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Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume
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Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "Novel Antimicrobial Agents".

Deadline for manuscript submissions: closed (31 July 2023) | Viewed by 26513

Special Issue Editor

Dr. Maria Fernanda N. N. Carvalho

E-Mail Website
Guest Editor
Instituto Superior Técnico, University of Lisbon, 1049-001 Lisbon, Portugal
Interests: synthesis of coordination and organic compounds; medicinal chemistry; drugs; bioactive compounds; redox properties
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleague,

You are invited to communicate your recent scientific achievements concerning new strategies to fight microbial infections in the MDPI Special Issue “Synthesis and Biological Activity of Antimicrobial Agents” (2nd Volume). At the moment, infection with the SARS-CoV-2 virus is a threat that has been clearly perceived all over the world. Less widespread and broadcast is the concern regarding microorganisms such as bacteria and fungi, especially for those with depleted immune systems. According to The Lancet (Jan 2022), 4.95 million people died in 2019 due to antimicrobial resistance to commercially available antimicrobials.

Compounds, both those that are natural or synthetic, that are able to fight the increasing number of bacteria, fungi, and viruses and resistance to the currently available antimicrobials are necessary. The synthesis, characterization, and evaluation of the antimicrobial properties of organic or coordinated compounds is a key step to identify promising new antimicrobial agents. Other relevant steps are the study of redox properties, reaction mechanisms, and bioinformatic analysis to understand, redesign, and optimize the characteristics of potential active molecules.

The aim of this Special Issue is to put together significant research on molecules that have the potential to contribute to reducing the number of fatalities caused by bacteria or fungi as well as controlling emerging microorganisms in agricultural crops and food.

Dr. Maria Fernanda N. N. Carvalho
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Antibiotics is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2900 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • bacteria
  • fungi
  • organic compounds
  • coordination compounds
  • synthesis
  • bioinformatic analysis

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Published Papers (16 papers)

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Editorial

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5 pages, 203 KiB  
Editorial
Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume
by Maria Fernanda N. N. Carvalho
Antibiotics 2023, 12(11), 1564; https://doi.org/10.3390/antibiotics12111564 - 26 Oct 2023
Viewed by 784
Abstract
Microorganisms are abundant and necessary [...] Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)

Research

Jump to: Editorial, Review

14 pages, 2382 KiB  
Article
Antimicrobial Effect of Low-Fluoride Toothpastes Containing Polyphosphate and Polyols: An In Vitro Assessment of Inhibition Zones
by Igor Zen, Alberto Carlos Botazzo Delbem, Thayse Yumi Hosida, Caio Sampaio, Leonardo Antônio de Morais, Tamires Passadori Martins, Douglas Roberto Monteiro and Juliano Pelim Pessan
Antibiotics 2023, 12(8), 1333; https://doi.org/10.3390/antibiotics12081333 - 18 Aug 2023
Cited by 1 | Viewed by 1072
Abstract
This study evaluated the antimicrobial effect of toothpastes containing 200 ppm fluoride (200F), xylitol (X, 16%), erythritol (E, 4%), and sodium trimetaphosphate (TMP, 0.25%), alone or in different associations, against Streptococcus mutans (SM), Lactobacillus casei (LC), Actinomyces israelii (AI), and Candida albicans (CA). [...] Read more.
This study evaluated the antimicrobial effect of toothpastes containing 200 ppm fluoride (200F), xylitol (X, 16%), erythritol (E, 4%), and sodium trimetaphosphate (TMP, 0.25%), alone or in different associations, against Streptococcus mutans (SM), Lactobacillus casei (LC), Actinomyces israelii (AI), and Candida albicans (CA). Suspensions of the micro-organisms were added to a BHI Agar medium. Five wells were made on each plate to receive toothpaste suspensions at different dilutions. Toothpastes containing no actives (placebo) or 1100 ppm F (1100F) were used as negative and positive controls. Two-way ANOVA and Tukey’s HDS test were used (p < 0.05). For SM, the largest halo was for 200F+TMP at all dilutions, followed by the 200F+X+E toothpaste (p < 0.001). For LC, the overall trend showed that the polyols effectively inhibited microbial growth, and the association with the other compounds enhanced such effects (p < 0.001). For AI, a less-defined trend was observed. For CA, the experimental toothpaste (200F+X+E+TMP) was consistently more effective than the other treatments, followed by 200F+X+E (p < 0.001). The association of polyols and TMP in a low-fluoride toothpaste effectively reduced the growth of cariogenic micro-organisms (SM, CA, and LC), suggesting that this formulation could be an interesting alternative for children due to its low fluoride content. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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25 pages, 3441 KiB  
Article
New N-acyl Thiourea Derivatives: Synthesis, Standardized Quantification Method and In Vitro Evaluation of Potential Biological Activities
by Roxana Roman, Lucia Pintilie, Miron Teodor Căproiu, Florea Dumitrașcu, Diana Camelia Nuță, Irina Zarafu, Petre Ioniță, Mariana Carmen Chifiriuc, Cornel Chiriță, Alina Moroșan, Marcela Popa, Coralia Bleotu and Carmen Limban
Antibiotics 2023, 12(5), 807; https://doi.org/10.3390/antibiotics12050807 - 25 Apr 2023
Cited by 2 | Viewed by 1742
Abstract
New N-acyl thiourea derivatives with heterocyclic rings have been synthesized by first obtaining isothiocyanate, which further reacted with a heterocyclic amine, characterized by (FT-IR, NMR spectroscopy and FT-ICR) and tested for their in vitro antimicrobial, anti-biofilm and antioxidant activities to obtain a drug [...] Read more.
New N-acyl thiourea derivatives with heterocyclic rings have been synthesized by first obtaining isothiocyanate, which further reacted with a heterocyclic amine, characterized by (FT-IR, NMR spectroscopy and FT-ICR) and tested for their in vitro antimicrobial, anti-biofilm and antioxidant activities to obtain a drug candidate in a lead-optimization process. From the tested compounds, those bearing benzothiazole (1b) and 6-methylpyridine (1d) moieties revealed anti-biofilm activity against E. coli ATCC 25922 at MBIC values of 625 µg/mL. Compound 1d exhibited the highest antioxidant capacity (~43%) in the in vitro assay using 1,1-diphenyl-2-picrylhydrazyl (DPPH). Considering the in vitro results, the highest anti-biofilm and antioxidant activities were obtained for compound 1d. Therefore, a reversed-phase high-performance liquid chromatography (RP-HPLC) method has been optimized and validated for the quantitative determination of compound 1d. The detection and quantitation limits were 0.0174 μg/mL and 0.0521 μg/mL, respectively. The R2 correlation coefficient of the LOQ and linearity curves were greater than 0.99, over the concentration range of 0.05 μg/mL–40 μg/mL. The precision and accuracy of the analytical method were within 98–102%, confirming that the method is suitable for the quantitative determination of compound 1d in routine quality control analyses. Evaluating the results, the promising potential of the new N-acyl thiourea derivatives bearing 6-methylpyridine moiety will be further investigated for developing agents with anti-biofilm and antioxidant activities. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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17 pages, 2845 KiB  
Article
Synthesis, Molecular Docking Study, and Biological Evaluation of New 4-(2,5-Dimethyl-1H-pyrrol-1-yl)-N’-(2-(substituted)acetyl)benzohydrazides as Dual Enoyl ACP Reductase and DHFR Enzyme Inhibitors
by Mater H. Mahnashi, Pooja Koganole, Prem Kumar S. R., Sami S. Ashgar, Ibrahim Ahmed Shaikh, Shrinivas D. Joshi and Ali S. Alqahtani
Antibiotics 2023, 12(4), 763; https://doi.org/10.3390/antibiotics12040763 - 16 Apr 2023
Cited by 1 | Viewed by 1416
Abstract
In this study, a new series of 4-(2,5-dimethyl-1H-pyrrol-1-yl)-N’-(2-(substituted)acetyl) benzohydrazides (5a–n) were prepared and new heterocycles underwent thorough characterization and evaluation for antibacterial activity; some of them underwent further testing for in vitro inhibition of enoyl ACP reductase [...] Read more.
In this study, a new series of 4-(2,5-dimethyl-1H-pyrrol-1-yl)-N’-(2-(substituted)acetyl) benzohydrazides (5a–n) were prepared and new heterocycles underwent thorough characterization and evaluation for antibacterial activity; some of them underwent further testing for in vitro inhibition of enoyl ACP reductase and DHFR enzymes. The majority of the synthesized molecules exhibited appreciable action against DHFR and enoyl ACP reductase enzymes. Some of the synthesized compounds also showed strong antibacterial and antitubercular properties. In order to determine the potential mode of action of the synthesized compounds, a molecular docking investigation was conducted. The results revealed binding interactions with both the dihydrofolate reductase and enoyl ACP reductase active sites. These molecules represent excellent future therapeutic possibilities with potential uses in the biological and medical sciences due to the compounds’ pronounced docking properties and biological activity. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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18 pages, 3037 KiB  
Article
Neutralizing Carbapenem Resistance by Co-Administering Meropenem with Novel β-Lactam-Metallo-β-Lactamase Inhibitors
by Nakita Reddy, Letisha Girdhari, Mbongeni Shungube, Arnoldus C. Gouws, Byron K. Peters, Kamal K. Rajbongshi, Sooraj Baijnath, Sipho Mdanda, Thandokuhle Ntombela, Thilona Arumugam, Linda A. Bester, Sanil D. Singh, Anil Chuturgoon, Per I. Arvidsson, Glenn E. M Maguire, Hendrik G. Kruger, Thavendran Govender and Tricia Naicker
Antibiotics 2023, 12(4), 633; https://doi.org/10.3390/antibiotics12040633 - 23 Mar 2023
Cited by 3 | Viewed by 2268
Abstract
Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an [...] Read more.
Virulent Enterobacterale strains expressing serine and metallo-β-lactamases (MBL) genes have emerged responsible for conferring resistance to hard-to-treat infectious diseases. One strategy that exists is to develop β-lactamase inhibitors to counter this resistance. Currently, serine β-lactamase inhibitors (SBLIs) are in therapeutic use. However, an urgent global need for clinical metallo-β-lactamase inhibitors (MBLIs) has become dire. To address this problem, this study evaluated BP2, a novel beta-lactam-derived β-lactamase inhibitor, co-administered with meropenem. According to the antimicrobial susceptibility results, BP2 potentiates the synergistic activity of meropenem to a minimum inhibitory concentration (MIC) of ≤1 mg/L. In addition, BP2 is bactericidal over 24 h and safe to administer at the selected concentrations. Enzyme inhibition kinetics showed that BP2 had an apparent inhibitory constant (Kiapp) of 35.3 µM and 30.9 µM against New Delhi Metallo-β-lactamase (NDM-1) and Verona Integron-encoded Metallo-β-lactamase (VIM-2), respectively. BP2 did not interact with glyoxylase II enzyme up to 500 µM, indicating specific (MBL) binding. In a murine infection model, BP2 co-administered with meropenem was efficacious, observed by the >3 log10 reduction in K. pneumoniae NDM cfu/thigh. Given the promising pre-clinical results, BP2 is a suitable candidate for further research and development as an (MBLI). Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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10 pages, 2550 KiB  
Article
The Activity of Calcium Glycerophosphate and Fluoride against Cariogenic Biofilms of Streptococcus mutans and Candida albicans Formed In Vitro
by Thamires Priscila Cavazana, Thayse Yumi Hosida, Caio Sampaio, Leonardo Antônio de Morais, Douglas Roberto Monteiro, Juliano Pelim Pessan and Alberto Carlos Botazzo Delbem
Antibiotics 2023, 12(2), 422; https://doi.org/10.3390/antibiotics12020422 - 20 Feb 2023
Cited by 2 | Viewed by 1313
Abstract
This study evaluated the effects of calcium glycerophosphate (CaGP), with or without fluoride (F), on dual-species biofilms of Streptococcus mutans and Candida albicans. The biofilms were treated three times with 0.125, 0.25, and 0.5% CaGP solutions, with or without 500 ppm F [...] Read more.
This study evaluated the effects of calcium glycerophosphate (CaGP), with or without fluoride (F), on dual-species biofilms of Streptococcus mutans and Candida albicans. The biofilms were treated three times with 0.125, 0.25, and 0.5% CaGP solutions, with or without 500 ppm F (NaF). Additionally, 500 and 1100 ppm F-solutions and artificial saliva served as controls. After the final treatment, the microbial viability and biofilm structure, metabolic activity, total biomass production, and the composition of the extracellular matrix composition were analyzed. Regardless of the presence of F, 0.25 and 0.5% CaGP promoted a higher biomass production and metabolic activity increase than the controls (p < 0.05). F-free CaGP solutions reduced bacterial cell population significantly more than the 500 ppm F group or the negative control (p < 0.05). All the groups reduced the proteins, and 0.5% CaGP combined with F led to the highest reduction in the carbohydrate and nucleic acids content of the extracellular matrix (p < 0.05). It can be concluded that CaGP alone affected the number of bacterial cells and, when combined with F, reduced its production of biomass, metabolic activity, and the expression of the extracellular matrix components. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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12 pages, 1562 KiB  
Article
Giving a Hand: Synthetic Peptides Boost the Antifungal Activity of Itraconazole against Cryptococcus neoformans
by Tawanny K. B. Aguiar, Ricardo M. Feitosa, Nilton A. S. Neto, Ellen A. Malveira, Francisco I. R. Gomes, Ana C. M. Costa, Cleverson D. T. Freitas, Felipe P. Mesquita and Pedro F. N. Souza
Antibiotics 2023, 12(2), 256; https://doi.org/10.3390/antibiotics12020256 - 27 Jan 2023
Cited by 1 | Viewed by 1299
Abstract
Cryptococcus neoformans is a multidrug-resistant pathogen responsible for infections in immunocompromised patients. Here, itraconazole (ITR), a commercial antifungal drug with low effectiveness against C. neoformans, was combined with different synthetic antimicrobial peptides (SAMPs), Mo-CBP3-PepII, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA. The Mo-CBP3-PepII was [...] Read more.
Cryptococcus neoformans is a multidrug-resistant pathogen responsible for infections in immunocompromised patients. Here, itraconazole (ITR), a commercial antifungal drug with low effectiveness against C. neoformans, was combined with different synthetic antimicrobial peptides (SAMPs), Mo-CBP3-PepII, RcAlb-PepII, RcAlb-PepIII, PepGAT, and PepKAA. The Mo-CBP3-PepII was designed based on the sequence of MoCBP3, purified from Moringa oleifera seeds. RcAlb-PepII and RcAlb-PepIII were designed using Rc-2S-Alb, purified from Ricinus communis seed cakes. The putative sequence of a chitinase from Arabidopsis thaliana was used to design PepGAT and PepKAA. All SAMPs have a positive liquid charge and a hydrophobic potential ranging from 41–65%. The mechanisms of action responsible for the combined effect were evaluated for the best combinations using fluorescence microscopy (FM). The synthetic peptides enhanced the activity of ITR by 10-fold against C. neoformans. Our results demonstrated that the combinations could induce pore formation in the membrane and the overaccumulation of ROS on C. neoformans cells. Our findings indicate that our peptides successfully potentialize the activity of ITR against C. neoformans. Therefore, synthetic peptides are potential molecules to assist antifungal agents in treating Cryptococcal infections. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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19 pages, 4482 KiB  
Article
Antimicrobial Activities and Mode of Flavonoid Actions
by Amal Thebti, Ahmed Meddeb, Issam Ben Salem, Coulibaly Bakary, Sami Ayari, Farhat Rezgui, Khadija Essafi-Benkhadir, Abdellatif Boudabous and Hadda-Imene Ouzari
Antibiotics 2023, 12(2), 225; https://doi.org/10.3390/antibiotics12020225 - 20 Jan 2023
Cited by 8 | Viewed by 2168
Abstract
The emergence of antibiotics-resistant bacteria has been a serious concern for medical professionals over the last decade. Therefore, developing new and effective antimicrobials with modified or different modes of action is a continuing imperative. In this context, our study focuses on evaluating the [...] Read more.
The emergence of antibiotics-resistant bacteria has been a serious concern for medical professionals over the last decade. Therefore, developing new and effective antimicrobials with modified or different modes of action is a continuing imperative. In this context, our study focuses on evaluating the antimicrobial activity of different chemically synthesized flavonoids (FLAV) to guide the chemical synthesis of effective antimicrobial molecules. A set of 12 synthesized molecules (4 chalcones, 4 flavones and 4 flavanones), bearing substitutions with chlorine and bromine groups at the C6′ position and methoxy group at the C4′ position of the B-ring were evaluated for antimicrobial activity toward 9 strains of Gram-positive and Gram-negative bacteria and 3 fungal strains. Our findings showed that most tested FLAV exhibited moderate to high antibacterial activity, particularly against Staphylococcus aureus with minimum inhibitory concentrations (MIC) between the range of 31.25 and 125 μg/mL and that chalcones were more efficient than flavones and flavanones. The examined compounds were also active against the tested fungi with a strong structure-activity relationship (SAR). Interestingly, leakage measurements of the absorbent material at 260 nm and scanning electron microscopy (SEM) demonstrated that the brominated chalcone induced a significant membrane permeabilization of S. aureus. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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21 pages, 2948 KiB  
Article
New Insights into the Mechanism of Antibacterial Action of Synthetic Peptide Mo-CBP3-PepI against Klebsiella pneumoniae
by Levi A. C. Branco, Pedro F. N. Souza, Nilton A. S. Neto, Tawanny K. B. Aguiar, Ayrles F. B. Silva, Rômulo F. Carneiro, Celso S. Nagano, Felipe P. Mesquita, Luina B. Lima and Cleverson D. T. Freitas
Antibiotics 2022, 11(12), 1753; https://doi.org/10.3390/antibiotics11121753 - 04 Dec 2022
Cited by 3 | Viewed by 1963
Abstract
Klebsiella pneumoniae is a multidrug-resistant opportunistic human pathogen related to various infections. As such, synthetic peptides have emerged as potential alternative molecules. Mo-CBP3-PepI has presented great activity against K. pneumoniae by presenting an MIC50 at a very low concentration [...] Read more.
Klebsiella pneumoniae is a multidrug-resistant opportunistic human pathogen related to various infections. As such, synthetic peptides have emerged as potential alternative molecules. Mo-CBP3-PepI has presented great activity against K. pneumoniae by presenting an MIC50 at a very low concentration (31.25 µg mL−1). Here, fluorescence microscopy and proteomic analysis revealed the alteration in cell membrane permeability, ROS overproduction, and protein profile of K. pneumoniae cells treated with Mo-CBP3-PepI. Mo-CBP3-PepI led to ROS overaccumulation and membrane pore formation in K. pneumoniae cells. Furthermore, the proteomic analysis highlighted changes in essential metabolic pathways. For example, after treatment of K. pneumoniae cells with Mo-CBP3-PepI, a reduction in the abundance of protein related to DNA and protein metabolism, cytoskeleton and cell wall organization, redox metabolism, regulation factors, ribosomal proteins, and resistance to antibiotics was seen. The reduction in proteins involved in vital processes for cell life, such as DNA repair, cell wall turnover, and protein turnover, results in the accumulation of ROS, driving the cell to death. Our findings indicated that Mo-CBP3-PepI might have mechanisms of action against K. pneumoniae cells, mitigating the development of resistance and thus being a potent molecule to be employed in producing new drugs against K. pneumoniae infections. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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12 pages, 1216 KiB  
Article
Synthesis and Antimicrobial Activity of Sulfenimines Based on Pinane Hydroxythiols
by Nikita O. Ilchenko, Denis V. Sudarikov, Roman V. Rumyantcev, Diana R. Baidamshina, Nargiza D. Zakarova, Monyr Nait Yahia, Airat R. Kayumov, Aleksandr V. Kutchin and Svetlana A. Rubtsova
Antibiotics 2022, 11(11), 1548; https://doi.org/10.3390/antibiotics11111548 - 04 Nov 2022
Cited by 4 | Viewed by 1318
Abstract
The widespread presence of multidrug-resistant pathogenic microorganisms challenges the development of novel chemotype antimicrobials, insensitive to microbial tools of resistance. To date, various monoterpenoids have been shown as potential antimicrobials. Among many classes of molecules with antimicrobial activity, terpenes and terpenoids are an [...] Read more.
The widespread presence of multidrug-resistant pathogenic microorganisms challenges the development of novel chemotype antimicrobials, insensitive to microbial tools of resistance. To date, various monoterpenoids have been shown as potential antimicrobials. Among many classes of molecules with antimicrobial activity, terpenes and terpenoids are an attractive basis for the design of antimicrobials because of their low toxicity and availability for various modifications. In this work, we report on the synthesis of sulfenimines from chiral trifluoromethylated and non-fluorinated pinane-type thiols. Final compounds were obtained with yields of up to 81%. Among the 13 sulfenimines obtained, 3 compounds were able to repress the growth of both bacteria (S. aureus, both MSSA and MRSA; P. aeruginosa) and fungi (C. albicans) with an MIC of 8–32 µg/mL. Although compounds exhibited relatively high cytotoxicity (the therapeutic index of 3), their chemotype can be used as a starter point for the development of disinfectants and antiseptics for targeting multidrug-resistant pathogens. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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13 pages, 1443 KiB  
Article
Exploring the Relationships between Structure and Antimicrobial Potency of Quinolinequinones
by Emel Mataracı-Kara, Nilüfer Bayrak, Mahmut Yıldız, Hatice Yıldırım and Amaç Fatih TuYuN
Antibiotics 2022, 11(10), 1397; https://doi.org/10.3390/antibiotics11101397 - 12 Oct 2022
Cited by 1 | Viewed by 1349
Abstract
Microorganisms are responsible for hospital infections, and methicillin-resistant Staphylococcus aureus is one of them. In looking for the most effective lead structures to cope with the rise of antimicrobial (antibiotic) resistance, we evaluated the antimicrobial profile of quinolinequinones for potential antimicrobial applications. 1,4-quinone [...] Read more.
Microorganisms are responsible for hospital infections, and methicillin-resistant Staphylococcus aureus is one of them. In looking for the most effective lead structures to cope with the rise of antimicrobial (antibiotic) resistance, we evaluated the antimicrobial profile of quinolinequinones for potential antimicrobial applications. 1,4-quinone molecules fused with heteroatom have been studied extensively for many years as a source of drugs and lead structures. The aims of this study were to evaluate the antimicrobial activity of quinolinequinones against bacterial and fungal strains, and to probe for potential lead structures. For this reason, the activity of these compounds against three different strains of Candida fungi (C. albicans, C. parapsilosis, and C. tropicalis) and Gram-positive and Gram-negative pathogenic bacteria were investigated, searching for potential lead compounds. Five of nine quinolinequinones showed activity mainly against the Gram-positive strains with a minimal inhibitory concentration within the Clinical and Laboratory Standards Institute (CLSI) levels. The results revealed that quinolinequinones have significant activity against bacteria including Staphylococcus aureus and Staphylococcus epidermidis, and fungi including Candida albicans and Candida parapsilosis. QQ1, QQ2, QQ3, QQ5, and QQ6 exhibited the highest growth inhibition against two essential species of the Gram-positive strains (Staphylococcus epidermidis and Staphylococcus aureus). Among these, four molecules (QQ2, QQ3, QQ5, and QQ6) were also active against Enterococcus faecalis, the other member of the Gram-positive strains. The antifungal profile of two quinolinequinones (QQ7 and QQ8) indicated that they were as effective as the reference drug Clotrimazole against Candida albicans. The same molecules also have potential inhibitory antifungal activity against Candida tropicalis. For better understanding, the most active two quinolinequinones (QQ2 and QQ6) were examined for biofilm inhibition and a time-kill kinetic study. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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10 pages, 917 KiB  
Article
Buffering Capacity and Effects of Sodium Hexametaphosphate Nanoparticles and Fluoride on the Inorganic Components of Cariogenic-Related Biofilms In Vitro
by Caio Sampaio, Alberto Carlos Botazzo Delbem, Thayse Yumi Hosida, Ana Vitória Pereira Fernandes, Guilherme dos Santos Gomes Alves, José Antônio Santos Souza, Douglas Roberto Monteiro and Juliano Pelim Pessan
Antibiotics 2022, 11(9), 1173; https://doi.org/10.3390/antibiotics11091173 - 30 Aug 2022
Cited by 1 | Viewed by 1437
Abstract
Despite the remarkable effects of sodium hexametaphosphate nanoparticles (HMPnano) on dental enamel de-/re-mineralization processes, information on the effects of these nanoparticles on biofilms is scarce. This study assessed the effects of HMPnano, with or without fluoride (F), on the inorganic components and pH [...] Read more.
Despite the remarkable effects of sodium hexametaphosphate nanoparticles (HMPnano) on dental enamel de-/re-mineralization processes, information on the effects of these nanoparticles on biofilms is scarce. This study assessed the effects of HMPnano, with or without fluoride (F), on the inorganic components and pH of Streptococcus mutans and Candida albicans dual-species biofilms. Solutions containing conventional/micro-sized HMP (HMPmicro) or HMPnano were prepared at 0.5% and 1%, with or without 1100 ppm F. A 1100 ppm F solution and pure artificial saliva were tested as positive and negative controls, respectively. The biofilms were treated three times and had their pH analyzed, and the concentrations of F, calcium, phosphorus, and HMP in the biofilm biomass and fluid were determined. In another set of experiments, after the last treatment, the biofilms were exposed to a 20% sucrose solution, and the biofilm pH and inorganic components were evaluated. The 1% HMPnano solution with F led to the highest biofilm pH, even after exposure to sucrose. The 1% HMPnano solution without F led to significantly higher phosphorus concentrations in comparison to all other groups. It can be concluded that 1% HMPnano and F influenced the biofilm pH, besides affecting most of the inorganic components of the dual-species biofilms. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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30 pages, 6727 KiB  
Article
Synthesis and Biological Evaluation of Novel Fusidic Acid Derivatives as Two-in-One Agent with Potent Antibacterial and Anti-Inflammatory Activity
by Borong Tu, Nana Cao, Bingjie Zhang, Wende Zheng, Jiahao Li, Xiaowen Tang, Kaize Su, Jinxuan Li, Zhen Zhang, Zhenping Yan, Dongli Li, Xi Zheng, Kun Zhang, Weiqian David Hong and Panpan Wu
Antibiotics 2022, 11(8), 1026; https://doi.org/10.3390/antibiotics11081026 - 30 Jul 2022
Cited by 4 | Viewed by 1635
Abstract
Fusidic acid (FA), a narrow-spectrum antibiotics, is highly sensitive to various Gram-positive cocci associated with skin infections. It has outstanding antibacterial effects against certain Gram-positive bacteria whilst no cross-resistance with other antibiotics. Two series of FA derivatives were synthesized and their antibacterial activities [...] Read more.
Fusidic acid (FA), a narrow-spectrum antibiotics, is highly sensitive to various Gram-positive cocci associated with skin infections. It has outstanding antibacterial effects against certain Gram-positive bacteria whilst no cross-resistance with other antibiotics. Two series of FA derivatives were synthesized and their antibacterial activities were tested. A new aromatic side-chain analog, FA-15 exhibited good antibacterial activity with MIC values in the range of 0.781–1.563 µM against three strains of Staphylococcus spp. Furthermore, through the assessment by the kinetic assay, similar characteristics of bacteriostasis by FA and its aromatic derivatives were observed. In addition, anti-inflammatory activities of FA and its aromatic derivatives were evaluated by using a 12-O-tetradecanoylphorbol-13-acetate (TPA) induced mouse ear edema model. The results also indicated that FA and its aromatic derivatives effectively reduced TPA-induced ear edema in a dose-dependent manner. Following, multiform computerized simulation, including homology modeling, molecular docking, molecular dynamic simulation and QSAR was conducted to clarify the mechanism and regularity of activities. Overall, the present work gave vital clues about structural modifications and has profound significance in deeply scouting for bioactive potentials of FA and its derivatives. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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21 pages, 5110 KiB  
Article
Tuning the Biological Activity of Camphorimine Complexes through Metal Selection
by Joana P. Costa, Teresa Pinheiro, Maria S. Martins, M. Fernanda N. N. Carvalho, Joana R. Feliciano, Jorge H. Leitão, Rafaela A. L. Silva, Joana F. Guerreiro, Luís M. C. Alves, Inês Custódio, João Cruz and Fernanda Marques
Antibiotics 2022, 11(8), 1010; https://doi.org/10.3390/antibiotics11081010 - 27 Jul 2022
Cited by 3 | Viewed by 1780
Abstract
The cytotoxic activity of four sets of camphorimine complexes based on the Cu(I), Cu(II), Ag(I), and Au(I) metal sites were assessed against the cisplatin-sensitive A2780 and OVCAR3 ovarian cancer cells. The results showed that the gold complexes were ca. one order of magnitude [...] Read more.
The cytotoxic activity of four sets of camphorimine complexes based on the Cu(I), Cu(II), Ag(I), and Au(I) metal sites were assessed against the cisplatin-sensitive A2780 and OVCAR3 ovarian cancer cells. The results showed that the gold complexes were ca. one order of magnitude more active than the silver complexes, which in turn were ca. one order of magnitude more active than the copper complexes. An important finding was that the cytotoxic activity of the Ag(I) and Au(I) camphorimine complexes was higher than that of cisplatin. Another relevant aspect was that the camphorimine complexes did not interact significantly with DNA, in contrast with cisplatin. The cytotoxic activity of the camphorimine complexes displayed a direct relationship with the cellular uptake by OVCAR3 cells, as ascertained by PIXE (particle-induced X-ray emission). The levels of ROS (reactive oxygen species) formation exhibited an inverse relationship with the reduction potentials for the complexes with the same metal, as assessed by cyclic voltammetry. In order to gain insight into the toxicity of the complexes, their cytotoxicity toward nontumoral cells (HDF and V79 fibroblasts) was evaluated. The in vivo cytotoxicity of complex 5 using the nematode Caenorhabditis elegans was also assessed. The silver camphorimine complexes displayed the highest selectivity coefficients (activity vs. toxicity). Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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23 pages, 5491 KiB  
Review
Photo-Antibacterial Activity of Two-Dimensional (2D)-Based Hybrid Materials: Effective Treatment Strategy for Controlling Bacterial Infection
by Neetu Talreja, Divya Chauhan and Mohammad Ashfaq
Antibiotics 2023, 12(2), 398; https://doi.org/10.3390/antibiotics12020398 - 16 Feb 2023
Cited by 3 | Viewed by 1914
Abstract
Bacterial contamination in water bodies is a severe scourge that affects human health and causes mortality and morbidity. Researchers continue to develop next-generation materials for controlling bacterial infections from water. Photo-antibacterial activity continues to gain the interest of researchers due to its adequate, [...] Read more.
Bacterial contamination in water bodies is a severe scourge that affects human health and causes mortality and morbidity. Researchers continue to develop next-generation materials for controlling bacterial infections from water. Photo-antibacterial activity continues to gain the interest of researchers due to its adequate, rapid, and antibiotic-free process. Photo-antibacterial materials do not have any side effects and have a minimal chance of developing bacterial resistance due to their rapid efficacy. Photocatalytic two-dimensional nanomaterials (2D-NMs) have great potential for the control of bacterial infection due to their exceptional properties, such as high surface area, tunable band gap, specific structure, and tunable surface functional groups. Moreover, the optical and electric properties of 2D-NMs might be tuned by creating heterojunctions or by the doping of metals/carbon/polymers, subsequently enhancing their photo-antibacterial ability. This review article focuses on the synthesis of 2D-NM-based hybrid materials, the effect of dopants in 2D-NMs, and their photo-antibacterial application. We also discuss how we could improve photo-antibacterials by using different strategies and the role of artificial intelligence (AI) in the photocatalyst and in the degradation of pollutants. Finally, we discuss was of improving the photo-antibacterial activity of 2D-NMs, the toxicity mechanism, and their challenges. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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16 pages, 2854 KiB  
Review
An Overview of Repurposed Drugs for Potential COVID-19 Treatment
by Kamini Govender and Anil Chuturgoon
Antibiotics 2022, 11(12), 1678; https://doi.org/10.3390/antibiotics11121678 - 22 Nov 2022
Cited by 4 | Viewed by 1997
Abstract
The COVID-19 pandemic caused by SARS-CoV-2 has placed severe constraints on healthcare systems around the globe. The SARS-CoV-2 virus has caused upheaval in the healthcare and economic sectors worldwide. On the 20th of May 2020, the World Health Organisation declared COVID-19 a global [...] Read more.
The COVID-19 pandemic caused by SARS-CoV-2 has placed severe constraints on healthcare systems around the globe. The SARS-CoV-2 virus has caused upheaval in the healthcare and economic sectors worldwide. On the 20th of May 2020, the World Health Organisation declared COVID-19 a global pandemic due to the unprecedented number of cases reported around the globe. As of the 4th of November 2022, there were 637,117,429 coronavirus cases reported globally by Worldometer stats, with 6,602,572 related deaths. In South Africa, there were approximately 4,029,496 coronavirus cases and 102,311 associated deaths. As such, there is a need for efficacious therapeutic regimes. There has been a paucity of knowledge encompassing the use of effective and specific antiviral drug therapies for treating COVID-19 since the outbreak. In this review, we provide valuable insights into the repurposing of current drugs for COVID-19. Drug repurposing provides a suitable option for the discovery of efficacious drugs for COVID-19, thereby decreasing the costs and turnaround times of drug development strategies. This review provides an overview of ten drugs, including antimalarial, antiparasitic, anti-inflammatory, nucleoside analogue, monoclonal-antibody drugs, that were repurposed for the potential treatment of COVID-19. Full article
(This article belongs to the Special Issue Synthesis and Biological Activity of Antimicrobial Agents, 2nd Volume)
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