Advances in Antimicrobial Compounds: Exploring Natural, Synthetic, and Repositioned Drugs

A special issue of Antibiotics (ISSN 2079-6382). This special issue belongs to the section "The Global Need for Effective Antibiotics".

Deadline for manuscript submissions: 31 July 2026 | Viewed by 3059

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Guest Editor
Department of Pharmacy-Pharmaceutical Sciences, University of Bari “Aldo Moro”, Bari, Italy
Interests: biological active compounds; antimicrobials; antiarrhythmics; anticancers; melatonergic drugs; voltage-gated sodium channel blockers
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Guest Editor
Department of Pharmacy-Pharmaceutical Sciences, University of Bari “Aldo Moro”, 70125 Bari, Italy
Interests: microbiology; medicinal chemistry; natural products; antimicrobial resistance
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In recent decades, the growing threat of antimicrobial resistance has driven intensive research into new compounds capable of effectively combating infections. This Special Issue, titled "Advances in Antimicrobial Compounds: Exploring Natural, Synthetic, and Repositioned Drugs", aims to gather innovative contributions spanning natural molecules, new synthetic agents with antimicrobial activity, and the repositioning of existing drugs for novel therapeutic applications. Natural products have historically been a rich source of antimicrobial compounds, providing structural diversity and unique mechanisms of action that continue to inspire drug development. Drug repositioning, or repurposing, i.e., identifying new antimicrobial applications for existing drugs that were initially developed for other diseases, is an alternative approach that offers significant advantages, including reduced development costs and accelerated regulatory approval, as the safety profiles of these compounds are often already well established. Additionally, synergy-based approaches—such as combining natural products with synthetic agents—are gaining attention for their potential to enhance efficacy, reduce toxicity, and mitigate resistance development. Original research articles, critical reviews, and methodological studies that explore aspects such as the design of new compounds, the assessment of their efficacy and safety, and the analysis of their mechanisms of action are welcomed. We also encourage contributions that investigate innovative approaches to overcoming the challenges posed by antimicrobial resistance, with the hope of stimulating the development of more effective and sustainable therapies for the future.

Dr. Alessia Carocci
Dr. Alexia Barbarossa
Guest Editors

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Keywords

  • antimicrobial compounds
  • natural products
  • synthetic agents
  • drug repositioning
  • antimicrobial resistance
  • synergistic approaches
  • mechanisms of action
  • drug development

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Published Papers (2 papers)

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Research

19 pages, 4620 KB  
Article
Phytochemical Characterization and Antimicrobial Properties of a Hydroalcoholic Extract of Tristerix corymbosus (L) Kuijt, a Chilean Mistletoe Species Hosted on Salix babylonica (L)
by Alejandro A. Hidalgo, Sergio A. Bucarey, Beatriz Sepúlveda, Sebastián Cumsille-Escandar, Alejandro Charmell, Nicolás A. Villagra, Andrés Barriga, Consuelo F. Martínez-Contreras, Jorge Escobar, José L. Martínez and Maité Rodríguez-Díaz
Antibiotics 2026, 15(1), 105; https://doi.org/10.3390/antibiotics15010105 - 21 Jan 2026
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Abstract
Background/Objectives: The genus Tristerix comprises at least ten species, found from southern Chile to Colombia in South America. In Chile, several species of these hemiparasitic plants are known as quitral or quintral. Quitral, mainly T. corymbosus (syn. T. tetrandus), is used in [...] Read more.
Background/Objectives: The genus Tristerix comprises at least ten species, found from southern Chile to Colombia in South America. In Chile, several species of these hemiparasitic plants are known as quitral or quintral. Quitral, mainly T. corymbosus (syn. T. tetrandus), is used in alternative medicine for its anti-inflammatory, digestive, hemostatic, hypocholesterolemic, and wound-healing properties. This study investigates the phytochemical composition and antimicrobial properties of T. corymbosus. Methods: A hydroalcoholic extract of T. corymbosus was prepared from leaves and small branches. The addition of methanol, on the extract, produced precipitation allowing us to isolate a methanol-soluble fraction, a brown powder obtained after filtration, and a tar-like residue remaining in the flask. These fractions were resuspended and tested for antimicrobial activity. Results: All fractions showed activity against Streptococcus pyogenes, but not E. coli. The brown powder exhibits the strongest potency against Gram-positive bacteria, some Gram-negative and C. albicans. HPLC-MS analysis revealed presence of lipidic compounds with surfactant properties. Conclusions: The abundant lipidic molecules present in the analyzed fraction likely account for the antimicrobial effects through affecting membrane structure of microorganisms supporting the traditional wound-healing uses of T. corymbosus in ancestral medicine. Full article
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20 pages, 827 KB  
Article
Exploring the Antibacterial, Anti-Inflammatory, and Antioxidant Properties of the Natural Food Supplement “Protegol” as a Supportive Strategy in Respiratory Tract Infections
by Alexia Barbarossa, Maria Pia Argentieri, Maria Valeria Diella, Eleonora Spinozzi, Filippo Maggi, Antonio Carrieri, Filomena Corbo, Antonio Rosato and Alessia Carocci
Antibiotics 2025, 14(12), 1260; https://doi.org/10.3390/antibiotics14121260 - 13 Dec 2025
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Abstract
Background/Objectives: Respiratory tract infections (RTIs) remain a leading cause of morbidity worldwide and are frequently associated with the emergence of multidrug-resistant pathogens. In this context, natural compounds represent a valuable source of novel antimicrobial and immunomodulatory agents. The present study aimed to [...] Read more.
Background/Objectives: Respiratory tract infections (RTIs) remain a leading cause of morbidity worldwide and are frequently associated with the emergence of multidrug-resistant pathogens. In this context, natural compounds represent a valuable source of novel antimicrobial and immunomodulatory agents. The present study aimed to evaluate the antibacterial, anti-inflammatory, and antioxidant activities of Protegol, a natural food supplement enriched in bioactive phytochemicals including hydroalcoholic extracts of propolis and hedge mustard (Sisymbrium officinale (L.) Scop.) aerial parts, together with honey, against clinically relevant bacterial strains and in cellular models of inflammation and oxidative stress. Furthermore, the ability of the multi-herbal formulation to alter the permeability of the bacterial cell wall was assessed. Methods: The antibacterial properties of Protegol were evaluated by determining its minimum inhibitory (MIC) and minimum bactericidal concentrations (MBC) against a panel of Gram-positive and Gram-negative bacteria, using the broth microdilution method. Cell wall permeability was investigated through the propidium iodide (PI) uptake assay. The anti-inflammatory potential was investigated in LPS-stimulated RAW 264.7 macrophages by measuring nitric oxide (NO) production with the Griess assay. The antioxidant activity was evaluated in BALB/3T3 fibroblasts exposed to hydrogen peroxide, using the DCFH-DA assay. Results: Protegol exhibited a broad-spectrum antibacterial effect, with MIC values ranging from 1.5 to 6.2 mg/mL and MBC values between 3.1 and 12.4 mg/mL. The strongest activity was observed against Staphylococcus aureus and Streptococcus pyogenes, including clinical isolates, while moderate efficacy was detected against resistant Klebsiella pneumoniae strains. PI uptake assays confirmed a dose-dependent disruption of bacterial membrane integrity, supporting a direct effect of Protegol on cell wall permeability. In macrophages, Protegol significantly and dose-dependently reduced NO release, lowering production to 44% at the highest concentration tested. In BALB/3T3 cells, Protegol markedly decreased ROS accumulation to 24% at the same concentration. Conclusions: Overall, the findings support the potential of Protegol as a natural adjuvant to the conventional therapies for respiratory tract health by counteracting bacterial pathogens, reducing inflammation, and mitigating oxidative stress, thereby supporting host defense mechanisms in the context of respiratory tract infections. Full article
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