Special Issue "Chemical Composition and Biological Activities of Essential Oils"

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Plant-Derived Antibiotics".

Deadline for manuscript submissions: closed (15 November 2020).

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Special Issue Editors

Dr. Edoardo Marco Napoli
E-Mail Website
Guest Editor
Institute of Biomolecular Chemistry, National Research Council ICB-CNR, 95126 Catania, Italy
Interests: natural compound chemistry; green chemistry; agro-industrial waste valorization; analytical chemistry; phytochemistry
Special Issues and Collections in MDPI journals
Dr. Maura Di Vito
E-Mail Website
Guest Editor
1. Dip. di Scienze e Tecnologie Agro-Alimentari (DISTAL) - University of Bologna, Bologna, Italy
2. Istituto di Microbiologia, Università Cattolica del Sacro Cuore Rome, Italy
3. Dip. di Scienze di Laboratorio e Infettivologiche, Fondazione Policlinico Universitario A. Gemelli IRCCS, Rome, Italy
Interests: essential oils; microbiology; human physio-pathology
Special Issues and Collections in MDPI journals

Special Issue Information

Dear Colleagues,

Essential oils extracted by distillation or hydrodistillation of aromatic plants are a complex mixture of volatile compounds with several biological activities. Their efficacy as antimicrobial agents is related to the activity of several components belonging to different chemical families that can act both in synergy with each other and with other antibiotics. The antibiotic resistance detected among pathogens is quick rising in the latest years, and the control of some of these microorganisms is becoming a planetary emergency for human and animal health. The control of the microbial growth is a problem of great importance also for the food industry (food deterioration and shelf life extension) and for the world of cultural heritage (indoor and outdoor phenomena of biodeterioration). Essential oils can play an important role in this scenario, due their recognized broad-spectrum antimicrobial activity. Therefore, the main subject of this Special Issue includes any essential oil-based approach to control microrganisms in areas such as human and veterinary medicine, entomology, food industry, agriculture, and cultural heritage. In addition, manuscripts concerning other essential oils areas of interest are welcome, such as:

  • Chemical composition of essential oils from endemic and rare medicinal/aromatic plants;
  • Innovative formulations and nanoformulations of essential oils;
  • Applications in human and veterinary medicine: e.g. anticancer, antiviral, antinflammatory, analgesic activities of essential oils;
  • Use of essential oils as animal feeding supplements;
  • Toxicological studies.

Dr. Edoardo Napoli
Dr. Maura Di Vito
Guest Editors

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Keywords

  • Essential oils
  • antibacterial activity
  • antifungal activity
  • anticancer activity
  • nanoformulations
  • toxicology

Published Papers (14 papers)

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Editorial

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Editorial
Toward a New Future for Essential Oils
Antibiotics 2021, 10(2), 207; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10020207 - 19 Feb 2021
Cited by 2 | Viewed by 861
Abstract
Essential oils (EOs) are peculiar phytocomplexes in the already widely varied world of natural bioactive substances [...] Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)

Research

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Article
Antifungal Activity and Chemical Composition of Seven Essential Oils to Control the Main Seedborne Fungi of Cucurbits
Antibiotics 2021, 10(2), 104; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10020104 - 22 Jan 2021
Cited by 2 | Viewed by 1052
Abstract
Essential oils represent novel alternatives to application of synthetic fungicides to control against seedborne pathogens. This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits. Cymbopogon citratus essential oil completely inhibited mycelial growth of Stagonosporopsis [...] Read more.
Essential oils represent novel alternatives to application of synthetic fungicides to control against seedborne pathogens. This study investigated seven essential oils for in vitro growth inhibition of the main seedborne pathogens of cucurbits. Cymbopogon citratus essential oil completely inhibited mycelial growth of Stagonosporopsis cucurbitacearum and Alternaria alternata at 0.6 and 0.9 mg/mL, respectively. At 1 mg/mL, Lavandula dentata, Lavandula hybrida, Melaleuca alternifolia, Laurus nobilis, and two Origanum majorana essential oils inhibited mycelia growth of A. alternata by 54%, 71%, 68%, 36%, 90%, and 74%, respectively. S. cucurbitacearum mycelia growth was more sensitive to Lavandula essential oils, with inhibition of ~74% at 1 mg/mL. To determine the main compounds in these essential oils that might be responsible for this antifungal activity, they were analyzed by gas chromatography–mass spectrometry (GC-MS). C. citratus essential oil showed cirtal as its main constituent, while L. dentata and L. nobilis essential oils showed eucalyptol. The M. alternifolia and two O. majorana essential oils had terpinen-4-ol as the major constituent, while for L. hybrida essential oil, this was linalool. Thus, in vitro, these essential oils can inhibit the main seedborne fungi of cucurbits, with future in vivo studies now needed to confirm these activities. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Nanoencapsulated Essential Oils with Enhanced Antifungal Activity for Potential Application on Agri-Food, Material and Environmental Fields
Antibiotics 2021, 10(1), 31; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10010031 - 01 Jan 2021
Cited by 4 | Viewed by 993
Abstract
Nanotechnology is a new frontier of this century that finds applications in various fields of science with important effects on our life and on the environment. Nanoencapsulation of bioactive compounds is a promising topic of nanotechnology. The excessive use of synthetic compounds with [...] Read more.
Nanotechnology is a new frontier of this century that finds applications in various fields of science with important effects on our life and on the environment. Nanoencapsulation of bioactive compounds is a promising topic of nanotechnology. The excessive use of synthetic compounds with antifungal activity has led to the selection of resistant fungal species. In this context, the use of plant essential oils (EOs) with antifungal activity encapsulated in ecofriendly nanosystems could be a new and winning strategy to overcome the problem. We prepared nanoencapsules containing the essential oils of Origanum vulgare (OV) and Thymus capitatus (TC) by the nanoprecipitation method. The colloidal suspensions were characterized for size, polydispersity index (PDI), zeta potential, efficiency of encapsulation (EE) and loading capacity (LC). Finally, the essential oil nanosuspensions were assayed against a panel of fourteen fungal strains belonging to the Ascomycota and Basidiomycota phyla. Our results show that the nanosystems containing thyme and oregano essential oils were active against various fungal strains from natural environments and materials. In particular, the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) values were two to four times lower than the pure essential oils. The aqueous, ecofriendly essential oil nanosuspensions with broad-spectrum antifungal activity could be a valid alternative to synthetic products, finding interesting applications in the agri-food and environmental fields. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Aniba rosaeodora (Var. amazonica Ducke) Essential Oil: Chemical Composition, Antibacterial, Antioxidant and Antitrypanosomal Activity
Antibiotics 2021, 10(1), 24; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10010024 - 30 Dec 2020
Cited by 3 | Viewed by 1153
Abstract
Aniba rosaeodora is one of the most widely used plants in the perfumery industry, being used as medicinal plant in the Brazilian Amazon. This work aimed to evaluate the chemical composition of A. rosaeodora essential oil and its biological activities. A. rosaeodora essential [...] Read more.
Aniba rosaeodora is one of the most widely used plants in the perfumery industry, being used as medicinal plant in the Brazilian Amazon. This work aimed to evaluate the chemical composition of A. rosaeodora essential oil and its biological activities. A. rosaeodora essential oil presented linalool (93.60%) as its major compound. The A. rosaeodora essential oil and linalool showed activity against all the bacteria strains tested, standard strains and marine environment bacteria, with the lower minimum inhibitory concentration being observed for S. aureus. An efficient antioxidant activity of A. rosaeodora essential oil and linalool (EC50: 15.46 and 6.78 µg/mL, respectively) was evidenced by the inhibition of the 2,2-azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical. The antitrypanosomal activity of A. rosaeodora essential oil and linalool was observed at high concentrations against epimatigote forms (inhibitory concentration for 50% of parasites (IC50): 150.5 ± 1.08 and 198.6 ± 1.12 µg/mL, respectively), and even higher against intracellular amastigotes of T. cruzi (IC50: 911.6 ± 1.15 and 249.6 ± 1.18 µg/mL, respectively). Both A. rosaeodora essential oil and linalool did not exhibit a cytotoxic effect in BALB/c peritoneal macrophages, and both reduced nitrite levels in unstimulated cells revealing a potential effect in NO production. These data revealed the pharmacological potential of A. rosaeodora essential oil and linalool, encouraging further studies. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Chemical Composition and Antimicrobial Activity of Selected Essential Oils against Staphylococcus spp. Isolated from Human Semen
Antibiotics 2020, 9(11), 765; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9110765 - 31 Oct 2020
Cited by 5 | Viewed by 792
Abstract
Staphylococcus spp. is not only a commensal bacteria but also a major human pathogen that causes a wide range of clinical infections. Recent evidence suggests that Staphylococcus has the ability to colonize the reproductive system and to affect its structure and functions. The [...] Read more.
Staphylococcus spp. is not only a commensal bacteria but also a major human pathogen that causes a wide range of clinical infections. Recent evidence suggests that Staphylococcus has the ability to colonize the reproductive system and to affect its structure and functions. The objective of this study was to determine the chemical properties and antibacterial effects of select essential oils (EOs): Amyris balsamifera L., Boswellia carterii Birdw., Canarium luzonicum (Blume) A. Gray, Cinnamomum camphora (L.) J. Presl., Cinnamomum camphora var. linaloolifera Y. Fuita, Citrus x aurantium L., Gaultheria procumbens L., Litsea cubeba (Lour.) Pers., Melaleuca ericifolia Smith., Melaleuca leucadendra L., Pogostemon cablin (Blanco) Benth., Citrus limon (L.) Osbeck, Santalum album L., and Vetiveria zizanoides (L.) Roberty against 50 Staphylococcus spp. cultures isolated from human semen, specifically Staphylococcus aureus, S. capiti, S. epidermidis, S. haemoliticus, and S. hominis. The disc diffusion and broth microdilution methods were used to assess the antimicrobial potential and to determine the minimum inhibitory concentration (MIC) of the selected EOs. The best anti-Staphylococcus activities were found with both methods for the essential oils of C. luzonicum (Blume) A. Gray, A. balsamifera, C. camphora, and P. cabli. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Origanum vulgare Essential Oil vs. a Commercial Mixture of Essential Oils: In Vitro Effectiveness on Salmonella spp. from Poultry and Swine Intensive Livestock
Antibiotics 2020, 9(11), 763; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9110763 - 31 Oct 2020
Cited by 2 | Viewed by 735
Abstract
Salmonella spp. represent a public health concern for humans and animals due to the increase of antibiotic resistances. In this scenario, the use of essential oils (EOs) could be a valid tool against Salmonella contamination of meat. This work compares the in vitro [...] Read more.
Salmonella spp. represent a public health concern for humans and animals due to the increase of antibiotic resistances. In this scenario, the use of essential oils (EOs) could be a valid tool against Salmonella contamination of meat. This work compares the in vitro effectiveness of an Italian mixture of feed additives based on EOs (GR-OLI) with EO of Origanum vulgare L., recently admitted by European Food Safety Authority (EFSA) for animal use. Twenty-nine Salmonella serotypes isolated from poultry and pig farms were used to assess GR-OLI and O. vulgare EO antimicrobial propeties. O. vulgare EO was active on the disaggregation of mature biofilm, while GR-OLI was capable of inhibiting biofilm formation and disaggregating preformed biofilm. Furthermore, GR-OLI inhibited bacterial adhesion to Caco-2 cells in a dose-dependent manner. Both products showed inhibition of bacterial growth at all time points tested. Finally, the synergistic action of GR-OLI with commonly used antibiotics against resistant strains was investigated. In conclusion, the mixture could be used both to reduce the meat contamination of Salmonella spp. before slaughter, and in synergy with low doses of ciprofloxacin against resistant strains. Although EOs as feed additives are already used in animal husbandry, no scientific study has ever highlighted their real antimicrobial potential. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Pimenta Oil as a Potential Treatment for Acinetobacter baumannii Wound Infection: In Vitro and In Vivo Bioassays in Relation to Its Chemical Composition
Antibiotics 2020, 9(10), 679; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9100679 - 07 Oct 2020
Cited by 6 | Viewed by 972
Abstract
Bacterial biofilm contributes to antibiotic resistance. Developing antibiofilm agents, more favored from natural origin, is a potential method for treatment of highly virulent multidrug resistant (MDR) bacterial strains; The potential of Pimenta dioica and Pimenta racemosa essential oils (E.Os) antibacterial and antibiofilm activities [...] Read more.
Bacterial biofilm contributes to antibiotic resistance. Developing antibiofilm agents, more favored from natural origin, is a potential method for treatment of highly virulent multidrug resistant (MDR) bacterial strains; The potential of Pimenta dioica and Pimenta racemosa essential oils (E.Os) antibacterial and antibiofilm activities in relation to their chemical composition, in addition to their ability to treat Acinetobacter baumannii wound infection in mice model were investigated; P. dioica leaf E.O at 0.05 µg·mL−1 efficiently inhibited and eradicated biofilm formed by A. baumannii by 85% and 34%, respectively. Both P. diocia and P. racemosa leaf E.Os showed a bactericidal action against A. baumanii within 6h at 2.08 µg·mL−1. In addition, a significant reduction of A. baumannii microbial load in mice wound infection model was found. Furthermore, gas chromatography mass spectrometry analysis revealed qualitative and quantitative differences among P. racemosa and P. dioica leaf and berry E.Os. Monoterpene hydrocarbons, oxygenated monoterpenes, and phenolics were the major detected classes. β-Myrcene, limonene, 1,8-cineole, and eugenol were the most abundant volatiles. While, sesquiterpenes were found as minor components in Pimenta berries E.O; Our finding suggests the potential antimicrobial activity of Pimenta leaf E.O against MDR A. baumannii wound infections and their underlying mechanism and to be further tested clinically as treatment for MDR A. baumannii infections. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Chemical Profiling and Discrimination of Essential Oils from Six Ferula Species Using GC Analyses Coupled with Chemometrics and Evaluation of Their Antioxidant and Enzyme Inhibitory Potential
Antibiotics 2020, 9(8), 518; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9080518 - 14 Aug 2020
Cited by 6 | Viewed by 1183
Abstract
The differences in the composition of essential oils obtained from the aerial parts of six Ferula species viz., F. caratavica (Fc), F. kuchistanica (Fk), F. pseudoreoselinum (Fp), F. samarcandica (Fs), F. tenuisecta (Ft) [...] Read more.
The differences in the composition of essential oils obtained from the aerial parts of six Ferula species viz., F. caratavica (Fc), F. kuchistanica (Fk), F. pseudoreoselinum (Fp), F. samarcandica (Fs), F. tenuisecta (Ft) and F. varia (Fv) were detected both qualitatively and semi-quantitatively using GC-MS and GC-FID analyses. One hundred and six metabolites were identified that account for 92.1, 96.43, 87.43, 95.95, 92.90 and 89.48% of Fc, Fk, Fp, Fs, Ft and Fv whole essential oils, respectively. The data from the GC-MS analyses were subjected to unsupervised pattern recognition chemometric analysis utilizing principal component analysis (PCA) to improve the visualization of such differences among the six species. Fk and Ft are very closely related to each other and were gathered together in one cluster. The antioxidant potential was assessed in vitro using different assays including 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), cupric reducing antioxidant capacity (CUPRAC), ferric reducing power (FRAP) and phosphomolybdenum (PM) assays. Ft and Fp exhibited the most notable antioxidant properties as evidenced by their pronounced activities in most of the antioxidant assays performed, followed by Fc. Fk showed the most effective tyrosinase inhibitory potential, which was estimated as 119.67 mgKAE/g oil, while Fp exhibited the most potent α-amylase inhibitory potential, which was equivalent to 2.61 mmol ACAE/g oil. Thus, it was concluded that Ferula species could serve as a promising natural antioxidant drug that could be included in different products and spices to alleviate hyperglycemia and used as a natural ingredient in pharmaceutical cosmetics to counteract hyperpigmentation. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Studying the Gene Expression of Penicillium rubens Under the Effect of Eight Essential Oils
Antibiotics 2020, 9(6), 343; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9060343 - 19 Jun 2020
Cited by 1 | Viewed by 1068
Abstract
Essential oils (EOs) are well-known for their beneficial properties against a broad range of microorganisms. For the better understanding of their mechanism of action in fungi, a microarray approach was used in order to evaluate the gene expression of Penicillium chrysogenum (recently renamed [...] Read more.
Essential oils (EOs) are well-known for their beneficial properties against a broad range of microorganisms. For the better understanding of their mechanism of action in fungi, a microarray approach was used in order to evaluate the gene expression of Penicillium chrysogenum (recently renamed P. rubens) exposed to the indirect contact (vapors) of eight EOs. The selection of assayed EOs was based on their antifungal activity. The extraction of RNA and the microarray hybridization procedure were optimized for the analysis of P. rubens. Gene ontology annotation was performed to investigate the functional analysis of the genes. To uncover the metabolic pathway of these differentially expressed genes, they were mapped into the KEGG BRITE pathway database. The transcriptomic analysis showed that, from a total of 12,675 genes, only 551 genes are annotated, and the other 12,124 genes encoded hypothetical proteins. Further bioinformatic analysis demonstrated that 1350 genes were upregulated and 765 downregulated at least with half (four) of the utilizing EOs. A microarray investigation has confirmed the main impact of EOs to metabolic processes in P. rubens involved in vital functions. Presumably, this is the first time that a microarray hybridization analysis was performed in order to evaluate the gene expression of P. rubens exposed to various EOs. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Morphological, Chemical, and Genetic Characteristics of Korean Native Thyme Bak-Ri-Hyang (Thymus quinquecostatus Celak.)
Antibiotics 2020, 9(6), 289; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9060289 - 28 May 2020
Cited by 2 | Viewed by 950
Abstract
Bak-ri-hyang (Thymus quinquecostatus Celak.) is an important medicinal and aromatic plant in Korea. T. quinquecostatus population and is always mixed with other thyme cultivars during cultivation and marketing. Hence, this study aimed to determine the genetic variability and the essential oil composition [...] Read more.
Bak-ri-hyang (Thymus quinquecostatus Celak.) is an important medicinal and aromatic plant in Korea. T. quinquecostatus population and is always mixed with other thyme cultivars during cultivation and marketing. Hence, this study aimed to determine the genetic variability and the essential oil composition of three Korean native thyme, T. quinquecostatus cultivars collected from the Wolchul, Jiri, and Odae mountains, in comparison with six commercial thyme cultivars (T. vulgaris), to distinguish Bak-ri-hyang from other thyme cultivars. The composition of essential oils obtained from nine individuals was analyzed by gas chromatography–mass spectrometry (GC–MS). The random amplified polymorphic DNA (RAPD) analysis was accomplished using 16 different primers. The GC–MS analysis revealed that Wolchul, creeping, golden, and orange cultivars belong to the geraniol chemotype. Whereas the Odae, lemon, and silver cultivars belong to the thymol chemotype. Further, linalool was the most abundant component in carpet and Jiri cultivars. The RAPD analysis demonstrated that all thyme cultivars showed characteristic RAPD patterns that allowed their identification. In total, 133 bands were obtained using 16 primers, and 124 bands were polymorphic, corresponding to 93.2% polymorphism. Cluster analysis of RAPD markers established the presence of clear separation from nine thyme cultivars. The highest dissimilarity and similarity coefficient of the RAPD markers were 0.58 and 0.98, respectively. According to the RAPD patterns, the nine thyme cultivars could be divided into two major clusters. Among three Korean cultivars, the Wolchul and Odae cultivars were placed into the same cluster, but they did not show identical clustering with their essential oil compositions. The findings of the present study suggest that RAPD analysis can be a useful tool for marker-assisted identification of T. quinquecostatus from other Thymus species. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Natural Oregano Essential Oil May Replace Antibiotics in Lamb Diets: Effects on Meat Quality
Antibiotics 2020, 9(5), 248; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9050248 - 12 May 2020
Cited by 4 | Viewed by 1707
Abstract
A study was conducted to investigate the effect of oregano essential oil (OEO) and monensin sodium on the oxidative stability, colour, texture, and the fatty acid profile of lamb meat (m. Longissimus lumborum). Twenty Dorper x Pelibuey lambs were randomly divided into [...] Read more.
A study was conducted to investigate the effect of oregano essential oil (OEO) and monensin sodium on the oxidative stability, colour, texture, and the fatty acid profile of lamb meat (m. Longissimus lumborum). Twenty Dorper x Pelibuey lambs were randomly divided into five treatments; control (CON), monensin sodium (SM, Rumensin 200® 33 mg/kg), a low level of OEO (LO, 0.2 g/kg dry matter (DM)), a medium level of OEO (MO, 0.3g/ kg DM), and a high level of OEO (HO, 0.4 g/kg DM). Dietary supplementation of OEO at any concentration lowered the compression strength in comparison with CON and SM. MO had the highest a* values (7.99) and fatty acid concentration (C16:1n7, C18:1n9c, C18:1n6c, C20:1n9, and C18:2n6c) during storage for 7 d at 3 °C. Lipid oxidation was not promoted (p > 0.05) by the moderated supplementation of oregano essential oil; however, OEO at 0.3 g/kg DM showed a slight lipid pro-oxidant effect. Dietary supplementation of MO and SM had the same effect on colour, tenderness, and the fatty acid profile of lamb (L. lumborum). It was demonstrated that oregano essential oil was beneficial for lambs feeding, and it could be a natural alternative to replace monensin in lamb diets with improvements in the quality of the meat. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
In Vitro Antimicrobial Activity of Frankincense Oils from Boswellia sacra Grown in Different Locations of the Dhofar Region (Oman)
Antibiotics 2020, 9(4), 195; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9040195 - 20 Apr 2020
Cited by 7 | Viewed by 1676
Abstract
Frankincense essential oils from Boswellia sacra have been commonly used to treat microbial infections from as early as the 11th century. The main feature of the plant is its gum resin, from which it is possible to obtain essential oils. In the present [...] Read more.
Frankincense essential oils from Boswellia sacra have been commonly used to treat microbial infections from as early as the 11th century. The main feature of the plant is its gum resin, from which it is possible to obtain essential oils. In the present study, we focused on the comparative study of the oils extracted from the resins of three different Boswellia sacra cultivars (Najdi, Sahli and Houjri). From each of frankincense resin three successive essential oil samples (Grade 1, Grade 2, Grade 3) were obtained. Houjri gum resin gave the lowest percentage (5%) of total essential oil content but showed the maximum number of volatile components in all three grades. Najdi Grade 2 essential oil showed a minimum inhibitory concentration (MIC) of 52 mg/mL toward relevant pathogens Staphylococcus aureus and Pseudomonas aeruginosa, and samples from Grade 2 of Sahily and Houjiri were particularly active against a dermatological strain Propionibacterium acnes, displaying MIC values of 0.264 and 0.66 mg/mL, respectively. Data obtained from in vitro studies showed that all essential oils had a significant antifungal effect against Candida albicans and Malassezia furfur, showing MIC values ranging from 54.56 to 0.246 mg/mL. This work aims to increase the number of substances available in the fight against pathogens and to combat the phenomenon of antibiotic resistance, encouraging the use of alternative resources, especially in non-clinical settings (farms, food processing, etc.). Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Article
Inhibition of Glucosyltransferase Activity and Glucan Production as an Antibiofilm Mechanism of Lemongrass Essential Oil against Escherichia coli O157:H7
Antibiotics 2020, 9(3), 102; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics9030102 - 29 Feb 2020
Cited by 9 | Viewed by 1755
Abstract
The resistance of Escherichia coli O157:H7 to disinfection is associated with its ability to form biofilms, mainly constituted by glucans produced by glucosyltransferases. Citral and geraniol, terpenes found in the essential oil of Cymbopogon citratus (EO), have proven antibacterial activity against planktonic E. [...] Read more.
The resistance of Escherichia coli O157:H7 to disinfection is associated with its ability to form biofilms, mainly constituted by glucans produced by glucosyltransferases. Citral and geraniol, terpenes found in the essential oil of Cymbopogon citratus (EO), have proven antibacterial activity against planktonic E. coli; however, no information was found about their efficacy and mode of action against E. coli biofilms. Therefore, the inhibitory effect of C. citratus EO, citral, and geraniol on glucans production and glucosyltransferase activity as anti-biofilm mechanism against E. coli was evaluated. EO, citral, and geraniol inhibited the planktonic growth of E. coli (minimal inhibitory concentration or MIC= 2.2, 1.0, and 3.0 mg/mL, respectively) and the bacterial adhesion (2.0, 2.0, and 4.0 mg/mL, respectively) on stainless steel. All compounds decreased the glucans production; citral and geraniol acted as uncompetitive inhibitors of glucosyltransferase activity (The half maximal inhibitory concentrations or IC50 were 8.5 and 6.5 µM, respectively). The evidence collected by docking analysis indicated that both terpenes could interact with the helix finger of the glucosyltransferase responsible for the polymer production. In conclusion, C. citratus EO, citral, and geraniol inhibited glucosyltransferase activity, glucans production, and the consequent biofilm formation of E. coli O157:H7. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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Brief Report
Is the Antimicrobial Activity of Hydrolates Lower than That of Essential Oils?
Antibiotics 2021, 10(1), 88; https://0-doi-org.brum.beds.ac.uk/10.3390/antibiotics10010088 - 18 Jan 2021
Cited by 3 | Viewed by 860
Abstract
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 [...] Read more.
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. Full article
(This article belongs to the Special Issue Chemical Composition and Biological Activities of Essential Oils)
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