other fields. However, the quality of EOs remain uncertain owing to their high volatility and susceptibility to oxidation, influenced by factors such as the harvesting season, extraction, and separation techniques. Additionally, the huge economic value of EOs has led to a market marked by widespread and varied adulteration, making the assessment of their quality challenging. Therefore, developing simple, quick, and effective identification techniques for EOs is essential. This review comprehensively summarizes the techniques for assessing EO quality and identifying adulteration. It covers sensory evaluation, physical and chemical property evaluation, and chemical composition analysis, which are widely used and of great significance for the quality evaluation and adulteration detection of EOs.

Eugenia caryophyllata, Cinnamomum sp., Mentha piperita ve Thymus vulgaris esansiyel yağların Aspergillus niger suşuna karşı antifungal aktivitesi

Aspergillus species are pollutants found in both food and air. The increase in the metabolic activity of Aspergillus leads to spoilage of foodstuffs and large economic losses. In addition, some Aspergillus species have the ability to produce aflatoxins and ochratoxins, secondary metabolites called, namely, mycotoxins. Especially mycotoxins are very important in terms of food safety and human health. Since the protection of human and animal health and the prevention of economic losses is a very important issue, our study aimed to determine the antifungal activity of Eugenia caryophyllata Thunb., Cinnamomum sp., Mentha piperita L. and Thymus vulgaris L. essential oils (EO) against Aspergillus niger Tiegh. NRRL 321 strain. In the second step, MIC and MFC values of EOs were determined. It was determined that the MIC value of Cinnamomum sp, M. piperita and T. vulgaris EOs was 0.01 µL/mL, and E. caryophyllata EO was 0.5 µL/mL. It was determined that E. caryophyllata, Mentha piperita and Thymus vulgaris EOs completely inhibited radial colony growth at MIC, 2xMIC and 4xMIC values. It was determined that the inhibition of radial growth of Cinnamomum sp. EO varies depending on the concentration, and the inhibition rate increases as the concentration increases. As a result, evaluations should be made considering the in vivo conditions that the tested EOs showed strong antifungal activity against the A. niger strain.

Efficacy and Potential Mechanism of Essential Oils of Three Labiatae Plants against the Pathogenic Fungi of Root Rot Disease in Atractylodes chinensis

Atractylodes chinensis has a high medicinal value and is widely cultivated. However, root rot disease seriously affects the yield and quality of A. chinensis. To develop green and safe pesticides, the inhibitory effect of essential oils (EOs) of three Labiatae plants on the pathogenic fungi that causes root rot disease in Atractylodes chinensis was investigated. The results showed that the Origanum vulgare EO and Thymus mongolicus EO exhibited strong inhibitory effects on Fusarium oxysporum, Fusarium solani, and Fusarium redolens, with 100% inhibition rate. The low MIC values of EOs and their main components against the three pathogenic fungi indicated that all of them showed strong fungicidal effects. The MIC values of O. vulgare EO against F. oxysporum, F. solani, and F. redolens were 2.60 mg/mL, 3.13 mg/mL, and 1.56 mg/mL, respectively. Analyses using scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that the O. vulgare EO severely damaged the cell wall and cell membrane of mycelial cells. The O. vulgare EO increased cell permeability, leading to a large leakage of cell contents (DNA and proteins). In addition, O. vulgare EO inhibited F. oxysporum by inducing ROS production and reducing the amount of intracellular GSH, leading to a large accumulation of ROS. This study showed that plant EOs have excellent fungicidal activity and can be used as novel natural and environmentally friendly pesticides for the control of root rot in A. chinensis.

Potentiation of Antibacterial Activity of Ciprofloxacin by Essential Oil of Cymbopogon citratus against Fluoroquinolone-resistant Staphylococcus aureus and Escherichia coli

Background: Essential oil (EO) of Cymbopogon citratus has been demonstrated to have antibacterial activities against both Gram negative and Gram positive bacteria. The study was, therefore, conducted to evaluate the effects of combined use of C. citratus and ciprofloxacin against fluoroquinolone-resistant Staphylococcus aureus (FQRSA) and Escherichia coli (FQREC).
 Methods: The antibacterial activity of the essential oil was evaluated by agar dilution method while the combination studies were done using Checker-board agar dilution technique.
 Results: The mean MIC values of EO against the FQRSA and FQREC were 0.043 + 0.01 mg/ml and 0.049 mg/ml respectively. When ciprofloxacin was combined with EO of lemongrass, 53.9, 28.3, 17.8 and 0.0 % of the FQRSA isolates showed indifference, additive, synergistic and antagonistic effects respectively. Similarly, when ciprofloxacin was combined with EO of lemongrass at different ratios, 44, 35.5, 20.6 and 0.0 % of the FQREC isolates showed combined effects of additivity, synergism, indifference and antagonism respectively.
 Conclusions: The results revealed the invitro antibacterial potency of Cymbopogon citratus oil against fluoroquinolone resistant S. aureus and E. coli. More importantly, the study has proved that the combined use of ciprofloxacin and essential oil of lemongrass has increased the sensitivity of both FQRSA and FQREC bacteria.

Cytotoxic Activity of Baccharis trimera (Less.) DC. Essential Oil in Tumor Cell Lines and its Role in Associated Death Mechanisms

This study evaluated the potential of Baccharis trimera essential oil (EO) and its components in cancer therapy through the application of cytotoxicity and cell death assays. Using gas chromatography analysis, the major components of the aerial parts of the essential oil were identified as (E)-caryophyllene (18.9%), bicyclogermacrene (15.6%), and germacrene D (10.5%). Baccharis trimera essential oil (5.8 μg/mL) and α-humulene (7.8 μg/mL) presented strong cytotoxic activity, while (E)-caryophyllene (11.5 μg/mL) and caryophyllene oxide (> 100.0 μg/mL) showed moderate and low activities, respectively, against MCF-7 cell lines. Against HepG2 cell lines, B. trimera essential oil (10.4 μg/mL), α-humulene (17.1 μg/mL), and caryophyllene oxide (19.4 μg/mL) exhibited moderate activity, while (E)-caryophyllene (52.3 μg/mL) displayed low activity against HepG2 cell lines. The selectivity index values of EO (MCF-7 and HepG2), α-humulene and (E)-caryophyllene (MCF-7), and caryophyllene oxide (HepG2) were found between 1.1 and 2.8, compared with MCF-10A cells. The annexin-V and Hoechst / propidium iodide assays performed with essential oil, (E)-caryophyllene, α-humulene, and caryophyllene oxide showed apoptosis and necrosis mechanisms for all cell lines. Based on these findings, B. trimera essential oil and its components can be considered as potential therapeutic agents against cancer.

Antifungal Activities of Different Essential Oils and Their Electrospun Nanofibers against Aspergillus and Penicillium Species Isolated from Bread.

Mold growth, especially Aspergillus spp. and Penicillium spp., deteriorates the quality of bakery products. Essential oils (EOs) have been categorized as good natural antimicrobials. Hereby, this study aimed to evaluate the antifungal activity of six EOs, ginger, cumin, cinnamon, black pepper, origanum, and clove, and their volatile compounds against fungal strains isolated from bread: Penicillium carneum DDS4, Aspergillus flavus DDS6, and Aspergillus niger DDS7 by disc diffusion and disc volatilization methods, respectively. Among EOs, cumin, cinnamon, origanum, and clove were found to be effective against fungal strains, and their minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) were determined. The observed lowest MIC value of EOs was obtained at 1000 μg/mL concentration, and the lowest MFC value was obtained from the results of clove at a concentration of 1000 μg/mL. Based on the MIC and MFC values, clove and cinnamon EOs were found to be more effective at lower concentrations. Electrospun nanofiber films of clove and cinnamon were produced with 6% poly(vinyl alcohol) (PVA), 2% β-cyclodextrin (β-CD), and 2% EO to overcome the unfavorable sensory impact of EOs on food products. The inhibitory activity of cinnamon EO film (2.64–2.51 log(CFU/mg)) was considerably lower than clove EO film (3.18–3.24 log(CFU/mg)) against P. carneum DDS4 and A. niger DDS7. Furthermore, these nanofiber films prevented fungal growth on bread samples visibly and were shown to be an alternative application for active food packaging.

Toxicity, Behavioral Effects, and Chitin Structural Chemistry of Reticulitermes flaviceps Exposed to Cymbopogon citratus EO and Its Major Constituent Citral.

Simple SummaryReticulitermes flaviceps, as a main wood-boring pest, causes economically significant damage to wood materials. In this study, gas chromatography–mass spectrometry was used to detect and characterize the chemical constituents of lemongrass essential oil (Cymbopogon citratus (DC.) Stapf.), and we evaluated the associated vapor insecticidal effect on R. flaviceps worker adults. Lemongrass EO and its major constituent, citral, presented significant vapor toxicity against R. flaviceps, where the walking and gripping abilities of treated insects were reduced. Chitin content, thermal stability, and crystallinity were also reduced in the treated worker adults. The results of this study suggest that lemongrass EO can potentially be used to develop eco-friendly natural remedies for the management of R. flaviceps.Botanical pesticides are considered the most promising alternative to synthetic pesticides, considering their less negative impacts on the environment and human health. Here, we analyzed the components of lemongrass Cymbopogon citratus essential oil (EO) and evaluated its vapor activity against Reticulitermes flaviceps, in terms of the walking and gripping abilities of workers. In addition, the effects of lemongrass EO and its major component on the cuticular content and structure of chitin in termites were also observed. Our results indicate that cis-citral (36.51%) was the main constituent of lemongrass. In the vapor toxicity assay, the LC50 values of lemongrass EO and citral were 0.328 and 0.177 μL/L, respectively. When worker antennae were treated with lemongrass EO and citral, their walking and gripping capabilities were significantly inhibited. In addition, the cuticular content, thermal stability, and crystallinity of chitin in the termites were decreased after treatment with citral. Collectively, this study provides a basis for developing and utilizing lemongrass and citral as a new environment-friendly insecticide resource to control R. flaviceps.

Antifungal Activity of Nanoemulsion of Iranian Tarragon (Artemisia dracunculus L.) Essential Oil

Background: Despite the considerable activity of herbal Essential Oils (EOs) as safe food preservatives, problems such as high volatility, low water solubility, and low stability in adverse environmental conditions restrict their use in food products. This work aimed to investigate in vitro antifungal activity of oil-in-water nanoemulsion of Iranian Artemisia dracunculus L. (tarragon) EO.
 Methods: Nanoemulsion of tarragon EO was formed by ultrasound method through blending 10 wt% of tarragon EO, 85 wt% water, and the mixture of 5 wt% surfactants (Tween® 80/Span® 80). The droplet size and zeta potential were measured. The antifungal activity was evaluated against four different fungi, Aspergillus niger, Penicillium spp., Fusarium spp., and Saccharomyces cerevisiae through determining Minimum Inhibitory Concentration (MIC), Minimum Fungicidal Concentration (MFC), and mycelial growth test. Data were statistically analyzed by the software of SPSS 22.0.
 Results: Main fragments of tarragon EO found to be beta-cis-ocimene, estragole, and beta-trans-ocimene. Nanodroplets had a zeta potential of -30 mV and an average diameter of 50 nm. For A. niger, Penicillium spp., Fusarium spp., and S. cerevisiae, the MIC and MFC values of nanoemulsion were identical and obtained at 1.50, 2.05, 1.61, and 1.14 µg/ml, respectively, while these values of free EO were higher and as follows: 2.81, 4.52, 3.75, and 2.40 µg/ml, respectively. Mycelial growth showed that encapsulated EO had the most fungitoxic potential against A. niger (inhibition 41%) and S. cerevisiae (inhibition 68%). Also, Penicillium spp. was the most resistant against both EO and nanoemulsion.
 Conclusion: The growth inhibitory activity of tarragon was significantly enhanced when encapsulated as nanoemulsion.

Deverra triradiata Hochst. ex Boiss. from the Northern Region of Saudi Arabia: Essential Oil Profiling, Plant Extracts and Biological Activities.

Devrra triradiata Hochst. ex Boiss is an occasional plant species in the Northern region of Saudi Arabia. The shrub is favored on sandy desert wadis, gypsaceous substrate, and sandy gravel desert. In folk medicine, the plant is used for many purposes; to relieve stomach pains, against intestinal parasites, and for the regulation of menstruation. The present study describes the chemical composition of the essential oils (EOs) of different plant parts of D. triradiata. In vivo and in vitro biological activities of plant extracts and essential oils were also studied. Phenylpropanoids, elemicin (flowers: 100%), dillapiole (Stems: 82.33%; and seeds: 82.61%), and apiol (roots: 72.16%) were identified as the major compounds. The highest antioxidant activity was recorded for the EOs of roots and stems (IC50 = 0.282 µg/mL and 0.706 µg/mL, respectively). For plant extracts, ethyl acetate showed the highest antioxidant activities (IC50 = 2.47 and 3.18 µg/mL). EOs showed high antifungal activity against yeasts with low azole susceptibilities (i.e., Malassezia spp. and Candida krusei). The MIC values of EOs ranged between 3.4 mg/mL and 56.4 mg/mL. The obtained results also showed phytotoxic potential of plant extracts both on the germination features of Triticum aestivum seeds and the vegetative growth of seedlings.

Effects of the extract and the essential oil of Allium sativum on tea mealy bug, Pseudococcus viburni Sigornet (Hemiptera: Pseudococcidae)

The effects of methanolic extract (ME) and essential oil (EO) of garlic were studied on the third-instar nymphs of Pseudococcus viburni Signoret to elucidate whether garlic essential oil and extract may cause mortality on tea mealybug and physiological disorders. The nymphs exposed to ME showed the LC50 values of 0.33 and 0.12% after 24 and 48 h while those were 0.42 and 0.31% in case of EO. The ED50 values of ME and EO were calculated to be 0.31 and 0.22%, respectively. The LC50 concentrations of Garlic ME and EO significantly increased the activities of general esterase and glutathione S-transferase. Meanwhile, treating P. viburni nymphs by ME and EO significantly increased the activities of aspartate- and alanine aminotransferases as well as ɤ-glutamyl transferase compared to control. The lower activity of lactate dehydrogenase was recorded in the nymphs treated by ME and EO compared to control but the significant increase of acid- and alkaline phosphatase activities was found in the nymphs treated by ME and EO, respectively. Finally, garlic ME and EO significantly decreased the content of protein and glycogen as storage macromolecules compared to control. Our results demonstrated garlic metabolites imposed significant mortality on the nymphs of P. viburni and prominently caused discrepancies in the physiological processes.

Essential oils from different Citrus species and evaluation of their in vitro antibacterial, antiacetylcholinesterase, anti-inflammatory and antifungal activities

Essential oils (EOs) from Citrus are not only economic, eco-friendly and natural alternatives to chemical preservatives but also have other biological applications. This study aimed to investigate the chemical composition of Citrus species (EOs from C. limonia, C. latifolia, C. sinensis and C. deliciosa fruit peel) to evaluate their in vitro antibacterial activity against Listeria monocytogenes, Yersinia enterocolitica, Staphylococcus aureus, Clostridium botulinum and Bacillus cereus. The chemotaxis model, which was used for evaluating their anti-inflammatory activity, showed that EOs exhibited effective results when the dose was 100 µg/mL. Regarding all antimicrobial activities, minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. EOs showed satisfactory antifungal activity against Malassezia furfur (MIC values between 32.5 and 62.5 µg/mL). Citrus deliciosa, whose MIC = 95.8 µg/mL, inhibited acetylcholinesterase (AChE) more selectively. All EOs from Citrus spp. fruit peel showed good antibacterial activity against Yersinia enterocolitica (MIC = 62.5 µg/mL) and Staphylococcus aureus (MIC = 62.5 µg/mL), mainly the EO from C. deliciosa whose MIC values were 50 µg/mL for both. EOs were moderately active against Clostridium botulinum, Bacillus cereus and Listeria monocytogenes since MIC values ranged from 100 μg/mL to 400 μg/mL. Both GC-FID and GC-MS analyses revealed that the single major constituent determined in EOs is the terpene limonene. EOs from Citrus may be important active ingredients of several products to prevent bacterial growth in food, to attack the fungus that causes seborrheic dermatitis and to treat inflammatory processes. In short, the promising antiacetylcholinesterase activity of EOs under evaluation was attributed to the high concentration of the monoterpene limonene

Biological Activities of Citrus limon L. and Citrus sinensis L. Peel Essential Oils

In this study, the composition of essential oils (EOs) obtained from Citrus limon L. and Citrus sinensis L. peels and their biological activities on foodborne pathogenic bacteria and food-borne saprophytic yeasts and molds were investigated. In the lemon peel EO, 17 components were identified, mainly limonene (68.65 %) and γ-terpinene (10.81 %). Similarly, 8 components were determined in the orange peel EO, mainly limonene (95.51 %) and β-myrcene (1.98 %). The lemon and orange peel EOs showed a higher antibacterial effect on gram-positive bacteria used in the study compared to gram-negative bacteria. The highest antibacterial activity was detected on Staphylococcus aureus with 22.55 and 26.23 mm, respectively (P <0.05) The highest anti-fungal effects were determined at lemon peel EO, on Candida tropicalis (23.61 mm) and Rhizopus nigricans (14.15 mm) and orange peel EO, on Debaromyces hanseni spp hanseni (30.68 mm) and R. nigricans (17.23 mm) (P<0.05). The lowest minimum inhibitory concentration values were determined on S. aureus (0.023 mg/L, 0.006 mg/L), C. tropicalis (0.017 mg/L, 0.011 mg/L) and Aspergillus flavus (0.058 mg/L, 0.017 mg/mL) (P<0.05). The minimum bactericidal and fungicidal concentration values of lemon and orange peel EOs were determined on S. aureus (0.011 mg/L, 0.004 mg/L), C. tropicalis (0.011 mg/L, 0.003 mg/L) and Aspergillus flavus (0.023 mg/L, 0.015 mg/mL) (P<0.05).

Antimicrobial effect of laurel essential oil nanoemulsion on food-borne pathogens and fish spoilage bacteria

This research aimed to apply nanotechnology for nanoformulation of Laurus nobilis essential oil (EO) by ultrasonic emulsification method and characterization of nano-form: particle size, viscosity, polydispersity index, thermodynamic stability, and surface tension. The antimicrobial activity of laurel EO nanoemulsion (LEON) and laurel EO was also investigated against a panel of ten food-borne pathogens and fish spoilage bacteria. The GC–MS analysis of EO revealed that 1,8-Cineole was the main volatile compound. According to disc-diffusion results, LEON was more effective against Gram-positive pathogen bacteria of Staphylococcus aureus and Enterococcus faecalis than EO. Laurel oil demonstrated a higher inhibitory effect against fish spoilage bacteria (6.19 to 18.5 mm). The MICs values of LEON and laurel EO ranged from 6.25 to >25 mg/mL and from 1.56 to >25 mg/mL, respectively. Nanoemulsion and oil exhibited the best bactericidal activity against Pseudomonas luteola. Therefore, LEON can be developed as a natural antimicrobial agent in food industry.

In vitro evaluation of the antibacterial effects of Cinnamomum zeylanicum essential oil against clinical multidrug-resistant Shigella isolates.

As there are little data about the antimicrobial effects of the cinnamon essential oils (EO) against multidrug-resistant (MDR) Shigella species, this study aimed to evaluate the antibacterial activities of Cinnamomum zeylanicum EO against the clinical MDR Shigella isolates. Totally 50 MDR Shigella isolates including 17 (34%) S. flexneri, 20 (40%) S. sonnei, and 13 (26%) S. boydii were collected. The isolates were identified by standard phenotypic and molecular methods. The MDR phenotypes were determined as resistant to three antibiotic classes using disc diffusion. The C. zeylanicum EO was analyzed by gas chromatography/mass spectrometry (GC/MS). The minimum inhibitory concentration (MIC) of cinnamon EO was evaluated by microtiter broth dilution. The most Shigella isolates 38% (n = 19) were resistant to six antibiotics. The ampicillin-amikacin-cefotaxime-erythromycin-ciprofloxacin-cotrimoxazole resistotype was the most prevalent pattern detected in five S. sonnei, four S. boydii, and three S. flexneri isolates. The result of GC/MS revealed the cinnamaldehyde (84.8%) as the main ingredient of C. zeylanycum EO. The most susceptible strain to the C. zeylanycum EO was S. boydii (MIC range = 0.15-0.62μl/ml) followed by S. flexneri (MIC range = 0.07-1.25μl/ml), and S. sonnei (MIC range = 0.15-1.25μl/ml). The observed ranges of MIC and MBC values of cinnamon EO against Shigella spp. were 0.07-1.25μl/ml and 0.31-1.25μl/ml, respectively. The antibacterial effects of cinnamon EO in this study may increase the hope of finding suitable plant compounds to treat infections caused by MDR Shigella isolates.

Is the Antimicrobial Activity of Hydrolates Lower than That of Essential Oils?

Among the top five human infections requiring medical treatment is dermatitis. Treatment of bacterial and fungal skin infections is usually based on antibiotic therapy, which is often ineffective due to the involvement of antibiotic-resistant microbial strains. The aim of this study was to compare the antimicrobial activity of essential oils (EOs) and hydrolates (Hys) extracted from six aromatic plants grown in Italy (Lavandula angustifolia, Lavandula intermedia, Origanum hirtum, Satureja montana, Monarda didyma, and Monarda fistulosa) towards fungal (Candida albicans, Candida parapsilosis, Candida glabrata and Candida tropicalis; Trichophyton soudanense, Trichophyton tonsurans, Trichophyton rubrum, Trichophyton violaceum and Microsporum canis) and bacterial strains (Staphylococcus aureus MRSA, Staphylococcus aureus MSSA, Streptococcus pyogenes, E. faecalis, Enterococcus faecalis VRE, and Enterococcus faecium) potentially pathogenic for human skin. The composition and antimicrobial activity of EOs and Hys were evaluated using the Gas-chromatography mass spectrometry and micro dilution-broth test, respectively. The volatiles’ conversion factors (CFs) were calculated to compare the activity of Hys with that of the corresponding EOs. Data show that, although the minimum inhibitory concentration values of EOs are lower than the corresponding Hys, the volatiles contained in Hys are more effective at inhibiting microbial growth because they are active at lower concentrations.

Investigating the Potential of the Essential Oil Nanoemulsion of Zataria multiflora Boiss. on the Gene Expression of stx1A and stx2A in Escherichia coli as a Foodborne Pathogen

Background: Several occurrences of infections and intoxications have been globally announced as a result of the Escherichia coli contamination of foodstuffs. In addition, the emergence of antibiotic resistance in different geneses of bacteria is becoming a major concern for public/medical health authorities and researchers. Objective: Accordingly, this study determined the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the essential oil (EO) nanoemulsion (NEO) of Zataria multiflora Boiss against E. coli. Finally, different sub-MIC concentrations of the NEO of zataria EO on the growth rate and the gene expression of stx1A and stx2A were investigated as well. Materials and Methods: Oil in water NEO was formed by the phase inversion technique. The mean diameter of droplets and the zeta potential of NEO were determined, and then the MIC and MBC of EO and NEO were estimated using the broth microdilution method. Eventually, the growth rate and expressions of the stx1A and stx2A genes of E. coli were evaluated after exposure to various sub-MICs. Results: Based on the results, carvacrol was the main constituent of the EO, and NEO droplets had an average size of 61.5 nm and a zeta potential of -27 mV. Further, the MIC values of EO and NEO were 0.45 ± 0.17 and 0.25 ± 0.10 mg/mL, and their MBCs were found 0.55 ± 0.20 and 0.30 ± 0.05 mg/mL, respectively. Furthermore, NEO expressed a stronger inhibitory effect against E. coli growth compared to pure EO. At 75% MIC of EO, the transcriptional rate of stx1A and stx2A decreased 2.24 and 2.66 times at the end of the 72-hour period compared with the control, respectively. After 72 hours, treatment with 75% MIC of NEO resulted in the down-regulation of stx1A and stx2A as 4.75 and 4.80 fold, respectively. Conclusion: The greater activity of the NEO of Z. multiflora Boiss. in comparison with pure EO for slowing down the growth of E. coli and Shiga toxin production shows its potential as a novel ‘green’ food-grade preservative.

Microencapsulation and Antimicrobial Activity of Plant Essential Oil Against Ralstonia solanacearum

Ralstonia solanacearum is a common plant bacterium, and the improper use of chemicals to control this bacterium is harmful to the environment. Many undeveloped aromatic plants and green plant waste can be used for the preparation of essential oils (EOs). EOs have various biological activities, such as bacteriostatic, insecticidal and anti-oxidation, and are currently in the exploration stage for the control of R. solanacearum. In the present study, the inhibitory activity of ten EOs against R. solanacearum was determined by an antibacterial test. To prolong the duration of antibacterial activity, microcapsules of EOs were prepared by the complex coacervation method, and the optimal preparation conditions were obtained by central composite design method. The results showed that cinnamon EOs had the strongest antibacterial activity. For GIM1.71, GIM1.74, GIM1.76, GMI1000 and RS-5, the EC50 values of cinnamon EOs were 0.055 mg/mL, 0.071 mg/mL, 0.03 mg/mL, 0.067 mg/mL and 0.063 mg/mL, respectively. The preparation condition of cinnamon EOs microcapsules was as follows: the core-wall ratio was 4.35:1, the ratio of chitosan and sodium alginate was 0.15:1, and the calcium chloride concentration was 0.95 wt%. The encapsulation efficiency was 87.32%, and the average particle size of microcapsule was 870.4 μm. The release rate of microcapsule was 44.53% at 100 °C for 6 h and the release of the core materials in microcapsules was in line with Korsmeyer–Peppas release kinetics. Microcapsules placed at room temperature for 7 days still had significant antibacterial activity against five species of R. solanacearum. Due to its good stability and antibacterial activity, cinnamon EOs microcapsules will have great market application prospects as antibacterial agents.

In vitro antimicrobial activity of Spiranthera odoratissima A. St. Hil. essential oils against foodborne pathogens and food spoilage bacteria

In Brazilian folk medicine, Spiranthera odoratissima has been used to treat rheumatism, infection and abdominal pain. Essential oils (EOs) are technological options that may be employed in natural foods due to their antimicrobial activities. This paper aimed to investigate the chemical composition and in vitro antibacterial effects of EOs from S. odoratissima leaves and flowers against foodborne and spoilage bacteria Listeria monocytogenes, Salmonella enteritidis, Salmonella typhimurium, Yersinia enterocolitica, Staphylococcus aureus, Escherichia coli, Clostridium botulinum, Bacillus cereus and Pseudomonas aeruginosa. Minimum inhibitory concentration (MIC) values of EOs were calculated by the broth microdilution method on 96-well microplates. Both GC-FID and GC-MS analyses revealed that the major components determined in EOs from S. odoratissima leaves were β-caryophyllene (23.8%), bicyclogermacrene (10.8%) and δ-cadinene (7.1%). Major constituents found in EOs from its flowers were β-caryophyllene (14.1%), spathulenol (8.1%) and γ-cadinene (7.2%). EOs from S. odoratissima leaves and flowers showed strong antibacterial activity against Yersinia enterocolitica (MIC = 0.30 mg/mL), Staphylococcus aureus (MIC = 0.12 mg/mL), Clostridium botulinum (MIC = 0.30 mg/mL), Bacillus cereus (MIC = 0.20 mg/mL) and Listeria monocytogenes (MIC = 0.25 mg/mL). These EOs could be important natural alternatives to prevent bacterial growth in food products.

Raising the Efficiency of Lemon Trees to Produce Essential Oil by Exogenous Cysteine Under Various Soil Structures

Lemon essential oil (EO) has several biological activities especially against breast carcinoma cells. Cysteine (CYS) and soil structures play an important role in the production of lemon EO. The application of CYS in various soils is one way of scientific technique which leads to a modification of the EO production. Thus, the aim of this investigation was to evaluate the lemon EO extracted from leaves and peels under CYS rates and soil structures. Lemon trees were exposed to different rates (0.0, 0.2 and 0.4 g/L) of CYS in sand and clay soils. The EO isolated from leaves and peels by steam distillation, then analyzed by GC/MS. Obtained results indicated that different changes were recorded in the composition of leaf and peel oils in response to CYS levels and both soils. Limonene, neral, geranial and neryl acetate were the major components of leaf EO while limonene and γ-terpinene were the main constituent in peel EO. CYS at 0.4 g/L resulted in the maximum values of EO (%) and major constituents in both soils. Various chemical groups (monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons and oxygenated sesquiterpenes) were changed with CYS application x soil textures. Production of EO with CYS is required because the application of CYS produced significant variation in the EO composition of lemon especially under various soils.