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Antimicrobial Properties of Natural Products
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Antimicrobial Properties of Natural Products

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

Deadline for manuscript submissions: closed (31 December 2019) | Viewed by 124018

Special Issue Editor

Prof. Dr. Raphaël E. Duval

E-Mail Website
Guest Editor
Dean, Faculty of Pharmacy, Université de Lorraine, CNRS, L2CM, 54000 Nancy, France
Interests: research of new anti-infectives; development of new strategies to fight antimicrobial resistance
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Antimicrobial resistance has become a major public health issue during these last years. According to a (very) recent study published in LID [1], multidrug-resistant bacteria were responsible for 30,000 deaths in Europe alone in 2015. Antibacterial resistance is such that there is a real risk of reaching a therapeutic dead end in which there are no longer effective molecules for treating infectious diseases. Furthermore, this situation is global, since we also find antimicrobial resistance in fungi or viruses. Bearing in mind that the therapeutic arsenal that we have at our disposal to fight against fungal and viral infections (excluding HIV and HCV) is very limited, it is therefore urgent to look for new antimicrobial molecules. Concomitantly, and for several years now, the search for natural compounds with antimicrobial activities has been a growing field of research.

The aim of this Special Issue is to highlight recent advances in research on natural products with antimicrobial properties (i.e., antibacterial, antiviral, or antifungal). This Special Issue may include original research articles and reviews on the antimicrobial properties of extracts, fractions, purified compounds, synergistic mixtures against bacteria, viruses, or fungi encountered in human infectious diseases, to identify promising natural compounds that could allow us to respond to the urgency of finding new antimicrobials.

Prof. Dr. Raphaël E. Duval
Guest Editor

1. Cassini A., Högberg L.D., Plachouras D., Quattrocchi A., Hoxha A., Simonsen G.S., Colomb-Cotinat M., Kretzschmar M.E., Devleesschauwer B., Cecchini M., Ait Ouakrim D., Oliveira T.C., Struelens M.J., Suetens C., Monnet D.L. and the Burden of AMR Collaborative Group. Attributable deaths and disability-adjusted life-years caused by infections with antibiotic-resistant bacteria in the EU and the European Economic Area in 2015: a population-level modelling analysis. Lancet Infect Dis. http://dx.doi.org/10.1016/S1473-3099(18)30605-4

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Keywords

  • Natural products
  • Antibacterials
  • Antivirals
  • Antifungals

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Published Papers (24 papers)

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18 pages, 3805 KiB  
Article
Cytotoxic Action of Artemisinin and Scopoletin on Planktonic Forms and on Biofilms of Candida Species
by Sourav Das, Lilla Czuni, Viktória Báló, Gábor Papp, Zoltán Gazdag, Nóra Papp and Tamás Kőszegi
Molecules 2020, 25(3), 476; https://doi.org/10.3390/molecules25030476 - 22 Jan 2020
Cited by 15 | Viewed by 3257
Abstract
We investigated the antifungal activities of purified plant metabolites artemisinin (Ar) and scopoletin (Sc) including inhibition, effects on metabolic activities, viability, and oxidative stress on planktonic forms and on preformed biofilms of seven Candida species. The characteristic minimum inhibitory concentration (MIC90) [...] Read more.
We investigated the antifungal activities of purified plant metabolites artemisinin (Ar) and scopoletin (Sc) including inhibition, effects on metabolic activities, viability, and oxidative stress on planktonic forms and on preformed biofilms of seven Candida species. The characteristic minimum inhibitory concentration (MIC90) of Ar and Sc against Candida species ranged from 21.83–142.1 µg/mL and 67.22–119.4 µg/mL, respectively. Drug concentrations causing ≈10% CFU decrease within 60 min of treatments were also determined (minimum effective concentration, MEC10) using 100-fold higher CFUs than in the case of MIC90 studies. Cytotoxic effects on planktonic and on mature biofilms of Candida species at MEC10 concentrations were further evaluated with fluorescent live/dead discrimination techniques. Candida glabrata, Candida guilliermondii, and Candida parapsilosis were the species most sensitive to Ar and Sc. Ar and Sc were also found to promote the accumulation of intracellular reactive oxygen species (ROS) by increasing oxidative stress at their respective MEC10 concentrations against the tested planktonic Candida species. Ar and Sc possess dose-dependent antifungal action but the underlying mechanism type (fungistatic and fungicidal) is not clear yet. Our data suggest that Ar and Sc found in herbal plants might have potential usage in the fight against Candida biofilms. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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19 pages, 4725 KiB  
Article
Antimicrobial Activity of Protein Fraction from Naja ashei Venom against Staphylococcus epidermidis
by Aleksandra Bocian, Ewa Ciszkowicz, Konrad K. Hus, Justyna Buczkowicz, Katarzyna Lecka-Szlachta, Monika Pietrowska, Vladimír Petrilla, Monika Petrillova, Ľubomír Legáth and Jaroslav Legáth
Molecules 2020, 25(2), 293; https://doi.org/10.3390/molecules25020293 - 10 Jan 2020
Cited by 21 | Viewed by 4483
Abstract
One of the key problems of modern infectious disease medicine is the growing number of drug-resistant and multi-drug-resistant bacterial strains. For this reason, many studies are devoted to the search for highly active antimicrobial substances that could be used in therapy against bacterial [...] Read more.
One of the key problems of modern infectious disease medicine is the growing number of drug-resistant and multi-drug-resistant bacterial strains. For this reason, many studies are devoted to the search for highly active antimicrobial substances that could be used in therapy against bacterial infections. As it turns out, snake venoms are a rich source of proteins that exert a strong antibacterial effect, and therefore they have become an interesting research material. We analyzed Naja ashei venom for such antibacterial properties, and we found that a specific composition of proteins can act to eliminate individual bacterial cells, as well as the entire biofilm of Staphylococcus epidermidis. In general, we used ion exchange chromatography (IEX) to obtain 10 protein fractions with different levels of complexity, which were then tested against certified and clinical strains of S. epidermidis. One of the fractions (F2) showed exceptional antimicrobial effects both alone and in combination with antibiotics. The protein composition of the obtained fractions was determined using mass spectrometry techniques, indicating a high proportion of phospholipases A2, three-finger toxins, and L-amino acids oxidases in F2 fraction, which are most likely responsible for the unique properties of this fraction. Moreover, we were able to identify a new group of low abundant proteins containing the Ig-like domain that have not been previously described in snake venoms. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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15 pages, 3780 KiB  
Article
Antimicrobial Susceptibility and Antibacterial Mechanism of Limonene against Listeria monocytogenes
by Yingjie Han, Zhichang Sun and Wenxue Chen
Molecules 2020, 25(1), 33; https://doi.org/10.3390/molecules25010033 - 20 Dec 2019
Cited by 160 | Viewed by 6369
Abstract
Limonene is a monoterpenoid compound, which is founded in a lot of plants’ essential oils with good antibacterial activity against food-borne pathogens, but it has an ambiguous antimicrobial susceptibility and mechanism against Listeria monocytogenes (L. monocytogenes). In this study, the antimicrobial susceptibility [...] Read more.
Limonene is a monoterpenoid compound, which is founded in a lot of plants’ essential oils with good antibacterial activity against food-borne pathogens, but it has an ambiguous antimicrobial susceptibility and mechanism against Listeria monocytogenes (L. monocytogenes). In this study, the antimicrobial susceptibility of Limonene to L. monocytogenes was studied, and some new sights regarding its antibacterial mechanism were further explored. Scanning electron microscopy (SEM) verified that limonene caused the destruction of the cell integrity and wall structure of L. monocytogenes. The increase in conductivity and the leakage of intracellular biomacromolecules (nucleic acids and proteins) confirmed that limonene had an obvious effect on cell membrane permeability. The results of Propidium Iodide (PI) fluorescence staining were consistent with the results of the conductivity measurements. This indicated that limonene treatment caused damage to the L. monocytogenes cell membrane. Furthermore, the decrease in ATP content, ATPase (Na+K+-ATPase, Ca2+-ATPase) activity and respiratory chain complex activity indicated that limonene could hinder ATP synthesis by inhibiting the activity of the respiratory complex and ATPase. Finally, differential expression of proteins in the respiratory chain confirmed that limonene affected respiration and energy metabolism by inhibiting the function of the respiratory chain complex. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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16 pages, 3117 KiB  
Article
Study on Antibacterial and Quorum-Sensing Inhibition Activities of Cinnamomum camphora Leaf Essential Oil
by Wenting Wang, Dongxiang Li, Xiaoqin Huang, Huixiang Yang, Ziwen Qiu, Liting Zou, Qin Liang, Yu Shi, Yingxiang Wu, Shaohua Wu, Chao Yang and Yongyu Li
Molecules 2019, 24(20), 3792; https://doi.org/10.3390/molecules24203792 - 21 Oct 2019
Cited by 41 | Viewed by 5178
Abstract
Many essential oils (EOs) regulate the quorum-sensing (QS) system of pathogens and inhibit the virulence expression. Interference with QS can potentially reduce bacterial multidrug resistance and aid the biological control of bacterial disease. In the present work, the antibacterial and anti-QS activities of [...] Read more.
Many essential oils (EOs) regulate the quorum-sensing (QS) system of pathogens and inhibit the virulence expression. Interference with QS can potentially reduce bacterial multidrug resistance and aid the biological control of bacterial disease. In the present work, the antibacterial and anti-QS activities of Cinnamomum camphora leaf EO were investigated. A total of 23 chemical components with relative levels ≥0.11%, including a large number of terpene compounds, were identified in C. camphora leaf EO by gas chromatography–mass spectrometry (GC-MS). The principal component was linalool, followed by eucalyptol, with relative levels of 51.57% and 22.07%, respectively. The minimum inhibitory concentration (MIC) and antibacterial activity of C. camphora EO were examined, and P. aeruginosa and E. coli ATCC25922 showed the highest and lowest sensitivity to C. camphora EO, respectively. Tests of QS inhibitory activity revealed that C. camphora EO significantly decreased the production of violacein and biofilm biomass in C. violaceum, with the maximum inhibition rates of 63% and 77.64%, respectively, and inhibited the biofilm formation and swarming movement, independent of affecting the growth of C. violaceum. Addition of C. camphora EO also resulted in downregulation of the expression of the acyl-homoserine lactones (AHL) synthesis gene (cviI) and transcription regulator (cviR), and inhibited the expression of QS-regulated virulence genes, including vioA, vioB, vioC, vioD, vioE, lasA, lasB, pilE3, and hmsHNFR. Collectively, the prominent antibacterial activity and anti-QS activities clearly support that C. camphora EO acts as a potential antibacterial agent and QS inhibitor in the prevention of bacterial contamination. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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14 pages, 4816 KiB  
Article
In Vitro Antimicrobial Activities of Organic Acids and Their Derivatives on Several Species of Gram-Negative and Gram-Positive Bacteria
by Lauren Kovanda, Wen Zhang, Xiaohong Wei, Jia Luo, Xixi Wu, Edward Robert Atwill, Stefan Vaessen, Xunde Li and Yanhong Liu
Molecules 2019, 24(20), 3770; https://doi.org/10.3390/molecules24203770 - 19 Oct 2019
Cited by 76 | Viewed by 8369 | Correction
Abstract
The objective of this study was to determine the in vitro antimicrobial activity of several organic acids and their derivatives against Gram-positive (G+) and Gram-negative (G−) bacteria. Butyric acid, valeric acid, monopropionin, monobutyrin, valerate glycerides, monolaurin, sodium formate, and ProPhorce—a mixture of sodium [...] Read more.
The objective of this study was to determine the in vitro antimicrobial activity of several organic acids and their derivatives against Gram-positive (G+) and Gram-negative (G−) bacteria. Butyric acid, valeric acid, monopropionin, monobutyrin, valerate glycerides, monolaurin, sodium formate, and ProPhorce—a mixture of sodium formate and formic acid (40:60 w/v)—were tested at 8 to 16 concentrations from 10 to 50,000 mg/L. The tested bacteria included G− bacteria (Escherichia coli, Salmonella enterica Typhimurium, and Campylobacter jejuni) and G+ bacteria (Enterococcus faecalis, Clostridium perfringens, Streptococcus pneumoniae, and Streptococcus suis). Antimicrobial activity was expressed as minimum inhibitory concentration (MIC) of tested compounds that prevented growth of tested bacteria in treated culture broth. The MICs of butyric acid, valeric acid, and ProPhorce varied among bacterial strains with the lowest MIC of 500–1000 mg/L on two strains of Campylobacter. Sodium formate at highest tested concentrations (20,000 mg/L) did not inhibit the growth of Escherichia coli, Salmonella Typhimurium, and Enterococcus faecalis, but sodium formate inhibited the growth of other tested bacteria with MIC values from 2000 to 18,800 mg/L. The MIC values of valerate glycerides, monolaurin, and monobutyrin ranged from 2500 to 15,000 mg/L in the majority of bacterial strains. Monopropionin did not inhibit the growth of all tested bacteria, with the exception that the MIC of monopropionin was 11,300 mg/L on Clostridia perfringens. Monolaurin strongly inhibited G+ bacteria, with the MIC value of 10 mg/L against Streptococcus pneumoniae. The MIC tests indicated that organic acids and their derivatives exhibit promising antimicrobial effects in vitro against G− and G+ bacteria that are resistant to antimicrobial drugs. The acid forms had stronger in vitro antimicrobial activities than ester forms, except that the medium chain fatty acid ester monolaurin exhibited strong inhibitory effects on G+ bacteria. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
13 pages, 852 KiB  
Article
In Silico and In Vitro Anti-Helicobacter Pylori Effects of Combinations of Phytochemicals and Antibiotics
by Pedro Fong, Chon-Hou Hao, Chi-Cheng Io, Pou-Io Sin and Li-Rong Meng
Molecules 2019, 24(19), 3608; https://doi.org/10.3390/molecules24193608 - 7 Oct 2019
Cited by 15 | Viewed by 4628
Abstract
Helicobacter pylori infection is a WHO class 1 carcinogenic factor of gastric adenocarcinoma. In the past decades, many studies have demonstrated the increasing trend of antibiotic resistance and pointed out the necessity of new effective treatment. This study was aimed at identifying phytochemicals [...] Read more.
Helicobacter pylori infection is a WHO class 1 carcinogenic factor of gastric adenocarcinoma. In the past decades, many studies have demonstrated the increasing trend of antibiotic resistance and pointed out the necessity of new effective treatment. This study was aimed at identifying phytochemicals that can inhibit H. pylori and possibly serve as adjuvant treatments. Here, in silico molecular docking and drug-like properties analyses were performed to identify potential inhibitors of urease, shikimate kinase and aspartate-semialdehyde dehydrogenase. These three enzymes are targets of the treatment of H. pylori. Susceptibility and synergistic testing were performed on the selected phytochemicals and the positive control antibiotic, amoxicillin. The in-silico study revealed that oroxindin, rosmarinic acid and verbascoside are inhibitors of urease, shikimate kinase and aspartate-semialdehyde dehydrogenase, respectively, in which, oroxindin has the highest potency against H. pylori, indicated by a minimum inhibitory concentration (MIC) value of 50 μg/mL. A combination of oroxindin and amoxicillin demonstrated additive effects against H. pylori, as indicated by a fractional inhibitory concentration (FIC) value of 0.75. This study identified phytochemicals that deserve further investigation for the development of adjuvant therapeutic agents to current antibiotics against H. pylori. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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14 pages, 339 KiB  
Article
Hechtia glomerata Zucc: Phytochemistry and Activity of Its Extracts and Major Constituents Against Resistant Bacteria
by Tommaso Stefani, Elvira Garza-González, Verónica M. Rivas-Galindo, María Yolanda Rios, Laura Alvarez and María del Rayo Camacho-Corona
Molecules 2019, 24(19), 3434; https://doi.org/10.3390/molecules24193434 - 21 Sep 2019
Cited by 12 | Viewed by 3286
Abstract
Hechtia glomerata Zucc. is used both as a source of food and in ethnomedicine to treat various diseases derived from bacterial infections such as bronchitis, laryngitis, nephritis, whooping cough, urethritis, and sepsis. There are no previous reports about its chemistry and biological activities. [...] Read more.
Hechtia glomerata Zucc. is used both as a source of food and in ethnomedicine to treat various diseases derived from bacterial infections such as bronchitis, laryngitis, nephritis, whooping cough, urethritis, and sepsis. There are no previous reports about its chemistry and biological activities. Therefore, the aims of this study were to identify components from organic and aqueous extracts of H. glomerata and test the extracts and major isolate compounds against resistant bacteria. Hexane, CHCl3/MeOH, and aqueous extracts were prepared and analyzed by different chromatographic techniques. Structural elucidation was carried out by NMR spectroscopy and X-ray diffraction. The antibacterial activities of extracts, phytochemicals, and semisynthetic derivatives against resistant bacteria were determined by the broth micro-dilution method. From the hexane extract nonacosane (1), hexatriacontanyl stearate (2), hexacosanol (3), oleic acid (4), and β-sitosterol (5) were isolated and characterized. From the CHCl3/MeOH extract, p-coumaric acid (6), margaric acid (7), caffeic acid (8), daucosterol (9), and potassium chloride (10) were isolated and characterized. A total of 58 volatile compounds were identified by GC-MS from the hexane extract and two solids were isolated from the CHCl3/MeOH extract. The UPLC-QTOF-MS analysis of the aqueous extract allowed the identification of 55 polar compounds. Hexane and aqueous extracts showed antibacterial activity against ESBL Escherichia coli, and three strains of Klebsiella pneumoniae ESBL, NDM-1 +, and OXA-48 with MIC values of 500 µg/mL. The CHCl3/MeOH extract was devoid of activity. The activity of phytocompounds and their semisynthetic derivatives toward resistant bacteria was weak. The most active compound was β-sitosterol acetate, with a MIC value of 100 µg/mL against carbapenem-resistant A. baumannii. This is the first report of the secondary metabolites of H. glomerata Zucc. and the activity of its extracts and major pure compounds against resistant bacterial strains. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
12 pages, 2041 KiB  
Article
Antifungal Effects and Potential Mechanism of Essential Oils on Collelotrichum gloeosporioides In Vitro and In Vivo
by Dan Wang, Jing Zhang, Xiaoman Jia, Li Xin and Hao Zhai
Molecules 2019, 24(18), 3386; https://doi.org/10.3390/molecules24183386 - 18 Sep 2019
Cited by 34 | Viewed by 4196
Abstract
The development of natural essential oil as an alternative to synthetic chemicals in the control of postharvest decay is currently in the spotlight. In the present study, the efficacy of seven essential oils in suppressing Collelotrichum gloeosporioides identified from sweet cherry was evaluated [...] Read more.
The development of natural essential oil as an alternative to synthetic chemicals in the control of postharvest decay is currently in the spotlight. In the present study, the efficacy of seven essential oils in suppressing Collelotrichum gloeosporioides identified from sweet cherry was evaluated in vitro and clove oil was proved to be the most promising inhibitor. Thus, the antifungal properties and potential mechanisms of clove oil in vitro and in vivo by fumigation and contact treatments were intensively investigated. For C. gloeosporioides, the minimal inhibitory concentrations (MIC) of clove oil in air and contact phase were 80 and 300 μL/L in vitro testing, respectively. Based on the radial growth of C. gloeosporioides mycelium in medium, the fumgitoxic ability of essential oil was observed in a dose-dependent manner, which was not as dramatic as that under in vivo conditions. Furthermore, scanning electron microscopy and transmission electron microscopy of C. gloeosporioides exposed to clove oil exhibited obviously deleterious morphological and ultrastructural alterations confirming the disruption of fungal cell wall and endomembrane system, which resulted in increasing in permeability and causing the loss of intracellular constituents. In future, essential oils, combined with nano-emulsification approaches, could be good candidates as safe and effective antifungal agents for fungal spoilage of fresh commodities. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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18 pages, 4861 KiB  
Article
Antimicrobial Activity and Proposed Action Mechanism of 3-Carene against Brochothrix thermosphacta and Pseudomonas fluorescens
by Huizhen Shu, Haiming Chen, Xiaolong Wang, Yueying Hu, Yonghuan Yun, Qiuping Zhong, Weijun Chen and Wenxue Chen
Molecules 2019, 24(18), 3246; https://doi.org/10.3390/molecules24183246 - 6 Sep 2019
Cited by 56 | Viewed by 4630
Abstract
3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive Brochothrix thermosphacta ACCC 03870 and Gram-negative Pseudomonas fluorescens ATCC 13525 were [...] Read more.
3-Carene is an antimicrobial monoterpene that occurs naturally in a variety of plants and has an ambiguous antibacterial mechanism against food-borne germs. The antibacterial effects and action mechanism of 3-carene against Gram-positive Brochothrix thermosphacta ACCC 03870 and Gram-negative Pseudomonas fluorescens ATCC 13525 were studied. Scanning electron microscopy (SEM) examination and leakage of alkaline phosphatase (AKP) verified that 3-carene caused more obvious damage to the morphology and wall structure of B. thermosphacta than P. fluorescens. The release of potassium ions and proteins, the reduction in membrane potential (MP), and fluorescein diacetate (FDA) staining further confirmed that the loss of the barrier function of the cell membrane and the leakage of cytoplasmic contents were due to the 3-carene treatment. Furthermore, the disorder of succinate dehydrogenase (SDH), malate dehydrogenase (MDH), pyruvate kinase (PK), and ATP content indicated that 3-carene could lead to metabolic dysfunction and inhibit energy synthesis. In addition, the results from the fluorescence analysis revealed that 3-carene could probably bind to bacterial DNA and affect the conformation and structure of genomic DNA. These results revealed that 3-carene had strong antibacterial activity against B. thermosphacta and P. fluorescens via membrane damage, bacterial metabolic perturbations, and genomic DNA structure disruption, interfering in cellular functions and even causing cell death. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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15 pages, 954 KiB  
Article
Antibacterial and Antispore Activities of Isolated Compounds from Piper cubeba L.
by Fatimah Alqadeeri, Yaya Rukayadi, Faridah Abbas and Khozirah Shaari
Molecules 2019, 24(17), 3095; https://doi.org/10.3390/molecules24173095 - 26 Aug 2019
Cited by 13 | Viewed by 3941
Abstract
Piper cubeba L. is the berry of a shrub that is indigenous to Java, Southern Borneo, Sumatra, and other islands in the Indian Ocean. The plant is usually used in folk traditional medicine and is an important ingredient in cooking. The purpose of [...] Read more.
Piper cubeba L. is the berry of a shrub that is indigenous to Java, Southern Borneo, Sumatra, and other islands in the Indian Ocean. The plant is usually used in folk traditional medicine and is an important ingredient in cooking. The purpose of this study was to isolate and purify the bioactive compounds from P. cubeba L. fractions. In addition, the isolated compounds were tested for their antibacterial and antispore activities against vegetative cells and spores of Bacillus cereus ATCC33019, B. subtilis ATCC6633, B. pumilus ATCC14884, and B. megaterium ATCC14581. The phytochemical investigation of the DCM fraction yielded two known compounds: β-asarone (1), and asaronaldehyde (2) were successfully isolated and identified from the methanol extract and its fractions of P. cubeba L. Results showed that exposing the vegetative cells of Bacillus sp. to isolated compounds resulted in an inhibition zone with a large diameter ranging between 7.21 to 9.61 mm. The range of the minimum inhibitory concentration (MIC) was between 63.0 to 125.0 µg/mL and had minimum bactericidal concentration (MBC) at 250.0 to 500.0 µg/mL against Bacillus sp. Isolated compounds at a concentration of 0.05% inactivated more than 3-Log10 (90.99%) of the spores of Bacillus sp. after an incubation period of four hours, and all the spores were killed at a concentration of 0.1%. The structures were recognizably elucidated based on 1D and 2D-NMR analyses (1H, 13C, COSY, HSQC, and HMBC) and mass spectrometry data. Compounds 1, and 2 were isolated for the first time from this plant. In conclusion, the two compounds show a promising potential of antibacterial and sporicidal activities against Bacillus sp. and thus can be developed as an anti-Bacillus agent. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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17 pages, 1087 KiB  
Article
Growth Biocontrol of Foodborne Pathogens and Spoilage Microorganisms of Food by Polish Propolis Extracts
by Katarzyna Pobiega, Karolina Kraśniewska, Jarosław L. Przybył, Katarzyna Bączek, Joanna Żubernik, Dorota Witrowa-Rajchert and Małgorzata Gniewosz
Molecules 2019, 24(16), 2965; https://doi.org/10.3390/molecules24162965 - 15 Aug 2019
Cited by 35 | Viewed by 3845
Abstract
Propolis is a natural mixture produced by bees from plant resin substances. This study focuses on the general characteristics of five samples of Polish extract propolis originating from agricultural areas. Chemical composition with high performance liquid chromatography‒diode array detector method, total content of [...] Read more.
Propolis is a natural mixture produced by bees from plant resin substances. This study focuses on the general characteristics of five samples of Polish extract propolis originating from agricultural areas. Chemical composition with high performance liquid chromatography‒diode array detector method, total content of flavonoids and polyphenols, and antioxidative activity were determined in the ethanol extracts of propolis (EEP) samples. Minimum inhibitory concentration (MIC), minimum bactericidal/fungicidal concentration (MBC/MFC) and time-kill curves were studied for foodborne pathogens and food spoilage microorganisms. In EEPs the predominant flavonoid compounds were pinocembrin, chrysin, pinobanksin, apigenin, and kaempferol and the predominant phenolic acids were p-coumaric acid, ferulic acid, and caffeic acid. A strong antioxidative action of propolis in vitro was observed (IC50 for DPPH radical was at the level of 0.9–2.1 µg/mL). EEPs had MIC values for bacteria in the range of 1–16 mg/mL, whereas MIC for fungi ranged from 2 to 32 mg/mL. Extract of propolis originating from southern Poland was distinguished by higher content of bioactive components, and stronger antioxidative and antimicrobial activity than EPPs from the remaining areas of Poland. The results indicate the possibility of applying ethanol extracts from Polish propolis to protect food against microbiological spoilage. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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14 pages, 2740 KiB  
Article
Antibacterial Activity and Mode of Action of Dihydromyricetin from Ampelopsis grossedentata Leaves against Food-Borne Bacteria
by Xiao-Nian Xiao, Fan Wang, Yi-Ting Yuan, Jing Liu, Yue-Zhen Liu and Xing Yi
Molecules 2019, 24(15), 2831; https://doi.org/10.3390/molecules24152831 - 3 Aug 2019
Cited by 46 | Viewed by 4835
Abstract
Dihydromyricetin (DMY) has recently attracted increased interest due to its considerable health-promoting activities but there are few reports on its antibacterial activity and mechanism. In this paper, the activity and mechanisms of DMY from Ampelopsis grossedentata leaves against food-borne bacteria are investigated. Moreover, [...] Read more.
Dihydromyricetin (DMY) has recently attracted increased interest due to its considerable health-promoting activities but there are few reports on its antibacterial activity and mechanism. In this paper, the activity and mechanisms of DMY from Ampelopsis grossedentata leaves against food-borne bacteria are investigated. Moreover, the effects of pH, thermal-processing, and metal ions on the antibacterial activity of DMY are also evaluated. The results show that DMY exhibits ideal antibacterial activity on five types of food-borne bacteria (Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Salmonella paratyphi, and Pseudomonas aeruginosa). The activities of DMY against bacteria are extremely sensitive to pH, thermal-processing, and metal ions. The morphology of the tested bacteria is changed and damaged more seriously with the exposure time of DMY. Furthermore, the results of the oxidative respiratory metabolism assay and the integrity of the cell membrane and wall tests revealed that the death of bacteria caused by DMY might be due to lysis of the cell wall, leakage of intracellular ingredients, and inhibition of the tricarboxylic acid cycle (TCA) pathway. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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9 pages, 1345 KiB  
Article
Inhibitory Effects of Diketopiperazines from Marine-Derived Streptomyces puniceus on the Isocitrate Lyase of Candida albicans
by Heegyu Kim, Ji-Yeon Hwang, Jongheon Shin and Ki-Bong Oh
Molecules 2019, 24(11), 2111; https://doi.org/10.3390/molecules24112111 - 4 Jun 2019
Cited by 7 | Viewed by 2911
Abstract
The glyoxylate cycle is a sequence of anaplerotic reactions catalyzed by the key enzymes isocitrate lyase (ICL) and malate synthase, and plays an important role in the pathogenesis of microorganisms during infection. An icl-deletion mutant of Candida albicans exhibited reduced virulence in [...] Read more.
The glyoxylate cycle is a sequence of anaplerotic reactions catalyzed by the key enzymes isocitrate lyase (ICL) and malate synthase, and plays an important role in the pathogenesis of microorganisms during infection. An icl-deletion mutant of Candida albicans exhibited reduced virulence in mice compared with the wild type. Five diketopiperazines, which are small and stable cyclic peptides, isolated from the marine-derived Streptomyces puniceus Act1085, were evaluated for their inhibitory effects on C. albicans ICL. The structures of these compounds were elucidated based on spectroscopic data and comparisons with previously reported data. Cyclo(L-Phe-L-Val) was identified as a potent ICL inhibitor, with a half maximal inhibitory concentration of 27 μg/mL. Based on the growth phenotype of the icl-deletion mutants and icl expression analyses, we demonstrated that cyclo(L-Phe-L-Val) inhibits the gene transcription of ICL in C. albicans under C2-carbon-utilizing conditions. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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27 pages, 5076 KiB  
Article
Sarconesin II, a New Antimicrobial Peptide Isolated from Sarconesiopsis magellanica Excretions and Secretions
by Andrea Díaz-Roa, Abraham Espinoza-Culupú, Orlando Torres-García, Monamaris M. Borges, Ivan N. Avino, Flávio L. Alves, Antonio Miranda, Manuel A. Patarroyo, Pedro I. da Silva, Jr. and Felio J. Bello
Molecules 2019, 24(11), 2077; https://doi.org/10.3390/molecules24112077 - 31 May 2019
Cited by 13 | Viewed by 5436
Abstract
Antibiotic resistance is at dangerous levels and increasing worldwide. The search for new antimicrobial drugs to counteract this problem is a priority for health institutions and organizations, both globally and in individual countries. Sarconesiopsis magellanica blowfly larval excretions and secretions (ES) are an [...] Read more.
Antibiotic resistance is at dangerous levels and increasing worldwide. The search for new antimicrobial drugs to counteract this problem is a priority for health institutions and organizations, both globally and in individual countries. Sarconesiopsis magellanica blowfly larval excretions and secretions (ES) are an important source for isolating antimicrobial peptides (AMPs). This study aims to identify and characterize a new S. magellanica AMP. RP-HPLC was used to fractionate ES, using C18 columns, and their antimicrobial activity was evaluated. The peptide sequence of the fraction collected at 43.7 min was determined by mass spectrometry (MS). Fluorescence and electronic microscopy were used to evaluate the mechanism of action. Toxicity was tested on HeLa cells and human erythrocytes; physicochemical properties were evaluated. The molecule in the ES was characterized as sarconesin II and it showed activity against Gram-negative (Escherichia coli MG1655, Pseudomonas aeruginosa ATCC 27853, P. aeruginosa PA14) and Gram-positive (Staphylococcus aureus ATCC 29213, Micrococcus luteus A270) bacteria. The lowest minimum inhibitory concentration obtained was 1.9 μM for M. luteus A270; the AMP had no toxicity in any cells tested here and its action in bacterial membrane and DNA was confirmed. Sarconesin II was documented as a conserved domain of the ATP synthase protein belonging to the Fli-1 superfamily. The data reported here indicated that peptides could be alternative therapeutic candidates for use in infections against Gram-negative and Gram-positive bacteria and eventually as a new resource of compounds for combating multidrug-resistant bacteria. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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13 pages, 1508 KiB  
Article
Betulinic Acid Prevents the Acquisition of Ciprofloxacin-Mediated Mutagenesis in Staphylococcus aureus
by Alexsander Rodrigues Carvalho Junior, Arthur Lima de Berredo Martins, Brenda da Silva Cutrim, Deivid Martins Santos, Hermerson Sousa Maia, Mari Silma Maia da Silva, Adrielle Zagmignan, Maria Raimunda Chagas Silva, Cristina de Andrade Monteiro, Giselle Maria Skelding Pinheiro Guilhon, Antônio José Cantanhede Filho and Luís Cláudio Nascimento da Silva
Molecules 2019, 24(9), 1757; https://doi.org/10.3390/molecules24091757 - 7 May 2019
Cited by 7 | Viewed by 3158
Abstract
The occurrence of damage on bacterial DNA (mediated by antibiotics, for example) is intimately associated with the activation of the SOS system. This pathway is related to the development of mutations that might result in the acquisition and spread of resistance and virulence [...] Read more.
The occurrence of damage on bacterial DNA (mediated by antibiotics, for example) is intimately associated with the activation of the SOS system. This pathway is related to the development of mutations that might result in the acquisition and spread of resistance and virulence factors. The inhibition of the SOS response has been highlighted as an emerging resource, in order to reduce the emergence of drug resistance and tolerance. Herein, we evaluated the ability of betulinic acid (BA), a plant-derived triterpenoid, to reduce the activation of the SOS response and its associated phenotypic alterations, induced by ciprofloxacin in Staphylococcus aureus. BA did not show antimicrobial activity against S. aureus (MIC > 5000 µg/mL), however, it (at 100 and 200 µg/mL) was able to reduce the expression of recA induced by ciprofloxacin. This effect was accompanied by an enhancement of the ciprofloxacin antimicrobial action and reduction of S. aureus cell volume (as seen by flow cytometry and fluorescence microscopy). BA could also increase the hyperpolarization of the S. aureus membrane, related to the ciprofloxacin action. Furthermore, BA inhibited the progress of tolerance and the mutagenesis induced by this drug. Taken together, these findings indicate that the betulinic acid is a promising lead molecule in the development helper drugs. These compounds may be able to reduce the S. aureus mutagenicity associated with antibiotic therapies. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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17 pages, 1793 KiB  
Article
Topical Application of Cinnamaldehyde Promotes Faster Healing of Skin Wounds Infected with Pseudomonas aeruginosa
by Thiago A.F. Ferro, Eliene B. Souza, Mariela A.M. Suarez, João F.S. Rodrigues, Domingos M.S. Pereira, Saulo J.F. Mendes, Laoane F. Gonzaga, Márcia C.A.M. Machado, Maria R.Q. Bomfim, João B. Calixto, Jack L. Arbiser, Valério Monteiro-Neto, Eunice André and Elizabeth S. Fernandes
Molecules 2019, 24(8), 1627; https://doi.org/10.3390/molecules24081627 - 25 Apr 2019
Cited by 32 | Viewed by 5629
Abstract
Wound healing can be delayed following colonization and infection with the common bacterium Pseudomonas aeruginosa. While multiple therapies are used for their treatment, these are ineffective, expensive, and labour-intensive. Thus, there is an enormous unmet need for the treatment of infected wounds. [...] Read more.
Wound healing can be delayed following colonization and infection with the common bacterium Pseudomonas aeruginosa. While multiple therapies are used for their treatment, these are ineffective, expensive, and labour-intensive. Thus, there is an enormous unmet need for the treatment of infected wounds. Cinnamaldehyde, the major component of cinnamon oil, is well known for its antimicrobial properties. Herein, we investigated the effects of sub-inhibitory concentrations of cinnamaldehyde in the virulence of P. aeruginosa. We also assessed its healing potential in P. aeruginosa-infected mouse skin wounds and the mechanisms involved in this response. Sub-inhibitory concentrations of cinnamaldehyde reduced P. aeruginosa metabolic rate and its ability to form biofilm and to cause haemolysis. Daily topical application of cinnamaldehyde on P. aeruginosa-infected skin wounds reduced tissue bacterial load and promoted faster healing. Lower interleukin-17 (IL-17), vascular endothelial growth factor (VEGF) and nitric oxide levels were detected in cinnamaldehyde-treated wound samples. Blockage of transient receptor potential ankyrin 1, the pharmacological target of cinnamaldehyde, abrogated its healing activity and partially reversed the inhibitory actions of this compound on VEGF and IL-17 generation. We suggest that topical application of sub-inhibitory concentrations of cinnamaldehyde may represent an interesting approach to improve the healing of P. aeruginosa-infected skin wounds. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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16 pages, 3501 KiB  
Article
Anticandidal Potential of Stem Bark Extract from Schima superba and the Identification of Its Major Anticandidal Compound
by Chun Wu, Hong-Tan Wu, Qing Wang, Guey-Horng Wang, Xue Yi, Yu-Pei Chen and Guang-Xiong Zhou
Molecules 2019, 24(8), 1587; https://doi.org/10.3390/molecules24081587 - 22 Apr 2019
Cited by 4 | Viewed by 2974
Abstract
Plant-derived extracts are a promising source of new drugs. Schima superba is traditionally used in China for heat clearing, detoxification, and treatment of furuncles. In this study, the anticandidal properties and mechanism of action of S. superba (SSE) were explored using a stem [...] Read more.
Plant-derived extracts are a promising source of new drugs. Schima superba is traditionally used in China for heat clearing, detoxification, and treatment of furuncles. In this study, the anticandidal properties and mechanism of action of S. superba (SSE) were explored using a stem bark extract. SSE possessed high polyphenol and saponin contents of 256.6 ± 5.1 and 357.8 ± 31.5 µg/mg, respectively. A clear inhibition zone was observed for C. albicans growth through the disc diffusion method and the 50% inhibition of C. albicans by SSE was 415.2 µg/mL. Transcriptomic analysis in C. albicans treated with different doses of SSE was conducted through RNA-seq. Average values of 6068 genes and 20,842,500 clean reads were identified from each sample. Among these samples, 1680 and 1956 genes were differentially expressed genes (DEGs) from the SSE treatments of 0.2 and 0.4 mg/mL, respectively. C. albicans growth was inhibited by the changes in gene expression associated with the cell wall and membrane composition including the regulation of chitin degradation and ergosterol biosynthesis. This result could be reflected in the irregularly wrinkled morphology of the ruptured cell as revealed through SEM analysis. ESI-MS and NMR analyses revealed that the major compound purified from SSE was sasanquasaponin III and the 50% inhibition of C. albicans was 93.1 µg/mL. In summary, the traditional Chinese medicine S. superba can be applied as an anticandidal agent in complementary and alternative medicine. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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12 pages, 502 KiB  
Article
Antibacterial and Biofilm Inhibitory Activity of Medicinal Plant Essential Oils Against Escherichia coli Isolated from UTI Patients
by Rihab Lagha, Fethi Ben Abdallah, Badriah Osama AL-Sarhan and Yassin Al-Sodany
Molecules 2019, 24(6), 1161; https://doi.org/10.3390/molecules24061161 - 23 Mar 2019
Cited by 78 | Viewed by 8753
Abstract
Urinary tract infections (UTIs), caused by Escherichia coli 80% to 85% of the time, are one of the most important causes of morbidity and health care spending affecting persons of all ages. These infections lead to many difficult problems, especially increasing resistance to [...] Read more.
Urinary tract infections (UTIs), caused by Escherichia coli 80% to 85% of the time, are one of the most important causes of morbidity and health care spending affecting persons of all ages. These infections lead to many difficult problems, especially increasing resistance to antibiotic drugs. Bacterial biofilms play an important role in UTIs, responsible for persistent infections leading to recurrences and relapses. In this study, we have investigated the antibacterial activity of five medicinal plant essential oils against UTIs caused by E. coli using disc diffusion and minimal inhibition concentration (MIC) methods. In addition, biofilm inhibitory action of oils was realized by crystal violet. Gas chromatography–mass spectrometry (GC–MS) analysis showed a variability between oils in terms of compound numbers as well as their percentages. Antibacterial activity was observed only in cases of Origanum majorana, Thymus zygis and Rosmarinus officinalis, while Juniperus communis and Zingiber officinale did not showed any effect towards E. coli isolates. T. zygis essential oil demonstrated the highest antibacterial activity against E. coli isolates, followed by O. majorana and R. officinalis. Further, oils showed high biofilm inhibitory action with a percentage of inhibition that ranged from 14.94% to 94.75%. R. officinalis oil had the highest antibiofilm activity followed by T. zygis and O. majorana. Accordingly, tested oils showed very effective antibacterial and antibiofilm activities against E. coli UTIs and can be considered as good alternative for antibiotics substitution. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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14 pages, 1149 KiB  
Article
The Pros and Cons of Cystic Fibrosis (CF) Patient Use of Herbal Supplements Containing Pulmonaria officinalis L. Extract: the Evidence from an In Vitro Study on Staphylococcus aureus CF Clinical Isolates
by Beata Sadowska, Urszula Wójcik, Justyna Krzyżanowska-Kowalczyk, Mariusz Kowalczyk, Anna Stochmal, Joanna Rywaniak, Julia Burzyńska and Barbara Różalska
Molecules 2019, 24(6), 1151; https://doi.org/10.3390/molecules24061151 - 22 Mar 2019
Cited by 5 | Viewed by 4942
Abstract
The justification for the use of herbal supplements with Pulmonaria officinalis L. extract (POE) in the case of staphylococcal lung colonization/infections characteristic for cystic fibrosis (CF), was examined in vitro. The impact of POE phenolic-rich fraction on the virulence attributes of CF-associated Staphylococcus [...] Read more.
The justification for the use of herbal supplements with Pulmonaria officinalis L. extract (POE) in the case of staphylococcal lung colonization/infections characteristic for cystic fibrosis (CF), was examined in vitro. The impact of POE phenolic-rich fraction on the virulence attributes of CF-associated Staphylococcus aureus (S. aureus) clinical strains has been assessed, including pathogen adhesion, biofilm formation on native and protein-conditioned surfaces (mucin, elastin), mature biofilm eradication, staphylococcal protein A expression, α-toxin release, and S. a. adhesion to A549 cells. Cytotoxicity of the extract to lung epithelial cells was also investigated. It was found that POE has bacteriostatic effects at MIC 1–2 mg/mL, recognized as of limited efficacy, but at MIC/subMICs it targeted virulence not viability. It usually decreased S. aureus adhesion and less frequently inhibited biofilm formation on native and protein-conditioned surfaces. Observed effect seems to be related to significant reduction by POE of sortase A activity. However, in some cases POE favored the creation of biofilm by staphylococci and S. aureus adhesion to the lung epithelium was not limited. On the other side POE caused significant decrease of S. a. α-toxin synthesis and slightly weakened the expression of SpA. When used at supraMICs POE eradicated mature biofilm, but in some cases with unsatisfying outcomes. Promisingly, POE has been recognized as a safe product, with no cytotoxicity up to 4 mg/mL. These results reflect the positive, negative or neutral anti-staphylococcal properties of POE. It seems that POE may be beneficial as a prophylactic, but not as a therapeutic or supportive agent in the area of CF—integrative medicine. However, introduction the official recommendations needs further in vivo studies. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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16 pages, 5578 KiB  
Article
Evaluation of the Inhibitory Effects of (E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-(naphthalen-1-yl)prop-2-en-1-one (DiNap), a Natural Product Analog, on the Replication of Type 2 PRRSV In Vitro and In Vivo
by Amina Khatun, Sun You Park, Nadeem Shabir, Salik Nazki, A-Rum Kang, Chang-Gi Jeong, Byoung-Joo Seo, Myeon-Sik Yang, Bumseok Kim, Young Ho Seo and Won-Il Kim
Molecules 2019, 24(5), 887; https://doi.org/10.3390/molecules24050887 - 3 Mar 2019
Cited by 1 | Viewed by 3907
Abstract
DiNap [(E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-(naphthalen-1-yl)prop-2-en-1-one], an analog of a natural product (the chalcone flavokawain), was synthesized and characterized in this study. Porcine reproductive and respiratory syndrome virus (PRRSV) is the most challenging threat to the swine industry worldwide. Currently, commercially available vaccines are ineffective [...] Read more.
DiNap [(E)-1-(2-hydroxy-4,6-dimethoxyphenyl)-3-(naphthalen-1-yl)prop-2-en-1-one], an analog of a natural product (the chalcone flavokawain), was synthesized and characterized in this study. Porcine reproductive and respiratory syndrome virus (PRRSV) is the most challenging threat to the swine industry worldwide. Currently, commercially available vaccines are ineffective for controlling porcine reproductive and respiratory syndrome (PRRS) in pigs. Therefore, a pharmacological intervention may represent an alternative control measure for PRRSV infection. Hence, the present study evaluated the effects of DiNap on the replication of VR2332 (a prototype strain of type 2 PRRSV). Initially, in vitro antiviral assays against VR2332 were performed in MARC-145 cells and porcine alveolar macrophages (PAMs). Following this, a pilot study was conducted in a pig model to demonstrate the effects of DiNap following VR2332 infection. DiNap inhibited VR2332 replication in both cell lines in a dose-dependent manner, and viral growth was completely suppressed at concentrations ≥0.06 mM, without significant cytotoxicity. Consistent with these findings, in the pig study, DiNap also reduced viral loads in the serum and lungs and enhanced the weight gain of pigs following VR2332 infection, as indicated by comparison of the DiNap-treated groups to the untreated control (NC) group. In addition, DiNap-treated pigs had fewer gross and microscopic lesions in their lungs than NC pigs. Notably, virus transmission was also delayed by approximately 1 week in uninfected contact pigs within the same group after treatment with DiNap. Taken together, these results suggest that DiNap has potential anti-PRRSV activity and could be useful as a prophylactic or post-exposure treatment drug to control PRRSV infection in pigs. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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11 pages, 1558 KiB  
Article
Astilbin Inhibits the Activity of Sortase A from Streptococcus mutans
by Junxian Wang, Yan Shi, Shisong Jing, Haisi Dong, Dacheng Wang and Tiedong Wang
Molecules 2019, 24(3), 465; https://doi.org/10.3390/molecules24030465 - 28 Jan 2019
Cited by 30 | Viewed by 5164
Abstract
Streptococcus mutans (S. mutans) is the primary etiological agent of dental caries. The S. mutans enzyme sortase A (SrtA) is responsible for anchoring bacterial cell wall surface proteins involved in host cell attachment and biofilm formation. Thus, SrtA is an attractive [...] Read more.
Streptococcus mutans (S. mutans) is the primary etiological agent of dental caries. The S. mutans enzyme sortase A (SrtA) is responsible for anchoring bacterial cell wall surface proteins involved in host cell attachment and biofilm formation. Thus, SrtA is an attractive target for inhibiting dental caries caused by S. mutans-associated acid fermentation. In this study, we observed that astilbin, a flavanone compound extracted from Rhizoma Smilacis Glabrae, has potent inhibitory activity against the S. mutans SrtA, with an IC50 of 7.5 μg/mL. In addition, astilbin was proven to reduce the formation of biofilm while without affecting the growth of S. mutans. The results of a molecular dynamics simulation and a mutation analysis revealed that the Arg213, Leu111, and Leu116 of SrtA are important for the interaction between SrtA and astilbin. The results of this study demonstrate the potential of using astilbin as a nonbactericidal agent to modulate pathogenicity of S. mutans by inhibiting the activity of SrtA. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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Review

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18 pages, 1242 KiB  
Review
Selected Fungal Natural Products with Antimicrobial Properties
by Dorota Jakubczyk and Francois Dussart
Molecules 2020, 25(4), 911; https://doi.org/10.3390/molecules25040911 - 18 Feb 2020
Cited by 53 | Viewed by 7632
Abstract
Fungal natural products and their effects have been known to humankind for hundreds of years. For example, toxic ergot alkaloids produced by filamentous fungi growing on rye poisoned thousands of people and livestock throughout the Middle Ages. However, their later medicinal applications, followed [...] Read more.
Fungal natural products and their effects have been known to humankind for hundreds of years. For example, toxic ergot alkaloids produced by filamentous fungi growing on rye poisoned thousands of people and livestock throughout the Middle Ages. However, their later medicinal applications, followed by the discovery of the first class of antibiotics, penicillins and other drugs of fungal origin, such as peptidic natural products, terpenoids or polyketides, have altered the historically negative reputation of fungal “toxins”. The development of new antimicrobial drugs is currently a major global challenge, mainly due to antimicrobial resistance phenomena. Therefore, the structures, biosynthesis and antimicrobial activity of selected fungal natural products are described here. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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22 pages, 1003 KiB  
Review
Essential Oils and Their Natural Active Compounds Presenting Antifungal Properties
by Maurine D’agostino, Nicolas Tesse, Jean Pol Frippiat, Marie Machouart and Anne Debourgogne
Molecules 2019, 24(20), 3713; https://doi.org/10.3390/molecules24203713 - 15 Oct 2019
Cited by 87 | Viewed by 9761
Abstract
The current rise in invasive fungal infections due to the increase in immunosuppressive therapies is a real concern. Moreover, the emergence of resistant strains induces therapeutic failures. In light of these issues, new classes of antifungals are anticipated. Therefore, the plant kingdom represents [...] Read more.
The current rise in invasive fungal infections due to the increase in immunosuppressive therapies is a real concern. Moreover, the emergence of resistant strains induces therapeutic failures. In light of these issues, new classes of antifungals are anticipated. Therefore, the plant kingdom represents an immense potential of natural resources to exploit for these purposes. The aim of this review is to provide information about the antifungal effect of some important essential oils, and to describe the advances made in determining the mechanism of action more precisely. Finally, the issues of toxicity and resistance of fungi to essential oils will be discussed. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
16 pages, 2792 KiB  
Review
Macrocyclic Diterpenoids from Euphorbiaceae as A Source of Potent and Selective Inhibitors of Chikungunya Virus Replication
by Simon Remy and Marc Litaudon
Molecules 2019, 24(12), 2336; https://doi.org/10.3390/molecules24122336 - 25 Jun 2019
Cited by 22 | Viewed by 4368
Abstract
Macrocyclic diterpenoids produced by plants of the Euphorbiaceae family are of considerable interest due to their high structural diversity; and their therapeutically relevant biological properties. Over the last decade many studies have reported the ability of macrocyclic diterpenoids to inhibit in cellulo the [...] Read more.
Macrocyclic diterpenoids produced by plants of the Euphorbiaceae family are of considerable interest due to their high structural diversity; and their therapeutically relevant biological properties. Over the last decade many studies have reported the ability of macrocyclic diterpenoids to inhibit in cellulo the cytopathic effect induced by the chikungunya virus. This review; which covers the years 2011 to 2019; lists all macrocyclic diterpenoids that have been evaluated for their ability to inhibit viral replication. The structure–activity relationships and the probable involvement of protein kinase C in their mechanism of action are also detailed. Full article
(This article belongs to the Special Issue Antimicrobial Properties of Natural Products)
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