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Essential Oils as Antimicrobial and Anti-infectious Agents II

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (15 December 2020) | Viewed by 104255

Special Issue Editor


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Guest Editor
Department of Pharmacy, School of Medicine and Surgery, University of Naples Federico II, Via D. Montesano 49, 80131 Naples, Italy
Interests: natural products; secondary metabolites; structure elucidation; essential oils; NMR spectroscopy; GC-MS and LC-MS
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Special Issue Information

Dear Colleagues,

In the last decades, infectious diseases have continued to be a major health concern worldwide, causing important epidemiological, financial, and logistical implications. Essential oils (EOs) are considered an important source for new natural antimicrobials, particularly for multidrug-resistant bacteria, pathogenic fungi, viruses, and parasites. EOs may provide an interesting option to replace the use of conventional antimicrobials with a low cost and safe medicinal or could be used in addition to them in order to decrease their potential risk of toxicity. This Special Issue, following the success of the first issue in 2018, aims to attract contributions on all aspects of the chemistry and antimicrobial activity of essential oils. Original research articles and reviews that make substantial advances within this field are invited to contribute to this editorial project.

Prof. Daniela Rigano
Guest Editor

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Keywords

  • Essential oils
  • Antimicrobials
  • Bacterial infections
  • Fungi
  • Viruses
  • Parasites
  • Resistance

Published Papers (19 papers)

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Research

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17 pages, 1667 KiB  
Article
Phytochemical Profile and In Vitro Antioxidant, Antimicrobial, Vital Physiological Enzymes Inhibitory and Cytotoxic Effects of Artemisia jordanica Leaves Essential Oil from Palestine
by Nidal Jaradat
Molecules 2021, 26(9), 2831; https://doi.org/10.3390/molecules26092831 - 10 May 2021
Cited by 14 | Viewed by 3457
Abstract
Artemisia jordanica (AJ) is one of the folkloric medicinal plants and grows in the arid condition used by Palestinian Bedouins in the Al-Naqab desert for the treatment of diabetes and gastrointestinal infections. The current investigation aimed, for the first time, to characterize the [...] Read more.
Artemisia jordanica (AJ) is one of the folkloric medicinal plants and grows in the arid condition used by Palestinian Bedouins in the Al-Naqab desert for the treatment of diabetes and gastrointestinal infections. The current investigation aimed, for the first time, to characterize the (AJ) essential oil (EO) components and evaluate EO’s antioxidant, anti-obesity, antidiabetic, antimicrobial, anti-inflammatory, and cytotoxic activities. The gas chromatography-mass spectrometer (GC-MS) technique was utilized to characterize the chemical ingredients of (AJ) EO, while validated biochemical approaches were utilized to evaluate the antioxidant, anti-obesity and antidiabetic. The microbicidal efficacy of (AJ) EO was measured utilizing the broth microdilution assay. Besides, the cytotoxic activity was estimated utilizing the (MTS) procedure. Finally, the anti-inflammatory activity was measured utilizing a COX inhibitory screening test kit. The analytical investigation revealed the presence of 19 molecules in the (AJ) EO. Oxygenated terpenoids, including bornyl acetate (63.40%) and endo-borneol (17.75%) presented as major components of the (AJ) EO. The EO exhibited potent antioxidant activity compared with Trolox, while it showed a weak anti-lipase effect compared with orlistat. In addition, the tested EO displayed a potent α-amylase suppressing effect compared with the positive control acarbose. Notably, the (AJ) EO exhibited strong α-glucosidase inhibitory potential compared with the positive control acarbose. The EO had has a cytotoxic effect against all the screened tumor cells. In fact, (AJ) EO showed potent antimicrobial properties. Besides, the EO inhibited the enzymes COX-1 and COX-2, compared with the anti-inflammatory drug ketoprofen. The (AJ) EO has strong antioxidant, antibacterial, antifungal, anti-α-amylase, anti-α-glucosidase, and COX inhibitory effects which could be a favorite candidate for the treatment of various neurodegenerative diseases caused by harmful free radicals, microbial resistance, diabetes, and inflammations. Further in-depth investigations are urgently crucial to explore the importance of such medicinal plants in pharmaceutical production. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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13 pages, 1741 KiB  
Article
Essential Oil from Melaleuca leucadendra: Antimicrobial, Antikinetoplastid, Antiproliferative and Cytotoxic Assessment
by Lianet Monzote, Alexander M. Scherbakov, Ramón Scull, Prabodh Satyal, Paul Cos, Andrey E. Shchekotikhin, Lars Gille and William N. Setzer
Molecules 2020, 25(23), 5514; https://doi.org/10.3390/molecules25235514 - 25 Nov 2020
Cited by 15 | Viewed by 4355
Abstract
Essential oils (EOs) are known for their use in cosmetics, food industries, and traditional medicine. This study presents the chemical composition and therapeutic properties against kinetoplastid and eukaryotic cells of the EO from Melaleucaleucadendra (L.) L. (Myrtaceae). Forty-five compounds were identified in [...] Read more.
Essential oils (EOs) are known for their use in cosmetics, food industries, and traditional medicine. This study presents the chemical composition and therapeutic properties against kinetoplastid and eukaryotic cells of the EO from Melaleucaleucadendra (L.) L. (Myrtaceae). Forty-five compounds were identified in the oil by GC-MS, containing a major component the 1,8-cineole (61%). The EO inhibits the growth of Leishmania amazonensis and Trypanosoma brucei at IC50 values <10 μg/mL. However, 1,8 cineole was not the main compound responsible for the activity. Against malignant (22Rv1, MCF-7, EFO-21, including resistant sublines MCF-7/Rap and MCF-7/4OHTAMO) and non-malignant (MCF-10A, J774A.1 and peritoneal macrophage) cells, IC50 values from 55 to 98 μg/mL and from 94 to 144 μg/mL were obtained, respectively. However, no activity was observed on Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, Aspergillus niger, Candida parapsilosis, Microsporum canis, or Trypanosoma cruzi. The EO was able to control the lesion size and parasite burden in the model of cutaneous leishmaniasis in BALB/c mice caused by L. amazonensis compared to untreated animals (p < 0.05) and similar with those treated with Glucantime® (p > 0.05). This work constitutes the first evidence of antiproliferative potentialities of EO from M. leucadendra growing in Cuba and could promote further preclinical investigations to confirm the medical value of this plant, in particular for leishmaniasis treatment. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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18 pages, 1704 KiB  
Article
Natural Preparations Based on Orange, Bergamot and Clove Essential Oils and Their Chemical Compounds as Antimicrobial Agents
by Vlad Tiberiu Alexa, Camelia Szuhanek, Antoanela Cozma, Atena Galuscan, Florin Borcan, Diana Obistioiu, Cristina Adriana Dehelean and Daniela Jumanca
Molecules 2020, 25(23), 5502; https://doi.org/10.3390/molecules25235502 - 24 Nov 2020
Cited by 15 | Viewed by 3323
Abstract
Since ancient times complementary therapies have been based on the use of medicinal plants, natural preparations and essential oils in the treatment of various diseases. Their use in medical practice is recommended in view of their low toxicity, pharmacological properties and economic impact. [...] Read more.
Since ancient times complementary therapies have been based on the use of medicinal plants, natural preparations and essential oils in the treatment of various diseases. Their use in medical practice is recommended in view of their low toxicity, pharmacological properties and economic impact. This paper aims to test the antimicrobial effect of natural preparation based on clove, orange and bergamot essential oils on a wide range of microorganisms that cause infections in humans including: Streptococcus pyogenes, Staphylococcus aureus, Shigella flexneri, Candida parapsilosis, Candida albicans, Pseudomonas aeruginosa, Escherichia coli, Salmonella typhimurium and Haemophilus influenza. Three natural preparations such as one-component emulsions: clove (ECEO), bergamote (EBEO), and orange (EOEO), three binary: E(BEO/CEO), E(BEO/OEO), E(CEO/OEO) and a tertiary emulsion E(OEO/BEO/CEO) were obtained, characterized and tested for antimicrobial effects. Also, the synergistic/antagonistic effects, generated by the presence of the main chemical compounds, were studied in order to recommend a preparation with optimal antimicrobial activity. The obtained results underline the fact that the monocomponent emulsion ECEO shows antimicrobial activity, while EOEO and EBEO do not inhibit the development of the analyzed strains. In binary or tertiary emulsions E(BEO/CEO), E(CEO/OEO) and E(OEO/ BEO/CEO) the antimicrobial effect of clove oil is potentiated due to the synergism exerted by the chemical compounds of essential oils. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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16 pages, 962 KiB  
Article
Unravelling the Antifungal Effect of Red Thyme Oil (Thymus vulgaris L.) Compounds in Vapor Phase
by Loris Pinto, Maria Addolorata Bonifacio, Elvira De Giglio, Stefania Cometa, Antonio F. Logrieco and Federico Baruzzi
Molecules 2020, 25(20), 4761; https://doi.org/10.3390/molecules25204761 - 16 Oct 2020
Cited by 33 | Viewed by 3723
Abstract
The aim of this work was to evaluate the antifungal activity in vapor phase of thymol, p-cymene, and γ-terpinene, the red thyme essential oil compounds (RTOCs). The Minimum Inhibitory Concentration (MIC) of RTOCs was determined against postharvest spoilage fungi of the genera Botrytis [...] Read more.
The aim of this work was to evaluate the antifungal activity in vapor phase of thymol, p-cymene, and γ-terpinene, the red thyme essential oil compounds (RTOCs). The Minimum Inhibitory Concentration (MIC) of RTOCs was determined against postharvest spoilage fungi of the genera Botrytis, Penicillium, Alternaria, and Monilinia, by measuring the reduction of the fungal biomass after exposure for 72 h at 25 °C. Thymol showed the lowest MIC (7.0 µg/L), followed by γ-terpinene (28.4 µg/L) and p-cymene (40.0 µg/L). In the case of P. digitatum ITEM 9569, resistant to commercial RTO, a better evaluation of interactions among RTOCs was performed using the checkerboard assay and the calculation of the Fractional Inhibitory Concentration Index (FICI). During incubation, changes in the RTOCs concentration were measured by GC-MS analysis. A synergistic effect between thymol (0.013 ± 0.003 L/L) and γ-terpinene (0.990 ± 0.030 L/L) (FICI = 0.50) in binary combinations, and between p-cymene (0.700 ± 0.010 L/L) and γ-terpinene (0.290 ± 0.010 L/L) in presence of thymol (0.008 ± 0.001 L/L) (FICI = 0.19), in ternary combinations was found. The synergistic effect against the strain P. digitatum ITEM 9569 suggests that different combinations among RTOCs could be defined to control fungal strains causing different food spoilage phenomena. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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17 pages, 3420 KiB  
Article
Antibacterial Activity and Mechanism of Ginger Essential Oil against Escherichia coli and Staphylococcus aureus
by Xin Wang, Yi Shen, Kiran Thakur, Jinzhi Han, Jian-Guo Zhang, Fei Hu and Zhao-Jun Wei
Molecules 2020, 25(17), 3955; https://doi.org/10.3390/molecules25173955 - 30 Aug 2020
Cited by 143 | Viewed by 17791
Abstract
Though essential oils exhibit antibacterial activity against food pathogens, their underlying mechanism is understudied. We extracted ginger essential oil (GEO) using supercritical CO2 and steam distillation. A chemical composition comparison by GC-MS showed that the main components of the extracted GEOs were [...] Read more.
Though essential oils exhibit antibacterial activity against food pathogens, their underlying mechanism is understudied. We extracted ginger essential oil (GEO) using supercritical CO2 and steam distillation. A chemical composition comparison by GC-MS showed that the main components of the extracted GEOs were zingiberene and α-curcumene. Their antibacterial activity and associated mechanism against Staphylococcus aureus and Escherichia coli were investigated. The diameter of inhibition zone (DIZ) of GEO against S. aureus was 17.1 mm, with a minimum inhibition concentration (MIC) of 1.0 mg/mL, and minimum bactericide concentration (MBC) of 2.0 mg/mL. For E. coli, the DIZ was 12.3 mm with MIC and MBC values of 2.0 mg/mL and 4.0 mg/mL, respectively. The SDS-PAGE analysis revealed that some of the electrophoretic bacterial cell proteins bands disappeared with the increase in GEO concentration. Consequently, the nucleic acids content of bacterial suspension was raised significantly and the metabolic activity of bacteria was markedly decreased. GEO could thus inhibit the expression of some genes linked to bacterial energy metabolism, tricarboxylic acid cycle, cell membrane-related proteins, and DNA metabolism. Our findings speculate the bactericidal effects of GEO primarily through disruption of the bacterial cell membrane indicating its suitability in food perseveration. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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11 pages, 1658 KiB  
Article
Clove Oil (Syzygium aromaticum L.) Activity against Alicyclobacillus acidoterrestris Biofilm on Technical Surfaces
by Alina Kunicka-Styczyńska, Agnieszka Tyfa, Dariusz Laskowski, Aleksandra Plucińska, Katarzyna Rajkowska and Krystyna Kowal
Molecules 2020, 25(15), 3334; https://doi.org/10.3390/molecules25153334 - 22 Jul 2020
Cited by 11 | Viewed by 3152
Abstract
Acidotermophilic bacteria Alicyclobacillus acidoterrestris is one of the main contaminants in the fruit industry forming biofilms which are difficult to remove from the production line by conventional methods. An alternative approach aims for the use of essential oils to prevent Alicyclobacillus biofilm development. [...] Read more.
Acidotermophilic bacteria Alicyclobacillus acidoterrestris is one of the main contaminants in the fruit industry forming biofilms which are difficult to remove from the production line by conventional methods. An alternative approach aims for the use of essential oils to prevent Alicyclobacillus biofilm development. The effect of clove essential oil on A. acidoterrestris biofilms on glass and polyvinyl chloride surfaces under static and agitated culture conditions was investigated by atomic force microscopy and the plate count method. The medium-flow and the type of technical surface significantly influenced A. acidoterrestris biofilm. The PVC was colonized in a greater extent comparing to glass. Clove essential oil in 0.05% (v/v) caused 25.1–65.0% reduction of biofilms on the technical surfaces along with substantial changes in their morphology by a decrease in the biofilm: height, surface roughness, and surface area difference. The oil also induced alteration in individual bacterial cells length and visible increase of their roughness. Clove essential oil seems to release EPS from biofilm and thus induce detachment of bacteria from the surface. Due to anti-A. acidoterrestris biofilm activity, the clove oil may be used in the juice industry to hinder a development of A. acidoterrestris biofilms on production surfaces. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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27 pages, 9073 KiB  
Article
Antimicrobial Activity of Different Artemisia Essential Oil Formulations
by Sourav Das, Barbara Vörös-Horváth, Tímea Bencsik, Giuseppe Micalizzi, Luigi Mondello, Györgyi Horváth, Tamás Kőszegi and Aleksandar Széchenyi
Molecules 2020, 25(10), 2390; https://doi.org/10.3390/molecules25102390 - 21 May 2020
Cited by 23 | Viewed by 5069
Abstract
The extreme lipophilicity of essential oils (EOs) impedes the measurement of their biological actions in an aqueous environment. We formulated oil in water type Pickering Artemisia annua EO nanoemulsions (AEP) with surface-modified Stöber silica nanoparticles (20 nm) as the stabilizing agent. The antimicrobial [...] Read more.
The extreme lipophilicity of essential oils (EOs) impedes the measurement of their biological actions in an aqueous environment. We formulated oil in water type Pickering Artemisia annua EO nanoemulsions (AEP) with surface-modified Stöber silica nanoparticles (20 nm) as the stabilizing agent. The antimicrobial activity of AEP and its effects on mature Candida biofilms were compared with those of Tween 80 stabilized emulsion (AET) and ethanolic solution (AEE) of the Artemisia EO. The antimicrobial activity was evaluated by using the minimum inhibitory concentrations (MIC90) and minimum effective concentrations (MEC10) of the compounds. On planktonic bacterial and fungal cells beside growth inhibition, colony formation (CFU/mL), metabolic activity, viability, intracellular ATP/total protein (ATP/TP), along with reactive oxygen species (ROS) were also studied. Artemisia annua EO nanoemulsion (AEP) showed significantly higher antimicrobial activity than AET and AEE. Artemisia annua EO nanoemulsions (AEP) generated superoxide anion and peroxides-related oxidative stress, which might be the underlying mode of action of the Artemisia EO. Unilamellar liposomes, as a cellular model, were used to examine the delivery efficacy of the EO of our tested formulations. We could demonstrate higher effectiveness of AEP in the EO components’ donation compared to AET and AEE. Our data suggest the superiority of the AEP formulation against microbial infections. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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17 pages, 1321 KiB  
Article
Comparative Evaluation of Essential Oils from Medicinal-Aromatic Plants of Greece: Chemical Composition, Antioxidant Capacity and Antimicrobial Activity against Bacterial Fish Pathogens
by Thekla I. Anastasiou, Manolis Mandalakis, Nikos Krigas, Thomas Vézignol, Diamanto Lazari, Pantelis Katharios, Thanos Dailianis and Efthimia Antonopoulou
Molecules 2020, 25(1), 148; https://doi.org/10.3390/molecules25010148 - 30 Dec 2019
Cited by 28 | Viewed by 4690
Abstract
The administration of antibiotics in aquaculture has raised concern about the impact of their overuse in marine ecosystems, seafood safety and consumers’ health. This “green consumerism” has forced researchers to find new alternatives against fish pathogens. The present study focused on 12 Mediterranean [...] Read more.
The administration of antibiotics in aquaculture has raised concern about the impact of their overuse in marine ecosystems, seafood safety and consumers’ health. This “green consumerism” has forced researchers to find new alternatives against fish pathogens. The present study focused on 12 Mediterranean medicinal-aromatic plants as potential antimicrobials and antioxidant agents that could be used in fish aquaculture. In vitro assays showed that the essential oils (EOs) from all studied plants had anti-bacterial and antioxidant properties, with their efficacy being dependent on their chemical composition. More specifically, EOs rich in carvacrol, p-cymene and γ-terpinene exhibited not only the strongest inhibitory activity against the growth of bacterial pathogens (inhibitory concentration: 26–88 μg mL−1), but also the greatest total antioxidant capacity (ABTS: 2591–5879 μmole mL−1; CUPRAC: 931–2733 μmole mL−1). These compounds were mainly found in the EOs from Greek oregano (Origanum vulgare subsp. hirtum), Spanish oregano (Thymbra capitata) and savoury (Satureja thymbra) collected from cultivations in Greece. The specific EOs stand out as promising candidates for the treatment of bacterial diseases and oxidative stress in farmed fish. Further in vivo experiments are needed to fully understand the effects of EO dietary supplementation on fish farming processes. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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15 pages, 793 KiB  
Article
The Effect of Ten Essential Oils on Several Cutaneous Drug-Resistant Microorganisms and Their Cyto/Genotoxic and Antioxidant Properties
by Katarína Kozics, Mária Bučková, Andrea Puškárová, Viktória Kalászová, Terézia Cabicarová and Domenico Pangallo
Molecules 2019, 24(24), 4570; https://doi.org/10.3390/molecules24244570 - 13 Dec 2019
Cited by 39 | Viewed by 6425
Abstract
In this study, we determined the antimicrobial activity of ten essential oils (EOs)—oregano, thyme, clove, arborvitae, cassia, lemongrass, melaleuca, eucalyptus, lavender, and clary sage—against drug-resistant microorganisms previously isolated from patients with skin infections. The essential oil compositions were determined using gas chromatography coupled [...] Read more.
In this study, we determined the antimicrobial activity of ten essential oils (EOs)—oregano, thyme, clove, arborvitae, cassia, lemongrass, melaleuca, eucalyptus, lavender, and clary sage—against drug-resistant microorganisms previously isolated from patients with skin infections. The essential oil compositions were determined using gas chromatography coupled to mass spectrometry (GC/MS). The assayed bacteria included Pseudomonas aeruginosa, Proteus vulgaris, Citrobacter koseri, and Klebsiella pneumoniae. Two drug-resistant yeasts (Candida albicans and Candida parapsilosis) were also involved in our survey. Oregano, thyme, cassia, lemongrass and arborvitae showed very strong antibacterial and antifungal activity against all tested strains. These results show that these essential oils may be effective in preventing the growth of the drug-resistant microorganisms responsible for wound infections. In this study, the genotoxic effects of tested essential oils on healthy human keratinocytes HaCaT were evaluated using the comet assay for the first time. These results revealed that none of the essential oils induced significant DNA damage in vitro after 24 h. Moreover, the treatment of HaCaT cells with essential oils increased the total antioxidant status (TAS) level. The obtained results indicate that EOs could be used as a potential source of safe and potent natural antimicrobial and antioxidant agents in the pharmaceutical and food industries. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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12 pages, 791 KiB  
Article
Chemical Composition and Antimicrobial Activity of Artemisia herba-alba and Origanum majorana Essential Oils from Morocco
by Ghita Amor, Lucia Caputo, Antonietta La Storia, Vincenzo De Feo, Gianluigi Mauriello and Taoufiq Fechtali
Molecules 2019, 24(22), 4021; https://doi.org/10.3390/molecules24224021 - 6 Nov 2019
Cited by 57 | Viewed by 4626
Abstract
Essential oils (EOs) are one of the most important groups of plant metabolites responsible for their biological activities. This study was carried out to study the chemical composition and the antimicrobial effects of Artemisia herba-alba and Origanum majorana essential oils against some Gram-positive [...] Read more.
Essential oils (EOs) are one of the most important groups of plant metabolites responsible for their biological activities. This study was carried out to study the chemical composition and the antimicrobial effects of Artemisia herba-alba and Origanum majorana essential oils against some Gram-positive and Gram-negative bacteria, and a fungal strain isolated from spoiled butter. The plants were collected in the region Azzemour of South West Morocco and the EOs, extracted by hydrodistillation, were analyzed by GC-MS. The antimicrobial activity was determined using the agar paper disc method. The main components of A. herba-alba EO were cis-thujone, trans-thujone and vanillyl alcohol; in O. majorana EO terpinen-4-ol, isopulegol and β-phellandrene predominated. Both essential oils exhibited growth inhibiting activities in a concentration-dependent manner on several microorganism species. Our results demonstrated that O. majorana and A. herba-alba EOs could be effective natural antibacterial agents in foods. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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17 pages, 1966 KiB  
Article
Chemical Composition and Antimicrobial Effectiveness of Ocimum gratissimum L. Essential Oil Against Multidrug-Resistant Isolates of Staphylococcus aureus and Escherichia coli
by Ramaiana Soares Melo, Águida Maria Albuquerque Azevedo, Antônio Mateus Gomes Pereira, Renan Rhonalty Rocha, Rafaela Mesquita Bastos Cavalcante, Maria Nágila Carneiro Matos, Pedro Henrique Ribeiro Lopes, Geovany Amorim Gomes, Tigressa Helena Soares Rodrigues, Hélcio Silva dos Santos, Izabelly Linhares Ponte, Renata Albuquerque Costa, Gabriel Sousa Brito, Francisco Eduardo Aragão Catunda Júnior and Victor Alves Carneiro
Molecules 2019, 24(21), 3864; https://doi.org/10.3390/molecules24213864 - 26 Oct 2019
Cited by 50 | Viewed by 7431
Abstract
The study investigated the antimicrobial activity of the essential oil extract of Ocimum gratissimum L. (EOOG) against multiresistant microorganisms in planktonic and biofilm form. Hydrodistillation was used to obtain the EOOG, and the analysis of chemical composition was done by gas chromatography coupled [...] Read more.
The study investigated the antimicrobial activity of the essential oil extract of Ocimum gratissimum L. (EOOG) against multiresistant microorganisms in planktonic and biofilm form. Hydrodistillation was used to obtain the EOOG, and the analysis of chemical composition was done by gas chromatography coupled with mass spectrometry (GC/MS) and flame ionization detection (GC/FID). EOOG biological activity was verified against isolates of Staphylococcus aureus and Escherichia coli, using four strains for each species. The antibacterial action of EOOG was determined by disk diffusion, microdilution (MIC/MBC), growth curve under sub-MIC exposure, and the combinatorial activity with ciprofloxacin (CIP) and oxacillin (OXA) were determined by checkerboard assay. The EOOG antibiofilm action was performed against the established biofilm and analyzed by crystal violet, colony-forming unit count, and SEM analyses. EOOG yielded 1.66% w/w, with eugenol as the major component (74.83%). The MIC was 1000 µg/mL for the most tested strains. The growth curve showed a lag phase delay for both species, mainly S. aureus, and reduced the growth level of E. coli by half. The combination of EOOG with OXA and CIP led to an additive action for S. aureus. A significant reduction in biofilm biomass and cell viability was verified for S. aureus and E. coli. In conclusion, EOOG has relevant potential as a natural alternative to treat infections caused by multiresistant strains. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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10 pages, 407 KiB  
Article
Enhanced Killing of Candida krusei by Polymorphonuclear Leucocytes in the Presence of Subinhibitory Concentrations of Melaleuca alternifolia and “Mentha of Pancalieri” Essential Oils
by Vivian Tullio, Janira Roana, Daniela Scalas and Narcisa Mandras
Molecules 2019, 24(21), 3824; https://doi.org/10.3390/molecules24213824 - 23 Oct 2019
Cited by 8 | Viewed by 2413
Abstract
The aim of this study was to evaluate the influence of tea tree oil (TTO) and “Mentha of Pancalieri” essential oil (MPP) on intracellular killing of Candida krusei, often resistant to conventional drugs, by polymorphonuclear leucocytes (PMNs). Intracellular killing was investigated by incubating [...] Read more.
The aim of this study was to evaluate the influence of tea tree oil (TTO) and “Mentha of Pancalieri” essential oil (MPP) on intracellular killing of Candida krusei, often resistant to conventional drugs, by polymorphonuclear leucocytes (PMNs). Intracellular killing was investigated by incubating yeasts and PMNs with essential oils (EOs) at 1/4 and 1/8 × MIC (Minimal Inhibitory Concentration), in comparison with anidulafungin, used as a reference drug. Killing values were expressed as Survival Index (SI) values. The cytotoxicity of EOs was evaluated by 3-[4,-5-dimethylthiazole-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay. Both EOs were more efficaceous at 1/8 × MIC than 1/4 × MIC, with killing values higher than observed in EO-free systems and in presence of anidulafungin, indicating that the decreasing concentrations did not cause lower candidacidal activity. This better activity at 1/8 × MIC is probably due to the EOs’ toxicity at 1/4 × MIC, suggesting that at higher concentrations EOs might interfere with PMNs functionality. TTO and MPP at 1/8 × MIC significantly increased intracellular killing by PMNs through their direct action on the yeasts (both EOs) or on phagocytic cells (MPP), suggesting a positive interaction between EOs and PMNs to eradicate intracellular C. krusei. These data showed a promising potential application of TTO and “Mentha of Pancalieri” EO as natural adjuvants in C. krusei infection management. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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12 pages, 1287 KiB  
Article
Evaluation of the Antifungal Activity of Mentha x piperita (Lamiaceae) of Pancalieri (Turin, Italy) Essential Oil and Its Synergistic Interaction with Azoles
by Vivian Tullio, Janira Roana, Daniela Scalas and Narcisa Mandras
Molecules 2019, 24(17), 3148; https://doi.org/10.3390/molecules24173148 - 29 Aug 2019
Cited by 37 | Viewed by 7390
Abstract
The promising antimicrobial activity of essential oils (EOs) has led researchers to use them in combination with antimicrobial drugs in order to reduce drug toxicity, side effects, and resistance to single agents. Mentha x piperita, known worldwide as “Mentha of Pancalieri”, is [...] Read more.
The promising antimicrobial activity of essential oils (EOs) has led researchers to use them in combination with antimicrobial drugs in order to reduce drug toxicity, side effects, and resistance to single agents. Mentha x piperita, known worldwide as “Mentha of Pancalieri”, is produced locally at Pancalieri (Turin, Italy). The EO from this Mentha species is considered as one of the best mint EOs in the world. In our research, we assessed the antifungal activity of “Mentha of Pancalieri” EO, either alone or in combination with azole drugs (fluconazole, itraconazole, ketoconazole) against a wide panel of yeast and dermatophyte clinical isolates. The EO was analyzed by GC-MS, and its antifungal properties were evaluated by minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) parameters, in accordance with the CLSI guidelines, with some modifications. The interaction of EO with azoles was evaluated through the chequerboard and isobologram methods. The results suggest that this EO exerts a fungicidal activity against yeasts and a fungistatic activity against dermatophytes. Interaction studies with azoles indicated mainly synergistic profiles between itraconazole and EO vs. Candida spp., Cryptococcus neoformans, and Trichophyton mentagrophytes. Thus, the “Mentha of Pancalieri” EO may act as a potential antifungal agent and could serve as a natural adjuvant for fungal infection treatment. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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13 pages, 1507 KiB  
Article
The Influence of Essential Oil Compounds on Antibacterial Activity of Mupirocin-Susceptible and Induced Low-Level Mupirocin-Resistant MRSA Strains
by Paweł Kwiatkowski, Agata Pruss, Bartosz Wojciuk, Barbara Dołęgowska, Anna Wajs-Bonikowska, Monika Sienkiewicz, Monika Mężyńska and Łukasz Łopusiewicz
Molecules 2019, 24(17), 3105; https://doi.org/10.3390/molecules24173105 - 27 Aug 2019
Cited by 27 | Viewed by 5229
Abstract
Because of the bacterial drug resistance development, it is reasonable to investigate chemical compounds capable of preventing the spread of resistance to mupirocin (MUP), commonly used in staphylococcal eradication. The objective of the study was to verify the influence of essential oil compounds [...] Read more.
Because of the bacterial drug resistance development, it is reasonable to investigate chemical compounds capable of preventing the spread of resistance to mupirocin (MUP), commonly used in staphylococcal eradication. The objective of the study was to verify the influence of essential oil compounds (EOCs) on the antibacterial activity of MUP against mupirocin-susceptible (MupS) and induced low-level mupirocin-resistant (MupRL) methicillin-resistant Staphylococcus aureus (MRSA) strains. The following parameters were examined: MRSAMupS and MRSAMupRL susceptibility to EOCs (1,8-cineole, eugenol, carvacrol, linalool, (-)-menthone, linalyl acetate, and trans-anethole), the bacterial cell size distribution, and chemical composition by the use of Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopies. The MRSAMupS and MRSAMupRL strains were susceptible to all tested EOCs. 1,8-cineole and (-)-menthone showed synergistic activity against MRSAMupS in combination with mupirocin, whereas 1,8-cineole exhibited synergistic activity against MRSAMupRL as well. In-depth analysis showed that both MRSAMupS and MRSAMupRL displayed similar distributions of the bacterial cell size. The FTIR and Raman spectra of the MRSAMupS and MRSAMupRL strains showed differences in some regions. New bands in the MRSAMupRL Raman spectrum were observed. It was concluded that the use of 1,8-cineole in combination with mupirocin can increase the mupirocin activity against the MRSAMupS and MRSAMupRL strains. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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13 pages, 1656 KiB  
Article
Analysis of Chemical Composition and Assessment of Cytotoxic, Antimicrobial, and Antioxidant Activities of the Essential Oil of Meriandra dianthera Growing in Saudi Arabia
by Ramzi A. Mothana, Fahd A. Nasr, Jamal M. Khaled, Mohammed AL-Zharani, Omar M. Noman, Nael Abutaha, Adnan J. Al-Rehaily, Omar M. Almarfadi, Ashok Kumar and Mine Kurkcuoglu
Molecules 2019, 24(14), 2647; https://doi.org/10.3390/molecules24142647 - 22 Jul 2019
Cited by 6 | Viewed by 3597
Abstract
The essential oil of Meriandra dianthera (Konig ex Roxb.) Benth. (Synonym: Meriandra bengalensis, Lamiaceae) collected from Saudi Arabia was studied utilizing GC and GC/MS. Forty four constituents were identified, representing 96.8% of the total oil. The M. dianthera essential oil (MDEO) was [...] Read more.
The essential oil of Meriandra dianthera (Konig ex Roxb.) Benth. (Synonym: Meriandra bengalensis, Lamiaceae) collected from Saudi Arabia was studied utilizing GC and GC/MS. Forty four constituents were identified, representing 96.8% of the total oil. The M. dianthera essential oil (MDEO) was characterized by a high content of oxygenated monoterpenes (76.2%). Camphor (54.3%) was the major compound in MDEO followed by 1,8-cineole (12.2%) and camphene (10.4%). Moreover, MDEO was assessed for its cytotoxic, antimicrobial, and antioxidant activities. MDEO demonstrated an interesting cytotoxic activity against all cancer cell lines with IC50 values of 83.6 to 91.2 μg/mL, especially against MCF-7 cancer cells. Using labeling with annexin VFITC and/or propidium iodide (PI) dyes and flow cytometer analysis, the apoptosis induction was quantitatively confirmed for MCF-7 cells. The MDEO exhibited a considerable antimicrobial activity against all bacterial and fungal strains with minimum inhibitory concentration (MIC)-values of 0.07 to 1.25 mg/mL. The most sensitive microbial strain was Staphylococcus aureus (MIC: 0.07 mg/mL). Minimum bactericidal concentration (MBC) or minimum fungicidal concentration (MFC) values were determined one time higher than that of MIC’s. Additionally, the MDEO revealed a strong activity for reducing β-carotene bleaching with a total antioxidant value of 72.6% and significant DPPH free radical scavenging activity (78.4%) at the concentration 1000 μg/mL. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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16 pages, 4524 KiB  
Article
Antimicrobial and Phytotoxic Activity of Origanum heracleoticum and O. majorana Essential Oils Growing in Cilento (Southern Italy)
by Teresa Della Pepa, Hazem S. Elshafie, Raffaele Capasso, Vincenzo De Feo, Ippolito Camele, Filomena Nazzaro, Maria Rosa Scognamiglio and Lucia Caputo
Molecules 2019, 24(14), 2576; https://doi.org/10.3390/molecules24142576 - 16 Jul 2019
Cited by 70 | Viewed by 4722
Abstract
There is a growing interest in a potential use of essential oils (EOs) as a replacement for traditional pesticides and herbicides. The aims of this study were to: (i) Identify the chemical composition of the two EOs derived from Origanum heracleoticum L. and [...] Read more.
There is a growing interest in a potential use of essential oils (EOs) as a replacement for traditional pesticides and herbicides. The aims of this study were to: (i) Identify the chemical composition of the two EOs derived from Origanum heracleoticum L. and O. majorana L., (ii) evaluate the in vitro antifungal activity of the EOs against some postharvest phytopathogens (Botrytis cinerea, Penicillium expansum, Aspergillus niger and Monilinia fructicola), (iii) evaluate the in vitro antibacterial activity against Bacillus megaterium, Clavibacter michiganensis, Xanthomonas campestris, Pseudomonas fluorescens and P. syringae pv. phaseolicola, (iv) evaluate the effect of both studied EOs on the spore germination percentage and their minimum inhibitory concentration (MIC) against M. fructicola, and (v) study the possible phytotoxicity of the two EOs and their major constituents, carvacrol for O. heracleoticum and terpinen-4-ol for O. majorana, against tha germination and initial radicle growth of radish, lettuce, garden cress and tomato. The two EOs demonstrated promising in vitro antimicrobial and antifungal activities against all tested microorganisms. EOs showed high inhibition of spore germination percentage at the minimal inhibitory concentration of 500 and 2000 µg/mL, respectively. Moreover, both germination and radical elongation of selected plant species were sensitive to the oils. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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Review

Jump to: Research

19 pages, 1012 KiB  
Review
Trypanocidal Essential Oils: A Review
by Mayara Castro de Morais, Jucieudo Virgulino de Souza, Carlos da Silva Maia Bezerra Filho, Silvio Santana Dolabella and Damião Pergentino de Sousa
Molecules 2020, 25(19), 4568; https://doi.org/10.3390/molecules25194568 - 6 Oct 2020
Cited by 14 | Viewed by 3360
Abstract
Trypanosomiases are diseases caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans, this includes Chagas disease and African trypanosomiasis. There are few therapeutic options, and there is low efficacy to clinical treatment. Therefore, the search for new drugs for the [...] Read more.
Trypanosomiases are diseases caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans, this includes Chagas disease and African trypanosomiasis. There are few therapeutic options, and there is low efficacy to clinical treatment. Therefore, the search for new drugs for the trypanosomiasis is urgent. This review describes studies of the trypanocidal properties of essential oils, an important group of natural products widely found in several tropical countries. Seventy-seven plants were selected from literature for the trypanocidal activity of their essential oils. The main chemical constituents and mechanisms of action are also discussed. In vitro and in vivo experimental data show the therapeutic potential of these natural products for the treatment of infections caused by species of Trypanosoma. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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22 pages, 1608 KiB  
Review
Recent Advances in the Application of Antibacterial Complexes Using Essential Oils
by Tae Jin Cho, Sun Min Park, Hary Yu, Go Hun Seo, Hye Won Kim, Sun Ae Kim and Min Suk Rhee
Molecules 2020, 25(7), 1752; https://doi.org/10.3390/molecules25071752 - 10 Apr 2020
Cited by 41 | Viewed by 5755
Abstract
Although antibacterial spectrum of essential oils (EOs) has been analyzed along with consumers’ needs on natural biocides, singular treatments generally require high concentration of EOs and long-term exposures to eliminate target bacteria. To overcome these limitations, antibacterial complex has been developed and this [...] Read more.
Although antibacterial spectrum of essential oils (EOs) has been analyzed along with consumers’ needs on natural biocides, singular treatments generally require high concentration of EOs and long-term exposures to eliminate target bacteria. To overcome these limitations, antibacterial complex has been developed and this review analyzed previous reports regarding the combined antibacterial effects of EOs. Since unexpectable combined effects (synergism or antagonism) can be derived from the treatment of antibacterial complex, synergistic and antagonistic combinations have been identified to improve the treatment efficiency and to avoid the overestimation of bactericidal efficacy, respectively. Although antibacterial mechanism of EOs is not yet clearly revealed, mode of action regarding synergistic effects especially for the elimination of pathogens by using low quantity of EOs with short-term exposure was reported. Whereas comprehensive analysis on previous literatures for EO-based disinfectant products implies that the composition of constituents in antibacterial complexes is variable and thus analyzing the impact of constituting substances (e.g., surfactant, emulsifier) on antibacterial effects is further needed. This review provides practical information regarding advances in the EO-based combined treatment technologies and highlights the importance of following researches on the interaction of constituents in antibacterial complex to clarify the mechanisms of antibacterial synergism and/or antagonism. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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24 pages, 2281 KiB  
Review
Essential Oils and Mono/bi/tri-Metallic Nanocomposites as Alternative Sources of Antimicrobial Agents to Combat Multidrug-Resistant Pathogenic Microorganisms: An Overview
by Nagaraj Basavegowda, Jayanta Kumar Patra and Kwang-Hyun Baek
Molecules 2020, 25(5), 1058; https://doi.org/10.3390/molecules25051058 - 27 Feb 2020
Cited by 47 | Viewed by 6598
Abstract
Over the past few decades, many pathogenic bacteria have become resistant to existing antibiotics, which has become a threat to infectious disease control worldwide. Hence, there has been an extensive search for new, efficient, and alternative sources of antimicrobial agents to combat multidrug-resistant [...] Read more.
Over the past few decades, many pathogenic bacteria have become resistant to existing antibiotics, which has become a threat to infectious disease control worldwide. Hence, there has been an extensive search for new, efficient, and alternative sources of antimicrobial agents to combat multidrug-resistant pathogenic microorganisms. Numerous studies have reported the potential of both essential oils and metal/metal oxide nanocomposites with broad spectra of bioactivities including antioxidant, anticancer, and antimicrobial attributes. However, only monometallic nanoparticles combined with essential oils have been reported on so far with limited data. Bi- and tri-metallic nanoparticles have attracted immense attention because of their diverse sizes, shapes, high surface-to-volume ratios, activities, physical and chemical stability, and greater degree of selectivity. Combination therapy is currently blooming and represents a potential area that requires greater attention and is worthy of future investigations. This review summarizes the synergistic effects of essential oils with other antimicrobial combinations such as mono-, bi-, and tri-metallic nanocomposites. Thus, the various aspects of this comprehensive review may prove useful in the development of new and alternative therapeutics against antibiotic resistant pathogens in the future. Full article
(This article belongs to the Special Issue Essential Oils as Antimicrobial and Anti-infectious Agents II)
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