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Essential Oils of Plants (Chemical Composition, Variation and Properties)
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Essential Oils of Plants (Chemical Composition, Variation and Properties)

A topical collection in Plants (ISSN 2223-7747). This collection belongs to the section "Phytochemistry".

Viewed by 74629

Editors

Dr. Jésus Palá-Pául

E-Mail Website
Collection Editor
Dpto. Biodiversity Ecology and Evolution, Faculty of Biology, Complutense University of Madrid, 28040 Madrid, Spain
Interests: essential oils; chemical composition; seasonal variation; chemotypes; antibacterial activity; antifungal activity
Special Issues, Collections and Topics in MDPI journals
Dr. Joe Brophy

E-Mail Website
Collection Editor
School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia
Interests: essential oils chemistry; the oil’s relationship to the botany of the species; insect chemistry; natural product chemistry
Special Issues, Collections and Topics in MDPI journals

Topical Collection Information

Dear Colleagues,

Essential oils are important for the plants that produce them, as well as the humans that have learnt to extract and use them since the beginning of civilization. Nowadays, their constituent secondary metabolites are not only very important for the fragrance industry, but also for the chemical and pharmaceutical industries. Essential oils have numerous uses, and knowledge related to essential oils is implicated in most fields of research: biology, ecology, genetics, conservation, climatic change, medicine, etc. For this Topical Collection, we invite you to contribute papers focused on updating current knowledge on this incredible topic.

Dr. Jésus Palá-Pául
Dr. Joe Brophy
Collection Editors

Manuscript Submission Information

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Keywords

  • essential oils
  • chemical composition
  • seasonal variation
  • chemotypes
  • antibacterial activity
  • antifungal activity

Published Papers (21 papers)

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2024

Jump to: 2023, 2022

13 pages, 481 KiB  
Review
Interaction Between Heavy Metals Posed Chemical Stress and Essential Oil Production of Medicinal Plants
by Katalin Hubai and Nora Kováts
Plants 2024, 13(20), 2938; https://doi.org/10.3390/plants13202938 - 20 Oct 2024
Viewed by 1190
Abstract
Plants exposed to abiotic stressors show diverse physiological, biochemical, and molecular responses. Biosynthesis of plant secondary metabolites—including essential oils—is a vital plant defense mechanism. As these bioactive compounds are widely used in the pharmaceutical, cosmetic and food industries, it is essential to understand [...] Read more.
Plants exposed to abiotic stressors show diverse physiological, biochemical, and molecular responses. Biosynthesis of plant secondary metabolites—including essential oils—is a vital plant defense mechanism. As these bioactive compounds are widely used in the pharmaceutical, cosmetic and food industries, it is essential to understand how their production is affected in various environments. While interaction between specific abiotic stressors such as salt stress has been widely studied, relatively less information is available on how essential oil production is affected by toxic contaminants. Present review intends to give an insight into the possible interaction between chemical stress and essential oil production, with special regard to soil and air pollution. Available studies clearly demonstrate that heavy metal induced stress does affect quantity and quality of EOs produced, however, pattern seems ambiguous as nature of effect depends on the plant taxon and on the EO. Considering mechanisms, genetic studies clearly prove that exposure to heavy metals influences the expression of genes being responsible for EO synthesis. Full article
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2023

Jump to: 2024, 2022

17 pages, 1003 KiB  
Article
Exploring the Antimicrobial Properties of 99 Natural Flavour and Fragrance Raw Materials against Pathogenic Bacteria: A Comparative Study with Antibiotics
by Zuzanna Bacińska, Kinga Baberowska, Alicja Karolina Surowiak, Lucyna Balcerzak and Daniel Jan Strub
Plants 2023, 12(21), 3777; https://doi.org/10.3390/plants12213777 - 6 Nov 2023
Viewed by 2267
Abstract
Currently, one of the most serious global problems is the increasing incidence of infectious diseases. This is closely related to the increase in antibiotic use, which has resulted in the development of multidrug resistance in microorganisms. Another problem is the numerous microbiological contaminations [...] Read more.
Currently, one of the most serious global problems is the increasing incidence of infectious diseases. This is closely related to the increase in antibiotic use, which has resulted in the development of multidrug resistance in microorganisms. Another problem is the numerous microbiological contaminations of cosmetic products, which can lead to dangerous bacterial infections in humans. Natural fragrance raw materials exhibit a wide spectrum of biological properties, including antimicrobial properties. Despite their prevalence and availability on the commercial market, there is little research into their effects on multidrug-resistant microorganisms. This study examines the inhibitory effect of natural substances on Gram-positive and Gram-negative bacteria. For this purpose, screening and appropriate assays were carried out to determine the minimum inhibitory concentration (MIC) value of individual substances, using the alamarBlueTM reagent. The lowest MIC values were observed for Staphylococcus aureus (black seed (Nigella sativa) expressed oil, MIC = 25 µg/mL), Kocuria rhizophila (fir balsam absolute, MIC = 12.5 µg/mL), and Pseudomonas putida (cubeb oil and fir balsam absolute, MIC = 12.5 µg/mL). The most resistant Gram-negative species was Enterobacter gergoviae, while Staphylococcus epidermidis was the most resistant Gram-positive species. Full article
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11 pages, 1937 KiB  
Article
A New Leaf Essential Oil from Endemic Gynoxys laurifolia (Kunth) Cass. of Southern Ecuador: Chemical and Enantioselective Analyses
by Gianluca Gilardoni, Luis Rubén Lara, Nixon Cumbicus and Omar Malagón
Plants 2023, 12(15), 2878; https://doi.org/10.3390/plants12152878 - 6 Aug 2023
Cited by 5 | Viewed by 1508
Abstract
The fresh leaves of Gynoxys laurifolia (Kunth) Cass. (Asteraceae), collected in the province of Loja (Ecuador), were submitted to steam distillation, producing an essential oil with a yield of 0.02% by weight. This volatile fraction, described here for the first time, was submitted to [...] Read more.
The fresh leaves of Gynoxys laurifolia (Kunth) Cass. (Asteraceae), collected in the province of Loja (Ecuador), were submitted to steam distillation, producing an essential oil with a yield of 0.02% by weight. This volatile fraction, described here for the first time, was submitted to qualitative (GC–MS) and quantitative (GC–FID) chemical analyses, on two orthogonal columns (non-polar and polar stationary phase). A total of 90 components, corresponding to 95.9–95.0% by weight on the non-polar and polar stationary phase, respectively, were detected and quantified with at least one column. Major constituents (≥3%) were: germacrene D (18.9–18.0%), (E)-β-caryophyllene (13.2–15.0%), α-pinene (11.0–10.3%), β-pinene (4.5–4.4%), β-phellandrene (4.0–3.0%), bicyclogermacrene (4.0–3.0%), and bakkenolide A (3.2–3.4%). This essential oil was dominated by sesquiterpene hydrocarbons (about 45%), followed by monoterpene hydrocarbons (about 25–30%). This research was complemented with the enantioselective analysis of some common chiral terpenes, carried out through 2,3-diethyl-6-tert-butyldimethylsilyl-β-cyclodextrin and 2,3-diacetyl-6-tert-butyldimethylsilyl-β-cyclodextrin as stationary phase chiral selectors. As a result, (1S,5S)-(−)-β-pinene, (R)-(−)-α-phellandrene, (R)-(−)-β-phellandrene, (S)-(−)-limonene, (S)-(+)-linalyl acetate, and (S)-(−)-germacrene D were observed as enantiomerically pure compounds, whereas α-pinene, linalool, terpinene-4-ol, and α-terpineol were present as scalemic mixtures. Finally, sabinene was practically racemic. Due to plant wildness and the relatively low distillation yield, no industrial applications can be identified, in the first instance for this essential oil. The focus of the present study is therefore academic. Full article
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12 pages, 1067 KiB  
Article
Chemical Constituents, Enantiomer Content, Antioxidant and Anticholinesterase Activities of Valeriana microphylla Kunth Essential Oil
by Gabriela Aguilar, James Calva, Luis Cartuche, Melissa Salinas and Chabaco Armijos
Plants 2023, 12(11), 2155; https://doi.org/10.3390/plants12112155 - 30 May 2023
Cited by 2 | Viewed by 1766
Abstract
The study of the essential oil (EO) from aerial parts (stems and leaves) of Valeriana microphylla Kunth (Valerianaceae), collected from the Saraguro community in the southern region of Ecuador, was analyzed for the first time. A total of 62 compounds were identified in [...] Read more.
The study of the essential oil (EO) from aerial parts (stems and leaves) of Valeriana microphylla Kunth (Valerianaceae), collected from the Saraguro community in the southern region of Ecuador, was analyzed for the first time. A total of 62 compounds were identified in V. microphylla EO by GC-FID and GC-MS on nonpolar DB-5ms and polar HP-INNOWax columns. The most abundant components (>5%) detected on DB-5ms and polar HP-INNOWax columns were α-gurjunene (11.98, 12.74%), germacrene D (11.47, 14.93%), E-caryophyllene (7.05, 7.78%), and α-copaene (6.76, 6.91%), respectively. In addition, the enantioselective analysis, carried out on a chiral column, showed (+)-α-pinene and (R)-(+)-germacrene as enantiomerically pure compounds (enantiomeric excess = 100%). The antioxidant activity was high for the radicals ABTS (SC50 = 41.82 µg/mL) and DPPH (SC50 = 89.60 µg/mL), and finally, the EO was shown to be inactive to the enzyme acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE), as both values were >250 µg/mL. Full article
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21 pages, 1344 KiB  
Review
Health-Promoting Properties and Potential Application in the Food Industry of Citrus medica L. and Citrus × clementina Hort. Ex Tan. Essential Oils and Their Main Constituents
by Rosa Tundis, Jianbo Xiao, Ana Sanches Silva, Filipa Carreiró and Monica Rosa Loizzo
Plants 2023, 12(5), 991; https://doi.org/10.3390/plants12050991 - 21 Feb 2023
Cited by 15 | Viewed by 3877
Abstract
Citrus is an important genus in the Rutaceae family, with high medicinal and economic value, and includes important crops such as lemons, orange, grapefruits, limes, etc. The Citrus species is rich sources of carbohydrates, vitamins, dietary fibre, and phytochemicals, mainly including limonoids, flavonoids, [...] Read more.
Citrus is an important genus in the Rutaceae family, with high medicinal and economic value, and includes important crops such as lemons, orange, grapefruits, limes, etc. The Citrus species is rich sources of carbohydrates, vitamins, dietary fibre, and phytochemicals, mainly including limonoids, flavonoids, terpenes, and carotenoids. Citrus essential oils (EOs) consist of several biologically active compounds mainly belonging to the monoterpenes and sesquiterpenes classes. These compounds have demonstrated several health-promoting properties such as antimicrobial, antioxidant, anti-inflammatory, and anti-cancer properties. Citrus EOs are obtained mainly from peels, but also from leaves and flowers, and are widely used as flavouring ingredients in food, cosmetics, and pharmaceutical products. This review focused on the composition and biological properties of the EOs of Citrus medica L. and Citrus clementina Hort. Ex Tan and their main constituents, limonene, γ-terpinene, myrcene, linalool, and sabinene. The potential applications in the food industry have been also described. All the articles available in English or with an abstract in English were extracted from different databases such as PubMed, SciFinder, Google Scholar, Web of Science, Scopus, and Science Direct. Full article
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17 pages, 2780 KiB  
Article
Correspondence between the Compositional and Aromatic Diversity of Leaf and Fruit Essential Oils and the Pomological Diversity of 43 Sweet Oranges (Citrus x aurantium var sinensis L.)
by Vincent Ferrer, Noémie Paymal, Gilles Costantino, Mathieu Paoli, Carole Quinton, Félix Tomi and François Luro
Plants 2023, 12(5), 990; https://doi.org/10.3390/plants12050990 - 21 Feb 2023
Cited by 3 | Viewed by 1960
Abstract
Orange (Citrus x aurantium var sinensis) is the most widely consumed citrus fruit, and its essential oil, which is made from the peel, is the most widely used in the food, perfume, and cosmetics industries. This citrus fruit is an interspecific hybrid [...] Read more.
Orange (Citrus x aurantium var sinensis) is the most widely consumed citrus fruit, and its essential oil, which is made from the peel, is the most widely used in the food, perfume, and cosmetics industries. This citrus fruit is an interspecific hybrid that would have appeared long before our era and would result from two natural crosses between mandarin and pummelo hybrids. This single initial genotype was multiplied by apomictic reproduction and diversified by mutations to produce hundreds of cultivars selected by men essentially based on phenotypic characteristics of appearance, spread of maturity, and taste. Our study aimed to assess the diversity of essential oil composition and variability in the aroma profile of 43 orange cultivars representing all morphotypes. In agreement with the mutation-based evolution of orange trees, the genetic variability tested with 10 SSR genetic markers was null. The oils from peels and leaves extracted by hydrodistillation were analyzed for composition by GC (FID) and GC/MS and for aroma profile by the CATA (Check All That Apply) method by panelists. Oil yield varied between varieties by a factor of 3 for PEO and a factor of 14 for LEO between maximum and minimum. The composition of the oils was very similar between cultivars and was mainly dominated by limonene (>90%). However, small variations were observed as well as in the aromatic profile, with some varieties clearly distinguishing themselves from the others. This low chemical diversity contrasts with the pomological diversity, suggesting that aromatic variability has never been a selection criterion in orange trees. Full article
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21 pages, 774 KiB  
Article
Essential Oil Composition of Seven Bulgarian Hypericum Species and Its Potential as a Biopesticide
by Ivanka Semerdjieva, Valtcho D. Zheljazkov, Ivayla Dincheva, Neshka Piperkova, Vasilina Maneva, Charles L. Cantrell, Tess Astatkie, Albena Stoyanova and Tanya Ivanova
Plants 2023, 12(4), 923; https://doi.org/10.3390/plants12040923 - 17 Feb 2023
Cited by 5 | Viewed by 2144
Abstract
Hypericum species and especially H. perforatum L. are well known for their therapeutic applications. The present study assessed the essential oil (EO) composition, and antifungal and aphid suppression activity of seven Bulgarian Hypericum species. The EOs were analyzed by GC–MS–FID. Two experiments were [...] Read more.
Hypericum species and especially H. perforatum L. are well known for their therapeutic applications. The present study assessed the essential oil (EO) composition, and antifungal and aphid suppression activity of seven Bulgarian Hypericum species. The EOs were analyzed by GC–MS–FID. Two experiments were conducted. In the first experiment, H. perforatum, H. maculatum, and H. hirsutum were used. Additionally, the EO composition of H. perforatum extracted via hydrodistillation (ClevA) and via commercial steam distillation (Com) were compared. The second experiment compared the EOs of H. perforatum, H. cerastoides, H. rumeliacum, H. montbretii, and H. calycinum (flowers and leaves) extracted via hydrodistillation and collected with n-hexane. Overall, the EO constituents belonged to four classes, namely alkanes, monoterpenes, sesquiterpenes, and fatty acids. The main class for compounds in H. maculatum and H. perforatum (section Hypericum) were sesquiterpenes for both experiments except for H. perforatum (Com). Hypericum montbretii (section Drosocarpium) EO had monoterpenes (38.09%) and sesquiterpenes (37.09%) as major groups, while H. hirsutum EO (section Taeniocarpium) contained predominately alkanes (67.19%). Hypericum hirsutum EO contained cedrol (5.04%), found for the first time in Hypericum species. Fatty acids were the main compounds in H. cerastoides (section Campylopus), while monoterpenes were the most abundant class in H. rumeliacum and H. calycinum EOs. α-Pinene and germacrene D were the major EO constituents of all analyzed Hypericum species except for H. hirsutum and H. cerastoides. Hypericum perforatum EO (Com) had significant repellent and insecticidal activity against two aphid species, Rhopalosiphum padi (Bird Cherry-oat aphid) and Sitobion avenae (English grain aphid) at concentrations of 0%, 1%, 2.5%, 3.5%, 4.5%, and 5%. The tested EOs did not show significant activity against selected economically important agricultural fungal pathogens Fusarium spp., Botrytis cinerea, Colletotrichum spp., Rhizoctonia solani, and Aspergillus sp. The EO of the Hypericum species found in the Bulgarian flora could be utilized for the development of new biopesticides for aphid control. Full article
15 pages, 5232 KiB  
Article
A New Essential Oil from the Leaves of Gynoxys rugulosa Muschl. (Asteraceae) Growing in Southern Ecuador: Chemical and Enantioselective Analyses
by Yessenia E. Maldonado, Omar Malagón, Nixon Cumbicus and Gianluca Gilardoni
Plants 2023, 12(4), 849; https://doi.org/10.3390/plants12040849 - 14 Feb 2023
Cited by 14 | Viewed by 2359
Abstract
An essential oil, distilled from the leaves of the Andean species Gynoxys rugulosa Muschl., is described in the present study for the first time. The chemical composition was qualitatively and quantitatively determined by GC–MS and GC–FID, respectively. On the one hand, the qualitative [...] Read more.
An essential oil, distilled from the leaves of the Andean species Gynoxys rugulosa Muschl., is described in the present study for the first time. The chemical composition was qualitatively and quantitatively determined by GC–MS and GC–FID, respectively. On the one hand, the qualitative composition was obtained by comparing the mass spectrum and the linear retention index of each component with data from literature. On the other hand, the quantitative composition was determined by calculating the relative response factor of each constituent, according to its combustion enthalpy. Both analyses were carried out with two orthogonal columns of nonpolar and polar stationary phases. A total of 112 compounds were detected and quantified with at least one column, corresponding to 87.3–93.0% of the whole oil mass. Among the 112 detected components, 103 were identified. The main constituents were α-pinene (5.3–6.0%), (E)-β-caryophyllene (2.4–2.8%), α-humulene (3.0–3.2%), germacrene D (4.9–6.5%), δ-cadinene (2.2–2.3%), caryophyllene oxide (1.6–2.2%), α-cadinol (3.8–4.4%), 1-nonadecanol (1.7–1.9%), 1-eicosanol (0.9–1.2%), n-tricosane (3.3–3.4%), 1-heneicosanol (4.5–5.8%), n-pentacosane (5.8–7.1%), 1-tricosanol (4.0–4.5%), and n-heptacosane (3.0–3.5%). Furthermore, an enantioselective analysis was carried out on the essential oil, by means of two cyclodextrin-based capillary columns. The enantiomers of α-pinene, β-pinene, sabinene, α-phellandrene, β-phellandrene, linalool, α-copaene, terpinen-4-ol, α-terpineol, and germacrene D were detected, and the respective enantiomeric excess was calculated. Full article
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29 pages, 2477 KiB  
Review
Current Trends for Lavender (Lavandula angustifolia Mill.) Crops and Products with Emphasis on Essential Oil Quality
by Ioana Crișan, Andreea Ona, Dan Vârban, Leon Muntean, Rodica Vârban, Andrei Stoie, Tania Mihăiescu and Adriana Morea
Plants 2023, 12(2), 357; https://doi.org/10.3390/plants12020357 - 12 Jan 2023
Cited by 35 | Viewed by 11347
Abstract
Lavender is in the research spotlight due to its increasing economic importance, while market demand is expected to continue to grow. Among the hundreds of essential-oil-bearing plants, Lavandula angustifolia Mill. remains one of the most valuable. This paper explores the lavender chain timeline [...] Read more.
Lavender is in the research spotlight due to its increasing economic importance, while market demand is expected to continue to grow. Among the hundreds of essential-oil-bearing plants, Lavandula angustifolia Mill. remains one of the most valuable. This paper explores the lavender chain timeline from crop to products, examining the expanding knowledge on the characteristics, phytochemical profile and functional potential of lavender that could lead to new products and uses. Lavender crops can be expanded without competing for productive land, instead using marginal, contaminated or unproductive land. A novel cultivation trend proposes leveraging agri-background biodiversity, arbuscular mycorrhiza and the natural enemies of pests for healthy crops. Together with breeding efforts targeting highly performant genotypes with complex volatile profiles coupled with resistance to specific biotic (particularly Phytoplasma) and abiotic (salt, heavy metals) stressors, industry could have a steady supply of high-quality raw material. Besides the expansion of the uses of essential oil in cosmetics, pharmaceuticals, food and environmental and agri-applications, novel channels have appeared for the use of the solid by-product, which is rich in polyphenols and polysaccharides; these channels have the potential to create additional streams of value. The stabilization and optimization of techno-functional delivery systems through the encapsulation of essential oil can extend shelf-life and enhance biological activity efficiency. Full article
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2022

Jump to: 2024, 2023

18 pages, 603 KiB  
Review
Essential Oils in the Treatment of Various Types of Acne—A Review
by Renata Nurzyńska-Wierdak, Dominika Pietrasik and Magdalena Walasek-Janusz
Plants 2023, 12(1), 90; https://doi.org/10.3390/plants12010090 - 24 Dec 2022
Cited by 12 | Viewed by 8705
Abstract
Acne is a chronic, common disease that poses a significant therapeutic, psychological and social problem. The etiopathogenesis of this disease is not fully understood. Drugs used in general and external therapy should have anti-seborrhoeic, anticomadogenic, bactericidal, bacteriostatic, and anti-inflammatory properties. Acne treatment is [...] Read more.
Acne is a chronic, common disease that poses a significant therapeutic, psychological and social problem. The etiopathogenesis of this disease is not fully understood. Drugs used in general and external therapy should have anti-seborrhoeic, anticomadogenic, bactericidal, bacteriostatic, and anti-inflammatory properties. Acne treatment is often associated with the long-term use of antibiotics, contributing to the global antibiotic resistance crisis. In order to solve this problem, attention has been paid to essential oils and their terpene components with potent antimicrobial, anti-inflammatory, and antioxidant properties. Research shows that certain essential oils effectively reduce inflammatory acne lesions through mechanisms related to the sebaceous glands, colonization of Cutibacterium acnes, and reactive oxygen species (ROS). An example is tea tree oil (TTO), a more commonly used topical agent for treating acne. TTO has antimicrobial and anti-inflammatory activity. The paper presents the latest scientific information on the activity and potential use of specific essential oils in treating acne. Evidence of antibacterial, anti-inflammatory, and antioxidant activity of several essential oils and their main components was presented, indicating the possibility of using them in the treatment of acne. Full article
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20 pages, 884 KiB  
Review
Healthy Zerumbone: From Natural Sources to Strategies to Improve Its Bioavailability and Oral Administration
by María Dolores Ibáñez, Noelia M. Sánchez-Ballester and María Amparo Blázquez
Plants 2023, 12(1), 5; https://doi.org/10.3390/plants12010005 - 20 Dec 2022
Cited by 10 | Viewed by 3292
Abstract
Zerumbone is a multifunctional compound with antimicrobial, antitumor, hyperalgesic, antioxidant and anti-inflammatory applications, and constitutes a point molecule for the future synthesis of derivatives with improved efficiency. This monocyclic sesquiterpenoid is found in high content in wild ginger (Zingiber zerumbet Smith), a [...] Read more.
Zerumbone is a multifunctional compound with antimicrobial, antitumor, hyperalgesic, antioxidant and anti-inflammatory applications, and constitutes a point molecule for the future synthesis of derivatives with improved efficiency. This monocyclic sesquiterpenoid is found in high content in wild ginger (Zingiber zerumbet Smith), a perennial herb with economic importance as an ornamental as well as a medicinal plant. The presence of zerumbone is a distinctive feature that allows identification and differentiation from other species, not only in Zingiber, but also in Curcuma, Alpinia, Boesenbergia, Ethlingera and Ammomum spp., as well as related families (Costaceaee). To successfully use zerumbone in areas such as medicine, food and agriculture, further research on improving its low solubility and bioavailability, as well as its preservation, is a major current priority. In addition, despite its promising pharmacological activities, preclinical and clinical studies are required to demonstrate and evaluate the in vivo efficacy of zerumbone. Full article
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15 pages, 984 KiB  
Article
The Effect of the Height of Coppicing and Harvest Season on the Yield and Quality of the Essential Oil of Kunzea ambigua
by Chanjoo Park, Sandra M. Garland and Dugald C. Close
Plants 2023, 12(1), 20; https://doi.org/10.3390/plants12010020 - 20 Dec 2022
Cited by 1 | Viewed by 1902
Abstract
Kunzea ambigua is a small shrub belonging to the Myrtaceae family and the leaves are steam-distilled to produce a therapeutically active essential oil. With production moving from wild-harvested to orchardised stands, there is a need for harvest management of kunzea oil. This study [...] Read more.
Kunzea ambigua is a small shrub belonging to the Myrtaceae family and the leaves are steam-distilled to produce a therapeutically active essential oil. With production moving from wild-harvested to orchardised stands, there is a need for harvest management of kunzea oil. This study compared the regrowth, essential oil content and composition of kunzea plants after harvesting vegetative material to a depth of 0.2 m above ground level (shallow-cut), relative to plants cut to a depth of 0.1 m above ground level (deep-cut) over the 2018/2019 growing season. Increased vegetative biomass accounted for the increased oil yield and was caused by consistently higher growth rates of 50 to 60% across all seasons in shallow-cut crops relative to those subject to deep-cut. Total soluble sugar concentrations were higher in the leaves and lower in the roots of deep-cut treated plants compared to the other treatments, indicating defoliated K. ambigua responds by mobilising sugars into above-ground biomass. The overall essential oil content of leaves was constant regardless of season, though the oil yield for shallow-cut was 1.9-fold higher at 11.79 ± 0.23 g/m2 compared to deep-cut (6.24 ± 0.18 g/m2). An interactive effect of harvest intensity with season was recorded for all major components except for a non-significant effect of season on terpinen-4-ol. Bicyclogermacrene and α-pinene were elevated in both shallow- and deep-cut treatments relative to control (un-cut) in spring, possibly due to the plant defense response after de-foliation. The highest percentage of bioactive compounds (1,8-cineole and viridiflorol) were present in autumn. Therefore, the recovery of biomass post-harvest is optimised by shallow-cut harvests, and the profile of kunzea oil can be manipulated to elevate levels of specific bioactive components by selecting to crop in autumn/spring. Full article
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13 pages, 782 KiB  
Article
Antiviral Activity of Selected Essential Oils against Cucumber Mosaic Virus
by Elżbieta Paduch-Cichal, Ewa Mirzwa-Mróz, Patrycja Wojciechowska, Katarzyna Bączek, Olga Kosakowska, Zenon Węglarz and Marek Stefan Szyndel
Plants 2023, 12(1), 18; https://doi.org/10.3390/plants12010018 - 20 Dec 2022
Cited by 1 | Viewed by 2487
Abstract
The aim of the study was to assess the antiviral activity of selected essential oils (EOs) against Cucumber mosaic virus (CMV), both in vitro and in vivo. The observations were made using Chenopodium quinoa as a local host. The EOs were obtained from [...] Read more.
The aim of the study was to assess the antiviral activity of selected essential oils (EOs) against Cucumber mosaic virus (CMV), both in vitro and in vivo. The observations were made using Chenopodium quinoa as a local host. The EOs were obtained from Greek oregano, thyme, and costmary. Their chemical composition was determined using GC/FID followed by GC/MS. The dominant compound in oregano EO was carvacrol (59.41%), in thyme EO—thymol (59.34%), and in costmary EO—β-thujone (90.60%). Among the analysed EOs, thyme EO exhibited the most promising effects against CMV. However, its activity was influenced by the time of application. In an in vivo experiment, thyme EO showed protective (pre-inoculation) rather than curative (post-inoculation) activity. Full article
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13 pages, 4296 KiB  
Article
Antimicrobial, Antibiofilm, and Antioxidant Properties of Essential Oil of Foeniculum vulgare Mill. Leaves
by Michela Di Napoli, Giusy Castagliuolo, Natale Badalamenti, Viviana Maresca, Adriana Basile, Maurizio Bruno, Mario Varcamonti and Anna Zanfardino
Plants 2022, 11(24), 3573; https://doi.org/10.3390/plants11243573 - 17 Dec 2022
Cited by 15 | Viewed by 3070
Abstract
Foeniculum vulgare (Apiaceae) is an aromatic fennel with important practices in medicinal and traditional fields, used in the treatment of digestive complications, and gastrointestinal and respiratory disorders. Its leaves and stems, tender and fresh, are used in the production of pasta dressing and [...] Read more.
Foeniculum vulgare (Apiaceae) is an aromatic fennel with important practices in medicinal and traditional fields, used in the treatment of digestive complications, and gastrointestinal and respiratory disorders. Its leaves and stems, tender and fresh, are used in the production of pasta dressing and main courses, while its seeds, with a strong smell of anise, are excellent flavoring for baked goods, meat dishes, fish, and alcoholic beverages. The aim of this work is concerning the extraction of essential oil (EO) from the leaves of F. vulgare subsp. vulgare var. vulgare, investigating antimicrobial, antibiofilm, and antioxidant efficacy. In particular, GC-MS analysis showed how the chemical composition of EO was influenced by the massive presence of monoterpene hydrocarbons (α-pinene 33.75%) and phenylpropanoids (estragole 25.06%). F. vulgare subsp. vulgare var. vulgare EO shows excellent antimicrobial activity against both Gram-positive and Gram-negative strains. This EO can inhibit biofilm formation at very low concentrations and has a good ability to scavenge oxygen radicals in vitro. F. vulgare subsp. vulgare var. vulgare EO also has an increased activity of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) enzymes and decreased ROS levels in zymosan opsonized PMNs (OZ). Full article
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13 pages, 1349 KiB  
Article
Effects of Essential Oil Fumigation on Potato Sprouting at Room-Temperature Storage
by Jena L. Thoma, Charles L. Cantrell and Valtcho D. Zheljazkov
Plants 2022, 11(22), 3109; https://doi.org/10.3390/plants11223109 - 15 Nov 2022
Cited by 5 | Viewed by 2387
Abstract
As a global staple, potato plays an important role in meeting human dietary needs and alleviating malnutrition. Potato sprouting during storage is a major issue that threatens food security by increasing food waste and must therefore be controlled. Biopesticides, including essential oils (EOs), [...] Read more.
As a global staple, potato plays an important role in meeting human dietary needs and alleviating malnutrition. Potato sprouting during storage is a major issue that threatens food security by increasing food waste and must therefore be controlled. Biopesticides, including essential oils (EOs), have a history of use as potato sprout suppressants, and interest in their use has been renewed in response to stricter regulations on CIPC, the dominant chemical sprout suppressant over the last half-century. We evaluated twenty-one EOs as potential sprout suppressants in cv. Ranger Russet potatoes at room-temperature storage. Treatment with Artemisia herba-alba EO was the most effective at suppressing both sprout length and sprout number over a 90-day storage period. GC—MS—FID analysis of A. herba-alba EO revealed the presence of α-thujone, hexadecenoic acid, β-thujone, camphor, sabinene, and camphene at amounts >1%. Cistus ladanifer, Ocimum basilicum, Ormenis mixta, and Salvia sclarea EOs significantly reduced sprout length for shorter storage periods, whereas Cinnamomum zeylanicum (bark) and Laurus nobilis EOs also significantly reduced sprout number. Syzygium aromaticum (clove) EO did not significantly suppress sprouting at room temperature. These results indicate the potential of certain EOs to be used as sprout suppressants for room-temperature potato storage, providing needed alternatives for both organic and conventional potato industries. Full article
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14 pages, 1886 KiB  
Article
Evaluation of Essential Oils as Sprout Suppressants for Potato (Solanum tuberosum) at Room Temperature Storage
by Jena L. Thoma, Charles L. Cantrell and Valtcho D. Zheljazkov
Plants 2022, 11(22), 3055; https://doi.org/10.3390/plants11223055 - 11 Nov 2022
Cited by 6 | Viewed by 2684
Abstract
Chlorpropham (CIPC) has been the dominant method of chemical sprout suppression for the last half-century. However, stricter regulations including outright bans on its use in several countries has prompted investigation into alternative products to replace it. Growing interest in organic foods has increased [...] Read more.
Chlorpropham (CIPC) has been the dominant method of chemical sprout suppression for the last half-century. However, stricter regulations including outright bans on its use in several countries has prompted investigation into alternative products to replace it. Growing interest in organic foods has increased focus on the use of biopesticides, including essential oils (EOs), as potential sprout suppressants in stored potato. We evaluated the potential of ten EOs for sprout suppression in potato cultivar Ranger Russet at room temperature. Treatment with Cymbopogon citratus EO was found to be the most effective sprout suppressant, completely suppressing sprouting over the 90-day storage period. The EOs of Myrtus communis and Melaleuca quinquenervia significantly reduced sprout length relative to the control but did not have any effect on sprout number. These findings demonstrate the potential of select EOs as effective potato sprout suppressants that could replace CIPC use in this industry while also giving more power to organic potato producers and processors to control sprouting in their operations. Full article
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16 pages, 3719 KiB  
Article
Essential Oil and Non-Volatile Metabolites from Kaunia longipetiolata (Sch.Bip. ex Rusby) R. M. King and H. Rob., an Andean Plant Native to Southern Ecuador
by Omar Malagón, Cinthia Bravo, Giovanni Vidari, Nixon Cumbicus and Gianluca Gilardoni
Plants 2022, 11(21), 2972; https://doi.org/10.3390/plants11212972 - 3 Nov 2022
Cited by 5 | Viewed by 2301
Abstract
Kaunia longipetiolata (Sch.Bip. ex Rusby) R. M. King and H. Rob. (Asteraceae) is a plant native to southern Ecuador. The dry leaves afforded, by steam distillation, an essential oil that was qualitatively and quantitatively analyzed by GC-MS and GC-FID, respectively, on two orthogonal [...] Read more.
Kaunia longipetiolata (Sch.Bip. ex Rusby) R. M. King and H. Rob. (Asteraceae) is a plant native to southern Ecuador. The dry leaves afforded, by steam distillation, an essential oil that was qualitatively and quantitatively analyzed by GC-MS and GC-FID, respectively, on two orthogonal columns of different polarity. Sesquiterpenes predominated in the volatile fraction, among which α-zingiberene (19.7–19.1%), ar-curcumene (17.3–18.1%), caryophyllene oxide (5.1–5.3%), (Z)-β-caryophyllene (3.0–3.1%), (2Z,6Z)-farnesal (2.6–3.6%), and spathulenol (2.0–2.1%) were the major components. In addition to the identified compounds, two main unidentified constituents (possibly oxygenated sesquiterpenes) with probable molecular masses of 292 and 230, respectively, were detected. They constituted about 5% and 8% (w/w), respectively, of the whole essential oil. The oil chemical composition was complemented with the enantioselective analysis of ten chiral components. Four scalemic mixtures and six enantiomerically pure terpenes were identified. An enantiomeric excess (ee) was determined for (1R,5R)-(+)-β-pinene (65.0%), (R)-(−)-α-phellandrene (94.6%), (S)-(+)-linalool (15.0%), and (R)-(−)-terpinen-4-ol (33.8%). On the other hand, (1R,5R)-(+)-α-pinene, (1R,5R)-(+)-sabinene, (S)-(−)-limonene, (S)-(+)-β-phellandrene, (1R,2S,6S,7S,8S)-(−)-α-copaene, and (R)-(+)-germacrene D were enantiomerically pure. Finally, the non-volatile fraction obtained by extraction of the leaves with MeOH was investigated. Eight known compounds were isolated by liquid column chromatographic separations. Their structures were determined by NMR spectroscopy as dehydroleucodine, kauniolide, (3S,3aR,4aR,6aS,9aS,9bR)-3-hydroxy-1,4a-dimethyl-7-methylene-5,6,6a,7,9a,9b-hexahydro-3H-oxireno[2′,3′:8,8a]azuleno[4,5-b]furan-8(4aH)-one, novanin, bisabola-1,10-diene-3,4-trans-diol, (R)-2-(2-(acetoxymethyl)oxiran-2-yl)-5-methylphenyl isobutyrate, eupalitin-3-O-glucoside, and 3,5-di-O-caffeoylquinic acid. Literature data about the identified metabolites indicate that K. longipetiolata is a rich source of biologically active natural products. Full article
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17 pages, 3367 KiB  
Article
Investigations of the Chemical Composition and Aromatic Properties of Peel Essential Oils throughout the Complete Phase of Fruit Development for Two Cultivars of Sweet Orange (Citrus sinensis (L.) Osb.)
by Vincent Ferrer, Noémie Paymal, Carole Quinton, Félix Tomi and François Luro
Plants 2022, 11(20), 2747; https://doi.org/10.3390/plants11202747 - 17 Oct 2022
Cited by 12 | Viewed by 3311
Abstract
The peel essential oil (PEO) of sweet orange is used for flavoring liquors or foods and in the perfumery and cosmetics industry. The fruit maturity stage can modify the essential oil composition and aromatic properties, but little information is available on the evolution [...] Read more.
The peel essential oil (PEO) of sweet orange is used for flavoring liquors or foods and in the perfumery and cosmetics industry. The fruit maturity stage can modify the essential oil composition and aromatic properties, but little information is available on the evolution of PEO during the entire time set of fruit development. In this study, the yield, chemical composition and aromatic profile over the three phases of orange development were monitored. Four fruit traits (peel color, weight, acidity and sweetness) were recorded to characterize fruit development. Fruits of two sweet orange cultivars were sampled every two weeks from June to May of the next year. PEO was obtained by hydrodistillation and analyzed by gas chromatography coupled with a flame ionization detector (GC-FID). Compounds were identified with GC coupled with mass spectrometry (GC/MS). Ten expert panelists using the descriptor intensity method described the aromatic profile of PEO samples. The PEO composition was richer in oxygenated compounds at early fruit development stages, with an aromatic profile presenting greener notes. During fruit growth (Phases I and II), limonene’s proportion increased considerably as a few aliphatic aldehydes brought the characteristic of orange aroma. During fruit maturation (from November to March), the PEO composition and aromatic profile were relatively stable. Later, some modifications were observed. Regardless of the fruit development stage, the two sweet oranges presented distinct PEO compositions and aromatic profiles. These results constitute a temporal reference for the chemical and aromatic evolution of sweet orange PEO in the fruit development process under Mediterranean conditions. During the first two phases of fruit development, many changes occur in the PEO composition and aroma, suggesting that their exploitation could create new products. Full article
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27 pages, 1638 KiB  
Review
Review of the Leaf Essential Oils of the Genus Backhousia Sens. Lat. and a Report on the Leaf Essential Oils of B. gundarara and B. tetraptera
by Bruce F. Bowden, Joseph J. Brophy and Betsy R. Jackes
Plants 2022, 11(9), 1231; https://doi.org/10.3390/plants11091231 - 2 May 2022
Cited by 1 | Viewed by 1850
Abstract
A review of the leaf oils of the 13 species now recognised in the genus Backhousia is presented. This review carries on from, and incorporates data from, an earlier (1995) review of the then recognised eight species. The leaf oils of two new [...] Read more.
A review of the leaf oils of the 13 species now recognised in the genus Backhousia is presented. This review carries on from, and incorporates data from, an earlier (1995) review of the then recognised eight species. The leaf oils of two new species of Backhousia, B. gundarara and B. tetraptera are reported for the first time. B. gundarara contains a mixture of mono- and sesquiterpenes, with α-pinene (14%) and spathulenol (11%) being the main members. In B. tetraptera, the principal component of the mainly terpenoid leaf oil is myrtenyl acetate (20–40%). The review also incorporates the two species of the genus Choricarpia, which have been subsumed into Backhousia, viz. B. leptopetala and B. subargentea. Due to its history in Backhousia, Syzygium anisatum, which has been transferred out of Backhousia, is included in the review for historical reasons. Full article
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17 pages, 4508 KiB  
Article
Chemical and Biological Characterization of Melaleuca alternifolia Essential Oil
by Petra Borotová, Lucia Galovičová, Nenad L. Vukovic, Milena Vukic, Eva Tvrdá and Miroslava Kačániová
Plants 2022, 11(4), 558; https://doi.org/10.3390/plants11040558 - 20 Feb 2022
Cited by 36 | Viewed by 6761
Abstract
The essential oil of Melaleuca alternifolia, commonly known as tea tree oil, has many beneficial properties due to its bioactive compounds. The aim of this research was to characterize the tea tree essential oil (TTEO) from Slovakia and its biological properties, which [...] Read more.
The essential oil of Melaleuca alternifolia, commonly known as tea tree oil, has many beneficial properties due to its bioactive compounds. The aim of this research was to characterize the tea tree essential oil (TTEO) from Slovakia and its biological properties, which are specific to the chemical composition of essential oil. Gas chromatography/mass spectroscopy revealed that terpinen-4-ol was dominant with a content of 40.3%. γ-Terpinene, 1,8-cineole, and p-cymene were identified in contents of 11.7%, 7.0%, and 6.2%, respectively. Antioxidant activity was determined at 41.6% radical inhibition, which was equivalent to 447 μg Trolox to 1 mL sample. Antimicrobial activity was observed by the disk diffusion method against Gram-positive (G+), Gram-negative (G−) bacteria and against yeasts, where the best antimicrobial activity was against Enterococcus faecalis and Candida albicans with an inhibition zone of 10.67 mm. The minimum inhibitory concentration showed better susceptibility by G+ and G− planktonic cells, while yeast species and biofilm-forming bacteria strains were more resistant. Antibiofilm activity was observed against Pseudomonas fluorescens and Salmonella enterica by MALDI-TOF, where degradation of the protein spectra after the addition of essential oil was obtained. Good biological properties of tea tree essential oil allow its use in the food industry or in medicine as an antioxidant and antimicrobial agent. Full article
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20 pages, 36605 KiB  
Article
Chemical Composition, Antioxidant, In Vitro and In Situ Antimicrobial, Antibiofilm, and Anti-Insect Activity of Cedar atlantica Essential Oil
by Miroslava Kačániová, Lucia Galovičová, Veronika Valková, Hana Ďuranová, Jana Štefániková, Natália Čmiková, Milena Vukic, Nenad L. Vukovic and Przemysław Łukasz Kowalczewski
Plants 2022, 11(3), 358; https://doi.org/10.3390/plants11030358 - 28 Jan 2022
Cited by 13 | Viewed by 4349
Abstract
The present study was designed to evaluate commercial cedar essential oil (CEO), obtained by hydrodistillation from cedar wood, in relationship to its chemical composition and antioxidant, in vitro and in situ antimicrobial, antibiofilm, and anti-insect activity. For these purposes, gas chromatography–mass spectrometry, DPPH [...] Read more.
The present study was designed to evaluate commercial cedar essential oil (CEO), obtained by hydrodistillation from cedar wood, in relationship to its chemical composition and antioxidant, in vitro and in situ antimicrobial, antibiofilm, and anti-insect activity. For these purposes, gas chromatography–mass spectrometry, DPPH radical-scavenging assay, agar and disc diffusion, and vapor phase methods were used. The results from the volatile profile determination showed that δ-cadinene (36.3%), (Z)-β-farnesene (13.8%), viridiflorol (7.3%), and himachala-2,4-diene (5.4%) were the major components of the EO chemical constitution. Based on the obtained results, a strong antioxidant effect (81.1%) of the CEO was found. CEO is characterized by diversified antimicrobial activity, and the zones of inhibition ranged from 7.33 to 21.36 mm in gram-positive and gram-negative bacteria, and from 5.44 to 13.67 mm in yeasts and fungi. The lowest values of minimal inhibition concentration (MIC) were noted against gram-positive Micrococcus luteus (7.46 µL/mL) and against yeast Candida krusei (9.46 µL/mL). It seems that the vapor phase of CEO can inhibit the growth of the microscopic filamentous fungi of the genus Penicillium according to in situ antifungal analysis on bread, carrots, and celery. This finding confirms the impact of CEO on the change in the protein structure of older biofilms of Pseudomonas fluorescens and Salmonella enterica subsp. enterica. Insecticidal activity of a vapor phase has also been demonstrated against Pyrrhocoris apterus. CEO showed various advantages on antimicrobial activity, and it is an ideal substitute for food safety. 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: Chemical composition, antioxidant, antimicrobial in vitro, in situ, antibiofilm and anti-insect activity of Cedar atlantica essential oil
Authors: Miroslava Kačániová
Affiliation: Department of Microbiology, Faculty of Biotechnology and Food Science, Slovak University of Agriculture in Nitra, Nitra, Slovakia
Abstract: The essential oils were obtained by hydro-distillation from Cedar wood. Cedar atlantica belongs to plants known for their many biological properties. The present study was designed to evaluate commercial cedar essential oil (CEO) in relationship to its chemical composition, antioxidant activity, in vitro and in situ antimicrobial, antibiofilm and anti-insect activity. For these purposes, gas chromatography-mass spectrometry and disc diffusion methods were used. The results from the volatile profile determination showed that δ-cadinene (36.3%), (Z)-β-farnesene (13.8%), viridiflorol (7.3%), and himachala-2,4-diene (5.4%) were the major components of the EO chemical constitution. The results indicate that the essential oils from wood tar of Cedrus atlantica possess a strong antioxidant activity (81.1%). The antimicrobial activity was neither weak or very strong and inhibition zones ranged from 7.33 to 21.36 mm in gram positive and gram-negative bacteria and from 5.44 to 13.67 mm in yeasts and fungi. The lowest values of MIC were determined against M. luteus in gram positive and negative bacteria as well as against C. krusei in yeasts and fungi. It seems that the vapor phase of CEO can inhibit the growth of the microscopic filamentous fungi of the genus Penicillium according to in situ antifungal analysis on bread, carrot, and celery. This finding confirms the impact of CEO on the change in the protein structure of older biofilms of P. fluorescens and S. Enteritidis. Also, the insecticidal activity against the Pyrrhocoris apterus in the gas phase was detected. CEO showed various advantages on antimicrobial activity, and it is an ideal substitute for food safety.

Title: Chemical and biological characterisation of Melaleuca alternifolia essential oil
Authors: Miroslava Kačániová
Affiliation: Department of Microbiology, Faculty of Biotechnology and Food Science, Slovak University of Agriculture in Nitra, Nitra, Slovakia
Abstract: The essential oil from Melaleuca alternifolia, commonly known as Tea tree oil, has been applied in cosmetics, medicine, and food industry for many years due to the properties of their bioactive compounds. The aim of the research was to characterise the Tea tree oil from Slovakia and its biological properties that are specific to chemical composition of essential oil. Gas chromatography/mass spectroscopy revealed that 4-terpinenol was dominant with content 40.3 %. γ-terpinene 1,8-cineol, and p-cymene were identified in content 11.7 %, 7.0 %, and 6.2 % respectively. The antioxidant activity was measured, and the value was determined at 41,6 % inhibition of radical which was equivalent to 447 μg Trolox to 1 ml of sample. The antimicrobial activity was observed by disk diffusion method and minimum inhibitory concentration against gram-positive, gram-negative bacteria and against yeasts. The antibiofilm activity was observed against P. fluorescens and S. Enteritidis by MALDI TOF where degradation of the protein spectra after addition of essential oil was obtained.

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