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Special Issue "Recent Research Advances in Essential Oils: From Green Extraction and Synthesis to Sustainable Applications and Utilization"

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

Deadline for manuscript submissions: closed (31 December 2019).

Special Issue Editors

Dr. Valtcho Jeliazkov
E-Mail Website
Guest Editor
Prof. Dr. Murray B Isman
E-Mail Website
Guest Editor
Faculty of Land and Food Systems, 248-2357 Main Mall, Vancouver, BC, Canada
Interests: entomology and toxicology
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Farid Chemat
grade E-Mail Website
Guest Editor
Université d´Avignon et des Pays du Vaucluse, 84029 Avignon, France
Interests: green extraction; alternative solvents; innovative technologies; original procedures; microwave; ultrasound; intensification
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Vassya Bankova
E-Mail Website
Guest Editor
Chemistry of Natural Products Laboratory, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria
Interests: natural products chemistry; medicinal plants; phytochemical analysis; bioactive natural products; bee products; propolis
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Niko Radulović
E-Mail Website
Guest Editor
Department of Chemistry, Faculty of Science and Mathematics, University of Niš, Niš, Serbia

Special Issue Information

Dear Colleagues,

Plant natural products or secondary metabolites include essential (volatile) oils (EOs). The EO components are produced by plants in order to protect them from pathogenic bacteria, fungi and viruses, as well as to repel herbivores and act as insecticides against herbivorous insects. The role of EOs as allelochemicals determines their pronounced biological activity.

Interest in EOs is increasing, as they are economically important, and are preferred by consumers as flavor and fragrance materials over synthetic chemicals. EO utilization is expanding rapidly in different areas such as alternatives to synthetic plant hormones and growth regulators, as biopesticides, as agents to reduce methane production in ruminant animals and overall anthropogenic greenhouse production, and the development of new drugs and products. This Special Issue will provide some of the recent knowledge and discoveries in the area of EO production, extraction, phytochemistry, and utilization. Consumer preferences towards natural products vs synthetics are driving the production and utilization of EOs. In the last decade, another trend, 'ethical consumerism', has expanded in scope and scale and has become mainstream. This originally environmentally-related behavior now encompasses issues of human health, animal welfare, human rights, country of origin, fair trade, and others. This is a way for consumers to try to avoid corporate practices of which they disapprove, through their choice of various products. Consumers are also willing to absorb the price of more natural and ethically-produced goods. 

Global production and trade in EOs as flavors and fragrances in foods and beverages, as fragrances in household products, and for aromatherapy have made many of these materials widely available at modest cost. The exemption of certain EOs and their major constituents from registration by the US EPA facilitated their commercialization as pesticides, and the use of such products has now expanded into Latin America and the EU. Prolific research on the use of EOs as alternatives to plant growth hormones and pesticides should lead to the use of many such oils from various sources and regions in years to come.

This Special Issue will focus on “Recent advances in EOs: From green extraction and synthesis to sustainable applications and utilization”.

Dr. Valtcho Jeliazkov
Dr. Murray Isman
Prof. Dr. Farid Chemat
Prof. Dr. Vassya Bankova
Prof. Dr. Niko Radulović
Guest Editors

Manuscript Submission Information

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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

  • Volatile oils
  • Green chemistry
  • Innovative extraction
  • Dual utilization
  • Biopesticides
  • EOS as growth regulators

Published Papers (16 papers)

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Research

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Article
Toxic, Radical Scavenging, and Antifungal Activity of Rhododendron tomentosum H. Essential Oils
Molecules 2020, 25(7), 1676; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25071676 - 05 Apr 2020
Cited by 2 | Viewed by 1054
Abstract
The chemical composition of eight (seven shoot and one inflorescence) essential oils (EOs) of Rh. tomentosum H. plants growing in Eastern Lithuania is reported. The plant material was collected during different phases of vegetation (from April to October). The oils were obtained by [...] Read more.
The chemical composition of eight (seven shoot and one inflorescence) essential oils (EOs) of Rh. tomentosum H. plants growing in Eastern Lithuania is reported. The plant material was collected during different phases of vegetation (from April to October). The oils were obtained by hydrodistillation from air-dried aerial parts (leaves and inflorescences). In total, up to 70 compounds were identified by GC−MS and GC (flame-ionization detector, FID); they comprised 91.0 ± 4.7%–96.2 ± 3.1% of the oil content. Sesquiterpene hydrocarbons (54.1 ± 1.5%–76.1 ± 4.5%) were found to be the main fraction. The major compounds were palustrol (24.6 ± 2.6%–33.5 ± 4.4%) and ledol (18.0 ± 2.9%–29.0 ± 5.0%). Ascaridol isomers (7.0 ± 2.4%–14.0 ± 2.4% in three oils), myrcene (7.2 ± 0.3% and 10.1 ± 1.3%), lepalol (3.3 ± 0.3% and 7.9 ± 3.0%), and cyclocolorenone isomers (4.1 ± 2.5%) were determined as the third main constituents. The toxic activity of marsh rosemary inflorescence and shoot oils samples was evaluated using a brine shrimp (Artemia sp.) bioassay. LC50 average values (11.23–20.50 µg/mL) obtained after 24 h of exposure revealed that the oils were notably toxic. The oil obtained from shoots gathered in September during the seed-ripening stage and containing appreciable amounts of palustrol (26.0 ± 2.5%), ledol (21.5 ± 4.0%), and ascaridol (7.0 ± 2.4%) showed the highest toxic activity. Radical scavenging activity of Rh. tomentosum EOs depended on the plant vegetation stage. The highest activities were obtained for EOs isolated from young shoots collected in June (48.19 ± 0.1 and 19.89 ± 0.3 mmol/L TROLOX (6-hydroxy-2,5,7,8-tetra-methylchromane-2-carboxylic acid) equivalent obtained by, respectively, ABTS+ (2,2′-amino-bis(ethylbenzothiazoline-6-sulfonic acid) diammonium salt) and DPPH(2,2-diphenyl-1-picrylhydrazyl) assays). Agar disc diffusion assay against pathogenic yeast Candida parapsilosis revealed the potential antifungal activity of EOs. An alternative investigation of antifungal activity employed mediated amperometry at yeast Saccharomyces cerevisiae-modified electrodes. The subjection of yeast cells to vapors of EO resulted in a three to four-fold increase of electrode responses due to the disruption of yeast cell membranes. Full article
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Article
Essential Oil-Based Design and Development of Novel Anti-Candida Azoles Formulation
Molecules 2020, 25(6), 1463; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25061463 - 24 Mar 2020
Cited by 7 | Viewed by 1219
Abstract
Candida is the most common fungal class, causing both superficial and invasive diseases in humans. Although Candida albicans is the most common cause of fungal infections in humans, C. auris is a new emergent serious pathogen causing complications similar to those of C. [...] Read more.
Candida is the most common fungal class, causing both superficial and invasive diseases in humans. Although Candida albicans is the most common cause of fungal infections in humans, C. auris is a new emergent serious pathogen causing complications similar to those of C. albicans. Both C. albicans and C. auris are associated with high mortality rates, mainly because of their multidrug-resistance patterns against most available antifungal drugs. Although several compounds were designed against C. albicans, very few or none were tested on C. auris. Therefore, it is urgent to develop novel effective antifungal drugs that can accommodate not only C. albicans, but also other Candida spp., particularly newly emergent one, including C. auris. Inspired by the significant broad-spectrum antifungal activities of the essential oil cuminaldehyde and the reported wide incorporation of azoles in the antifungal drugs, a series of compounds (UoST1-11) was designed and developed. The new compounds were designed to overcome the toxicity of the aldehyde group of cuminaldehyde and benefit from the antifungal selectivity of azoles. The new developed UoST compounds showed significant anti-Candida activities against both Candida species. The best candidate compound, UoST5, was further formulated into polymeric nanoparticles (NPs). The new formula, UoST5-NPs, showed similar activities to the nanoparticles-free drug, while providing only 25% release after 24 h, maintainng prolonged activity up to 48 h and affording no toxicity. In conclusion, new azole formulations with significantly enhanced activities against C. albicans and C. auris, while maintaining prolonged action and no toxicities at lower concentrations, were developed. Full article
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Article
Modified Clerodanes from the Essential Oil of Dodonea viscosa Leaves
Molecules 2020, 25(4), 850; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25040850 - 14 Feb 2020
Viewed by 968
Abstract
Dodonea viscosa (L.) Jacq from Reunion Island (Indian Ocean) was investigated for its leaf essential oil composition. The plant was extracted by hydrodistillation and its essential oil analysed by gas chromatography coupled to mass spectrometry. This study revealed that oxygenated nor-diterpenes and diterpenes [...] Read more.
Dodonea viscosa (L.) Jacq from Reunion Island (Indian Ocean) was investigated for its leaf essential oil composition. The plant was extracted by hydrodistillation and its essential oil analysed by gas chromatography coupled to mass spectrometry. This study revealed that oxygenated nor-diterpenes and diterpenes were one of the major chemical classes (> 50%) mainly consisting of three modified cyclopropylclerodanes containing a bicyclo[5.4.0]undecane ring system: one new furanoid norditerpene, dodovisate C, and two furanoid diterpenes, the known methyl dodovisate A and the new methyl iso-dodovisate A. These three compounds were isolated by liquid chromatography and their structures established on the basis of spectroscopic studies. The absolute configuration of dodovisate C was elucidated through a joint experimental and theoretical (B3LYP/6-311+G(d,p)) electronic circular dichroism study. The relative configurations of methyl dodovisate A and methyl iso-dodovisate A were determined using linear regressions of theoretical chemical shifts versus experimental values with the (B3LYP/6-311+G(d,p)) method. Full article
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Article
Diagnostic Potential of FT-IR Fingerprinting in Botanical Origin Evaluation of Laurus nobilis L. Essential Oil is Supported by GC-FID-MS Data
Molecules 2020, 25(3), 583; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25030583 - 29 Jan 2020
Cited by 5 | Viewed by 1181
Abstract
The last years, non-targeted fingerprinting by Fourier-transform infrared (FT-IR) spectroscopy has gained popularity as an alternative to classical gas chromatography (GC)-based methods because it may allow fast, green, non-destructive and cost-effective assessment of quality of essential oils (EOs) from single plant species. As [...] Read more.
The last years, non-targeted fingerprinting by Fourier-transform infrared (FT-IR) spectroscopy has gained popularity as an alternative to classical gas chromatography (GC)-based methods because it may allow fast, green, non-destructive and cost-effective assessment of quality of essential oils (EOs) from single plant species. As the relevant studies for Laurus nobilis L. (bay laurel) EO are limited, the present one aimed at exploring the diagnostic potential of FT-IR fingerprinting for the identification of its botanical integrity. A reference spectroscopic dataset of 97 bay laurel EOs containing meaningful information about the intra-species variation was developed via principal component analysis (PCA). This dataset was used to train a one-class model via soft independent modelling class analogy (SIMCA). The model was challenged against commercial bay laurel and non-bay laurel EOs of non-traceable production history. Overall, the diagnostic importance of spectral bands at 3060, 1380–1360, 1150 and 1138 cm−1 was assessed using GC-FID-MS data. The findings support the introduction of FT-IR as a green analytical technique in the quality control of these often mislabeled and/or adulterated precious products. Continuous evaluation of the model performance against newly acquired authentic EOs from all producing regions is needed to ensure validity over time. Full article
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Article
Chemical Composition of Essential Oil from Flower Heads of Arnica Chamissonis Less. under a Nitrogen Impact
Molecules 2019, 24(24), 4454; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24244454 - 05 Dec 2019
Cited by 2 | Viewed by 1414
Abstract
Chamisso arnica (Arnica chamissonis Less.) is a valuable plant species used in the pharmaceutical industry due to the content of many pharmacologically active substances and the similarity of its chemical composition to that of Arnica montana—a medicinal plant commonly used in [...] Read more.
Chamisso arnica (Arnica chamissonis Less.) is a valuable plant species used in the pharmaceutical industry due to the content of many pharmacologically active substances and the similarity of its chemical composition to that of Arnica montana—a medicinal plant commonly used in pharmacy and cosmetics. The similarity of the two plant species implies that chamisso arnica can be a pharmaceutical substitute for the mountain arnica, i.e., an endangered and endemic plant species in Europe. Chamisso arnica extracts exhibit anti-inflammatory and antiradical activity and possesses high antioxidant properties that might be helpful in preventing or delaying the progress of free radical dependent diseases. The attributes of A. chamissonis are mainly related to the content and chemical composition of essential oil. Therefore, the objective of this study was to characterize the chemical composition of essential oil derived from A. chamissonis flower heads under a nitrogen impact. The experiment was performed on experimental fields in mid-eastern Poland on two soil types (sandy and loamy soils). The nitrogen fertilizer was applied as ammonium sulfate (control, 30, 60, 90, and 120 kg N ha−1). Collection of flower heads was carried out in the full flowering phase, which was characterized by the highest content of essential oil. The chemical composition of essential oil was examined using GC-MS. Among the 75 ingredients of the volatile oil of chamisso arnica flower heads, alpha-pinene, cumene, p-cymene, germacrene D, spathulenol, decanal, caryophyllene oxide, beta-pinene, and benzene acetaldehyde were present at relatively high levels. Both the nitrogen application and the soil type had an effect on the oil concentration and the yield of the main constituents (alpha-pinene and germacrene D) with pharmacological value. Different levels of nitrogen application could be considered as a relevant way to modify the chemical composition and to increase the essential oil production. Full article
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Article
Essential Oil from Arnica Montana L. Achenes: Chemical Characteristics and Anticancer Activity
Molecules 2019, 24(22), 4158; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24224158 - 16 Nov 2019
Cited by 13 | Viewed by 2209
Abstract
Mountain arnica Arnica montana L. is a source of several metabolite classes with diverse biological activities. The chemical composition of essential oil and its major volatile components in arnica may vary depending on the geographical region, environmental factors, and plant organ. The objective [...] Read more.
Mountain arnica Arnica montana L. is a source of several metabolite classes with diverse biological activities. The chemical composition of essential oil and its major volatile components in arnica may vary depending on the geographical region, environmental factors, and plant organ. The objective of this study was to characterize the chemical composition of essential oil derived from A. montana achenes and to investigate its effect on induction of apoptosis and autophagy in human anaplastic astrocytoma MOGGCCM and glioblastoma multiforme T98G cell lines. The chemical composition of essential oil extracted from the achenes was examined with the use of Gas Chromatography–Mass Spectrometry GC-MS. Only 16 components of the essential oil obtained from the achenes of 3-year-old plants and 18 components in the essential oil obtained from the achenes of 4-year-old plants constituted ca. 94.14% and 96.38% of the total EO content, respectively. The main components in the EO from the arnica achenes were 2,5-dimethoxy-p-cymene (39.54 and 44.65%), cumene (13.24 and 10.71%), thymol methyl ether (8.66 and 8.63%), 2,6-diisopropylanisole (8.55 and 8.41%), decanal (7.31 and 6.28%), and 1,2,2,3-tetramethylcyclopent-3-enol (4.33 and 2.94%) in the 3- and 4-year-old plants, respectively. The essential oils were found to exert an anticancer effect by induction of cell death in anaplastic astrocytoma and glioblastoma multiforme cells. The induction of apoptosis at a level of 25.7–32.7% facilitates the use of this secondary metabolite in further studies focused on the development of glioma therapy in the future. Probably, this component plays a key role in the anticancer activity against the MOGGCCM and T98G cell lines. The present study is the first report on the composition and anticancer activities of essential oil from A. montana achenes, and further studies are required to explore its potential for future medicinal purposes. Full article
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Article
Synergistic/Antagonistic Potential of Natural Preparations Based on Essential Oils Against Streptococcus mutans from the Oral Cavity
Molecules 2019, 24(22), 4043; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24224043 - 07 Nov 2019
Cited by 5 | Viewed by 2029
Abstract
The present paper addresses a thematic of interest in preventive dental medicine, namely the possibility of using essential oils (EOs) for the inhibition of the development of Streptococcus mutans (S. mutans) in the oral cavity, as a viable alternative to chemical [...] Read more.
The present paper addresses a thematic of interest in preventive dental medicine, namely the possibility of using essential oils (EOs) for the inhibition of the development of Streptococcus mutans (S. mutans) in the oral cavity, as a viable alternative to chemical products with protective role in oral health. For this purpose, four EOs (cinnamon, clove, bergamote, and orange) were chemically characterized by gas chromatography coupled with mass spectrometry (GC-MS) and in vitro tested against S. mutans (ATCC 25175). The results obtained revealed the antibacterial effect on S. mutans exercised by the essential oils of clove (CLEO), bergamote (BEO), and orange (OEO), which were included in the production of natural emulsion-type preparations with application in dental medicine. In order to highlight the synersistic/antagonistic effects generated by the chemical constituent of essential oils, binary and tertiary emulsions were prepared and used in saliva-enhanced medium against S. mutans. The saliva tests proved the synergistic effect exercised by the active components of EOs tested from tertiary emulsions, which cause an inhibition of the development of S. mutans in oral cavities. Full article
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Article
Effect of the Chemical Composition of Free-Terpene Hydrocarbons Essential Oils on Antifungal Activity
Molecules 2019, 24(19), 3532; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24193532 - 29 Sep 2019
Cited by 4 | Viewed by 1767
Abstract
In this study, Carum carvi L. essential oil (CEO) and Origanum majorana L. essential oil (MEO) was steam-distillated under reduced pressure. We henceforth obtained three fractions for each essential oil: CF1, CF2, CF3, MF1, MF [...] Read more.
In this study, Carum carvi L. essential oil (CEO) and Origanum majorana L. essential oil (MEO) was steam-distillated under reduced pressure. We henceforth obtained three fractions for each essential oil: CF1, CF2, CF3, MF1, MF2, and MF3. Then, these fractions were characterized using the gas chromatography–mass spectrometry (GC-MS) technique. The results indicated that some fractions were rich in oxygenated compounds (i.e., CF2, CF3, MF2, and MF3) with concentrations ranging from 79.21% to 98.56%. Therefore, the influence of the chemical composition of the essential oils on their antifungal activity was studied. For this purpose, three food spoilage fungi were isolated, identified, and inoculated in vitro, in order to measure the antifungal activity of CEO, MEO, and their fractions. The results showed that stronger fungi growth inhibitions (FGI) (above 95%) were found in fractions with higher percentages of oxygenated compounds, especially with (−)-carvone and terpin-4-ol as the major components. Firstly, this work reveals that the free-terpenes hydrocarbons fractions obtained from MEO present higher antifungal activity than the raw essential oil against two families of fungi. Then, it suggests that the isolation of (−)-carvone (97.15 ± 5.97%) from CEO via vacuum distillation can be employed successfully to improve antifungal activity by killing fungi (FGI = 100%). This study highlights that separation under reduced pressure is a simple green method to obtain fractions or to isolate compounds with higher biological activity useful for pharmaceutical products or natural additives in formulations. Full article
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Article
Antitumor, Antiviral, and Anti-Inflammatory Efficacy of Essential Oils from Atractylodes macrocephala Koidz. Produced with Different Processing Methods
Molecules 2019, 24(16), 2956; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24162956 - 15 Aug 2019
Cited by 9 | Viewed by 1895
Abstract
Atractylodes macrocephala Koidz. has been used as an invigorating spleen drug for eliminating dampness and phlegm in China. According to recent researches, different processing methods may affect the drug efficacy, so we collected A. macrocephala from the Zhejiang Province, produced with different processing [...] Read more.
Atractylodes macrocephala Koidz. has been used as an invigorating spleen drug for eliminating dampness and phlegm in China. According to recent researches, different processing methods may affect the drug efficacy, so we collected A. macrocephala from the Zhejiang Province, produced with different processing methods, crude A. macrocephala (CA) and bran-processed A. macrocephala (BA), then analyzed its essential oils (EOs) by GC/MS. The results showed 34 components representing 98.44% of the total EOs of CA were identified, and 46 components representing 98.02% of the total EOs of BA were identified. Atractylone is the main component in A. macrocephala. Compared with CA, BA has 46 detected compounds, 28 of which were identical, and 6 undetected compounds. Pharmacodynamic results revealed that the EOs of CA and atractylone exhibited more effective anticancer activity in HepG2, MCG803, and HCT-116 cells than the EOs of BA; while the EOs of BA exhibited simple antiviral effect on viruses H3N2, both the EOs and atractylone show anti-inflammatory activity by inhibiting the lipopolysaccharide (LPS)-induced nitric oxide (NO) production in ANA-1 cells. Full article
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Article
Downscaling of Industrial Turbo-Distillation to Laboratory Turbo-Clevenger for Extraction of Essential Oils. Application of Concepts of Green Analytical Chemistry
Molecules 2019, 24(15), 2734; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24152734 - 27 Jul 2019
Cited by 3 | Viewed by 1437
Abstract
In the effort of innovation towards green analytical chemistry concepts and considering the six principles of green extraction, the industrial turbodistillation process was downscaled into a laboratory apparatus turbo-Clevenger (TC) for the extraction of essential oils. Turbodistillation is used as an industrial purpose [...] Read more.
In the effort of innovation towards green analytical chemistry concepts and considering the six principles of green extraction, the industrial turbodistillation process was downscaled into a laboratory apparatus turbo-Clevenger (TC) for the extraction of essential oils. Turbodistillation is used as an industrial purpose for the extraction of essential oils from hard matrixes such as wood, barks, seeds. In this work, a TC and the conventional technique of hydrodistillation (HD, Clevenger apparatus) are used for the extraction of essential oils from three spices with hard structures (Illicium verum, Schinus terebinthifolius, and Cinnamomum cassia) and are compared. This study shows that the essential oils extracted by TC in 30 min were quantitatively (yield and kinetics profile) and qualitatively (aromatic profile) similar to those obtained using conventional hydrodistillation in 3 h. This process, which gave a reduced extraction time, was perfectly adapted to the extraction of hard matrixes. Full article
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Article
Antibacterial Activity of Terpenes and Terpenoids Present in Essential Oils
Molecules 2019, 24(13), 2471; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24132471 - 05 Jul 2019
Cited by 121 | Viewed by 4800
Abstract
Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of [...] Read more.
Background: The antimicrobial activity of essential oils has been reported in hundreds of studies, however, the great majority of these studies attribute the activity to the most prevalent compounds without analyzing them independently. Therefore, the aim was to investigate the antibacterial activity of 33 free terpenes commonly found in essential oils and evaluate the cellular ultrastructure to verify possible damage to the cellular membrane. Methods: Screening was performed to select substances with possible antimicrobial activity, then the minimal inhibitory concentrations, bactericidal activity and 24-h time-kill curve studies were evaluated by standard protocols. In addition, the ultrastructure of control and death bacteria were evaluated by scanning electron microscopy. Results: Only 16 of the 33 compounds had antimicrobial activity at the initial screening. Eugenol exhibited rapid bactericidal action against Salmonella enterica serovar Typhimurium (2 h). Terpineol showed excellent bactericidal activity against S. aureus strains. Carveol, citronellol and geraniol presented a rapid bactericidal effect against E. coli. Conclusions: The higher antimicrobial activity was related to the presence of hydroxyl groups (phenolic and alcohol compounds), whereas hydrocarbons resulted in less activity. The first group, such as carvacrol, l-carveol, eugenol, trans-geraniol, and thymol, showed higher activity when compared to sulfanilamide. Images obtained by scanning electron microscopy indicate that the mechanism causing the cell death of the evaluated bacteria is based on the loss of cellular membrane integrity of function. The present study brings detailed knowledge about the antimicrobial activity of the individual compounds present in essential oils, that can provide a greater understanding for the future researches. Full article
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Article
Hydrodistillation Extraction Kinetics Regression Models for Essential Oil Yield and Composition in Juniperus virginiana, J. excelsa, and J. sabina
Molecules 2019, 24(5), 986; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24050986 - 11 Mar 2019
Cited by 6 | Viewed by 1559
Abstract
The chemical profile and antioxidant capacity of Juniperus virginiana, J. excelsa, and J. sabina essential oil (EO) fractions as a function of time was the subject of this study. The hypothesis was that, capturing EO in sequential timeframes during hydrodistillation would [...] Read more.
The chemical profile and antioxidant capacity of Juniperus virginiana, J. excelsa, and J. sabina essential oil (EO) fractions as a function of time was the subject of this study. The hypothesis was that, capturing EO in sequential timeframes during hydrodistillation would generate fractions containing unique compositions and antioxidant capacity. In J. virginiana, the highest limonene (43%) was found in the 0–5 min oil fraction, with safrole (37%) being highest in the 10–20 and 20–40 min fractions, and elemol (34%) being highest in the 160–240 min fraction. In J. excelsa, α-pinene (34-36%) was the highest in the 0–5 min fraction and in the control (non-stop 0–240 min distillation) oil, limonene (39%) was the highest in the 0–10 min fractions and cedrol (50-53%) was the highest in the 40–240 min fractions. In J. sabina, sabinene (80%) was highest in the 0–3 min fraction. The highest antioxidant capacity of J. virginiana was demonstrated by the 5–10 min fraction; the one in J. sabina by the 3–10 min fraction; and, the one in J. excelsa, by the control. The kinetics regression models that were developed can predict EO composition of the three juniper species eluted at different timeframes. Various industries could benefit from the results from this study. Full article
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Communication
Chemical Composition and Antimicrobial Activity of Laurus nobilis L. Essential Oils from Bulgaria
Molecules 2019, 24(4), 804; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24040804 - 22 Feb 2019
Cited by 43 | Viewed by 3645
Abstract
Laurel, Laurus nobilis L. is an evergreen plant belonging to the Lauraceae family, native to Southern Europe and the Mediterranean area. This is the first report on the composition and bioactivity of laurel essential oil (EO) from Bulgaria. The oil yield was 0.78%, [...] Read more.
Laurel, Laurus nobilis L. is an evergreen plant belonging to the Lauraceae family, native to Southern Europe and the Mediterranean area. This is the first report on the composition and bioactivity of laurel essential oil (EO) from Bulgaria. The oil yield was 0.78%, 0.80%, and 3.25% in the fruits, twigs, and leaves, respectively. The main constituents in the fruit EO were 1,8-cineole (33.3%), α-terpinyl acetate (10.3%), α-pinene (11.0%), β-elemene (7.5%), sabinene (6.3%), β-phellandrene (5.2%), bornyl acetate (4.4%), and camphene (4.3%); those in the twig EO were 1,8-cineole (48.5%), α-terpinyl acetate (13.1%), methyl eugenol (6.6%), β-linalool (3.8%), β-pinene (3.4%), sabinene (3.3%) and terpinene-4-ol (3.3%); and the ones in the leaf EO were 1,8-cineole (41.0%), α-terpinyl acetate (14.4%), sabinene (8.8%), methyl eugenole (6.0%), β-linalool (4.9%), and α-terpineol (3.1%). The antibacterial and antifungal properties of laurel EOs were examined according to the agar well diffusion method. The leaf EO showed antibacterial and antifungal activities against almost all strains of the microorganisms tested, whereas the twig EO was only able to inhibit Staphylococcus aureus. Pseudomonas aeruginosa ATCC 9027 and Escherichia coli ATCC 8739 were the bacterial strains that showed the highest resistance to the laurel EO. The results can benefit the EO industry and biopesticide development. Full article
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Communication
Chemical Composition of the Essential Oil of the Endemic Species Micromeria frivaldszkyana (Degen) Velen.
Molecules 2019, 24(3), 440; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules24030440 - 26 Jan 2019
Cited by 2 | Viewed by 1125
Abstract
Micromeria frivaldszkyana is an endemic species found only in Bulgaria. Its essential oil (EO) composition is unknown. This study assessed the EO yield and composition of M. frivaldszkyana as a function of the location and of drying prior to the EO extraction. M. [...] Read more.
Micromeria frivaldszkyana is an endemic species found only in Bulgaria. Its essential oil (EO) composition is unknown. This study assessed the EO yield and composition of M. frivaldszkyana as a function of the location and of drying prior to the EO extraction. M. frivaldszkyana was sampled from two natural habitats, Uzana and Shipka in the Balkan Mountains; the EO was extracted via hydrodistillation and analyzed on GC/MS. The plants from the two locations had distinct EO composition. The EO content (in dried material) was 0.18% (Uzana) and 0.26% (Shipka). Monoterpene ketones were the major group of the EO constituents. Also, hydrocarbons predominated in the EO from Shipka, and alcohols predominated in the EO from Uzana. The EO from Uzana had a greater concentration of menthone (56% vs. 17% from Shipka) and neomenthol (7.8% vs. 2.4%). Conversely, the EO from Shipka had greater concentrations of pulegone (50% vs. 20% from Uzana), limonene (10.1% vs. 2.6%), and germacrene D (3.4% vs. 1.1%). Drying prior to the EO extraction altered the concentration of some constituents. This is the first report of M. frivaldszkyana EO yield and composition. The EO showed some similarities with the chemical profile of other Micromeria species, but overall, it has an unique chemical profile and may have distinctive applications. Full article

Review

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Review
Essential Oil Phytocomplex Activity, a Review with a Focus on Multivariate Analysis for a Network Pharmacology-Informed Phytogenomic Approach
Molecules 2020, 25(8), 1833; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25081833 - 16 Apr 2020
Cited by 6 | Viewed by 2234
Abstract
Thanks to omic disciplines and a systems biology approach, the study of essential oils and phytocomplexes has been lately rolling on a faster track. While metabolomic fingerprinting can provide an effective strategy to characterize essential oil contents, network pharmacology is revealing itself as [...] Read more.
Thanks to omic disciplines and a systems biology approach, the study of essential oils and phytocomplexes has been lately rolling on a faster track. While metabolomic fingerprinting can provide an effective strategy to characterize essential oil contents, network pharmacology is revealing itself as an adequate, holistic platform to study the collective effects of herbal products and their multi-component and multi-target mediated mechanisms. Multivariate analysis can be applied to analyze the effects of essential oils, possibly overcoming the reductionist limits of bioactivity-guided fractionation and purification of single components. Thanks to the fast evolution of bioinformatics and database availability, disease-target networks relevant to a growing number of phytocomplexes are being developed. With the same potential actionability of pharmacogenomic data, phytogenomics could be performed based on relevant disease-target networks to inform and personalize phytocomplex therapeutic application. Full article
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Review
Honey Volatiles as a Fingerprint for Botanical Origin—A Review on their Occurrence on Monofloral Honeys
Molecules 2020, 25(2), 374; https://0-doi-org.brum.beds.ac.uk/10.3390/molecules25020374 - 16 Jan 2020
Cited by 18 | Viewed by 2198
Abstract
Honeys have specific organoleptic characteristics, with nutritional and health benefits, being highly appreciated by consumers, not only in food but also in the pharmaceutical and cosmetic industries. Honey composition varies between regions according to the surrounding flora, enabling its characterization by source or [...] Read more.
Honeys have specific organoleptic characteristics, with nutritional and health benefits, being highly appreciated by consumers, not only in food but also in the pharmaceutical and cosmetic industries. Honey composition varies between regions according to the surrounding flora, enabling its characterization by source or type. Monofloral honeys may reach higher market values than multifloral ones. Honey’s aroma is very specific, resulting from the combination of volatile compounds present in low concentrations. The authentication of honey’s complex matrix, according to its botanical and/or geographical origin, represents a challenge nowadays, due to the different sorts of adulteration that may occur, leading to the search for reliable marker compounds for the different monofloral honeys. The existing information on the volatiles of monofloral honeys is scarce and disperse. In this review, twenty monofloral honeys and honeydews, from acacia, buckwheat, chestnut, clover, cotton, dandelion, eucalyptus, fir tree, heather, lavender, lime tree, orange, pine, rape, raspberry, rhododendron, rosemary, strawberry tree, sunflower and thyme, were selected for volatile comparison purposes. Taking into consideration the country of origin, the technique of isolation and analysis, the five main volatiles from each of the honeys are compared. Whereas some compounds were found in several types of monofloral honey, and thus not considered good volatile markers, some monofloral honeys revealed characteristic volatile compounds independently of their provenance. Full article
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