Special Issue "Identification of Phytochemicals and Derivatives against Infectious Diseases"

A special issue of Pharmaceuticals (ISSN 1424-8247). This special issue belongs to the section "Natural Products".

Deadline for manuscript submissions: 15 December 2021.

Special Issue Editors

Prof. Dr. Eduarda M. P. Silva
E-Mail Website
Guest Editor
1. Institute of Research and Advanced Training in Health Sciences and Technologies (IINFACTS), CESPU, Rua Central de Gandra, 1317, 4585-116, Gandra PRD, Portugal
2. LAQV-REQUIMTE, Department of Chemistry Sciences, Faculty of Pharmacy, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal
Interests: organic chemistry; analytical chemistry; mass spectrometry; heterocyclic compounds

Special Issue Information

Dear Colleagues,

Infectious diseases are a global health concern, as clearly shown by the 2019 WHO-compiled list of the top 10 health threats, of which 6 are infectious disease-related. The emergence and increase of multidrug resistance and infectious disease outbreaks (such as the coronavirus, influenza, or Ebola viruses) are the cause of significant morbidity and mortality rising worldwide for these diseases. Moreover, there is a lack of development of new candidates to tackle the huge demand related to controlling these epidemics. This demand has triggered, in recent years, a renewed interest in medicinal plants and natural products as a source of novel pharmacologically active compounds for drug discovery.

The recognition of flora biological activity importance is ancient, and the use of plants in folk medicine and its ethnomedical applications around the globe is, to date, rather significant. Plants are true manufacturing units for the production of important pharmaceuticals. The chemical diversity that can be discovered from plant-derived natural products along with the recognition of new therapeutic targets by the increasing number of genomics studies can lead to the development of new medicinal drugs able to hold the emerging era of antibiotic resistance.

This Special Issue, “Identification of Phytochemicals and Derivatives against Infectious Diseases”, invites authors to contribute with review or original research articles dedicated to the most recent advances on the discovery of plant-based bioactive compounds with anti-infectious disease properties. The contributions include the discovery of new compounds and their structural elucidation, as well as the in vitro and in vivo assessment of the biological properties against infectious diseases, namely, antibacterial, antiviral, antiparasitic, and antifungal. Studies concerning the elucidation of mechanisms of action of new phytochemicals and structural–activity studies directing toward the synthesis of more bioactive derivatives are also welcomed.

Prof. Dr. Eduarda M. P. Silva
Prof. Dr. Diana Cláudia Pinto
Guest Editors

Manuscript Submission Information

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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. Pharmaceuticals 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 1800 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

  • Infectious disease
  • Natural products
  • Phytochemical
  • Biologically active

Published Papers (4 papers)

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Research

Article
Investigation of the Antibacterial Activity and Efflux Pump Inhibitory Effect of Cycas thouarsii R.Br. Extract against Klebsiella pneumoniae Clinical Isolates
Pharmaceuticals 2021, 14(8), 756; https://0-doi-org.brum.beds.ac.uk/10.3390/ph14080756 - 01 Aug 2021
Viewed by 761
Abstract
The vast spread of multidrug-resistant bacteria has encouraged researchers to explore new antimicrobial compounds. This study aimed to investigate the phytochemistry and antibacterial activity of Cycas thouarsii R.Br. leaves extract against Klebsiella pneumoniae clinical isolates. The minimum inhibitory concentration (MIC) values of C. [...] Read more.
The vast spread of multidrug-resistant bacteria has encouraged researchers to explore new antimicrobial compounds. This study aimed to investigate the phytochemistry and antibacterial activity of Cycas thouarsii R.Br. leaves extract against Klebsiella pneumoniae clinical isolates. The minimum inhibitory concentration (MIC) values of C. thouarsii extract ranged from 4 to 32 µg/mL. The impact of the treatment of the isolates with sub-inhibitory concentrations of C. thouarsii extract was investigated on the bacterial growth, membrane integrity, inner and outer membrane permeability, membrane depolarization, and bacterial morphology using a scanning electron microscope (SEM) and on the efflux activity using qRT-PCR. Interestingly, most K. pneumoniae isolates treated with C. thouarsii extract showed growth inhibition—a decrease in membrane integrity. In addition, we observed various morphological changes, a significant increase in inner and outer membrane permeability, a non-significant change in membrane depolarization, and a decrease in efflux activity after treatment. The phytochemical investigation of C. thouarsii extract revealed the isolation of one new biflavonoid, 5,7,7″,4‴-tetra-O-methyl-hinokiflavone (3), and five known compounds, stigmasterol (1), naringenin (2), 2,3-dihydrobilobetin (4), 4′,4‴-O-dimethyl amentoflavone (5), and hinokiflavone (6), for the first time. Moreover, the pure compounds′ MICs′ ranged from 0.25 to 2 µg/mL. Thus, C. thouarsii could be a potential source for new antimicrobials. Full article
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Article
In Vitro Culture of Rosmarinus officinalis L. in a Temporary Immersion System: Influence of Two Phytohormones on Plant Growth and Carnosol Production
Pharmaceuticals 2021, 14(8), 747; https://0-doi-org.brum.beds.ac.uk/10.3390/ph14080747 - 29 Jul 2021
Viewed by 636
Abstract
Emerging infectious diseases have become a major global problem with public health and economic consequences. It is an urgent need to develop new anti-infective therapies. The natural diterpene carnosol exhibit a wide variety of interesting antibacterial and antiviral properties, and it is considered [...] Read more.
Emerging infectious diseases have become a major global problem with public health and economic consequences. It is an urgent need to develop new anti-infective therapies. The natural diterpene carnosol exhibit a wide variety of interesting antibacterial and antiviral properties, and it is considered a theoretical inhibitor of COVID-19 Mpro. However, this compound is present in the family Lamiaceae in low quantities. To obtain carnosol in concentrations high enough to develop pharmacological studies, we evaluated the efficiency of a micropropagation protocol of Rosmarinus officinalis using a solid medium and a temporary immersion system (TIS), as well as the effect of 6-benzylaminopurine (6-BAP) and α-naphthaleneacetic acid (NAA) on the growth of shoots. Moreover, we developed and validated an analytical method to quantify carnosol using the H-point standard additions method in the high-performance liquid chromatography diode array detector (HPLC-DAD). After 30 days of culture, TIS produced the maximum number of shoots per explant (24.33 ± 1.15) on a liquid medium supplemented with 6-BAP at 5.0 mg L−1. Next, we also evaluated the effect of immersion time and frequency for TIS. After 72 days of culture, the best results were obtained with an immersion cycle of 1 min every 12 h, yielding 170.33 ± 29.40 shoots. The quantification of carnosol on the samples was performed at a flow rate of 1.2 mL min−1 using binary isocratic mobile phase system 60:40 (v/v) 10 mM formic acid (pH 3.0) (A) and acetonitrile (B) on a reverse-phase column. The content of carnosol in the in vitro cultures was around 8-fold higher than in the wild plant. The present study represents an efficient alternative method to obtain carnosol for its pre-clinical and clinical development. Full article
Article
Antimicrobial Activity of a Library of Thioxanthones and Their Potential as Efflux Pump Inhibitors
Pharmaceuticals 2021, 14(6), 572; https://0-doi-org.brum.beds.ac.uk/10.3390/ph14060572 - 15 Jun 2021
Cited by 1 | Viewed by 1354
Abstract
The overexpression of efflux pumps is one of the causes of multidrug resistance, which leads to the inefficacy of drugs. This plays a pivotal role in antimicrobial resistance, and the most notable pumps are the AcrAB-TolC system (AcrB belongs to the resistance-nodulation-division family) [...] Read more.
The overexpression of efflux pumps is one of the causes of multidrug resistance, which leads to the inefficacy of drugs. This plays a pivotal role in antimicrobial resistance, and the most notable pumps are the AcrAB-TolC system (AcrB belongs to the resistance-nodulation-division family) and the NorA, from the major facilitator superfamily. In bacteria, these structures can also favor virulence and adaptation mechanisms, such as quorum-sensing and the formation of biofilm. In this study, the design and synthesis of a library of thioxanthones as potential efflux pump inhibitors are described. The thioxanthone derivatives were investigated for their antibacterial activity and inhibition of efflux pumps, biofilm formation, and quorum-sensing. The compounds were also studied for their potential to interact with P-glycoprotein (P-gp, ABCB1), an efflux pump present in mammalian cells, and for their cytotoxicity in both mouse fibroblasts and human Caco-2 cells. The results concerning the real-time ethidium bromide accumulation may suggest a potential bacterial efflux pump inhibition, which has not yet been reported for thioxanthones. Moreover, in vitro studies in human cells demonstrated a lack of cytotoxicity for concentrations up to 20 µM in Caco-2 cells, with some derivatives also showing potential for P-gp modulation. Full article
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Article
Repurposing of Some Natural Product Isolates as SARS-COV-2 Main Protease Inhibitors via In Vitro Cell Free and Cell-Based Antiviral Assessments and Molecular Modeling Approaches
Pharmaceuticals 2021, 14(3), 213; https://0-doi-org.brum.beds.ac.uk/10.3390/ph14030213 - 04 Mar 2021
Cited by 8 | Viewed by 1132
Abstract
The emergence of the SARS-CoV-2 pandemic has prompted scientists to search for an efficient antiviral medicine to overcome the rapid spread and the marked increase in the number of patients worldwide. In this regard natural products could be a potential source of substances [...] Read more.
The emergence of the SARS-CoV-2 pandemic has prompted scientists to search for an efficient antiviral medicine to overcome the rapid spread and the marked increase in the number of patients worldwide. In this regard natural products could be a potential source of substances active against coronavirus infections. A systematic computer-aided virtual screening approach was carried out using commercially available natural products found on the Zinc Database in addition to an in-house compound library to identify potential natural product inhibitors of SARS-CoV-2 main protease (MPRO). The top eighteen hits from the screening were selected for in vitro evaluation on the viral protease (SARS-CoV-2 MPRO). Five compounds (naringenin, 2,3′,4,5′,6-pentahydroxybenzophenone, apigenin-7-O-glucoside, sennoside B, and acetoside) displayed high activity against the viral protein. Acteoside showed similar activity to the positive control GC376. The most potent compounds were tested in vitro on SARS-CoV-2 Egyptian strain where only naringenin showed moderate anti-SARS-CoV-2 activity at non-cytotoxic micromolar concentrations in vitro with a significant selectivity index (CC50/IC50 = 178.748/28.347 = 6.3). Moreover; a common feature pharmacophore model was generated to explain the requirements for enzyme inhibition by this diverse group of active ligands. These results pave a path for future repurposing and development of natural products to aid in the battle against COVID-19. Full article
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