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Plant Extracts and Antimicrobials, Second Edition

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A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Antimicrobial Agents and Resistance".

Deadline for manuscript submissions: 31 July 2025 | Viewed by 8052

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Dr. Paola Angelini

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Guest Editor

Department of Applied Biology, University of Perugia, 06121 Perugia, Italy
Interests: biodiversity; biological activities; dermatophyte; essential oils; medicinal plants; mushrooms; non-volatile extracts
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Dr. Giancarlo Angeles Flores

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Guest Editor

Pharmacy Department, University of Chieti, Via dei Vestini 31, Chieti 66100, Italy
Interests: medicinal plants and fungi; dermatophytes; microorganisms; human pathogenic fungi and bacteria; antimicrobials; biological assays
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Prof. Dr. Roberto Venanzoni

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Guest Editor

Department of Chemistry, Biology and Biotechnology, University of Perugia, 06121 Perugia, Italy
Interests: botany; vegatation science; biological activities; dermatophyte; plants; fungal extracts
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Special Issue Information

Dear Colleagues,

This Special Issue is a continuation of our previous Special Issue, “Plant Extracts and Antimicrobials” (https://www.mdpi.com/si/114873).

Microbial pathogenicity and other infectious diseases have been controlled by the use of commercially available antimicrobial drugs in recent years. Antimicrobial drugs have, however, been overused and misused in the general population, which led to an increase in drug resistance rates among several microorganisms. Hence, in recent years, antimicrobial drug resistance has been recognized as a major global health threat. Medicinal plants are an important source of pharmacologically active secondary compounds such as coumarins, flavonoids, phenolics, alkaloids, terpenoids, tannins, lectin, polypeptides, and polyacetylenes. Numerous articles reporting on the antimicrobial activity of plant extracts have been published. Industrial hemp is one of many examples; recent studies have shown that inflorescence water extract and essential oils from this plant have antifungal activity against dermatophytes (Orlando et al. 2021). In this Special Issue dedicated to “Plant Extracts and Antimicrobials”, research papers and reviews about the research on new antimicrobial plant extracts or molecules, at a laboratory scale or at a pilot level, are welcome. The alternative use of plant extracts or compounds in food, beverage, supplements, and cosmetics can also be part of this Special Issue.

Topics that are particularly of interest include but are not limited to the following:

Production of plant compounds with antimicrobial properties;
Industrial applications and scaling up;
Methods to increase the active compounds’ yield (e.g., bioelicitation);
Product extraction and characterization;
Plant tissue culture in vitro and biochemical pathways;
Bioactivity of wild specimens versus cultivated specimens;
In vitro and in vivo tests;
Microbial species and strain screening.

Dr. Paola Angelini
Dr. Giancarlo Angeles Flores
Prof. Dr. Roberto Venanzoni
Guest Editors

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. Microorganisms 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 2700 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

antibacterials
antifungals
antivirals
bioactive compounds
biofilms
dermatophytes
drug resistance
food
beverages and supplements
pathogenics
mode of action
plant extracts
screening
spices

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Published Papers (7 papers)

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Research

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18 pages, 3194 KiB

Open AccessArticle

Green Myco-Synthesis of Zinc Oxide Nanoparticles Using Cortinarius sp.: Hepatoprotective, Antimicrobial, and Antioxidant Potential for Biomedical Applications

by Uzma Fazal, Ahmad Zada, Muhammad Hanif, Shiou Yih Lee, Mohammad Faisal, Abdulrahman A. Alatar, Tahira Sultana and Sohail

Microorganisms 2025, 13(5), 956; https://doi.org/10.3390/microorganisms13050956 - 22 Apr 2025

Viewed by 358

Abstract

The transformative effect of nanotechnology is revolutionizing medicine by introducing new therapeutic approaches. This study explores the utilization of aqueous extract from mushroom (Cortinarius sp.) used as a reducing agent to prepare zinc oxide myco-nanoparticles (ZnO-MNPs) in an eco-friendly manner. The synthesis of ZnO-MNPs has been confirmed by various characterization studies, including UV-vis spectroscopy, which revealed an absorption peak at 378 nm; X-ray diffraction (XRD) analysis, which revealed a wurtzite hexagonal structure; and Fourier transform infrared spectra (FTIR), which showed stabilizing agents around the ZnO-MNPs. The effectiveness of ZnO-MNPs as an anti-cancer agent was evaluated by monitoring liver biochemical parameters against hepatotoxicity caused by carbon tetrachloride (CCl₄) in Balb C mice. The results showed that the levels of catalase, glutathione (GSH), and total protein were significantly lower, while alanine aminotransferase (ALT), aspartate aminotransferase (ASAT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), melanin dialdehyde (MDA), and total bilirubin (TB) were significantly higher in each of the CCl₄ treatment groups. ZnO-MNP treatment significantly reduced the toxicological effects of CCl₄ but did not completely restore the accumulation. The antimicrobial efficacy of ZnO-MNPs was investigated and showed potential results against common pathogens, including Bacillus subtilis (29.05 ± 0.76), Bacillus meurellus (27.05 ± 0.5), Acetobacter rhizospherensis (23.36 ± 0.5), and Escherichia coli (25.86 ± 0.80), while antifungal activity was relatively lower. Moreover, the 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay showed that ZnO-MNPs are strong antioxidant agents. Overall, these findings highlight the effectiveness of myco-synthesized ZnO-NPs in combating pathogenic diseases, their promising role in cancer therapy, and their potential as a biomaterial option for future therapeutic applications. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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18 pages, 3286 KiB

Open AccessCommunication

Preliminary Data on the Antiviral Activity of Helleborus bocconei subsp. intermedius Root Extracts Against Animal Herpesviruses

by Paola Galluzzo, Santina Di Bella, Sergio Migliore, Maria Valeria Raimondi, Roberta Bivacqua, Gigliola Borgonovo, Salvatore Princiotto, Antonella Girgenti, Laura Palumbo, Salvatore Dara, Annalisa Guercio, Rosa Alduina, Guido Ruggero Loria and Vincenza Cannella

Microorganisms 2025, 13(4), 891; https://doi.org/10.3390/microorganisms13040891 - 12 Apr 2025

Viewed by 350

Abstract

Orthoherpesviridae is a large family of enveloped DNA virus. Among the most significant animal-infecting viruses are bovine alphaherpesvirus 1 (BoAHV1), caprine alphaherpesvirus 1 (CpAHV1) and equid alphaherpesvirus 1 (EqAHV1). Research into new methods to combat herpesvirus infections is ongoing. The aim of this study was to evaluate the antiviral activity of three extracts of the Helleborus bocconei roots against BoAHV1, CpAHV1 and EqAHV1. The roots were air-dried, extracted with methanol (MeOH) and then partitioned between n-butanol (n-BuOH) and water. All three extracts were tested for cytotoxicity on MDBK and RK-13 cells, and for antiviral activity. Two non-cytotoxic concentrations were assessed for their anti-BoAHV1, anti-CpAHV1 and anti-EqAHV1effects. Cells were incubated with the extracts for 72 h under three experimental conditions: pretreatment before viral infection, treatment post virus infection and simultaneous viral infection and treatment with extracts. The n-BuOH extract (BE) at 0.62 µg/mL inhibited the cytopathic effects of all three viruses in the simultaneous assay. Additionally, no cytopathic effect was observed in MDBK cells infected with CpAHV1and treated with 0.31 µg/mL BE post virus infection. Therefore, the BE contains molecules or groups of molecules potentially useful for developing an alternative therapy against herpesvirus (HV) infection. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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18 pages, 1348 KiB

Open AccessArticle

Phyllanthus emblica: Phytochemistry, Antimicrobial Potential with Antibiotic Enhancement, and Toxicity Insights

by Gagan Tiwana, Ian Edwin Cock and Matthew James Cheesman

Microorganisms 2025, 13(3), 611; https://doi.org/10.3390/microorganisms13030611 - 6 Mar 2025

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Abstract

Phyllanthus emblica Linn. (commonly known as Amla or Indian Gooseberry) is commonly used in Ayurvedic medicine to treat respiratory infections, skin disorders, and gastrointestinal issues. The fruit contains an abundance of polyphenols, which contribute to its strong antioxidant properties. The antibacterial activity of fruit extracts derived from P. emblica against Escherichia coli, Staphylococcus aureus, and Klebsiella pneumoniae was determined along with the antibiotic-resistant variants extended-spectrum β-lactamase (ESBL) E. coli, methicillin-resistant S. aureus (MRSA), and ESBL K. pneumoniae. Disc diffusion and broth dilution assays were conducted to assess the activity of aqueous, methanolic, and ethyl acetate extracts, with large zones of inhibition of up to 15 mm on agar observed for S. aureus and MRSA. Minimum inhibitory concentration (MIC) values ranging from 158 to 1725 µg/mL were calculated. The aqueous and methanolic extracts of P. emblica were less active against E. coli, ESBL E. coli, K. pneumoniae, and ESBL K. pneumoniae, with the only noteworthy MIC (633 µg/mL) observed for the aqueous extract against K. pneumoniae. Interestingly, a lack of inhibition was observed on agar for any of the extracts against these bacteria. Liquid chromatography–mass spectrometry (LC-MS) analysis identified several notable flavonoids, phenolic acids, terpenoids, and tannins. Notably, Artemia nauplii bioassays indicated that all extracts were nontoxic. The antibacterial activity and absence of toxicity in P. emblica extracts suggest their potential as candidates for antibiotic development, highlighting the need for further mechanistic and phytochemical investigations. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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15 pages, 1735 KiB

Open AccessArticle

The Impact of Compounds Released from Damaged Salad Leaves on the Growth and Virulence of Listeria monocytogenes

by Asma Alsharif, Lama Aldawsari, Giannis Koukkidis and Primrose Freestone

Microorganisms 2025, 13(2), 252; https://doi.org/10.3390/microorganisms13020252 - 24 Jan 2025

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Abstract

Background: Fresh produce such as leafy green salads have recently become recognized as a potential source of food-borne infection by enteric pathogens This study investigated whether compounds released from damaged salad leaves were recognized by Listeria monocytogenes strain EGD and if they impacted its growth and virulence. Methods: The effects of extracts of salad leaves or salad bag fluids were tested on the growth, biofilm formation, and colonization of salad leaves and host cell virulence. Results: The presence of salad extract at a concentration of less than 0.5% v/v and salad bag fluids at a concentration of 10% v/v enhanced the growth in water and serum-based medium by more than 10,000 times over un-supplemented control cultures. Light and scanning electron microscopy, as well as eukaryotic Caco-2 and Galleria mellonella models of infection, showed that leafy green extracts from rocket, lettuce, spinach, and their salad bag fluids significantly increased the ability of Listeria to establish biofilms and infect host cells. Conclusions: This investigation showed that salad leaf extracts can markedly enhance bacterial virulence, which has implications for bagged salad leaf consumer safety if the leaves become contaminated with pathogenic bacteria such as Listeria. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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19 pages, 1244 KiB

Open AccessArticle

Phytochemical Analysis and Antimicrobial Activity of Terminalia bellirica (Gaertn.) Roxb. and Terminalia chebula Retz. Fruit Extracts Against Gastrointestinal Pathogens: Enhancing Antibiotic Efficacy

by Gagan Tiwana, Ian Edwin Cock and Matthew James Cheesman

Microorganisms 2024, 12(12), 2664; https://doi.org/10.3390/microorganisms12122664 - 22 Dec 2024

Cited by 1 | Viewed by 1903

Abstract

Terminalia bellirica (Gaertn) Roxb. and Terminalia chebula Retz. are significant botanicals in ancient Ayurvedic medicine. They are renowned for their therapeutic properties, notably in addressing gastrointestinal (GI) diseases. These plants have undergone thorough examination related to their antibacterial, anti-inflammatory, and antioxidant properties, which make them highly efficient natural treatments for controlling gastrointestinal infections. The current research demonstrated the antibacterial efficacy of fruit extracts of Terminalia bellirica and Terminalia chebula against Bacillus cereus, Shigella sonnei, Shigella flexneri, and Salmonella typhimurium. We performed disc diffusion and liquid microdilution experiments to evaluate the antibacterial efficacy. All extracts of Terminalia bellirica and Terminalia chebula showed good antibacterial effects against B. cereus and S. flexneri. The minimum inhibitory concentration (MIC) values ranged from 94 µg/mL to 556 µg/mL. The methanolic extracts from both plants also showed noteworthy antibacterial activity against S. sonnei and S. typhimurium, with MIC values of 755 µg/mL for both. Fractional inhibitory concentration studies revealed additive interactions between some conventional antibiotics and the plant extracts when used concurrently. Liquid chromatography–mass spectrometry (LC-MS) analyses revealed that the T. bellirica and T. chebula extracts contained various tannins including methyl gallate, propyl gallate, gallic acid, and ellagic acid. Lethality assays conducted using Artemia franciscana Kellogg nauplii indicated that all the plant extracts are non-toxic. The antibacterial properties and absence of toxicity in T. bellirica and T. chebula fruit extracts indicate their potential for antibiotic development, warranting additional mechanistic and phytochemical studies. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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16 pages, 6148 KiB

Open AccessArticle

Syringaldehyde Exhibits Antibacterial and Antioxidant Activities against Mycobacterium marinum Infection

by Da Wen, Chaoqun Meng, Yazhi Feng, Lin Shen, Yiyao Liu, Wei Sun, Guangxin Chen and Changxin Wu

Microorganisms 2024, 12(2), 348; https://doi.org/10.3390/microorganisms12020348 - 7 Feb 2024

Cited by 2 | Viewed by 1711

Abstract

Tuberculosis (TB) is caused by infection with Mycobacterium tuberculosis (Mtb), which has a unique resistance to many antimicrobial agents. TB has emerged as a significant worldwide health issue because of the rise of multidrug-resistant strains causing drug-resistant TB (DR-TB). As a result, the development of new drugs or effective strategies is crucial for patients with TB. Mycobacterium marinum (Mm) and Mtb are both species of mycobacteria. In zebrafish, Mm proliferates and forms chronic granulomatous infections, which are similar to Mtb infections in lung tissue. Syringaldehyde (SA) is a member of the phenolic aldehyde family found in various plants. Here, we investigated its antioxidative and antibacterial properties in Mm-infected cells and zebrafish. Our results demonstrated that SA inhibits Mm-infected pulmonary epithelial cells and inhibits the proliferation of Mm in Mm-infected zebrafish, suggesting that SA provides an antibacterial effect during Mm infection. Further study demonstrated that supplementation with SA inhibits the production of malondialdehyde (MDA) and reactive oxygen species (ROS) and increases the levels of reduced glutathione (GSH) in Mm-infection-induced macrophages. SA inhibits the levels of MDA in Mm-infected zebrafish, suggesting that SA exerts antioxidative effects in vivo. Additionally, we found that SA promotes the expression of NRF2/HO-1/NQO-1 and the activation of the AMPK-α1/AKT/GSK-3β signaling pathway. In summary, our data demonstrated that SA exerts antioxidative and antibacterial effects during Mm infection both in vivo and in vitro and that the antioxidative effects of SA may be due to the regulation of NRF2/HO-1/NQO-1 and the AMPK-α1/AKT/GSK-3β signaling pathway. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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22 pages, 1113 KiB

Open AccessReview

Advancements in Antibacterial Therapy: Feature Papers

by Giancarlo Angeles Flores, Gaia Cusumano, Roberto Venanzoni and Paola Angelini

Microorganisms 2025, 13(3), 557; https://doi.org/10.3390/microorganisms13030557 - 1 Mar 2025

Cited by 1 | Viewed by 1201

Abstract

Antimicrobial resistance (AMR) is a growing global health crisis that threatens the efficacy of antibiotics and modern medical interventions. The emergence of multidrug-resistant (MDR) pathogens, exacerbated by the misuse of antibiotics in healthcare and agriculture, underscores the urgent need for innovative solutions. (1) Background: AMR arises from complex interactions between human, animal, and environmental health, further aggravated by the overuse and inadequate regulation of antibiotics. Conventional treatments are increasingly ineffective, necessitating alternative strategies. Emerging approaches, including bacteriophage therapy, antimicrobial peptides (AMPs), nanotechnology, microbial extracellular vesicles (EVs), and CRISPR-based antimicrobials, provide novel mechanisms that complement traditional antibiotics in combating resistant pathogens. (2) Methods: This review critically analyzes advanced antibacterial strategies in conjunction with systemic reforms such as antimicrobial stewardship programs, the One Health framework, and advanced surveillance tools. These methods can enhance resistance detection, guide interventions, and promote sustainable practices. Additionally, economic, logistical, and regulatory challenges impeding their implementation are evaluated. (3) Results: Emerging technologies, such as CRISPR and nanotechnology, exhibit promising potential in targeting resistance mechanisms. However, disparities in resource distribution and regulatory barriers hinder widespread adoption. Public–private partnerships and sustainable agriculture practices are critical to overcoming these obstacles. (4) Conclusions: A holistic and integrated approach is essential for mitigating the impact of AMR. By aligning innovative therapeutic strategies with global health policies, fostering interdisciplinary collaboration, and ensuring equitable resource distribution, we can develop a sustainable response to this 21st-century challenge. Full article

(This article belongs to the Special Issue Plant Extracts and Antimicrobials, Second Edition)

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