Special Issue "Isolation and Utilization of Essential Oils: As Antimicrobials and Boosters of Antimicrobial Drug Activity"

A special issue of Processes (ISSN 2227-9717). This special issue belongs to the section "Pharmaceutical Processes".

Deadline for manuscript submissions: 30 November 2021.

Special Issue Editors

Dr. Elwira Sieniawska
E-Mail Website
Guest Editor
Department of Pharmacognosy, Medical University of Lublin, 20-093 Lublin, Poland
Interests: My research interest is phytochemical analysis of plant extracts and dietary supplements. Recently, I have focused on isolation and utilization of components of essential oils as antimicrobials and boosters of antimicrobial drugs activity. The liquid chromatography–mass spectrometry analysis of bacterial metabolites produced under stress conditions is also in my interest.
Prof. Greige-Gerges Helene
E-Mail Website
Guest Editor
Bioactive Molecules Research Laboratory, Faculty of Science, Lebanese University, P.O. Box 6573/14 Badaro, Museum, Beirut, Lebanon
Dr. Adriana Trifan
E-Mail Website1 Website2
Guest Editor
Department of Pharmacognosy, Faculty of Pharmacy, Grigore T. Popa University of Medicine and Pharmacy Iasi, Universitatii Street 16, 700115 Iasi, Romania
Interests: pharmacognosy; natural products chemistry; essential oils; antimicrobials
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Special Issue Information

Dear Colleagues,

In the search for new antimicrobial lead structures, interest in natural product-based screening has enjoyed a renaissance, driven by the fact that plants present a unique pool of compounds. Volatiles produced by plants and present in essential oils possess a broad spectrum of biological properties with applications in many revenue-generating sectors, such as the pharmaceutical, nutraceutical, cosmetic, perfume, agronomy, and sanitary industries. Essential oils are a complex blend of small volatile molecules which play an important role in plant-defensive response to various insults, including microbial attacks, and their broad-spectrum antimicrobial activities have generated impressive scientific reports. Further, due to their multicomponent nature, essential oils have low potential for the development of microbial resistance. New antimicrobial combination drugs which include natural products have recently become a research priority. Synergistic interactions between essential oil constituents and antimicrobials are very promising approaches to overcome microbial resistance. The combinations of essential oil constituents and antimicrobial drugs can exert a multitarget activity, being effective in reducing or reversing microbial resistance. Additionally, such combinations have the advantage of reduced effective doses of both antimicrobial and essential oils, being consequently less toxic than their components. The encapsulation of essential oils in nano- and microdelivery systems (molecular inclusion complexes, polymeric and colloidal systems) is another promising antimicrobial strategy that is currently being extensively investigated. Formulation of essential oils is an efficient approach to boost their antimicrobial activity against different pathogens and also allows overcoming some limitations due to their physicochemical properties, such as low water solubility, high volatility, and chemical instability.

This Special Issue on “Isolation and Utilization of Essential Oils: As Antimicrobials and Boosters of Antimicrobial Drugs Activity” aims to curate novel advances in the development and application of essential oils as antimicrobial agents via combinatorial and nano-based approaches.

Topics include but are not limited to:

  • The use of essential oils to prevent the emergence of antimicrobial resistance, to enhance the efficacy, and to minimize potential side effects of antimicrobial drugs;
  • Combination therapy associating conventional antimicrobial drugs and essential oil constituents as a promising strategy in overcoming antimicrobial resistance;
  • The mechanisms underlying antimicrobial enhancing or antimicrobial resistance reversal effects of essential oils constituents;
  • Small-scale formulations as an efficient approach to improve solubility, stability, and to provide controlled-release delivery of essential oils and to boost their antimicrobial activity against different pathogens;
  • Antimicrobial activity of drug delivery systems encapsulating essential oil compounds, with emphasis on their preparation methods and characteristics, benefits, mechanisms of action, and biocompatibility issues.

Dr. Elwira Sieniawska
Prof. Greige-Gerges Helene
Dr. Adriana Trifan
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. Processes is an international peer-reviewed open access monthly 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 2000 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

  • antimicrobials
  • essential oils
  • synergy
  • delivery systems
  • microbial resistance
  • small-scale formulations

Published Papers (6 papers)

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Research

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Open AccessArticle
Volatiles from Selected Apiaceae Species Cultivated in Poland—Antimicrobial Activities
Processes 2021, 9(4), 695; https://doi.org/10.3390/pr9040695 - 15 Apr 2021
Viewed by 142
Abstract
As part of our ongoing research on phytoconstituents that can act as promising antimicrobial agents, the essential oils of nine selected Apiaceae plants, cultivated in Poland, were studied. The volatiles of the aerial parts with fruits (herba cum fructi) of Silaum [...] Read more.
As part of our ongoing research on phytoconstituents that can act as promising antimicrobial agents, the essential oils of nine selected Apiaceae plants, cultivated in Poland, were studied. The volatiles of the aerial parts with fruits (herba cum fructi) of Silaum silaus, Seseli devenyense, Seseli libanotis,Ferula assa-foetida, Glehnia littoralis and Heracleum dulce, in addition to the fruits (fructi) of Torilis japonica and Orlaya grandiflora as well as of the aerial parts (herba) of Peucedanum luxurians were investigated through Gas Chromatography–Mass Spectrometry to identify more than 60 different metabolites. The essential oils from S. devenyense, H. dulce, T. japonica and P. luxurians are reported for the first time. All examined species were also assayed for their antimicrobial activities against several human pathogenic Gram-positive and -negative bacteria and fungi. The species H. dulce, S. devenyense and S. libanotis exerted the strongest antimicrobial activity, mostly against Gram-positive bacteria strains (MIC values 0.90–1.20 mg/mL). To the best of our knowledge, this is the first attempt to determine the antimicrobial activity of the above Apiaceae species. Full article
Open AccessArticle
Chemical Profiling of Pistacia lentiscus var. Chia Resin and Essential Oil: Ageing Markers and Antimicrobial Activity
Processes 2021, 9(3), 418; https://doi.org/10.3390/pr9030418 - 25 Feb 2021
Viewed by 379
Abstract
Chios Mastic Gum (CMG) and Chios Mastic Oil (CMO) are two unique products of the tree Pistacia lentiscus var. Chia, cultivated exclusively on the Greek island of Chios. In the present study, the method proposed by the European Pharmacopoeia for mastic identification [...] Read more.
Chios Mastic Gum (CMG) and Chios Mastic Oil (CMO) are two unique products of the tree Pistacia lentiscus var. Chia, cultivated exclusively on the Greek island of Chios. In the present study, the method proposed by the European Pharmacopoeia for mastic identification was employed using HPTLC together with an in-house method. A GC-MS methodology was also developed for the chemical characterization of CMOs. α-Pinene and β-myrcene were found in abundance in the fresh oils; however, in the oil of the aged collection, oxygenated monoterpenes and benzenoids such as verbenone, pinocarveol, and α-campholenal were found at the highest rates. Additionally, the antimicrobial activity of Chios Mastic Gums (CMGs) with their respective Chios Mastic Oils (CMOs) was evaluated, with growth tests against the fungi Aspergillus nidulans, Aspergillus fumigatus, Candida albicans, Mucor circinelloides, and Rhizopus oryzae, and the bacteria Escherichia coli, Pseudomonas aeruginosa and Bacillus subtilis, with the samples exhibiting a moderate activity. To our knowledge, this is the first time that an HPTLC method is proposed for the analysis of mastic and its essential oil and that a standardized methodology is followed for the distillation of CMO with a parallel assessment of the ageing effect on the oil’s composition. Full article
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Open AccessFeature PaperArticle
Biofilm Degradation of Nontuberculous Mycobacteria Formed on Stainless Steel Following Treatment with Immortelle (Helichrysum italicum) and Common Juniper (Juniperus communis) Essential Oils
Processes 2021, 9(2), 362; https://doi.org/10.3390/pr9020362 - 16 Feb 2021
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Abstract
Nontuberculous mycobacteria, like other opportunistic premise plumbing pathogens, produce resistant biofilms on various surfaces in the plumbing system including pipes, tanks, and fittings. Since standard methods of water disinfection are ineffective in eradicating biofilms, research into new agents is necessary. Essential oils (EOs) [...] Read more.
Nontuberculous mycobacteria, like other opportunistic premise plumbing pathogens, produce resistant biofilms on various surfaces in the plumbing system including pipes, tanks, and fittings. Since standard methods of water disinfection are ineffective in eradicating biofilms, research into new agents is necessary. Essential oils (EOs) have great potential as anti-biofilm agents. Therefore, the purpose of this research was to investigate the potential anti-biofilm effect of common juniper (Juniperus communis) and immortelle (Helichrysum italicum) EOs. Minimum inhibitory concentrations (MIC), minimum bactericidal concentrations (MBC), and minimum effective concentrations of EOs on Mycobacterium avium, M. intracellulare, and M. gordonae were tested. Additionally, biofilms on the surface of a stainless steel disc were treated with single or mixed concentration of EOs, in order to investigate their degeneration via the bacterial count and confocal laser scanning microscopy (CLSM). H. italicum EO showed the strongest biofilm degradation ability against all Mycobacteria strains that were tested. The strongest effect in the biofilm degradation after the single or mixed applications of EOs was observed against M. gordonae, followed by M. avium. The most resistant was the M. intracellulare biofilm. Synergistic combinations of J. communis and H. italicum EOs therefore seem to be an effective substance in biofilm degradation for use in small water systems such as baths or hot tubs. Full article
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Review

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Open AccessReview
Combination Therapy Involving Lavandula angustifolia and Its Derivatives in Exhibiting Antimicrobial Properties and Combatting Antimicrobial Resistance: Current Challenges and Future Prospects
Processes 2021, 9(4), 609; https://doi.org/10.3390/pr9040609 - 30 Mar 2021
Viewed by 277
Abstract
Antimicrobial resistance (AMR) has been identified as one of the biggest health threats in the world. Current therapeutic options for common infections are markedly limited due to the emergence of multidrug resistant pathogens in the community and the hospitals. The role of different [...] Read more.
Antimicrobial resistance (AMR) has been identified as one of the biggest health threats in the world. Current therapeutic options for common infections are markedly limited due to the emergence of multidrug resistant pathogens in the community and the hospitals. The role of different essential oils (EOs) and their derivatives in exhibiting antimicrobial properties has been widely elucidated with their respective mechanisms of action. Recently, there has been a heightened emphasis on lavender essential oil (LEO)’s antimicrobial properties and wound healing effects. However, to date, there has been no review published examining the antimicrobial benefits of lavender essential oil, specifically. Previous literature has shown that LEO and its constituents act synergistically with different antimicrobial agents to potentiate the antimicrobial activity. For the past decade, encapsulation of EOs with nanoparticles has been widely practiced due to increased antimicrobial effects and greater bioavailability as compared to non-encapsulated oils. Therefore, this review intends to provide an insight into the different aspects of antimicrobial activity exhibited by LEO and its constituents, discuss the synergistic effects displayed by combinatory therapy involving LEO, as well as to explore the significance of nano-encapsulation in boosting the antimicrobial effects of LEO; it is aimed that from the integration of these knowledge areas, combating AMR will be more than just a possibility. Full article
Open AccessFeature PaperReview
Contribution of Essential Oils to the Fight against Microbial Biofilms—A Review
Processes 2021, 9(3), 537; https://doi.org/10.3390/pr9030537 - 18 Mar 2021
Viewed by 358
Abstract
The increasing clinical use of artificial medical devices raises the issue of microbial contamination, which is a risk factor for the occurrence of biofilm-associated infections. A huge amount of scientific data highlights the promising potential of essential oils (EOs) to be used for [...] Read more.
The increasing clinical use of artificial medical devices raises the issue of microbial contamination, which is a risk factor for the occurrence of biofilm-associated infections. A huge amount of scientific data highlights the promising potential of essential oils (EOs) to be used for the development of novel antibiofilm strategies. We aimed to review the relevant literature indexed in PubMed and Embase and to identify the recent directions in the field of EOs, as a new modality to eradicate microbial biofilms. We paid special attention to studies that explain the mechanisms of the microbicidal and antibiofilm activity of EOs, as well as their synergism with other antimicrobials. The EOs are difficult to test for their antimicrobial activity due to lipophilicity and volatility, so we have presented recent methods that facilitate these tests. There are presented the applications of EOs in chronic wounds and biofilm-mediated infection treatment, in the food industry and as air disinfectants. This analysis concludes that EOs are a source of antimicrobial agents that should not be neglected and that will probably provide new anti-infective therapeutic agents. Full article
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Open AccessReview
Chitosan-Coating Effect on the Characteristics of Liposomes: A Focus on Bioactive Compounds and Essential Oils: A Review
Processes 2021, 9(3), 445; https://doi.org/10.3390/pr9030445 - 01 Mar 2021
Viewed by 345
Abstract
In recent years, liposomes have gained increasing attention for their potential applications as drug delivery systems in the pharmaceutic, cosmetic and food industries. However, they have a tendency to aggregate and are sensitive to degradation caused by several factors, which may limit their [...] Read more.
In recent years, liposomes have gained increasing attention for their potential applications as drug delivery systems in the pharmaceutic, cosmetic and food industries. However, they have a tendency to aggregate and are sensitive to degradation caused by several factors, which may limit their effectiveness. A promising approach to improve liposomal stability is to modify liposomal surfaces by forming polymeric layers. Among natural polymers, chitosan has received great interest due to its biocompatibility and biodegradability. This review discussed the characteristics of this combined system, called chitosomes, in comparison to those of conventional liposomes. The coating of liposomes with chitosan or its derivatives improved liposome stability, provided sustained drug release and increased drug penetration across mucus layers. The mechanisms behind these results are highlighted in this paper. Alternative assembly of polyelectrolytes using alginate, sodium hyaluronate, or pectin with chitosan could further improve the liposomal characteristics. Chitosomal encapsulation could also ensure targeted delivery and boost the antimicrobial efficacy of essential oils (EOs). Moreover, chitosomes could be an efficient tool to overcome the major drawbacks related to the chemical properties of EOs (low water solubility, sensitivity to oxygen, light, heat, and humidity) and their poor bioavailability. Overall, chitosomes could be considered as a promising strategy to enlarge the use of liposomes. Full article
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Title: Combination therapy involving Lavandula angustifolia and its derivatives in exhibiting antimicrobial properties: Current challenges and future prospects
Authors: Wye-Hong Leong; Kok-Song Lai; Swee-Hua Erin Lim
Affiliation: Perdana University- Royal College of Surgeons in Ireland, School of Medicine, 50490 Kuala Lumpur, Malaysia; Abu Dhabi Women’s College, Higher Colleges of Technology, 41012 Abu Dhabi, United Arab Emirates
Abstract: Antimicrobial resistance (AMR) has been identified as one of the biggest health threats in the world. Current therapeutic options for common infections are markedly limited due to the emergence of multidrug resistant pathogens in the community and the hospitals. The role of different essential oils and their derivatives in exhibiting antimicrobial properties has been widely elucidated with their respective mechanisms of action. Recently, there has been a heightened emphasis on lavender oil’s antimicrobial properties and wound healing effects. However, to date, there has been no review published examining the antimicrobial benefits of lavender oil, specifically. Several literature has shown that lavender essential oil and its constituents act synergistically with and different antimicrobial agents to enhance the antimicrobial activity. For the past decade, encapsulation of essential oils with nanoparticles has been widely practised due to increased antimicrobial effects and greater bioavailability as compared to non-encapsulated oils. Therefore, this review intends to provide an insight of the different aspects of antimicrobial activity exhibited by lavender oil and its constituents, synergistic effects displayed by combination therapy involving lavender oil, significance of nano-encapsulation in boosting the antimicrobial effects of lavender oil; where the integration of these knowledge will be pertinent in combating AMR.

Title: Degradation of the biofilm of non-tuberculous mycobacteria formed on stainless steel under the influence of immortelle and pine essential oils
Authors: DOLORES PERUČ
Affiliation: Croatia

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