Special Issue "Natural Compounds as Potential Antibacterial Agents"

A special issue of Medicines (ISSN 2305-6320).

Deadline for manuscript submissions: closed (30 April 2019).

Special Issue Editor

Guest Editor
Dr. Leena Hanski

Division of Pharmaceutical Biosciences, Faculty of Pharmacy, University of Helsinki,FI-00014 Helsinki, Finland
Website | E-Mail
Interests: pharmaceutical biology, antibacterial agents, antiviral agents, natural products, bioactivity screening, intracellular bacteria, bacterial persistence, anti-inflammatory activities

Special Issue Information

Dear colleagues,

Natural product research has a long and productive history in the search for antibacterial agents, highlighted by the significant proportion of antibiotics in current clinical use originating from these sources. Besides the registered drugs, natural compounds serve as antibacterials in a variety of complementary medicine applications, and investigating the safety and efficacy of these products is of critical importance. Owing to the fading efficacy of the current day antibacterials as a result of resistant and persistent bacterial strains, the need for new approaches in identifying and using natural compounds as antibacterials is highly relevant. This Special Issue focuses on the potential of natural compounds to combat the challenges caused by the current and emerging conditions resulting from bacterial infections. The topics of the submitted manuscripts may include, but are not limited to:

  • Identification of new bioactive antibacterials
  • Elucidating the mechanisms of action of antibacterial natural compounds
  • Natural compounds as adjuvants for conventional antibiotics
  • Formulation and pharmacokinetics of natural compound antibacterials
  • Targeting virulence factors
  • Postgenomics approaches for natural compound antibacterial research

Dr. Leena Hanski
Guest Editor

Manuscript Submission Information

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Keywords

  • Natural product, antibacterial agent, mechanism of action, antibiotic resistance, persistent infection, latent infection, virulence factor, normal microbiota

Published Papers (4 papers)

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Research

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Open AccessArticle
In Vitro Effect of the Traditional Medicine Hainosan (Painongsan) on Porphyromonas gingivalis
Received: 16 April 2019 / Revised: 5 May 2019 / Accepted: 15 May 2019 / Published: 20 May 2019
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Abstract
Background: Hainosan (Painongsan) is a traditional Japanese and Chinese medicine that is used to treat several purulent diseases, including gingivitis and periodontitis. This formulation contains three crude drug components: The dried immature fruit of Citrus aurantium (Aurantii Fructus Immaturus), the dried root [...] Read more.
Background: Hainosan (Painongsan) is a traditional Japanese and Chinese medicine that is used to treat several purulent diseases, including gingivitis and periodontitis. This formulation contains three crude drug components: The dried immature fruit of Citrus aurantium (Aurantii Fructus Immaturus), the dried root of Paeonia lactiflora (Paeoniae Radix), and the dried root of Platycodon grandiflorum (Platycodi Radix). Here we evaluated the in vitro antibacterial effects of hainosan extract (HNS) and extracts of its three components against Porphyromonas gingivalis, one of the pathogenic bacteria that causes periodontitis. Methods: The antibacterial activities of HNS and its components were examined by counting the number of colony-forming units (CFUs) and through transmission electron microscopy. Results: We found that HNS had direct antibacterial activity against three P. gingivalis isolates (JCM12257, JCM8525, and JCM19600), with HNS-treated cells being significantly smaller than those of untreated bacteria. Extracts of Platycodi Radix and Paeoniae Radix significantly suppressed the growth of P. gingivalis in a dose-dependent manner, with Platycodi Radix extract having the greatest antibacterial effect. In addition, P. gingivalis that were treated with Platycodi Radix extract were significantly larger than those treated with Aurantii Fructus Immaturus or Paeoniae Radix extracts. Further analysis showed that platycodin D, which is one of the ingredients of Platycodi Radix, reduced bacterial growth. Conclusions: Platycodi Radix is the active component in Hainosan and may represent a useful agent for the treatment of P. gingivalis-induced gingivitis and periodontitis. Full article
(This article belongs to the Special Issue Natural Compounds as Potential Antibacterial Agents)
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Open AccessArticle
Phytochemical Composition and Biological Activities of Wild Scolymus maculatus L.
Received: 21 March 2019 / Revised: 19 April 2019 / Accepted: 27 April 2019 / Published: 30 April 2019
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Abstract
Background: The wild population of spotted golden thistle, Scolymus maculatus, which belongs to the Compositae family, is believed to be one of the multi-curative wild plants mentioned in Flora Palaestina. This study aims to disclose the phytochemical composition, antioxidant potential, and [...] Read more.
Background: The wild population of spotted golden thistle, Scolymus maculatus, which belongs to the Compositae family, is believed to be one of the multi-curative wild plants mentioned in Flora Palaestina. This study aims to disclose the phytochemical composition, antioxidant potential, and antimicrobial activity of wild S. maculatus collected from the farms of Kabul, a village in northwest Galilee, for the first time. Methods: The phytochemical components of crude S. maculatus extracts from methanol, ethyl acetate, and n-hexane solvents were separated and identified using gas chromatography-mass spectrometry (GC-MS) in the electron impact (EI) mode. The free radical scavenging of the plant extracts was measured by DPPH assay. The microdilution test was used to determine the minimum inhibitory concentrations (MICs) of different S. maculatus extracts and to evaluate their antimicrobial activities. Results: Thirty-two phytochemicals were found in S. maculatus extracts including stigmasterol, γ-sitosterol, lupeol, lupeol acetate, and β-amyrin. Phytochemicals, such as 2-linoleoylglycerol, γ-sitosterol, β-amyrin, lupeol, (3α)-12-oleanen-3-yl acetate, and lupenyl acetate, were found to dominate the methanol extract. Most of these compounds were also observed in ethyl acetate and n-hexane extracts, but at different levels, in addition to some other minor compounds. The various extracts were investigated for their antioxidant and antimicrobial activity. The ethanolic and the methanolic extracts were shown to exhibit the highest free radical scavenging by DPPH assay with a half-maximally effective concentration (EC50) of 0.37 and 0.65 mg/mL respectively, while the other three extracts (aqueous, ethyl acetate and n-hexane) were less active and their EC50 (effective concentration at which DPPH radical was scavenged by 50%) were above 1.0 mg/mL. Moreover, MICs were determined to be effective against Staphylococcus aureus, Salmonella typhimurium, and Candida albicans microorganisms. Ethyl acetate and the ethanolic extracts are active against the three types of microorganisms at a minimum inhibitory concentration (MIC) of 0.5 mg/mL, while aqueous and the n-hexane extracts are inactive against Salmonella typhimurium. Conclusions: The results show that S. maculatus extracts are a rich source of compounds that can play an important role in human health, and in a broader context, in the treatment of various diseases, such antimicrobial and antioxidant-related ailments. Full article
(This article belongs to the Special Issue Natural Compounds as Potential Antibacterial Agents)
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Open AccessArticle
A New Approach for Indexing Honey for Its Heath/Medicinal Benefits: Visualization of the Concept by Indexing Based on Antioxidant and Antibacterial Activities
Medicines 2018, 5(4), 135; https://doi.org/10.3390/medicines5040135
Received: 29 November 2018 / Revised: 7 December 2018 / Accepted: 10 December 2018 / Published: 17 December 2018
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Abstract
Background: The goals of the current study were to address a new concept termed a health benefits’ index (HBI) and to verify the type of correlation between the pricing of honey and its HBI/medicinal properties. Diverse types of honey from different origins and [...] Read more.
Background: The goals of the current study were to address a new concept termed a health benefits’ index (HBI) and to verify the type of correlation between the pricing of honey and its HBI/medicinal properties. Diverse types of honey from different origins and places were investigated for their antioxidant and antimicrobial activity. Methods: We have utilized a modified protocol of the DPPH assay for measuring free radical scavenging and the microdilution test for the determination of antibacterial/antifungal minimum inhibitory concentrations (MICs). MICs were determined against Staphylococcus aureus, Escherichia coli, Salmonella typhimurium, and Candida albicans microorganisms. Employing a “combined benefits approach” enabled us to attach to each honey type a unique number of HBI that correlate with honey health and medicinal values. Results: The various types of honey demonstrated significant but variable antioxidant, antibacterial, and antifungal activities. Types of wildflower-labeled honey were found to have a wide range of HBI values and medicinal properties, probably due to their containing different nectar contents/phytochemicals. Moreover, an inconsiderable correlation was detected between the market prices of different types of honey and their HBIs. Conclusions: The proposed index of health benefits could be recalculated/updated following measurement of more and more medicinal properties, such as anti-inflammatory, antidiabetic, and anticancer activities. This index could be used as an effective tool for consumers of honey to evaluate the real value of the purchased product. Full article
(This article belongs to the Special Issue Natural Compounds as Potential Antibacterial Agents)
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Review

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Open AccessReview
Clinical and Basic Studies on Therapeutic Efficacy of Herbal Medicines against Mycobacterial Infections
Received: 14 May 2019 / Revised: 13 June 2019 / Accepted: 14 June 2019 / Published: 19 June 2019
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Abstract
The high incidence of tuberculosis (TB) in developing countries, the resurgence of TB in industrialized countries, and the worldwide increase in the prevalence of Mycobacterium avium complex infections are important global health concerns. However, the development of novel antimycobacterial drugs is currently making [...] Read more.
The high incidence of tuberculosis (TB) in developing countries, the resurgence of TB in industrialized countries, and the worldwide increase in the prevalence of Mycobacterium avium complex infections are important global health concerns. However, the development of novel antimycobacterial drugs is currently making very slow progress. Therefore, it is considered that devising improved administration protocols for clinical treatment against intractable mycobacteriosis using existing chemotherapeutics is more practical than awaiting the development of new antimycobacterial drugs. The regulation of host immune responses using immunoadjunctive agents may increase the efficacy of antimicrobial treatment against mycobacteriosis. In particular, the mild and long-term up-regulation of host immune reactions against mycobacterial pathogens using herbal medicines may be beneficial for such immunoadjunctive therapy. This review focuses on the current status regarding basic and clinical studies on protocols using herbal medicines, including medicinal plants, useful for the clinical treatment of intractable mycobacterial infections. Full article
(This article belongs to the Special Issue Natural Compounds as Potential Antibacterial Agents)
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