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Chemical Composition and Bioactivities of Essential Oils, 2nd Edition

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

Deadline for manuscript submissions: 30 April 2024 | Viewed by 8516

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Dr. Manuela Labbozzetta

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Department of Biological, Chemical and Pharmaceutical Science and Technology (STEBICEF), University of Palermo, Palermo, Italy
Interests: pharmacology; chemotherapy; multidrug resistance; natural products; pharmacognosy and phytotherapy
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Dear Colleagues,

The discovery of natural plant-based products is rightly recognized as a milestone in the history of health care, and their introduction into the market in combination with synthetic medicines has resolved many health concerns. As a result, the extraction of plant secondary metabolites such as essential oils (EOs) through steam or hydro-distillation processes has witnessed significant progress over the years. EOs are a complex mixture of various chemical compounds; primarily characterized by volatility, aroma, and low molecular weight. The diverse biological properties of EOs arise from the differences in their chemical constitution and structure. EOs play important roles in defense against external agents and participate in signal transduction pathways. The biological properties of EOs are widely documented by a large body of literature, demonstrating their antitumor, antibioceptive, antiviral, antiphlogistic and antimicrobial activity in vitro. Furthermore, essential oils contain several chemical classes of compounds whose heterogeneity of active moieties can help prevent the development of drug resistance. Therefore, due to their low toxicity, good pharmacokinetics and multitarget action, EOs represent important alternatives to synthetic chemicals as promising drugs for therapeutic use.

The purpose of the 2nd edition of this Special Issue, entitled "Chemical composition and bioactivity of essential oils", is to continue to provide an update on the phytochemical composition of plant extracts and to analyze the bioactivity of essential oils or their components in different models, in vitro and/or in vivo, also taking into account the possibility of using new site-specific EO delivery strategies.

Major topics of interest include, but are not limited to, the following:

Extraction, isolation and characterization of bioactive compounds from plant extracts;
Evaluation of the antioxidant, antitumor and antimicrobial activity of essential oils or their constituents;
Evaluation of the activity of essential oils in multi-drug resistance models;
Evaluation of the benefits of using emerging technologies for the efficient delivery of EOs into target cells also in combination with conventional chemotherapy drugs.

Dr. Manuela Labbozzetta
Guest Editor

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Keywords

bioactive natural compounds
essential oils
chemical characterization
the essential oil mechanism of action
the biological activities in vitro and in vivo
antitumor
antimicrobials
antioxidant
EOs delivery strategies

Published Papers (7 papers)

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Research

23 pages, 2653 KiB

Open AccessArticle

The Repellent Capacity against Sitophilus zeamais (Coleoptera: Curculionidae) and In Vitro Inhibition of the Acetylcholinesterase Enzyme of 11 Essential Oils from Six Plants of the Caribbean Region of Colombia

by Amner Muñoz-Acevedo, María C. González, Jesús E. Alonso and Karen C. Flórez

Molecules 2024, 29(8), 1753; https://doi.org/10.3390/molecules29081753 - 12 Apr 2024

Viewed by 298

Abstract

The repellent capacity against Sitophilus zeamais and the in vitro inhibition on AChE of 11 essential oils, isolated from six plants of the northern region of Colombia, were assessed using a modified tunnel-type device and the Ellman colorimetric method, respectively. The results were as follows: (i) the degree of repellency (DR) of the EOs against S. zeamais was 20–68% (2 h) and 28–74% (4 h); (ii) the IC₅₀ values on AChE were 5–36 µg/mL; likewise, the %inh. on AChE (1 µg/cm³ per EO) did not show any effect in 91% of the EO tested; (iii) six EOs (Bursera graveolens—bark, B. graveolens—leaves, B. simaruba—bark, Peperomia pellucida—leaves, Piper holtonii (1b*)—leaves, and P. reticulatum—leaves) exhibited a DR (53–74%) ≥ C⁺ (chlorpyrifos—61%), while all EOs were less active (8–60-fold) on AChE compared to chlorpyrifos (IC₅₀ of 0.59 µg/mL). Based on the ANOVA/linear regression and multivariate analysis of data, some differences/similarities could be established, as well as identifying the most active EOs (five: B. simaruba—bark, Pep. Pellucida—leaves, P. holtonii (1b*)—leaves, B. graveolens—bark, and B. graveolens—leaves). Finally, these EOs were constituted by spathulenol (24%)/β-selinene (18%)/caryophyllene oxide (10%)—B. simaruba; carotol (44%)/dillapiole (21%)—Pep. pellucida; dillapiole (81% confirmed by ¹H-/¹³C-NMR)—P. holtonii; mint furanone derivative (14%)/mint furanone (14%)—B. graveolens—bark; limonene (17%)/carvone (10%)—B. graveolens—leaves. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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17 pages, 2704 KiB

Open AccessArticle

Pinus koraiensis Essential Oil Attenuates the Pathogenicity of Superbacteria by Suppressing Virulence Gene Expression

by Ji-Hee Kim, Young-Hoi Kim, Bog-Im Park, Na-Young Choi and Kang-Ju Kim

Molecules 2024, 29(1), 37; https://doi.org/10.3390/molecules29010037 - 20 Dec 2023

Cited by 1 | Viewed by 686

Abstract

In the quest to combat infections attributable to antibiotic-resistant superbacteria, an essential oil derived from the needles of Pinus koraiensis Sieb. et Zucc. (PKEO) has emerged as a promising solution. In this study, we demonstrate that PKEO can be used to inhibit the growth, glucose metabolite acidogenicity, and biofilm formation of methicillin-resistant Staphylococcus aureus (MRSA). Quantitative PCR analysis provided direct evidence that PKEO reduces the mRNA expression of the accessory gene regulator A (agrA) and staphylococcal accessory regulator A (sarA), thereby indicating its inhibitory effect on pathogenic regulatory genes. Chromatographic analyses of PKEO identified terpene hydrocarbons as prominent essential oil constituents. These compounds, notably α-pinene, limonene, and β-caryophyllene, have been established to have antimicrobial properties. Our findings indicate that an oil derived from P. koraiensis can effectively combat antibiotic-resistant strains by disrupting the pathogenicity regulatory system, thereby establishing PKEO as a promising candidate for the treatment of MRSA infections. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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12 pages, 2060 KiB

Open AccessArticle

Exploring the Larvicidal and Repellent Potential of Taurus Cedar (Cedrus libani) Tar against the Brown Dog Tick (Rhipicephalus sanguineus sensu lato)

by Samed Koc, Zeynep Nur Gultekin, Sevval Kahraman, Aysegul Cengiz, Burak Polat, Cansu Caliskan, Tolga Yildirim, Ozge Tufan-Cetin and Huseyin Cetin

Molecules 2023, 28(23), 7689; https://doi.org/10.3390/molecules28237689 - 21 Nov 2023

Cited by 1 | Viewed by 1007

Abstract

This study investigated the potential acaricidal and repellent effects of tar obtained from the Lebanon cedar (Cedrus libani A. Rich.) against the brown dog tick species Rhipicephalus sanguineus sensu lato Latreille (Acari: Ixodidae). The goal was to find an alternative, safe, and effective way to eliminate ticks. Tar is traditionally extracted from cedar trees in the Antalya region of Türkiye. The composition of the tar is primarily characterized by a diverse mixture of terpenes, with β-himachalene (29.16%), α-atlantone (28.7%), ar-turmerone (8.82%), longifolene-(V4) (6.66%), α-himachalene (5.28%), and β-turmerone (5.12%) emerging as the predominant constituents. The toxic effects of tar on tick larvae were studied through larval immersion tests (LIT), and its repellent activity was evaluated using a new larval repellent activity test (LRAT). The results revealed significant acaricidal effects, with mortality rates of 77.7% and 82.2% for the Konyaalti and Kepez strains of the brown dog tick, respectively, in response to a 1% concentration of tar. LC₅₀ and LC₉₀ values were determined as 0.47% and 1.52% for the Kepez strain and 0.58% and 1.63% for the Konyaalti strain, respectively. When comparing the repellent effect of tar to the widely used synthetic repellent DEET, repellency rates of up to 100% were observed. As a result, this study establishes, for the first time, the larvicidal and repellent effects of C. libani tar on ticks. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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22 pages, 11949 KiB

Open AccessArticle

Potential of Natural Phenolic Compounds as Antimicrobial Agents against Multidrug-Resistant Staphylococcus aureus in Chicken Meat

by Alaa Eldin M. A. Morshdy, Karima M. E. Abdallah, Heba E. Abdallah, Fahad D. Algahtani, Mohamed Tharwat Elabbasy, Suleman Atique, Khursheed Ahmad, Mohammad A. A. Al-Najjar, Hossam M. Abdallah and Abdallah Fikry A. Mahmoud

Molecules 2023, 28(18), 6742; https://doi.org/10.3390/molecules28186742 - 21 Sep 2023

Cited by 1 | Viewed by 1187

Abstract

Staphylococcus aureus is one of the most widespread foodborne bacteria that cause high morbidity, mortality, and economic loss, primarily if foodborne diseases are caused by pathogenic and multidrug-resistant (MDR) strains. This study aimed to determine the prevalence of S. aureus in chicken meat in Egyptian markets. Thus, this study might be the first to assess the efficiency of different natural phenolic compounds as novel antibacterial agents against MDR S. aureus pathogens isolated from raw chicken meat in the Egyptian market. The incidence and quantification of pathogenic S. aureus were detected in retail raw chicken meat parts (breast, thigh, fillet, and giblets). In total, 73 out of 80 (91.3%) of the chicken meat parts were contaminated, with S. aureus as the only species isolated. Of the 192 identified S. aureus isolates, 143 were coagulase-positive S. aureus and 117 isolates were MDR (81.8%, 117/143). Twenty-two antibiotic resistance profile patterns were detected. One strain was randomly selected from each pattern to further analyze virulence and resistance genes. Extracted DNA was assessed for the presence of antibiotic-resistance genes, i.e., vancomycin-resistance (vanA), aminoglycosides-resistance (aacA–aphD), apramycin-resistance (apmA), and methicillin-resistance (mecA), penicillin-resistance (blaZ), and virulence genes staphylococcal enterotoxins (sea and seb), Panton–Valentine leucocidin (pvl), clumping factor A (clfA), and toxic shock syndrome toxin (tst). Clustering analyses revealed that six S. aureus strains harbored the most virulence and resistance genes. The activity of hydroquinone was significantly higher than thymol, carvacrol, eugenol, and protocatechuic acid. Therefore, phenolic compounds, particularly hydroquinone, could potentially alternate with conventional antibiotics against the pathogenic MDR S. aureus inhabiting raw chicken meat. Hence, this study indicates that urgent interventions are necessary to improve hygiene for safer meat in Egyptian markets. Moreover, hydroquinone could be a natural phenolic compound for inhibiting foodborne pathogens. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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16 pages, 907 KiB

Open AccessArticle

Antioxidant and Antibacterial Activity of Mexican Oregano Essential Oil, Extracted from Plants Occurring Naturally in Semiarid Areas and Cultivated in the Field and Greenhouse in Northern Mexico

by Ruben I. Marin-Tinoco, Angie Tatiana Ortega-Ramírez, Maricela Esteban-Mendez, Oscar Silva-Marrufo, Laura E. Barragan-Ledesma, Luis M. Valenzuela-Núñez, Edwin A. Briceño-Contreras, Maria A. Sariñana-Navarrete, Abelardo Camacho-Luis and Cayetano Navarrete-Molina

Molecules 2023, 28(18), 6547; https://doi.org/10.3390/molecules28186547 - 09 Sep 2023

Cited by 2 | Viewed by 1569

Abstract

In recent years, the determination of the antioxidant and antibacterial activity of essential oils in wild plants, such as Mexican oregano (Lippia graveolens Kunth), has become increasingly important. The objective was to compare the antioxidant and antibacterial activity of Mexican oregano essential oil obtained from plants occurring naturally in semiarid areas (Wild1 and Wild2), and those cultivated in the field (CField) and greenhouse (CGreenhouse) in northern Mexico. The Mexican oregano essential oil extraction was performed using the hydrodistillation method, the antioxidant activity was determined using the ABTS method, and the antibacterial activity was assessed through bioassays under the microwell method at nine different concentrations. The aim was to determine the diameter of the inhibition zone and, consequently, understand the sensitivity level for four bacterial species. The results revealed an antioxidant activity ranging from 90% to 94% at the sampling sites, with Wild1 standing out for having the highest average antioxidant activity values. Likewise, six out of the nine concentrations analyzed showed some degree of sensitivity for all the sampling sites. In this regard, the 25 µL mL⁻¹ concentration showed the highest diameter of inhibition zone values, highlighting the Wild2 site, which showed an average diameter greater than 30 mm for the four bacteria tested. Only in the case of S. typhi did the CGreenhouse site surpass the Wild2, with an average diameter of the inhibition zone of 36.7 mm. These findings contribute to the search for new antioxidant and antibacterial options, addressing the challenges that humanity faces in the quest for opportunities to increase life expectancy. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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15 pages, 3599 KiB

Open AccessArticle

Yield, Chemical Composition and Bioactivity of Essential Oils from Common Juniper (Juniperus communis L.) from Different Spanish Origins

by Luis Saúl Esteban, Irene Mediavilla, Virginie Xavier, Joana S. Amaral, Tânia C. S. P. Pires, Ricardo C. Calhelha, César López and Lillian Barros

Molecules 2023, 28(11), 4448; https://doi.org/10.3390/molecules28114448 - 30 May 2023

Cited by 2 | Viewed by 1609

Abstract

Essential oils (EOs) obtained from Juniperus communis L. are frequently used in the production of bioproducts. However, there are no studies regarding industrial crops’ production, allowing for better control of the quality and production of juniper EOs. To select the plant material for developing future crops of this species in northern Spain, four locations where this shrub species grows in the wild were selected and samples of both genera were collected. The EOs were obtained by steam distillation, and their chemical composition and bioactivity were evaluated. The results showed that the yield of EOs from male and female samples were within the usual reported ranges, varying between 0.24 and 0.58% (dry basis, d.b.). However, limonene content in three locations varied between 15 and 25%, which is between 100% and 200% higher than the values usually reported for other European countries. The antibacterial activity was determined by broth microdilution and showed that gram-positive bacteria were more susceptible to the tested EOs since, in general, lower MIC values were obtained compared to gram-negatives. The EOs from location 1 (L1F) and 2 (L2M) inhibited the growth of six out of the eight clinical strains tested. Samples from location 1 were particularly effective, exhibiting MBC against two gram-negative (E. coli and P. mirabilis) and one gram-positive bacteria (E. faecalis). Moreover, the majority of the EOs tested showed anti-inflammatory activity. Cytotoxic effect has been demonstrated in tumor cell lines, with the best results observed against gastric carcinoma (AGS) cells (GI₅₀ between 7 to 77 µg/mL). Although generally presenting higher GI₅₀, most samples also inhibited the growth of non-tumoral cells, particularly hepatocytes (PLP2 cells). Therefore, its use for their anti-proliferative activity should consider specific conditions to avoid damaging normal cells. Finally, the results and conclusions obtained led to the selection of the female shrubs from location 1 (L1F) as the plant material to be propagated in order to produce plants for a future juniper crop. Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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9 pages, 721 KiB

Open AccessCommunication

Essential Oil Composition of Grindelia squarrosa from Southern Idaho

by Ambika Poudel, Noura S. Dosoky, Prabodh Satyal, Kathy Swor and William N. Setzer

Molecules 2023, 28(9), 3854; https://doi.org/10.3390/molecules28093854 - 02 May 2023

Cited by 2 | Viewed by 1448

Abstract

Grindelia squarrosa is an arid lands herb that has been used in Native American traditional medicine, is a potential source of pharmacologically active compounds, and has been explored as a source of biofuel. The purpose of this work was to examine the essential oil composition of G. squarrosa from southern Idaho. Gas chromatographic methods revealed the essential oil of G. squarrosa var. serrulata to be rich in monoterpenoids, α-pinene (21.9%), limonene (17.1%), terpinolene (10.6%), and borneol (6.5%). The essential oil composition of G. squarrosa from Idaho is similar to that previously reported from specimens collected from Montana and confirms the volatile phytochemistry of plants growing in North America. The major essential oil components were screened for antimicrobial activity against respiratory and dermal pathogens. (–)-β-Pinene showed strong antibacterial activity against Streptococcus pneumoniae (MIC 39.1 μg/mL) and (–)-borneol showed strong activity against Staphylococcus aureus (MIC 78.1 μg/mL). Full article

(This article belongs to the Special Issue Chemical Composition and Bioactivities of Essential Oils, 2nd Edition)

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