Antimicrobial Activity of Plant-Derived Products and Synthetic Derivatives

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Plant-Derived Antibiotics".

Deadline for manuscript submissions: closed (28 February 2022) | Viewed by 74065

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Department of Chemistry, University of Patras, GR-26504 Rion, Patras, Greece
Interests: discovery and development of small organic molecules and of natural product analogues or derivatives with anticancer, antibacterial and antiparasitic activity; synthesis of multitarget inhibitors and of hybrids or bioconjugates aiming at improvement of the pharmacological profile of one or more bioactive molecules
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Universidad del Bio Bio, Chillan, Chile
Interests: Agricultural and Biological Sciences • Pharmacology, Toxicology and Pharmaceutics • Biochemistry, Genetics and Molecular Biology • Medicine • Chemistry • Chemical Engineering • Environmental Science • Materials Science • Health Professions • Neuroscience •
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Fine Chemicals and Natural Products Laboratory, CIDIE CONICET—Universidad Católica de Córdoba, Córdoba, Argentina
Interests: plant-derived products; antibacterial activity; anticancer activity; enzyme inhibitors; inhibitors of MDR efflux pumps; bioguided isolation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The management of bacterial infections is a great challenge for therapeutics, particularly because of the increasing emergence of microorganisms with multiresistance to antibiotics, a phenomenon with important implications for morbidity and mortality. Even though the number of drugs currently used in clinical practice of infectious diseases is high, the development of resistance necessitates the discovery of new effective agents. Natural products have been an endless source of compounds with great structural diversity, showing various modes of action against resistant microorganisms. The enormous potential of plant-derived products for providing new and active chemical entities encourages scientists to continue searching for them. These structures will enrich natural product libraries to be used for the discovery of lead compounds and the development of drug candidates for successful therapies against resistant organisms.

This Special Issue intends to collect cutting-edge research and review works illustrating the potential of extracts and active principles obtained from plants, as well as derivatives therefrom against microorganisms, with special attention to those with resistant phenotypes, and it also aims to bring together pharmacognosists, chemists, pharmacologists, toxicologists, biologists, computer-aided drug design scientists, and clinicians working as a multidisciplinary team in the area of natural products.

Dr. Constantinos M. Athanassopoulos
Prof. Carlos L. Cespedes Acuña
Prof. María Cecilia Carpinella
Guest Editors

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Keywords

  • plant extracts
  • plant-derived compounds
  • antibacterial activity
  • antifungal activity
  • resistant strains
  • synthetic natural product derivatives
  • multidrug resistance

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Published Papers (22 papers)

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11 pages, 477 KiB  
Article
Fabrication and Evaluation of W/O Emulsion Loaded with Linum usitatissimum Seeds Extract for Anti-Leishmaniasis Efficacy
by Barkat Ali Khan, Sumera Faiz, Muhammad Khalid Khan, Farid Menaa, Neli-Kinga Olah, Yosif Almoshari, Jawaher Abdullah Alamoudi and Saud Almawash
Antibiotics 2022, 11(4), 432; https://doi.org/10.3390/antibiotics11040432 - 23 Mar 2022
Viewed by 2012
Abstract
Leishmaniasis, remains a serious health problem in many developing countries with thousands of new cases recorded annually. Novel therapies are required as existing treatment regimens are limited by their high cost, high toxicity, increased parasite resistance, patient’s intolerance, and invasive means of long-duration [...] Read more.
Leishmaniasis, remains a serious health problem in many developing countries with thousands of new cases recorded annually. Novel therapies are required as existing treatment regimens are limited by their high cost, high toxicity, increased parasite resistance, patient’s intolerance, and invasive means of long-duration administration. With several studies reporting the anti-leishmaniasis promise of medicinal plants, interest in plants and herbal drugs is attracting much attention worldwide. In this pilot study, we analysed extracts of Linum usitatissimum seeds (LU) to identify essential phytochemicals and test their activity against cutaneous leishmaniasis both in-vitro and in-vivo. We performed phytochemical screening of LU seeds extract as well as its in-vitro leishmanicidal and anti-amastigote assays. Water-in-oil cream containing 10% LU crude extract (10 mg/mL) was then prepared. The stability of the cream was evaluated for 28 days at 8 °C, 25 °C and 40 °C. In-vivo efficacy and safety of the cream was performed in 26 patients with cutaneous leishmaniasis who agreed to participate voluntarily in the study. The active treatment period lasted for 3 weeks, while the follow-up period was extended to 4 months. During the active study period, images of skin lesions were taken before and after treatment. Analyses of LU seeds extract confirmed the presence of terpenoids, flavonoids, tannins, alkaloids, and polyphenols. In-vitro studies showed significant activity against promastigote and intracellular amastigote forms of Leishmaniamajor. The cream was pharmaceutically stable, although some minor changes were noticed in relation to its physical characteristics. In-vivo assessment of the cream showed a 69.23% cure rate with no side effects, allergy, or irritation. We conclude that our newly developed water in oil cream containing 10% LU seeds extract could be an effective and safe topical anti-leishmanial medication for patients with CL. Full article
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15 pages, 2167 KiB  
Article
Inhibition of MurA Enzyme from Escherichia coli and Staphylococcus aureus by Diterpenes from Lepechinia meyenii and Their Synthetic Analogs
by Macarena Funes Chabán, Martina Hrast, Rok Frlan, Dafni G. Graikioti, Constantinos M. Athanassopoulos and María Cecilia Carpinella
Antibiotics 2021, 10(12), 1535; https://doi.org/10.3390/antibiotics10121535 - 15 Dec 2021
Cited by 10 | Viewed by 3537
Abstract
Enzymes MurA and MurF, involved in bacterial cell wall synthesis, have been validated as targets for the discovery of novel antibiotics. A panel of plant-origin antibacterial diterpenes and synthetic analogs derived therefrom were investigated for their inhibitory properties on these enzymes from Escherichia [...] Read more.
Enzymes MurA and MurF, involved in bacterial cell wall synthesis, have been validated as targets for the discovery of novel antibiotics. A panel of plant-origin antibacterial diterpenes and synthetic analogs derived therefrom were investigated for their inhibitory properties on these enzymes from Escherichia coli and Staphylococcus aureus. Six compounds were proven to be effective for inhibiting MurA from both bacteria, with IC50 values ranging from 1.1 to 25.1 µM. To further mechanistically investigate the nature of binding and to explain the activity, these compounds were docked into the active site of MurA from E. coli. The aromatic ring of the active compounds showed a T-shaped π–π interaction with the phenyl ring of Phe328, and at least one hydrogen bond was formed between the hydroxy groups and Arg120 and/or Arg91. The results disclosed here establish new chemical scaffolds for the development of novel entities targeting MurA as potential antibiotics to combat the threat of pathogenic bacteria, particularly resistant strains. Full article
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10 pages, 1888 KiB  
Article
Antifungal Nanoformulation for Biocontrol of Tomato Root and Crown Rot Caused by Fusarium oxysporum f. sp. radicis-lycopersici
by Ricardo Aravena, Ximena Besoain, Natalia Riquelme, Aldo Salinas, Miryam Valenzuela, Eduardo Oyanedel, Wilson Barros, Yusser Olguin, Alejandro Madrid, Matias Alvear and Iván Montenegro
Antibiotics 2021, 10(9), 1132; https://doi.org/10.3390/antibiotics10091132 - 20 Sep 2021
Cited by 4 | Viewed by 3285
Abstract
Tomatoes (Solanum lycopersicum L.) are the most cultivated and important vegetable crop in the world. These plants can wilt during crop growth due to fusarium wilt (fusariosis), a disease that damages tomato vascular systems. The Fusarium isolated and analyzed in this work [...] Read more.
Tomatoes (Solanum lycopersicum L.) are the most cultivated and important vegetable crop in the world. These plants can wilt during crop growth due to fusarium wilt (fusariosis), a disease that damages tomato vascular systems. The Fusarium isolated and analyzed in this work correspond to Fusarium oxysporum f. sp. radicis-lycopersici. The isolates were molecularly identified, and analysis was done on the in vitro effects of the nanoemulsions (previously obtained from extracts of Chilean medicinal plants of the genera Psoralea and Escallonia) to inhibit mycelial and conidial germination of the isolates. Subsequently, the nanoemulsions were evaluated under greenhouse conditions for preventive control of fusariosis in the root and crown, with high levels of disease control observed using the highest concentrations of these nanoemulsions, at 250 and 500 ppm. Full article
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11 pages, 992 KiB  
Communication
In Vitro Antifungal Activity and Toxicity of Dihydrocarvone-Hybrid Derivatives against Monilinia fructicola
by Katy Díaz, Enrique Werner, Ximena Besoain, Susana Flores, Viviana Donoso, Bastian Said, Nelson Caro, Ernesto Vega, Iván Montenegro and Alejandro Madrid
Antibiotics 2021, 10(7), 818; https://doi.org/10.3390/antibiotics10070818 - 6 Jul 2021
Viewed by 2236
Abstract
The aim of this study was to synthesize a series of novel and known dihydrocarvone-hybrid derivatives (29) and to evaluate mycelial growth activity of hybrid molecules against two strains of Monilinia fructicola, as well as their toxicity. Dihydrocarvone-hybrid [...] Read more.
The aim of this study was to synthesize a series of novel and known dihydrocarvone-hybrid derivatives (29) and to evaluate mycelial growth activity of hybrid molecules against two strains of Monilinia fructicola, as well as their toxicity. Dihydrocarvone-hybrid derivatives have been synthesized under sonication conditions and characterized by FTIR, NMR, and HRMS. Antifungal efficacy against both strains of M. fructicola was determined by half maximal effective concentration (EC50) and toxicity using the brine shrimp lethality test (BSLT). Among the synthesized compounds, 7 and 8 showed the best activity against both strains of M. fructicola with EC50 values of 148.1 and 145.9 µg/mL for strain 1 and 18.1 and 15.7 µg/mL for strain 2, respectively, compared to BC 1000® (commercial organic fungicide) but lower than Mystic® 520 SC. However, these compounds showed low toxicity values, 910 and 890 µg/mL, respectively, compared to Mystic® 520 SC, which was highly toxic. Based on the results, these hybrid compounds could be considered for the development of more active, less toxic, and environmentally friendly antifungal agents against phytopathogenic fungi. Full article
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11 pages, 737 KiB  
Article
Preparation and Characterization of Bio-Nanocomposites Film of Chitosan and Montmorillonite Incorporated with Ginger Essential Oil and Its Application in Chilled Beef Preservation
by Yin-Ping Zhang, Xin Wang, Yi Shen, Kiran Thakur, Jian-Guo Zhang, Fei Hu and Zhao-Jun Wei
Antibiotics 2021, 10(7), 796; https://doi.org/10.3390/antibiotics10070796 - 30 Jun 2021
Cited by 21 | Viewed by 2763
Abstract
In this study, bio-nanocomposite films containing different proportions of ginger essential oil (GEO), chitosan (Ch), and montmorillonite (MMT) were prepared and characterized, and the antibacterial effect of bio-nanocomposite films on chilled beef was evaluated. Fourier transform infrared analysis showed a series of intense [...] Read more.
In this study, bio-nanocomposite films containing different proportions of ginger essential oil (GEO), chitosan (Ch), and montmorillonite (MMT) were prepared and characterized, and the antibacterial effect of bio-nanocomposite films on chilled beef was evaluated. Fourier transform infrared analysis showed a series of intense interactions among the components of the bio-nanocomposite films. The infiltration of GEO increased the thickness of the film, reduced the tensile strength of the film, and increased the percentage of breaking elongation and the water vapor permeability. The migration of phenols in the films began to increase exponentially and reached equilibrium at about 48 h. The bio-nanocomposite films (Ch +0.5% GEO group, and Ch + MMT + 0.5% GEO group) effectively delayed the rise of pH, hue angle, and moisture values of chilled beef with time and slowed down the lipid oxidation and the growth of surface microorganisms on chilled beef. Altogether, the prepared biological nanocomposites can be used as promising materials to replace commercial and non-degradable plastic films. Full article
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27 pages, 3340 KiB  
Article
South Africa’s Best BARK Medicines Prescribed at the Johannesburg Muthi Markets for Skin, Gut, and Lung Infections: MIC’s and Brine Shrimp Lethality
by Gugulethu P. Khumalo, Nicholas J. Sadgrove, Sandy F. Van Vuuren and Ben-Erik Van Wyk
Antibiotics 2021, 10(6), 681; https://doi.org/10.3390/antibiotics10060681 - 7 Jun 2021
Cited by 6 | Viewed by 3898
Abstract
Indigenous trade of medicinal plants in South Africa is a multi-million-rand industry and is still highly relevant in terms of primary health care. The purpose of this study was to identify today’s most traded medicinal barks, traditionally and contemporaneously used for dermatological, gastrointestinal, [...] Read more.
Indigenous trade of medicinal plants in South Africa is a multi-million-rand industry and is still highly relevant in terms of primary health care. The purpose of this study was to identify today’s most traded medicinal barks, traditionally and contemporaneously used for dermatological, gastrointestinal, and respiratory tract infections; then, to investigate the antimicrobial activity and toxicity of the respective extracts and interpret outcomes in light of pharmacokinetics. Thirty-one popularly traded medicinal barks were purchased from the Faraday and Kwa Mai-Mai markets in Johannesburg, South Africa. Information on the medicinal uses of bark-based medicines in modern commerce was recorded from randomly selected traders. The minimum inhibitory concentration (MIC) method was used for antimicrobial screening, and brine shrimp lethality was used to determine toxicity. New medicinal uses were recorded for 14 bark species. Plants demonstrating some broad-spectrum activities against tested bacteria include Elaeodendron transvaalense, Erythrina lysistemon, Garcinia livingstonei, Pterocelastrus rostratus, Rapanea melanophloeos, Schotia brachypetala, Sclerocarya birrea, and Ziziphus mucronata. The lowest MIC value of 0.004 mg/mL was observed against Staphylococcus epidermidis for a dichloromethane bark extract of E. lysistemon. The tested medicinal barks were shown to be non-toxic against the Artemia nauplii (brine shrimp) bioassay, except for a methanol extract from Trichilia emetica (69.52% mortality). Bacterial inhibition of bark extracts with minimal associated toxicity is consistent with the safety and valuable use of medicinal barks for local muthi market customers. Antimicrobial outcomes against skin and gastrointestinal pathogens are feasible because mere contact-inhibition is required in vivo; however, MIC values against respiratory pathogens require further explaining from a pharmacokinetics or pharmacodynamics perspective, particularly for ingested rather than smoked therapies. Full article
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23 pages, 3002 KiB  
Article
In Silico and In Vitro Screening of Antipathogenic Properties of Melianthus comosus (Vahl) against Pseudomonas aeruginosa
by Itumeleng T. Baloyi, Idowu J. Adeosun, Abdullahi A. Yusuf and Sekelwa Cosa
Antibiotics 2021, 10(6), 679; https://doi.org/10.3390/antibiotics10060679 - 5 Jun 2021
Cited by 12 | Viewed by 2935
Abstract
Bacterial quorum sensing (QS) system regulates pathogenesis, virulence, and biofilm formation, and together they contribute to nosocomial infections. Opportunistic pathogens, such as Pseudomonas aeruginosa, rely on QS for regulating virulence factors. Therefore, blocking the QS system may aid management of various infectious [...] Read more.
Bacterial quorum sensing (QS) system regulates pathogenesis, virulence, and biofilm formation, and together they contribute to nosocomial infections. Opportunistic pathogens, such as Pseudomonas aeruginosa, rely on QS for regulating virulence factors. Therefore, blocking the QS system may aid management of various infectious diseases caused by human pathogens. Plant secondary metabolites can thwart bacterial colonization and virulence. As such, this study was undertaken to evaluate three extracts from the medicinal plant, Melianthus comosus, from which phytochemical compounds were identified with potential to inhibit QS-dependent virulence factors in P. aeruginosa. Chemical profiling of the three extracts identified 1,2-benzene dicarboxylic acid, diethyl ester, neophytadiene and hexadecanoic acid as the common compounds. Validation of antibacterial activity confirmed the same MIC values of 0.78 mg/mL for aqueous, methanol and dichloromethane extracts while selected guanosine showed MIC 0.031 mg/mL. Molecular docking analysis showed anti-quorum sensing (AQS) potential of guanosine binding to CviR’ and 2UV0 proteins with varying docking scores of −5.969 and −8.376 kcal/mol, respectively. Guanosine inhibited biofilm cell attachment and biofilm development at 78.88% and 34.85%, respectively. Significant swimming and swarming motility restriction of P. aeruginosa were observed at the highest concentration of plant extracts and guanosine. Overall, guanosine revealed the best swarming motility restrictions. M. comosus extracts and guanosine have shown clear antibacterial effects and subsequent reduction of QS-dependent virulence activities against P.aeruginosa. Therefore, they could be ideal candidates in the search for antipathogenic drugs to combat P.aeruginosa infections. Full article
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10 pages, 1346 KiB  
Article
Diffusible Compounds Produced by Hanseniaspora osmophila and Gluconobacter cerinus Help to Control the Causal Agents of Gray Rot and Summer Bunch Rot of Table Grapes
by Matías Olivera, Ninoska Delgado, Fabiola Cádiz, Natalia Riquelme, Iván Montenegro, Michael Seeger, Guillermo Bravo, Wilson Barros-Parada, Romina Pedreschi and Ximena Besoain
Antibiotics 2021, 10(6), 664; https://doi.org/10.3390/antibiotics10060664 - 2 Jun 2021
Cited by 7 | Viewed by 2985
Abstract
Gray and summer bunch rot are important diseases of table grapes due to the high economic and environmental cost of their control with synthetic fungicides. The ability to produce antifungal compounds against the causal agents Botrytis, Aspergillus, Penicillium, and Rhizopus [...] Read more.
Gray and summer bunch rot are important diseases of table grapes due to the high economic and environmental cost of their control with synthetic fungicides. The ability to produce antifungal compounds against the causal agents Botrytis, Aspergillus, Penicillium, and Rhizopus of two microorganisms isolated from table grapes and identified as Hanseniaspora osmophila and Gluconobacter cerinus was evaluated. In dual cultures, both biocontrol agents (together and separately) inhibited in vitro mycelial growth of these pathogens. To identify the compounds responsible for the inhibitory effect, extractions were carried out with organic solvents from biocontrol agents separately. Through dual cultures with pathogens and pure extracts, only the hexane extract from H. osmophila showed an inhibitory effect against Botrytis cinerea. To further identify these compounds, the direct bioautography technique was used. This technique made it possible to determine the band displaying antifungal activity at Rf = 0.05–0.2. The compounds present in this band were identified by GC-MS and compared to the NIST library. The most abundant compounds, not previously reported, corresponded to alkanes, ketones, alcohols, and terpenoids. H. osmophila and G. cerinus have the potential to control the causal agents of gray and summer bunch rot of table grapes. Full article
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19 pages, 3936 KiB  
Article
Volatile Organic Compounds (VOCs) Produced by Gluconobacter cerinus and Hanseniaspora osmophila Displaying Control Effect against Table Grape-Rot Pathogens
by Ninoska Delgado, Matías Olivera, Fabiola Cádiz, Guillermo Bravo, Iván Montenegro, Alejandro Madrid, Claudia Fuentealba, Romina Pedreschi, Eduardo Salgado and Ximena Besoain
Antibiotics 2021, 10(6), 663; https://doi.org/10.3390/antibiotics10060663 - 1 Jun 2021
Cited by 16 | Viewed by 3876
Abstract
Table grapes (Vitis vinifera) are affected by botrytis bunch rot and summer bunch rot, the latter a complex disease caused by Botrytis cinerea, Aspergillus spp., Penicillium expansum and Rhizopus stolonifer. To search for biocontrol alternatives, a new bioproduct composed [...] Read more.
Table grapes (Vitis vinifera) are affected by botrytis bunch rot and summer bunch rot, the latter a complex disease caused by Botrytis cinerea, Aspergillus spp., Penicillium expansum and Rhizopus stolonifer. To search for biocontrol alternatives, a new bioproduct composed of Gluconobacter cerinus and Hanseniaspora osmophila, a consortium called PUCV-VBL, was developed for the control of fungal rots in table grapes. Since this consortium presents new biocontrol species, the effect of their VOCs (volatile organic compounds) was evaluated under in vitro and in vivo conditions. The VOCs produced by the PUCV-VBL consortium showed the highest mycelial inhibition against Botrytis cinerea (86%). Furthermore, H. osmophila was able to inhibit sporulation of A. tubingensis and P. expansum. VOCs’ effect in vivo was evaluated using berries from Red Globe, Thompson Seedless and Crimson Seedless grapes cultivars, demonstrating a mycelial inhibition by VOCs greater than 70% for all evaluated fungal species. The VOC identification of the PUCV-VBL consortium was analyzed by solid-phase microextraction coupled to gas chromatography-mass spectrometry (SPME-GCMS). A total 26 compounds were identified, including 1-butanol 3-methyl, propanoic acid ethyl ester, ethyl acetate, phenylethyl alcohol, isobutyl acetate and hexanoic acid ethyl ester. Our results show that VOCs are an important mode of action of the PUCV-VBL biological consortium. Full article
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15 pages, 5862 KiB  
Article
Rhodomyrtone Accumulates in Bacterial Cell Wall and Cell Membrane and Inhibits the Synthesis of Multiple Cellular Macromolecules in Epidemic Methicillin-Resistant Staphylococcus aureus
by Ozioma F. Nwabor, Sukanlaya Leejae and Supayang P. Voravuthikunchai
Antibiotics 2021, 10(5), 543; https://doi.org/10.3390/antibiotics10050543 - 7 May 2021
Cited by 6 | Viewed by 2371
Abstract
As the burden of antibacterial resistance worsens and treatment options become narrower, rhodomyrtone—a novel natural antibiotic agent with a new antibacterial mechanism—could replace existing antibiotics for the treatment of infections caused by multi-drug resistant Gram-positive bacteria. In this study, rhodomyrtone was detected within [...] Read more.
As the burden of antibacterial resistance worsens and treatment options become narrower, rhodomyrtone—a novel natural antibiotic agent with a new antibacterial mechanism—could replace existing antibiotics for the treatment of infections caused by multi-drug resistant Gram-positive bacteria. In this study, rhodomyrtone was detected within the cell by means of an easy an inexpensive method. The antibacterial effects of rhodomyrtone were investigated on epidemic methicillin-resistant Staphylococcus aureus. Thin-layer chromatography demonstrated the entrapment and accumulation of rhodomyrtone within the bacterial cell wall and cell membrane. The incorporation of radiolabelled precursors revealed that rhodomyrtone inhibited the synthesis of macromolecules including DNA, RNA, proteins, the cell wall, and lipids. Following the treatment with rhodomyrtone at MIC (0.5–1 µg/mL), the synthesis of all macromolecules was significantly inhibited (p ≤ 0.05) after 4 h. Inhibition of macromolecule synthesis was demonstrated after 30 min at a higher concentration of rhodomyrtone (4× MIC), comparable to standard inhibitor compounds. In contrast, rhodomyrtone did not affect lipase activity in staphylococci—both epidemic methicillin-resistant S. aureus and S. aureus ATCC 29213. Interfering with the synthesis of multiple macromolecules is thought to be one of the antibacterial mechanisms of rhodomyrtone. Full article
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18 pages, 10789 KiB  
Article
Involvement of a Multidrug Efflux Pump and Alterations in Cell Surface Structure in the Synergistic Antifungal Activity of Nagilactone E and Anethole against Budding Yeast Saccharomyces cerevisiae
by Yuki Ueda, Yuhei O. Tahara, Makoto Miyata, Akira Ogita, Yoshihiro Yamaguchi, Toshio Tanaka and Ken-ichi Fujita
Antibiotics 2021, 10(5), 537; https://doi.org/10.3390/antibiotics10050537 - 6 May 2021
Cited by 6 | Viewed by 2620
Abstract
Nagilactone E, an antifungal agent derived from the root bark of Podocarpus nagi, inhibits 1,3-β glucan synthesis; however, its inhibitory activity is weak. Anethole, the principal component of anise oil, enhances the antifungal activity of nagilactone E. We aimed to determine the [...] Read more.
Nagilactone E, an antifungal agent derived from the root bark of Podocarpus nagi, inhibits 1,3-β glucan synthesis; however, its inhibitory activity is weak. Anethole, the principal component of anise oil, enhances the antifungal activity of nagilactone E. We aimed to determine the combinatorial effect and underlying mechanisms of action of nagilactone E and anethole against the budding yeast Saccharomyces cerevisiae. Analyses using gene-deficient strains showed that the multidrug efflux pump PDR5 is associated with nagilactone E resistance; its transcription was gradually restricted in cells treated with the drug combination for a prolonged duration but not in nagilactone-E-treated cells. Green-fluorescent-protein-tagged Pdr5p was intensively expressed and localized on the plasma membrane of nagilactone-E-treated cells but not in drug-combination-treated cells. Quick-freeze deep-etch electron microscopy revealed the smoothening of intertwined fiber structures on the cell surface of drug-combination-treated cells and spheroplasts, indicating a decline in cell wall components and loss of cell wall strength. Anethole enhanced the antifungal activity of nagilactone E by enabling its retention within cells, thereby accelerating cell wall damage. The combination of nagilactone E and anethole can be employed in clinical settings as an antifungal, as well as a food preservative to restrict food spoilage. Full article
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13 pages, 6086 KiB  
Article
Sinapic Acid Suppresses SARS CoV-2 Replication by Targeting Its Envelope Protein
by Raha Orfali, Mostafa E. Rateb, Hossam M. Hassan, Mona Alonazi, Mokhtar R. Gomaa, Noura Mahrous, Mohamed GabAllah, Ahmed Kandeil, Shagufta Perveen, Usama Ramadan Abdelmohsen and Ahmed M. Sayed
Antibiotics 2021, 10(4), 420; https://doi.org/10.3390/antibiotics10040420 - 11 Apr 2021
Cited by 32 | Viewed by 3678
Abstract
SARS CoV-2 is still considered a global health issue, and its threat keeps growing with the emergence of newly evolved strains. Despite the success in developing some vaccines as a protective measure, finding cost-effective treatments is urgent. Accordingly, we screened a number of [...] Read more.
SARS CoV-2 is still considered a global health issue, and its threat keeps growing with the emergence of newly evolved strains. Despite the success in developing some vaccines as a protective measure, finding cost-effective treatments is urgent. Accordingly, we screened a number of phenolic natural compounds for their in vitro anti-SARS CoV-2 activity. We found sinapic acid (SA) selectively inhibited the viral replication in vitro with an half-maximal inhibitory concentration (IC50) value of 2.69 µg/mL with significantly low cytotoxicity (CC50 = 189.3 µg/mL). Subsequently, we virtually screened all currently available molecular targets using a multistep in silico protocol to find out the most probable molecular target that mediates this compound’s antiviral activity. As a result, the viral envelope protein (E-protein) was suggested as the most possible hit for SA. Further in-depth molecular dynamic simulation-based investigation revealed the essential structural features of SA antiviral activity and its binding mode with E-protein. The structural and experimental results presented in this study strongly recommend SA as a promising structural motif for anti-SARS CoV-2 agent development. Full article
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15 pages, 1017 KiB  
Article
Evaluation of the Antimicrobial Activity of Some Components of the Essential Oils of Plants Used in the Traditional Medicine of the Tehuacán-Cuicatlán Valley, Puebla, México
by Sebastián Candelaria-Dueñas, Rocío Serrano-Parrales, Marisol Ávila-Romero, Samuel Meraz-Martínez, Julieta Orozco-Martínez, José Guillermo Ávila-Acevedo, Ana María García-Bores, Carlos L. Cespedes-Acuña, Ignacio Peñalosa-Castro and Tzasna Hernandez-Delgado
Antibiotics 2021, 10(3), 295; https://doi.org/10.3390/antibiotics10030295 - 12 Mar 2021
Cited by 7 | Viewed by 2355
Abstract
In Tehuacán-Cuicatlán valley (Mexico), studies have been carried out on the essential oils of medicinal plants with antimicrobial activity and it was found that they present compounds in common such as: α-pinene, β-pinene, carvacrol, eugenol, limonene, myrcene, ocimene, cineole, methyl salicylate, farnesene, and [...] Read more.
In Tehuacán-Cuicatlán valley (Mexico), studies have been carried out on the essential oils of medicinal plants with antimicrobial activity and it was found that they present compounds in common such as: α-pinene, β-pinene, carvacrol, eugenol, limonene, myrcene, ocimene, cineole, methyl salicylate, farnesene, and thymol. The goal of this study was to assess the antimicrobial activity of essential oils’ compounds. The qualitative evaluation was carried out by the Kirby Baüer agar diffusion technique in Gram-positive bacteria (11 strains), Gram-negative bacteria (18 strains), and yeasts (8 strains). For the determination of the minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), the agar dilution method was used. All the evaluated compounds presented antimicrobial activity. The compounds eugenol and carvacrol showed the largest inhibition zones. Regarding yeasts, the compounds ocimene, cineole, and farnesene did not show any activity. The compounds eugenol, carvacrol, and thymol presented the lowest MIC; bactericidal effect was observed at MIC level for S. aureus 75MR, E. coli 128 MR, and C albicans CUSI, for different compounds, eugenol, carvacrol, and thymol. Finally, this study shows that the essential oils of plants used by the population of Tehuacán-Cuicatlán valley share compounds and some of them have antibacterial and fungicidal activity. Full article
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12 pages, 1581 KiB  
Article
Rhodomyrtone as a New Natural Antibiotic Isolated from Rhodomyrtus tomentosa Leaf Extract: A Clinical Application in the Management of Acne Vulgaris
by Suttiwan Wunnoo, Siwaporn Bilhman, Thanaporn Amnuaikit, Julalak C. Ontong, Sudarshan Singh, Sauvarat Auepemkiate and Supayang P. Voravuthikunchai
Antibiotics 2021, 10(2), 108; https://doi.org/10.3390/antibiotics10020108 - 22 Jan 2021
Cited by 11 | Viewed by 3269
Abstract
Rhodomyrtone, a plant-derived principal compound isolated from Rhodomyrtus tomentosa (Myrtaceae) leaf extract, was assessed as a potential natural alternative for the treatment of acne vulgaris. The clinical efficacy of a 1% liposomal encapsulated rhodomyrtone serum was compared with a marketed 1% clindamycin gel. [...] Read more.
Rhodomyrtone, a plant-derived principal compound isolated from Rhodomyrtus tomentosa (Myrtaceae) leaf extract, was assessed as a potential natural alternative for the treatment of acne vulgaris. The clinical efficacy of a 1% liposomal encapsulated rhodomyrtone serum was compared with a marketed 1% clindamycin gel. In a randomized and double-blind controlled clinical trial, 60 volunteers with mild to moderate acne severity were assigned to two groups: rhodomyrtone serum and clindamycin gel. The volunteers were instructed to apply the samples to acne lesions on their faces twice daily. A significant reduction in the total numbers of acne lesions was demonstrated in both treatment groups between week 2 and 8 (p < 0.05). Significant differences in acne numbers compared with the baseline were evidenced at week 2 onwards (p < 0.05). At the end of the clinical trial, the total inflamed acne counts in the 1% rhodomyrtone serum group were significantly reduced by 36.36%, comparable to 34.70% in the clindamycin-treated group (p < 0.05). Furthermore, a commercial prototype was developed, and a clinical assessment of 45 volunteers was performed. After application of the commercial prototype for 1 week, 68.89% and 28.89% of volunteers demonstrated complete and improved inflammatory acne, respectively. All of the subjects presented no signs of irritation or side effects during the treatment. Most of the volunteers (71.11%) indicated that they were very satisfied. Rhodomyrtone serum was demonstrated to be effective and safe for the treatment of inflammatory acne lesions. Full article
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13 pages, 2077 KiB  
Article
Effect of Citrus aurantium L. Essential Oil on Streptococcus mutans Growth, Biofilm Formation and Virulent Genes Expression
by Chahrazed Benzaid, Amine Belmadani, Lazhari Tichati, Ryad Djeribi and Mahmoud Rouabhia
Antibiotics 2021, 10(1), 54; https://doi.org/10.3390/antibiotics10010054 - 8 Jan 2021
Cited by 17 | Viewed by 3621
Abstract
In an oral cavity, dental caries, periodontal disease, and endodontic lesions are caused by well-known bacterial and fungal pathogens. Essential oils (EOs) have demonstrated antimicrobial activity suggesting their use for oral hygiene. The goal of this study was to evaluate the interaction of [...] Read more.
In an oral cavity, dental caries, periodontal disease, and endodontic lesions are caused by well-known bacterial and fungal pathogens. Essential oils (EOs) have demonstrated antimicrobial activity suggesting their use for oral hygiene. The goal of this study was to evaluate the interaction of bitter orange flower (Citrus aurantium L.) essential oil with cariogenic bacteria Streptococcus mutans and human gingival epithelial cells. After extraction, the chemical composition of the essential oil was analyzed by gas chromatography, and its antimicrobial activity was evaluated against the growth and the expression of virulent genes in S. mutans. Finally, the effects of this essential oil on human gingival epithelial cell adhesion and growth were assessed using cell adhesion and proliferation assays. We showed that the major constituents of the tested essential oil were limonene, linalool, and β-ocimene. The essential oil reduced the growth of S. mutans, and decreased expression of comC, comD, comE, gtfB, gtfC, and gbpB genes. It should, however, be noted that essential oil at high concentration was toxic to gingival epithelial cells. Overall, this study suggests that C. aurantium L. essential oil could be used to prevent/control oral infections. Full article
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22 pages, 2328 KiB  
Article
Fractionation and Hydrolyzation of Avocado Peel Extract: Improvement of Antibacterial Activity
by Igor Trujillo-Mayol, Nidia Casas-Forero, Edgar Pastene-Navarrete, Fabiana Lima Silva and Julio Alarcón-Enos
Antibiotics 2021, 10(1), 23; https://doi.org/10.3390/antibiotics10010023 - 30 Dec 2020
Cited by 12 | Viewed by 4487
Abstract
Avocado Hass (Persea americana Mill) peel extract (APE) has the potential as a natural ingredient to substitute for chemical preservatives. The objectives of this study were to assess the phytochemical composition by high-performance liquid chromatography–quadrupole time-of-flight mass/mass spectrometry (HPLC-qTOF-MS/MS), total phenolic content [...] Read more.
Avocado Hass (Persea americana Mill) peel extract (APE) has the potential as a natural ingredient to substitute for chemical preservatives. The objectives of this study were to assess the phytochemical composition by high-performance liquid chromatography–quadrupole time-of-flight mass/mass spectrometry (HPLC-qTOF-MS/MS), total phenolic content (TPC), proanthocyanidin (PAC) content, and antioxidant activity of the APE, the organic fraction (OF), the aqueous fraction (AF), and the acid-microwave hydrolyzed APE (HAPE), on the antibacterial activity (ABA). The results indicated that APE and OF contained (p ˂ 0.05) a higher phenolic composition and antioxidant activity than AF and HAPE. The ABA specified that Pseudomonas aeruginosa and Bacillus cereus were inhibited by all the extracts (minimal inhibitory concentration—MIC ≥ 500 µg/mL), Staphylococcus aureus was only significantly inhibited by APE (≥750 µg/mL), the same MIC was observed for the OF on Salmonella spp. and Listeria monocytogenes. The HAPE increased the inhibitory efficiency up to 25% on Escherichia coli and Salmonella spp. (MIC ≥ 750 µg/mL), and 83.34% on L. monocytogenes (MIC ≥ 125 µg/mL) compared to APE (MIC ≥ 750 µg/mL). Also, HAPE inhibited the biofilm formation at the lowest concentration (125 µg/mL); meanwhile, the biofilm disruption showed to be concentration-time-dependent (p ˃ 0.05) compared to amoxicillin. In conclusion, the fractionation and hydrolyzation of APE improved the ABA; thus, those strategies are useful to design new antimicrobial compounds. Full article
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12 pages, 1057 KiB  
Article
Sonochemical Synthesis of 2’-Hydroxy-Chalcone Derivatives with Potential Anti-Oomycete Activity
by Génesis López, Marco Mellado, Enrique Werner, Bastián Said, Patricio Godoy, Nelson Caro, Ximena Besoain, Iván Montenegro and Alejandro Madrid
Antibiotics 2020, 9(9), 576; https://doi.org/10.3390/antibiotics9090576 - 4 Sep 2020
Cited by 10 | Viewed by 3305
Abstract
This work reports on the synthesis of eight new 2′-hydroxy-chalcones with potential anti-phytopathogenic applications in agroindustry, AMONG others, via Claisen–Schmidt condensation and ultrasound assisted reaction. Assays showed three chalcones with allyl moieties strongly inhibited growth of phytopathogenic oomycete Phytophthora infestans; moreover, compound [...] Read more.
This work reports on the synthesis of eight new 2′-hydroxy-chalcones with potential anti-phytopathogenic applications in agroindustry, AMONG others, via Claisen–Schmidt condensation and ultrasound assisted reaction. Assays showed three chalcones with allyl moieties strongly inhibited growth of phytopathogenic oomycete Phytophthora infestans; moreover, compound 8a had a half maximal effective concentration (EC50) value (32.5 µg/mL) similar to that of metalaxyl (28.6 µg/mL). A software-aided quantitative structure–activity relationship (QSAR) analysis of the whole series suggests that the structural features of these new chalcones—namely, the fluoride, hydroxyl, and amine groups over the carbon 3′ of the chalcone skeleton—increase anti-oomycete activity. Full article
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13 pages, 730 KiB  
Article
Synthesis of Novel Stilbene–Coumarin Derivatives and Antifungal Screening of Monotes kerstingii-Specialized Metabolites Against Fusarium oxysporum
by Ghislain Wabo Fotso, Bathelemy Ngameni, Thomas E. Storr, Bonaventure Tchaleu Ngadjui, Sibongile Mafu and G. Richard Stephenson
Antibiotics 2020, 9(9), 537; https://doi.org/10.3390/antibiotics9090537 - 25 Aug 2020
Cited by 5 | Viewed by 2842
Abstract
Fusarium is one of the most toxigenic phytopathogens causing diseases and reduced agricultural productivity worldwide. Current chemical fungicides exhibit toxicity against non-target organisms, triggering negative environmental impact, and are a danger to consumers. In order to explore the chemical diversity of plants for [...] Read more.
Fusarium is one of the most toxigenic phytopathogens causing diseases and reduced agricultural productivity worldwide. Current chemical fungicides exhibit toxicity against non-target organisms, triggering negative environmental impact, and are a danger to consumers. In order to explore the chemical diversity of plants for potential antifungal applications, crude extract and fractions from Monotes kerstingii were screened for their activity against two multi-resistant Fusarium oxysporum strains: Fo32931 and Fo4287. Antifungal activity was evaluated by the determination of minimum inhibitory concentration (MIC) by broth dilution of fermentative yeasts using kinetic OD600 nm reading by a spectrophotometer. The n-butanol fraction showed the best activity against Fo4287. We screened eleven previously reported natural compounds isolated from different fractions, and a stilbene–coumarin 5-[(1E)-2-(4-hydroxyphenyl)ethenyl]-4,7-dimethoxy-3-methyl-2H-1-benzopyran-2-one (1) was the most active compound against both strains. Compound 1 was employed as a nucleophile with a selection of electrophilic derivatizing agents to synthesize five novel stilbene–coumarin analogues. These semisynthetic derivatives showed moderate activity against Fo32931 with only prenylated derivative exhibiting activity comparable to the natural stilbene–coumarin (1), demonstrating the key role of the phenolic group. Full article
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8 pages, 847 KiB  
Communication
Synthesis and Anti-Saprolegnia Activity of New 2’,4’-Dihydroxydihydrochalcone Derivatives
by Enrique Werner, Iván Montenegro, Bastian Said, Patricio Godoy, Ximena Besoain, Nelson Caro and Alejandro Madrid
Antibiotics 2020, 9(6), 317; https://doi.org/10.3390/antibiotics9060317 - 10 Jun 2020
Viewed by 2463
Abstract
In the present study, seven 2’,4’-dihydroxydihydrochalcone derivatives (compounds 39) were synthesized and their capacity as anti-Saprolegnia agents were evaluated against Saprolegnia parasitica, S. australis, S. diclina. Derivative 9 showed the best activity against the different strains, [...] Read more.
In the present study, seven 2’,4’-dihydroxydihydrochalcone derivatives (compounds 39) were synthesized and their capacity as anti-Saprolegnia agents were evaluated against Saprolegnia parasitica, S. australis, S. diclina. Derivative 9 showed the best activity against the different strains, with minimum inhibitory concentration (MIC) and minimum oomyceticidal concentration (MOC) values between 100–175 μg/mL and 100–200 μg/mL, respectively, compared with bronopol and fluconazole as positive controls. In addition, compound 9 caused damage and disintegration cell membrane of all Saprolegnia strains over the action of commercial controls. Full article
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Review

Jump to: Research

23 pages, 816 KiB  
Review
Interactions between Medical Plant-Derived Bioactive Compounds: Focus on Antimicrobial Combination Effects
by Natalia Vaou, Elisavet Stavropoulou, Chrysoula (Chrysa) Voidarou, Zacharias Tsakris, Georgios Rozos, Christina Tsigalou and Eugenia Bezirtzoglou
Antibiotics 2022, 11(8), 1014; https://doi.org/10.3390/antibiotics11081014 - 28 Jul 2022
Cited by 48 | Viewed by 5005
Abstract
It is accepted that the medicinal use of complex mixtures of plant-derived bioactive compounds is more effective than purified bioactive compounds due to beneficial combination interactions. However, synergy and antagonism are very difficult to study in a meticulous fashion since most established methods [...] Read more.
It is accepted that the medicinal use of complex mixtures of plant-derived bioactive compounds is more effective than purified bioactive compounds due to beneficial combination interactions. However, synergy and antagonism are very difficult to study in a meticulous fashion since most established methods were designed to reduce the complexity of mixtures and identify single bioactive compounds. This study represents a critical review of the current scientific literature on the combined effects of plant-derived extracts/bioactive compounds. A particular emphasis is provided on the identification of antimicrobial synergistic or antagonistic combinations using recent metabolomics methods and elucidation of approaches identifying potential mechanisms that underlie their interactions. Proven examples of synergistic/antagonistic antimicrobial activity of bioactive compounds are also discussed. The focus is also put on the current challenges, difficulties, and problems that need to be overcome and future perspectives surrounding combination effects. The utilization of bioactive compounds from medicinal plant extracts as appropriate antimicrobials is important and needs to be facilitated by means of new metabolomics technologies to discover the most effective combinations among them. Understanding the nature of the interactions between medicinal plant-derived bioactive compounds will result in the development of new combination antimicrobial therapies. Full article
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31 pages, 12405 KiB  
Review
Fungal Biofilms as a Valuable Target for the Discovery of Natural Products That Cope with the Resistance of Medically Important Fungi—Latest Findings
by Estefanía Butassi, Laura Svetaz, María Cecilia Carpinella, Thomas Efferth and Susana Zacchino
Antibiotics 2021, 10(9), 1053; https://doi.org/10.3390/antibiotics10091053 - 30 Aug 2021
Cited by 18 | Viewed by 4196
Abstract
The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017–May 2021) on the available information on essential oils, propolis, [...] Read more.
The development of new antifungal agents that target biofilms is an urgent need. Natural products, mainly from the plant kingdom, represent an invaluable source of these entities. The present review provides an update (2017–May 2021) on the available information on essential oils, propolis, extracts from plants, algae, lichens and microorganisms, compounds from different natural sources and nanosystems containing natural products with the capacity to in vitro or in vivo modulate fungal biofilms. The search yielded 42 articles; seven involved essential oils, two Brazilian propolis, six plant extracts and one of each, extracts from lichens and algae/cyanobacteria. Twenty articles deal with the antibiofilm effect of pure natural compounds, with 10 of them including studies of the mechanism of action and five dealing with natural compounds included in nanosystems. Thirty-seven manuscripts evaluated Candida spp. biofilms and two tested Fusarium and Cryptococcus spp. Only one manuscript involved Aspergillus fumigatus. From the data presented here, it is clear that the search of natural products with activity against fungal biofilms has been a highly active area of research in recent years. However, it also reveals the necessity of deepening the studies by (i) evaluating the effect of natural products on biofilms formed by the newly emerged and worrisome health-care associated fungi, C. auris, as well as on other non-albicans Candida spp., Cryptococcus sp. and filamentous fungi; (ii) elucidating the mechanisms of action of the most active natural products; (iii) increasing the in vivo testing. Full article
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30 pages, 4285 KiB  
Review
African Plant-Based Natural Products with Antivirulence Activities to the Rescue of Antibiotics
by Christian Emmanuel Mahavy, Pierre Duez, Mondher ElJaziri and Tsiry Rasamiravaka
Antibiotics 2020, 9(11), 830; https://doi.org/10.3390/antibiotics9110830 - 19 Nov 2020
Cited by 12 | Viewed by 3779
Abstract
The worldwide emergence of antibiotic-resistant bacteria and the thread of widespread superbug infections have led researchers to constantly look for novel effective antimicrobial agents. Within the past two decades, there has been an increase in studies attempting to discover molecules with innovative properties [...] Read more.
The worldwide emergence of antibiotic-resistant bacteria and the thread of widespread superbug infections have led researchers to constantly look for novel effective antimicrobial agents. Within the past two decades, there has been an increase in studies attempting to discover molecules with innovative properties against pathogenic bacteria, notably by disrupting mechanisms of bacterial virulence and/or biofilm formation which are both regulated by the cell-to-cell communication mechanism called ‘quorum sensing’ (QS). Certainly, targeting the virulence of bacteria and their capacity to form biofilms, without affecting their viability, may contribute to reduce their pathogenicity, allowing sufficient time for an immune response to infection and a reduction in the use of antibiotics. African plants, through their huge biodiversity, present a considerable reservoir of secondary metabolites with a very broad spectrum of biological activities, a potential source of natural products targeting such non-microbicidal mechanisms. The present paper aims to provide an overview on two main aspects: (i) succinct presentation of bacterial virulence and biofilm formation as well as their entanglement through QS mechanisms and (ii) detailed reports on African plant extracts and isolated compounds with antivirulence properties against particular pathogenic bacteria. Full article
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