Application of Gas Chromatography to Detect Volatile Secondary Metabolites from Natural Products of Pharmacological Interest

A special issue of Pharmaceuticals (ISSN 1424-8247). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: closed (15 December 2022) | Viewed by 18023

Special Issue Editor

Special Issue Information

Dear Colleagues,

Secondary metabolites, so called because they are not involved in basic vital functions, are organic compounds produced by bacteria, fungi and plants whose main function is to mediate the interactions between plant and animal ecosystems, in addition to playing a role in the defense against external attack (e.g., protecting plants against herbivores). Secondary metabolites of plant origin are widely used in the aromatic, medical and pharmaceutical sectors. Indeed, the extensive pharmacological effects of medicinal plants depend primarily on their phytochemical constituents.

Generally, the secondary metabolites extracted from plants are complex mixtures of compounds classified according to their chemical structure. Since plant chemistry underlies the therapeutic uses of herbs, a good understanding of the chemical composition is essential for a better understanding of the possible medicinal value of the plant itself. Gas chromatographic analysis followed by mass spectrometry is suitable for the separation and identification of volatile secondary metabolites, which include various classes of compounds such as hydrocarbons, ketones, alcohols, aldehydes, esters, acids, aromatics, and components containing sulfur and nitrogen.

Dr. Stefania Garzoli
Guest Editor

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Keywords

  • natural products
  • GC and GC/MS
  • secondary metabolites
  • phytochemicals
  • medicinal plants
  • volatile compounds
  • chemical analyses

Published Papers (7 papers)

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Research

19 pages, 2354 KiB  
Article
Chemical Composition and Antimicrobial Potential of a Plant-Based Substance for the Treatment of Seborrheic Dermatitis
by Viktor A. Filatov, Olesya Yu. Kulyak and Elena I. Kalenikova
Pharmaceuticals 2023, 16(3), 328; https://doi.org/10.3390/ph16030328 - 21 Feb 2023
Cited by 5 | Viewed by 3207
Abstract
Seborrheic dermatitis (SD) is the most prevalent dermatological disease, occurring in up to 50% of newborns, children, and adults around the world. The antibacterial and antifungal resistance contributed to the search for new natural substances and the development of a novel substance based [...] Read more.
Seborrheic dermatitis (SD) is the most prevalent dermatological disease, occurring in up to 50% of newborns, children, and adults around the world. The antibacterial and antifungal resistance contributed to the search for new natural substances and the development of a novel substance based on Melaleuca alternifolia (M. alternifolia) leaf oil (TTO), 1,8-cineole (eucalyptol), and α-(-)-bisabolol. Thus, this work aimed to determine the chemical composition of the novel plant-based substance and to evaluate its antimicrobial activity against standard microorganisms involved in the pathogenesis of SD. Moreover, the chemical composition of the substance was analyzed by gas chromatography coupled with mass spectrometry (GC/MS). Staphylococcus epidermidis (S. epidermidis), Staphylococcus aureus (S. aureus), Micrococcus luteus (M. luteus), and Candida albicans (C. albicans) were used for antimicrobial and antifungal assays by means of the broth microdilution method to determine the minimal inhibitory concentration (MIC). Finally, the substance’s ability to inhibit Malassezia furfur (M. furfur) was evaluated. Eighteen compounds from different chemical groups were identified by GC/MS. The major biologically active compounds of the substance were terpinen-4-ol (20.88%), 1,8-cineole (22.28%), (-)-α-bisabolol (25.73%), and o-cymene (8.16%). The results showed that the substance has a synergistic antimicrobial and antifungal activity, while S. epidermidis and C. albicans strains were the most susceptible. Furthermore, the substance inhibited M. furfur, which is a main pathogen involved in the pathogenesis of SD and clinical manifestations. It can be concluded that the novel plant-based substance has a promising potential against M. furfur and scalp commensal bacteria and may be helpful for the development of new drugs for treatment of dandruff and SD. Full article
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17 pages, 3507 KiB  
Article
Synergistic and Antibiofilm Effects of the Essential Oil from Croton conduplicatus (Euphorbiaceae) against Methicillin-Resistant Staphylococcus aureus
by Genil Dantas de Oliveira, Wilma Raianny Vieira da Rocha, José Filipe Bacalhau Rodrigues and Harley da Silva Alves
Pharmaceuticals 2023, 16(1), 55; https://doi.org/10.3390/ph16010055 - 30 Dec 2022
Cited by 7 | Viewed by 2416
Abstract
Bacterial resistance refers to the ability of bacteria to resist the action of some antibiotics due to the development of adaptation and resistance mechanisms. It is a serious public health problem, especially for diseases caused by opportunistic bacteria. In this context, the search [...] Read more.
Bacterial resistance refers to the ability of bacteria to resist the action of some antibiotics due to the development of adaptation and resistance mechanisms. It is a serious public health problem, especially for diseases caused by opportunistic bacteria. In this context, the search for new drugs, used alone or in combination, appears as an alternative for the treatment of microbial infections, and natural products, such as essential oils, are important in this process due to their structural diversity, which increases the probability for antimicrobial action. The objective of this study was to extract and identify the chemical components of the essential oil from Croton conduplicatus (EOCC), to evaluate the antimicrobial activity, to investigate the effect of the interaction between the EOCC and different antibiotics and to evaluate its antibiofilm potential. The EOCC was obtained by hydrodistillation. Based on chemical characterisation, 70 compounds were identified, with 1.8 cineole (13.15%), p-cymene (10.68%), caryophyllene (9.73%) and spathulenol (6.36%) being the major constituents. The minimum inhibitory concentration (MIC) values of EOCC were 256 and 512 µg mL−1 for methicillin-sensitive and -resistant Staphylococcus aureus strains (MSSA and MRSA), respectively. The combinations of EOCC with the antibiotics oxacillin and ampicillin were synergistic (OXA/EOCC and AMP/EOCC combined decreased the OXA MIC and AMP MIC to 0.5 and 0.25 for MSSA, respectively, and OXA/EOCC and AMP/EOCC combined decreased the OXA MIC and the AMP MIC to 1 and 0.5 for MRSA, respectively) and could modify the resistance profile of MSSA and MRSA strains. The results indicated that EOCC was also able to partially inhibit biofilm formation. Our study presents important information about the chemical composition of EOCC and its antimicrobial potential and provides a reference to determine the mechanisms of action of EOCC and its use in pharmaceutical formulations. Full article
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10 pages, 638 KiB  
Article
The Essential Oil from the Resurrection Plant Myrothamnus moschatus Is Effective against Arthropods of Agricultural and Medical Interest
by Roman Pavela, Marta Ferrati, Eleonora Spinozzi, Filippo Maggi, Riccardo Petrelli, Rianasoambolanoro Rakotosaona, Renato Ricciardi and Giovanni Benelli
Pharmaceuticals 2022, 15(12), 1511; https://doi.org/10.3390/ph15121511 - 3 Dec 2022
Cited by 2 | Viewed by 2302
Abstract
This work aimed to evaluate the chemical composition, insecticidal and acaricidal potential of the essential oil (EO) obtained from the resurrection plant Myrothamnus moschatus (Baill.) Baill. (Myrothamnaceae) from Madagascar. The EO bioactivity was evaluated against selected arthropod pests and vectors of agricultural and [...] Read more.
This work aimed to evaluate the chemical composition, insecticidal and acaricidal potential of the essential oil (EO) obtained from the resurrection plant Myrothamnus moschatus (Baill.) Baill. (Myrothamnaceae) from Madagascar. The EO bioactivity was evaluated against selected arthropod pests and vectors of agricultural and public health relevance. The most abundant volatile compounds were trans-pinocarveol (37.7 ± 4.2%) and pinocarvone (20.8 ± 3.1%), similar to the EO of the chemotype collected from the same region. Lethal concentrations (LC50) or doses (LD50) from acute toxicity tests were estimated for Musca domestica (L.) adults at 22.7 µg adult−1, for Spodoptera littoralis (Boisduval) larvae at 35.6 µg larva−1, for Culex quinquefasciatus (Say) at 43.6 µg mL−1, for adults of Metopolophium dirhodum (Walker) at 2.4 mL L−1, and for adults of Tetranychus urticae (Koch) at 1.2 mL L−1. The good insecticidal and acaricidal activities determined in this work may open a new perspective on the use of this plant as a source of botanical insecticide ingredients. The exploitation of this species could also be important for the African economy, helping local farmers cultivating this plant. Full article
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17 pages, 2053 KiB  
Article
Hydrosols of Veronica Species—Natural Source of Free Volatile Compounds with Potential Pharmacological Interest
by Marija Nazlić, Karla Akrap, Dario Kremer and Valerija Dunkić
Pharmaceuticals 2022, 15(11), 1378; https://doi.org/10.3390/ph15111378 - 9 Nov 2022
Cited by 4 | Viewed by 1426
Abstract
In this study, free volatile compounds (FVCs) were isolated from the water fractions (hydrosols) of 10 Croatian Veronica species obtained by hydrodistillation (HD) and microwave-assisted extraction (MAE). The use of different isolation techniques is important for the analysis of the influence of extraction [...] Read more.
In this study, free volatile compounds (FVCs) were isolated from the water fractions (hydrosols) of 10 Croatian Veronica species obtained by hydrodistillation (HD) and microwave-assisted extraction (MAE). The use of different isolation techniques is important for the analysis of the influence of extraction conditions on the qualitative and quantitative composition of the isolated constituents. The composition of the hydrosols was analyzed using gas chromatography and mass spectrometry. The compounds β-ionone and benzene acetaldehyde were detected in all 10 Veronica hydrosols studied. E-caryophyllene was also identified in all isolates except the MAE isolate of V. arvensis L. Caryophyllene oxide was isolated in all isolates apart from the HD isolate of V. catenata Pennell. (E)-β-Damascenone is significantly present in all isolates except the MAE isolates of V. catanata and V. cymbalaria Bodard. In these two species, α-muurolol was identified in a high percentage. The same basic phytochemical constituents and compounds characteristic of a given Veronica species suggest the importance of further research. Antioxidant activity was tested for all extracts using two methods, ORAC and DPPH. Therefore, it is crucial to identify as many specialized metabolites from Veronica species as possible, especially hydrosols, which are natural products of potential pharmacological interest. Full article
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14 pages, 3602 KiB  
Article
Chemical Composition and Antimicrobial Potential of Essential Oil of Acritopappus confertus (Gardner) R.M.King & H.Rob. (Asteraceae)
by Rafael Pereira da Cruz, José Walber Gonçalves Castro, Débora Odília Duarte Leite, Natália Kelly Gomes de Carvalho, José Weverton Almeida-Bezerra, Raimundo Luiz Silva Pereira, Fázia Fernandes Galvão Rodrigues, José Jailson Lima Bezerra, Adrielle Rodrigues Costa, Edna Mori, Pablo Antonio Maia de Farias, Henrique Douglas Melo Coutinho, Maria Flaviana Bezerra Morais-Braga, Marcello Iriti, José Galberto Martins da Costa and Fabíola Fernandes Galvão Rodrigues
Pharmaceuticals 2022, 15(10), 1275; https://doi.org/10.3390/ph15101275 - 17 Oct 2022
Cited by 1 | Viewed by 2147
Abstract
Microbial resistance has become a worrying problem in recent decades after the abusive use of antibiotics causing the selection of resistant microorganisms. In order to circumvent such resistance, researchers have invested efforts in the search for promising natural substances, such as essential oils. [...] Read more.
Microbial resistance has become a worrying problem in recent decades after the abusive use of antibiotics causing the selection of resistant microorganisms. In order to circumvent such resistance, researchers have invested efforts in the search for promising natural substances, such as essential oils. Thus, the objective of this work was to determine the chemical composition of the essential oil of Acritopappus confertus leaves, to evaluate its intrinsic effect and its effects in combination with drugs against pathogenic fungi and bacteria, in addition to verifying the inhibition of virulence in Candida strains. To this end, the oil was verified by gas chromatography coupled with mass spectrometry (GC/MS). Candida strains were used for antifungal assays by means of the serial microdilution technique, in order to determine the average inhibitory concentration (IC50), and for the modification assays, sub-inhibitory concentrations (MIC/8) were used. Finally, the natural product’s ability to inhibit the formation of filamentous structures was evaluated. In antibacterial tests, the MIC of the oil against strains of Staphylococcus aureus and Escherichia coli and its modifying effects in association with gentamicin, erythromycin, and norfloxacin were determined. The major constituent of the essential oil was the monoterpene myrcene (54.71%). The results show that the essential oil has an antifungal effect, with C. albicans strains being the most susceptible. Furthermore, the oil can potentiate the effect of fluconazole against strains of C. tropicalis and C. albicans. Regarding its effect on micromorphology, the oil was also able to inhibit the filaments in all strains. In combination with antibiotics, the oil potentiated the drug’s action by reducing the MIC against E. coli and S. aureus. It can be concluded that the essential oil of A. confertus has potential against pathogenic fungi and bacteria, making it a target for the development of an antimicrobial drug. Full article
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15 pages, 1608 KiB  
Article
Antioxidant, Antibacterial, Enzyme Inhibitory, and Anticancer Activities and Chemical Composition of Alpinia galanga Flower Essential Oil
by Yufeng Tian, Xiaoyan Jia, Qinqin Wang, Tingya Lu, Guodong Deng, Minyi Tian and Ying Zhou
Pharmaceuticals 2022, 15(9), 1069; https://doi.org/10.3390/ph15091069 - 27 Aug 2022
Cited by 7 | Viewed by 2192
Abstract
Alpinia galanga is widely cultivated for its essential oil (EO), which has been used in cosmetics and perfumes. Previous studies of A. galanga focussed mostly on the rhizome but seldom on the flower. Therefore, this study was designed to identify the chemical composition [...] Read more.
Alpinia galanga is widely cultivated for its essential oil (EO), which has been used in cosmetics and perfumes. Previous studies of A. galanga focussed mostly on the rhizome but seldom on the flower. Therefore, this study was designed to identify the chemical composition of A. galanga flower EO and firstly estimate its antioxidant, antibacterial, enzyme inhibitory, and anticancer activities. According to the results of the gas chromatography with flame ionization or mass selective detection (GC-FID/MS) analysis, the most abundant component of the EO was farnesene (64.3%), followed by farnesyl acetate (3.6%), aceteugenol (3.2%), eugenol (3.1%), E-nerolidol (2.9%), decyl acetate (2.4%), octyl acetate (2.0%), sesquirosefuran (1.9%), (E)-β-farnesene (1.7%), and germacrene D (1.5%). For the bioactivities, the EO exhibited moderate DPPH and ABTS radical scavenging effects with IC50 values of 138.62 ± 3.07 μg/mL and 40.48 ± 0.49 μg/mL, respectively. Moreover, the EO showed strong-to-moderate antibacterial activities with various diameter of inhibition zone (DIZ) (8.79–14.32 mm), minimal inhibitory concentration (MIC) (3.13–6.25 mg/mL), and minimal bactericidal concentration (MBC) (6.25–12.50 mg/mL) values against Staphylococcus aureus, Bacillus subtilis, Enterococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, and Proteus vulgaris. Interestingly, the EO possessed remarkable α-glucosidase inhibition (IC50 = 0.16 ± 0.03 mg/mL), which was equivalent to that of the positive control acarbose (IC50 = 0.15 ± 0.01 mg/mL) (p > 0.05). It showed moderate tyrosinase inhibition (IC50 = 0.62 ± 0.09 mg/mL) and weak inhibitory activity on acetylcholinesterase (AChE) (IC50 = 2.49 ± 0.24 mg/mL) and butyrylcholinesterase (BChE) (IC50 = 10.14 ± 0.59 mg/mL). Furthermore, the EO exhibited considerable selective cytotoxicity to K562 cells (IC50 = 41.55 ± 2.28 μg/mL) and lower cytotoxicity to non-cancerous L929 cells (IC50 = 120.54 ± 8.37 μg/mL), and it induced K562 cell apoptosis in a dose-dependent manner. Hence, A. galanga flower EO could be regarded as a bioactive natural product with great application potential in the pharmaceutical field. Full article
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20 pages, 11582 KiB  
Article
Hemp (Cannabis sativa L., Kompolti cv.) and Hop (Humulus lupulus L., Chinook cv.) Essential Oil and Hydrolate: HS-GC-MS Chemical Investigation and Apoptotic Activity Evaluation
by Elisa Ovidi, Valentina Laghezza Masci, Anna Rita Taddei, Jacopo Torresi, William Tomassi, Matteo Iannone, Antonio Tiezzi, Filippo Maggi and Stefania Garzoli
Pharmaceuticals 2022, 15(8), 976; https://doi.org/10.3390/ph15080976 - 8 Aug 2022
Cited by 9 | Viewed by 2880
Abstract
In this study, essential oils (EOs) and hydrolates (Hys) from Italian hemp (Cannabis sativa L. Kompolti cv.) and hop (Humulus Lupulus L., Chinook cv.) supply chains were chemically characterized and tested to investigate their apoptotic potential for the first time. Headspace–Gas [...] Read more.
In this study, essential oils (EOs) and hydrolates (Hys) from Italian hemp (Cannabis sativa L. Kompolti cv.) and hop (Humulus Lupulus L., Chinook cv.) supply chains were chemically characterized and tested to investigate their apoptotic potential for the first time. Headspace–Gas Chromatography–Mass Spectrometry (HS-GC-MS) techniques were performed to describe their volatile chemical profile, highlighting a composition rich in terpene derivatives such as monoterpenes and sesquiterpenes among which β-myrcene, limonene, β-caryophyllene and α-humulene were the main constituents of EOs; in contrast, linalool, cis-p-menth-2,8-dien-1-ol, terpinen-4-ol, α-terpineol, caryophyllene oxide, and τ-cadinol were found in the Hys. The cytotoxicity activity on human leukemia cells (HL60), human neuroblastoma cells (SH-SY5Y), human metastatic adenocarcinoma breast cells (MCF7), human adenocarcinoma breast cells (MDA), and normal breast epithelial cell (MCF10A) for the EOs and Hys was studied by MTT assay and cytofluorimetric analysis and scanning and transmission electron microscopy were performed to define ultrastructural changes and the mechanism of cells death for HL 60 cells. An induction of the apoptotic mechanism was evidenced for hemp and hop EOs after treatment with the corresponding EC50 dose. In addition, TEM and SEM investigations revealed typical characteristics induced by the apoptotic pathway. Therefore, thanks to the integration of the applied methodologies with the used techniques, this work provides an overview on the metabolomic profile and the apoptotic potential of hemp and hop EOs and, for the first time, also of Hys. The findings of this preliminary study confirm that the EOs and Hys from Cannabis and Humulus species are sources of bioactive molecules with multiple biological effects yet to be explored. Full article
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