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Special Issue "Aromatic Plant Extracts, Essential Oils and Their Compounds in Combination with Conventional and Not Conventional Antimicrobial Agents"

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Flavours and Fragrances".

Deadline for manuscript submissions: closed (31 December 2020).

Special Issue Editors

Prof. Dr. Vivian Tullio
E-Mail Website
Guest Editor
Department of Public Health and Pediatrics, Microbiology Division, University of Turin, 10126 Turin, Italy
Interests: bacteriological and mycological diagnostics; antimicrobial agents (antibiotics, essential oils, etc.) in vitro activity towards bacteria, yeasts, and filamentous mycetes; immunomodulatory activity of antibiotics and essential oils on the phagocyte–pathogen binomial, studying phagocytosis, intracellular killing, and citokynes release; antimicrobial activity of drug oxygen free/loaded delivery systems (nanodroplets, nanoparticles, nanobubbles, etc.); influence of probiotics on gut microbiome in infant
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Alessandra Guerrini
E-Mail Website
Guest Editor
Department of Life Sciences and Biotechnology (SVeB), University of Ferrara, Ferrara, Italy
Interests: essential oils; phenolics; extractive strategies; GC-MS; HPLC-DAD-MS; NMR; in vitro biological activity
Special Issues, Collections and Topics in MDPI journals
Dr. Domenico Cautela
E-Mail Website
Guest Editor
Stazione Sperimentale per le Industrie delle Essenze e dei Derivati dagli Agrumi (SSEA), Reggio Calabria, Italy
Interests: nutraceuticals; phytochemicals; secondary metabolites; natural products; essential oils; citrus, LC-MS; HRGC/HRMS
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Based on World Health Organization reports, antimicrobial resistance to well-known antibiotics is a major global threat of increasing concern to human and animal health. In fact, with the wide use of synthetic and semisynthetic antimicrobial drugs, their advantages and disadvantages have been highlighted over the years, including the spread of drug-resistant pathogens, and research has focused on the use of natural products as useful antimicrobial tools.

Currently, there is evidence that plant extracts, such as essential oils, may exert remarkable biological activities against viruses, bacteria, fungi, and parasites.

In addition, to overcome microbial resistance and reduce toxicity and side effects of antimicrobial drugs, the combinations of plant extracts/compounds with conventional antibiotics can be a possible solution from a therapeutic point of view. Some combined antibiotic therapies are already clinically available.

This Special Issue aims to collect contributions, research papers, and reviews related to the use of aromatic plant extracts (obtained by steam and dry distillation, mechanical extraction, supercritical fluid extraction, ultrasound assisted maceration, etc.) and pure compounds used in association with conventional and not conventional antimicrobial agents to enhance the antimicrobial efficacy, reduce microbial resistance to single agents, the amount of synthetic compounds, and at the same time their side effects.

The extracts and pure compounds must be chemically characterized, describing also the chirality of constituents where necessary.

Prof. Dr. Vivian Tullio
Prof. Dr. Alessandra Guerrini
Dr. Domenico Cautela
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2300 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Plant extracts and compounds
  • Essential oils
  • Chemical characterization and chirality
  • Antibiotics
  • Microorganisms
  • Antimicrobial agent association
  • Antimicrobial activity

Published Papers (6 papers)

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Research

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Article
Antifungal Activity of Melaleuca alternifolia Essential Oil (TTO) and Its Synergy with Itraconazole or Ketoconazole against Trichophyton rubrum
Molecules 2021, 26(2), 461; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020461 - 17 Jan 2021
Cited by 2 | Viewed by 1264
Abstract
Over the past 20–30 years, Trichophyton rubrum represented the most widespread dermatophyte with a prevalence accounting for 70% of dermatophytosis. The treatment for cutaneous infections caused by Trichophyton spp. are imidazoles (ketoconazole (KTZ)) and triazoles (itraconazole (ITZ)). T. rubrum can develop resistance to [...] Read more.
Over the past 20–30 years, Trichophyton rubrum represented the most widespread dermatophyte with a prevalence accounting for 70% of dermatophytosis. The treatment for cutaneous infections caused by Trichophyton spp. are imidazoles (ketoconazole (KTZ)) and triazoles (itraconazole (ITZ)). T. rubrum can develop resistance to azoles after prolonged exposure to subinhibitory concentrations resulting in therapeutic failures and chronic infections. These problems have stimulated the search for therapeutic alternatives, including essential oils, and their potential use in combination with conventional antifungals. The purpose of this study was to evaluate the antifungal activity of tea tree oil (TTO) (Melaleuca alternifolia essential oil) and the main components against T. rubrum and to assess whether TTO in association with KTZ/ITZ as reference drugs improves the antifungal activity of these drugs. We used a terpinen-4-ol chemotype (35.88%) TTO, and its antifungal properties were evaluated by minimum inhibitory and minimum fungicidal concentrations in accordance with the CLSI guidelines. The interaction between TTO and azoles was evaluated through the checkerboard and isobologram methods. The results demonstrated both the fungicide activity of TTO on T. rubrum and the synergism when it was used in combination with azoles. Therefore, this mixture may reduce the minimum effective dose of azole required and minimize the side effects of the therapy. Synergy activity offered a promise for combination topical treatment for superficial mycoses. Full article
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Article
Chemometric Screening of Fourteen Essential Oils for Their Composition and Biological Properties
Molecules 2020, 25(21), 5126; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25215126 - 04 Nov 2020
Cited by 3 | Viewed by 909
Abstract
Essential oils (EOs) obtained from aromatic plants are widely used worldwide, especially in cosmetic and food products due to their aroma and biological properties and health benefits. Some EOs have significant antimicrobial and antioxidant activities, and thus could effectively increase the shelf lives [...] Read more.
Essential oils (EOs) obtained from aromatic plants are widely used worldwide, especially in cosmetic and food products due to their aroma and biological properties and health benefits. Some EOs have significant antimicrobial and antioxidant activities, and thus could effectively increase the shelf lives of foodstuff and beverages. In this study, fourteen essential oils (clove, eucalyptus, fennel, lavender, oregano, palmarosa, pepper, star anise, tea tree, turmeric, Chinese yin yang, Japanese yin yang, and ylang ylang) from different medicinal plant families were screened by gas-chromatography–mass spectrometry (GC–MS) for their different chemical profiles and bioassays were performed to assess their antifungal and antioxidant activities. The results obtained were assessed by principal component analysis (PCA). PCA distinguished six groups characterized by different terpene chemotypes. Amongst the EOs studied, the clove EO showed the strongest antioxidant activity characterized by an EC50 of 0.36 µL/mL. The oregano EO had the greatest antiyeast activity characterized by a minimal inhibitory concentration of 10 µL/mL. In conclusion, clove and oregano EOs are strong antifungal and antioxidant agents, respectively, with great potential in the food industry to avoid spoilage and to increase shelf life. Full article
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Article
Effectiveness of Cymbopogon citratus Oil Encapsulated in Chitosan on Colletotrichum gloeosporioides Isolated from Capsicum annuum
Molecules 2020, 25(19), 4447; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25194447 - 28 Sep 2020
Cited by 1 | Viewed by 1201
Abstract
One of the principal etiological agents associated with losses in horticultural crops is the fungus Colletotrichum sp. This study aimed to evaluate the in vitro effectiveness of the essential oil (EO) from Cymbopogon citratus in chitosan supports for the control of Colletotrichum gloeosporioides [...] Read more.
One of the principal etiological agents associated with losses in horticultural crops is the fungus Colletotrichum sp. This study aimed to evaluate the in vitro effectiveness of the essential oil (EO) from Cymbopogon citratus in chitosan supports for the control of Colletotrichum gloeosporioides isolated from sweet pepper plants. Methods: The extraction and phytochemical analysis of the EO of C. citratus were performed along with its encapsulation in chitosan-agar in order to compare it with other techniques and determine its effect on C. gloeosporioides. Results: The EO from the citral chemotype (58%) encapsulated in the chitosan-agar, with an 83% encapsulation efficiency in mass percentage, resulted in the total inhibition of mycelial growth at a minimum inhibitory concentration of 1370 ppm. This concentration was effective in controlling the disease under greenhouse conditions. The effectivity of the capsules containing EO was superior to that of other controls using EO evaluated in vitro. The capsules demonstrated an effective period of 51 days, with an additional 30 days of effectiveness after a reinfection cycle, thus providing similar results to the control with Trichoderma sp. Conclusions: Chitosan capsules present a promising strategy in the use of C. citratus EO on C. gloeosporioides, and they are highly effective and stable under in vitro and field conditions Full article
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Review

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Review
Antifungal Properties of Essential Oils and Their Compounds for Application in Skin Fungal Infections: Conventional and Nonconventional Approaches
Molecules 2021, 26(4), 1093; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26041093 - 19 Feb 2021
Cited by 8 | Viewed by 1194
Abstract
Essential oils (EOs) are known to have varying degrees of antimicrobial properties that are mainly due to the presence of bioactive compounds. These include antiviral, nematicidal, antifungal, insecticidal and antioxidant properties. This review highlights the potential of EOs and their compounds for application [...] Read more.
Essential oils (EOs) are known to have varying degrees of antimicrobial properties that are mainly due to the presence of bioactive compounds. These include antiviral, nematicidal, antifungal, insecticidal and antioxidant properties. This review highlights the potential of EOs and their compounds for application as antifungal agents for the treatment of skin diseases via conventional and nonconventional approaches. A search was conducted using three databases (Scopus, Web of Science, Google Scholar), and all relevant articles from the period of 2010–2020 that are freely available in English were extracted. In our findings, EOs with a high percentage of monoterpenes showed strong ability as potential antifungal agents. Lavandula sp., Salvia sp., Thymus sp., Citrus sp., and Cymbopogon sp. were among the various species found to show excellent antifungal properties against various skin diseases. Some researchers developed advanced formulations such as gel, semi-solid, and ointment bases to further evaluate the effectiveness of EOs as antifungal agents. To date, most studies on the application of EOs as antifungal agents were performed using in vitro techniques, and only a limited number pursued in vivo and intervention-based research. Full article
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Review
An Overview of the Potential Therapeutic Applications of Essential Oils
Molecules 2021, 26(3), 628; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26030628 - 26 Jan 2021
Cited by 13 | Viewed by 1837
Abstract
The emergence of antimicrobial resistance (AMR) has urged researchers to explore therapeutic alternatives, one of which includes the use of natural plant products such as essential oils (EO). In fact, EO obtained from clove, oregano, thymus, cinnamon bark, rosemary, eucalyptus, and lavender have [...] Read more.
The emergence of antimicrobial resistance (AMR) has urged researchers to explore therapeutic alternatives, one of which includes the use of natural plant products such as essential oils (EO). In fact, EO obtained from clove, oregano, thymus, cinnamon bark, rosemary, eucalyptus, and lavender have been shown to present significant inhibitory effects on bacteria, fungi, and viruses; many studies have been done to measure EO efficacy against microorganisms. The strategy of combinatory effects via conventional and non-conventional methods revealed that the combined effects of EO–EO or EO–antibiotic exhibit enhanced efficacy. This paper aims to review the antimicrobial effects of EO, modes of EO action (membrane disruption, efflux inhibition, increase membrane permeability, and decrease in intracellular ATP), and their compounds’ potential as effective agents against bacteria, fungi, and viruses. It is hoped that the integration of EO applications in this work can be used to consider EO for future clinical applications. Full article
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Review
Synergistic Antimicrobial Effectiveness of Plant Essential Oil and Its Application in Seafood Preservation: A Review
Molecules 2021, 26(2), 307; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules26020307 - 09 Jan 2021
Cited by 6 | Viewed by 1218
Abstract
The synergistic potential of plant essential oils (EOs) with other conventional and non-conventional antimicrobial agents is a promising strategy for increasing antimicrobial efficacy and controlling foodborne pathogens. Spoilage microorganisms are one of main concerns of seafood products, while the prevention of seafood spoilage [...] Read more.
The synergistic potential of plant essential oils (EOs) with other conventional and non-conventional antimicrobial agents is a promising strategy for increasing antimicrobial efficacy and controlling foodborne pathogens. Spoilage microorganisms are one of main concerns of seafood products, while the prevention of seafood spoilage principally requires exclusion or inactivation of microbial activity. This review provides a comprehensive overview of recent studies on the synergistic antimicrobial effect of EOs combined with other available chemicals (such as antibiotics, organic acids, and plant extracts) or physical methods (such as high hydrostatic pressure, irradiation, and vacuum-packaging) utilized to reduce the growth of foodborne pathogens and/or to extend the shelf-life of seafood products. This review highlights the synergistic ability of EOs when used as a seafood preservative, discovering the possible routes of the combined techniques for the development of a novel seafood preservation strategy. Full article
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