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A special issue of Pharmaceutics (ISSN 1999-4923). This special issue belongs to the section "Drug Targeting and Design".

Deadline for manuscript submissions: closed (30 October 2021) | Viewed by 56646

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Prof. Dr. Aura Rusu

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Pharmaceutical and Therapeutical Chemistry Department, Faculty of Pharmacy, George Emil Palade University of Medicine, Pharmacy, Science and Technology of Târgu Mureș, 38 Gheorghe Marinescu Street, 540142 Targu Mureș, Romania
Interests: pharmaceutical chemistry; medicinal chemistry; drug design; antibacterial agents; metal complexes; drug analysis; capillary electrophoresis; patient–pharmacist communication
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Prof. Dr. Valentina Uivarosi

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General and Inorganic Chemistry Department, Faculty of Pharmacy, Carol Davila University of Medicine and Pharmacy, 6 Traian Vuia Street, Sector 2, 020956 Bucharest, Romania
Interests: design of new metal complexes with biological activity (e.g., antibacterial, anticancer, and antidiabetic activity); synthesis; characterization; DNA binding and protein interaction studies; cytotoxicity studies; drug repositioning
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Dr. Corneliu Tanase

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Department of Pharmaceutical Botany, Faculty of Pharmacy “George Emil Palade” University of Medicine, Pharmacy, Sciences and Technology of Târgu Mureș, 38 Gheorghe Marinescu Street, Târgu Mureș, 540139 Mureș, Romania
Interests: natural compounds; wood byproducts; nanomaterials; bioactivity; antimicrobial; antioxidant
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Special Issue Information

Dear Colleagues,

The design of new antibiotics is still considered the primary weapon in the fight against the growing phenomenon of bacterial resistance to known antibiotics. Pharmaceutical research is focused on new approaches that lead to novel successful compounds within a short time. A new trend is targeting old antibiotics and other compounds from various therapeutic classes for optimization and repositioning. Hybrid drugs that incorporate two active compounds into a single molecule could expand antibacterial activity and prevent bacterial resistance. Different metal complexes of antibiotics or other organic substances have already shown potential for antibacterial activity. Nanoparticles (e.g., silver nanoparticles) are very attractive in multiple medical applications. Thus, in the last decade, new classes of antibiotics have been sought. New types of compounds with antibacterial activity are in various research stages: proteic compounds, siderophores, quinoxolidinones, natural antibiotics, antibiotic resistance breakers, and others. This Special Issue aims to present the latest efforts towards the discovery of new antibiotics.

Prof. Dr. Aura Rusu
Prof. Dr. Valentina Uivarosi
Dr. Corneliu Tanase
Guest Editors

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Keywords

antibiotics
hybrid antibiotics
metal complexes
nanoparticles
silver nanoparticles
natural antibiotics
bioactive compounds
drug repurposing
drug repositioning
antibiotic resistance breakers
antibacterial drug resistance
antibiotic resistance

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Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development, 2nd Edition in Pharmaceutics (10 articles)

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Research

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13 pages, 2828 KiB

Open AccessArticle

Ceftriaxone Mediated Synthesized Gold Nanoparticles: A Nano-Therapeutic Tool to Target Bacterial Resistance

by Farhan Alshammari, Bushra Alshammari, Afrasim Moin, Abdulwahab Alamri, Turki Al Hagbani, Ahmed Alobaida, Abu Baker, Salman Khan and Syed Mohd Danish Rizvi

Pharmaceutics 2021, 13(11), 1896; https://doi.org/10.3390/pharmaceutics13111896 - 8 Nov 2021

Cited by 23 | Viewed by 4206

Abstract

Ceftriaxone has been a part of therapeutic regime for combating some of the most aggressive bacterial infections in the last few decades. However, increasing bacterial resistance towards ceftriaxone and other third generation cephalosporin antibiotics has raised serious clinical concerns especially due to their misuse in the COVID-19 era. Advancement in nanotechnology has converted nano-therapeutic vision into a plausible reality with better targeting and reduced drug consumption. Thus, in the present study, gold nanoparticles (GNPs) were synthesized by using ceftriaxone antibiotic that acts as a reducing as well as capping agent. Ceftriaxone-loaded GNPs (CGNPs) were initially characterized by UV-visible spectroscopy, DLS, Zeta potential, Electron microscopy and FT-IR. However, a TEM micrograph showed a uniform size of 21 ± 1 nm for the synthesized CGNPs. Further, both (CGNPs) and pure ceftriaxone were examined for their efficacy against Escherichia coli, Staphylococcus aureus, Salmonella abony and Klebsiella pneumoniae. CGNPs showed MIC₅₀ as 1.39, 1.6, 1.1 and 0.9 µg/mL against E. coli, S. aureus, S. abony and K. pneumoniae, respectively. Interestingly, CGNPs showed two times better efficacy when compared with pure ceftriaxone against the tested bacterial strains. Restoring the potential of unresponsive or less efficient ceftriaxone via gold nanoformulations is the most alluring concept of the whole study. Moreover, applicability of the findings from bench to bedside needs further validation. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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23 pages, 6697 KiB

Open AccessArticle

Development of Novel Peptides for the Antimicrobial Combination Therapy against Carbapenem-Resistant Acinetobacter baumannii Infection

by Joonhyeok Choi, Ahjin Jang, Young Kyung Yoon and Yangmee Kim

Pharmaceutics 2021, 13(11), 1800; https://doi.org/10.3390/pharmaceutics13111800 - 27 Oct 2021

Cited by 17 | Viewed by 3108

Abstract

Carbapenem-resistant Acinetobacter baumannii (CRAB) infection has a high mortality rate, making the development of novel effective antibiotic therapeutic strategies highly critical. Antimicrobial peptides can outperform conventional antibiotics regarding drug resistance and broad-spectrum activity. PapMA, an 18-residue hybrid peptide, containing N-terminal residues of papiliocin and magainin 2, has previously demonstrated potent antibacterial activity. In this study, PapMA analogs were designed by substituting Ala¹⁵ or Phe¹⁸ with Ala, Phe, and Trp. PapMA-3 with Trp¹⁸ showed the highest bacterial selectivity against CRAB, alongside low cytotoxicity. Biophysical studies revealed that PapMA-3 permeabilizes CRAB membrane via strong binding to LPS. To reduce toxicity via reduced antibiotic doses, while preventing the emergence of multi-drug resistant bacteria, the efficacy of PapMA-3 in combination with six selected antibiotics was evaluated against clinical CRAB isolates (C1–C5). At 25% of the minimum inhibition concentration, PapMA-3 partially depolarized the CRAB membrane and caused sufficient morphological changes, facilitating the entry of antibiotics into the bacterial cell. Combining PapMA-3 with rifampin significantly and synergistically inhibited CRAB C4 (FICI = 0.13). Meanwhile, combining PapMA-3 with vancomycin or erythromycin, both potent against Gram-positive bacteria, demonstrated remarkable synergistic antibiofilm activity against Gram-negative CRAB. This study could aid in the development of combination therapeutic approaches against CRAB. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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19 pages, 7760 KiB

Open AccessArticle

Characterization and Genome Analysis of Arthrobacter bangladeshi sp. nov., Applied for the Green Synthesis of Silver Nanoparticles and Their Antibacterial Efficacy against Drug-Resistant Human Pathogens

by Md. Amdadul Huq and Shahina Akter

Pharmaceutics 2021, 13(10), 1691; https://doi.org/10.3390/pharmaceutics13101691 - 15 Oct 2021

Cited by 17 | Viewed by 2386

Abstract

The present study describes the isolation and characterization of novel bacterial species Arthrobacter bangladeshi sp. nov., applied for the green synthesis of AgNPs, and investigates its antibacterial efficacy against drug-resistant pathogenic Salmonella Typhimurium and Yersinia enterocolitica. Novel strain MAHUQ-56^T is Gram-positive, aerobic, non-motile, and rod-shaped. Colonies were spherical and milky white. The strain showed positive activity for catalase and nitrate reductase, and the hydrolysis of starch, L-tyrosine, casein, and Tween 20. On the basis of the 16S rRNA gene sequence, strain MAHUQ-56^T belongs to the Arthrobacter genus and is most closely related to Arthrobacter pokkalii P3B162^T (98.6%). Arthrobacter bangladeshi MAHUQ-56^T has a genome 4,566,112 bp long (26 contigs) with 4125 protein-coding genes, 51 tRNA and 6 rRNA genes. The culture supernatant of Arthrobacter bangladeshi MAHUQ-56^T was used for the easy and green synthesis of AgNPs. Synthesized AgNPs were characterized by UV–vis spectroscopy, FE-TEM, XRD, DLS, and FT-IR. Synthesized AgNPs were spherical and 12–50 nm in size. FT-IR analysis revealed various biomolecules that may be involved in the synthesis process. Synthesized AgNPs showed strong antibacterial activity against multidrug-resistant pathogenic S. typhimurium and Y. enterocolitica. MIC values of the synthesized AgNPs against S. typhimurium and Y. enterocolitica were 6.2 and 3.1 ug/mL, respectively. The MBC of synthesized AgNPs for both pathogens was 12.5 ug/mL. FE-SEM analysis revealed the morphological and structural alterations, and damage of pathogens treated by AgNPs. These changes might disturb normal cellular functions, which ultimately leads to the death of cells. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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15 pages, 3514 KiB

Open AccessArticle

Titanium Dioxide Nanoparticles Induce Inhibitory Effects against Planktonic Cells and Biofilms of Human Oral Cavity Isolates of Rothia mucilaginosa, Georgenia sp. and Staphylococcus saprophyticus

by Saher Fatima, Khursheed Ali, Bilal Ahmed, Abdulaziz A. Al Kheraif, Asad Syed, Abdallah M. Elgorban, Javed Musarrat and Jintae Lee

Pharmaceutics 2021, 13(10), 1564; https://doi.org/10.3390/pharmaceutics13101564 - 26 Sep 2021

Cited by 16 | Viewed by 2913

Abstract

Multi-drug resistant (MDR) bacterial cells embedded in biofilm matrices can lead to the development of chronic cariogenesis. Here, we isolated and identified three Gram-positive MDR oral cocci, (1) SJM-04, (2) SJM-38, and (3) SJM-65, and characterized them morphologically, biochemically, and by 16S rRNA gene-based phylogenetic analysis as Georgenia sp., Staphylococcus saprophyticus, and Rothia mucilaginosa, respectively. These three oral isolates exhibited antibiotic-resistance against nalidixic acid, tetracycline, cefuroxime, methicillin, and ceftazidime. Furthermore, these Gram positive MDR oral cocci showed significant (p < 0.05) variations in their biofilm forming ability under different physicochemical conditions, that is, at temperatures of 28, 30, and 42 °C, pH of 6.4, 7.4, and 8.4, and NaCl concentrations from 200 to 1000 µg/mL. Exposure of oral isolates to TiO₂NPs (14.7 nm) significantly (p < 0.05) reduced planktonic cell viability and biofilm formation in a concentration-dependent manner, which was confirmed by observing biofilm architecture by scanning electron microscopy (SEM) and optical microscopy. Overall, these results have important implications for the use of tetragonal anatase phase TiO₂NPs (size range 5–25 nm, crystalline size 13.7 nm, and spherical shape) as an oral antibiofilm agent against Gram positive cocci infections. We suggest that TiO₂NPs pave the way for further applications in oral mouthwash formulations and antibiofilm dental coatings. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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21 pages, 2005 KiB

Open AccessArticle

Antimicrobial Properties of Lepidium sativum L. Facilitated Silver Nanoparticles

by Samir Haj Bloukh, Zehra Edis, Hamid Abu Sara and Mustafa Ameen Alhamaidah

Pharmaceutics 2021, 13(9), 1352; https://doi.org/10.3390/pharmaceutics13091352 - 27 Aug 2021

Cited by 15 | Viewed by 3666

Abstract

Antibiotic resistance toward commonly used medicinal drugs is a dangerously growing threat to our existence. Plants are naturally equipped with a spectrum of biomolecules and metabolites with important biological activities. These natural compounds constitute a treasure in the fight against multidrug-resistant microorganisms. The development of plant-based antimicrobials through green synthesis may deliver alternatives to common drugs. Lepidium sativum L. (LS) is widely available throughout the world as a fast-growing herb known as garden cress. LS seed oil is interesting due to its antimicrobial, antioxidant, and anti-inflammatory activities. Nanotechnology offers a plethora of applications in the health sector. Silver nanoparticles (AgNP) are used due to their antimicrobial properties. We combined LS and AgNP to prevent microbial resistance through plant-based synergistic mechanisms within the nanomaterial. AgNP were prepared by a facile one-pot synthesis through plant-biomolecules-induced reduction of silver nitrate via a green method. The phytochemicals in the aqueous LS extract act as reducing, capping, and stabilizing agents of AgNP. The composition of the LS-AgNP biohybrids was confirmed by analytical methods. Antimicrobial testing against 10 reference strains of pathogens exhibited excellent to intermediate antimicrobial activity. The bio-nanohybrid LS-AgNP has potential uses as a broad-spectrum microbicide, disinfectant, and wound care product. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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12 pages, 2161 KiB

Open AccessArticle

Inhibition of Indigoidine Synthesis as a High-Throughput Colourimetric Screen for Antibiotics Targeting the Essential Mycobacterium tuberculosis Phosphopantetheinyl Transferase PptT

by Alistair S. Brown, Jeremy G. Owen, James Jung, Edward N. Baker and David F. Ackerley

Pharmaceutics 2021, 13(7), 1066; https://doi.org/10.3390/pharmaceutics13071066 - 12 Jul 2021

Cited by 5 | Viewed by 2616

Abstract

A recently-validated and underexplored drug target in Mycobacterium tuberculosis is PptT, an essential phosphopantetheinyl transferase (PPTase) that plays a critical role in activating enzymes for both primary and secondary metabolism. PptT possesses a deep binding pocket that does not readily accept labelled coenzyme A analogues that have previously been used to screen for PPTase inhibitors. Here we report on the development of a high throughput, colourimetric screen that monitors the PptT-mediated activation of the non-ribosomal peptide synthetase BpsA to a blue pigment (indigoidine) synthesising form in vitro. This screen uses unadulterated coenzyme A, avoiding analogues that may interfere with inhibitor binding, and requires only a single-endpoint measurement. We benchmark the screen using the well-characterised Library of Pharmaceutically Active Compounds (LOPAC¹²⁸⁰) collection and show that it is both sensitive and able to distinguish weak from strong inhibitors. We further show that the BpsA assay can be applied to quantify the level of inhibition and generate consistent EC₅₀ data. We anticipate these tools will facilitate both the screening of established chemical collections to identify new anti-mycobacterial drug leads and to guide the exploration of structure-activity landscapes to improve existing PPTase inhibitors. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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23 pages, 3741 KiB

Open AccessArticle

Antibacterial Activity of Co(III) Complexes with Diamine Chelate Ligands against a Broad Spectrum of Bacteria with a DNA Interaction Mechanism

by Katarzyna Turecka, Agnieszka Chylewska, Michał Rychłowski, Joanna Zakrzewska and Krzysztof Waleron

Pharmaceutics 2021, 13(7), 946; https://doi.org/10.3390/pharmaceutics13070946 - 24 Jun 2021

Cited by 16 | Viewed by 3060

Abstract

Cobalt coordination complexes are very attractive compounds for their therapeutic uses as antiviral, antibacterial, antifungal, antiparasitic, or antitumor agents. Two Co(III) complexes with diamine chelate ligands ([CoCl₂(dap)₂]Cl (1) and [CoCl₂(en)₂]Cl (2)) (where dap = 1,3-diaminopropane, en = ethylenediamine) were synthesized and characterized by elemental analysis, an ATR technique, and a scan method and sequentially tested against Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration results revealed that anaerobic and microaerophilic bacteria were found to be the most sensitive; the serial passages assay presented insignificant increases in bacterial resistance to both compounds after 20 passages. The synergy assay showed a significant reduction in the MIC values of nalidixic acid when combined with Compounds (1) or (2). The assessment of cell damage by the complexes was performed using scanning electron microscopy, transmission electron microscopy, and confocal microscopy, which indicated cell membrane permeability, deformation, and altered cell morphology. DNA interaction studies of the Co(III) complexes with plasmid pBR322 using spectrophotometric titration methods revealed that the interaction between Complex (1) or (2) and DNA suggested an electrostatic and intercalative mode of binding, respectively. Furthermore, the DNA cleavage ability of compounds by agarose gel electrophoresis showed nuclease activity for both complexes. The results suggest that the effect of the tested compounds against bacteria can be complex. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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30 pages, 6289 KiB

Open AccessReview

The Development of Third-Generation Tetracycline Antibiotics and New Perspectives

by Aura Rusu and Emanuela Lorena Buta

Pharmaceutics 2021, 13(12), 2085; https://doi.org/10.3390/pharmaceutics13122085 - 5 Dec 2021

Cited by 87 | Viewed by 13029

Abstract

The tetracycline antibiotic class has acquired new valuable members due to the optimisation of the chemical structure. The first modern tetracycline introduced into therapy was tigecycline, followed by omadacycline, eravacycline, and sarecycline (the third generation). Structural and physicochemical key elements which led to the discovery of modern tetracyclines are approached. Thus, several chemical subgroups are distinguished, such as glycylcyclines, aminomethylcyclines, and fluorocyclines, which have excellent development potential. The antibacterial spectrum comprises several resistant bacteria, including those resistant to old tetracyclines. Sarecycline, a narrow-spectrum tetracycline, is notable for being very effective against Cutinebacterium acnes. The mechanism of antibacterial action from the perspective of the new compound is approached. Several severe bacterial infections are treated with tigecycline, omadacycline, and eravacycline (with parenteral or oral formulations). In addition, sarecycline is very useful in treating acne vulgaris. Tetracyclines also have other non-antibiotic properties that require in-depth studies, such as the anti-inflammatory effect effect of sarecycline. The main side effects of modern tetracyclines are described in accordance with published clinical studies. Undoubtedly, this class of antibiotics continues to arouse the interest of researchers. As a result, new derivatives are developed and studied primarily for the antibiotic effect and other biological effects. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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37 pages, 11273 KiB

Open AccessReview

Structural Characterization of the Millennial Antibacterial (Fluoro)Quinolones—Shaping the Fifth Generation

by Aura Rusu, Ioana-Andreea Lungu, Octavia-Laura Moldovan, Corneliu Tanase and Gabriel Hancu

Pharmaceutics 2021, 13(8), 1289; https://doi.org/10.3390/pharmaceutics13081289 - 18 Aug 2021

Cited by 29 | Viewed by 8502

Abstract

The evolution of the class of antibacterial quinolones includes the introduction in therapy of highly successful compounds. Although many representatives were withdrawn due to severe adverse reactions, a few representatives have proven their therapeutical value over time. The classification of antibacterial quinolones into generations is a valuable tool for physicians, pharmacists, and researchers. In addition, the transition from one generation to another has brought new representatives with improved properties. In the last two decades, several representatives of antibacterial quinolones received approval for therapy. This review sets out to chronologically outline the group of approved antibacterial quinolones since 2000. Special attention is given to eight representatives: besifloxacin, delafoxacin, finafloxacin, lascufloxacin, nadifloxacin and levonadifloxacin, nemonoxacin, and zabofloxacin. These compounds have been characterized regarding physicochemical properties, formulations, antibacterial activity spectrum and advantageous structural characteristics related to antibacterial efficiency. At present these new compounds (with the exception of nadifloxacin) are reported differently, most often in the fourth generation and less frequently in a new generation (the fifth). Although these new compounds’ mechanism does not contain essential new elements, the question of shaping a new generation (the fifth) arises, based on higher potency and broad spectrum of activity, including resistant bacterial strains. The functional groups that ensured the biological activity, good pharmacokinetic properties and a safety profile were highlighted. In addition, these new representatives have a low risk of determining bacterial resistance. Several positive aspects are added to the fourth fluoroquinolones generation, characteristics that can be the basis of the fifth generation. Antibacterial quinolones class continues to acquire new compounds with antibacterial potential, among other effects. Numerous derivatives, hybrids or conjugates are currently in various stages of research. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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32 pages, 30775 KiB

Open AccessReview

Myxobacteria as a Source of New Bioactive Compounds: A Perspective Study

by Mudasir Ahmad Bhat, Awdhesh Kumar Mishra, Mujtaba Aamir Bhat, Mohammad Iqbal Banday, Ommer Bashir, Irfan A. Rather, Safikur Rahman, Ali Asghar Shah and Arif Tasleem Jan

Pharmaceutics 2021, 13(8), 1265; https://doi.org/10.3390/pharmaceutics13081265 - 16 Aug 2021

Cited by 18 | Viewed by 4584

Abstract

Myxobacteria are unicellular, Gram-negative, soil-dwelling, gliding bacteria that belong to class δ-proteobacteria and order Myxococcales. They grow and proliferate by transverse fission under normal conditions, but form fruiting bodies which contain myxospores during unfavorable conditions. In view of the escalating problem of antibiotic resistance among disease-causing pathogens, it becomes mandatory to search for new antibiotics effective against such pathogens from natural sources. Among the different approaches, Myxobacteria, having a rich armor of secondary metabolites, preferably derivatives of polyketide synthases (PKSs) along with non-ribosomal peptide synthases (NRPSs) and their hybrids, are currently being explored as producers of new antibiotics. The Myxobacterial species are functionally characterized to assess their ability to produce antibacterial, antifungal, anticancer, antimalarial, immunosuppressive, cytotoxic and antioxidative bioactive compounds. In our study, we have found their compounds to be effective against a wide range of pathogens associated with the concurrence of different infectious diseases. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

51 pages, 9209 KiB

Open AccessReview

Ruthenium Complexes in the Fight against Pathogenic Microorganisms. An Extensive Review

by Alexandra-Cristina Munteanu and Valentina Uivarosi

Pharmaceutics 2021, 13(6), 874; https://doi.org/10.3390/pharmaceutics13060874 - 13 Jun 2021

Cited by 61 | Viewed by 6044

Abstract

The widespread use of antibiotics has resulted in the emergence of drug-resistant populations of microorganisms. Clearly, one can see the need to develop new, more effective, antimicrobial agents that go beyond the explored ‘chemical space’. In this regard, their unique modes of action (e.g., reactive oxygen species (ROS) generation, redox activation, ligand exchange, depletion of substrates involved in vital cellular processes) render metal complexes as promising drug candidates. Several Ru (II/III) complexes have been included in, or are currently undergoing, clinical trials as anticancer agents. Based on the in-depth knowledge of their chemical properties and biological behavior, the interest in developing new ruthenium compounds as antibiotic, antifungal, antiparasitic, or antiviral drugs has risen. This review will discuss the advantages and disadvantages of Ru (II/III) frameworks as antimicrobial agents. Some aspects regarding the relationship between their chemical structure and mechanism of action, cellular localization, and/or metabolism of the ruthenium complexes in bacterial and eukaryotic cells are discussed as well. Regarding the antiviral activity, in light of current events related to the Covid-19 pandemic, the Ru (II/III) compounds used against SARS-CoV-2 (e.g., BOLD-100) are also reviewed herein. Full article

(This article belongs to the Special Issue Focus on Antibiotics – New Challenges and Steps Forward in Discovery and Development)

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