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Antibacterial Agents from Natural Source

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Natural Products Chemistry".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 27065

Special Issue Editor


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Guest Editor
Laboratory of Antimicrobial Testing, Federal University of Uberlândia, Uberlândia 38405-320, MG, Brazil
Interests: antibacterial activity; medicinal plants; biofilm; anaerobe; natural products; medicinal chemistry; bioactive compounds; anti-virulence
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Special Issue Information

Dear Colleagues,

The golden age of antibiotics is now becoming something of the past. This is due not only to the increase in bacterial resistance against antibiotics, but also to the decrease in the investment by pharmacologic industries in the search for new antibacterial products. In this scenario, the search for new targets and antibacterial compounds that can control infections through natural products has become extremely relevant to advances in the knowledge frontier in this area.

The research of natural products with antibacterial potential, which aims to obtain active principles or chemical synthesis models to develop new drugs, has reflected the enormous interest of the scientific community in this field. Moreover, the research on the biodiversity of crude extracts, isolated compounds, derived synthetics, amongst other products, obtained from vegetal species, animal venom (vertebrate and invertebrate), and minerals, is playing an important role due to the rich terrestrial diversity and abundant possible sources. Therefore, this kind of research deserves to be further deepened.

The variety of molecules found in natural products has been contributing to the treatment of infectious diseases and they are a valuable resource in terms of to antibacterial control through products commercialized by the cosmetic, dentistry, food, plague-control industries, etc.

This Special Issue of Molecules will be dedicated to the publication of original research and reviews of bioactive compounds obtained from natural products with antibacterial potential in their different forms of expression: the chemical approach, biologic assays (in vitro and in vivo), new targets, and anti-virulence and in silico studies. Papers that describe the development of new alternatives and action mechanism strategies or pharmacokinetics and pharmacodynamics of molecules obtained from natural products are also welcome.

Prof. Dr. Carlos H. G. Martins
Guest Editor

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Keywords

  • natural products
  • antibacterial activity, anti-virulence
  • bioactive molecules
  • mechanisms and applications
  • biological activity
  • drug development
  • antibacterial peptides

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Published Papers (13 papers)

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Editorial

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3 pages, 171 KiB  
Editorial
Special Issue Editorial: “Antibacterial Agents from Natural Sources”
by Carlos Henrique G. Martins
Molecules 2024, 29(3), 644; https://doi.org/10.3390/molecules29030644 - 30 Jan 2024
Viewed by 472
Abstract
Antibacterials derived from natural sources represent a fascinating and promising field of research in the quest for effective and sustainable solutions to bacterial infections [...] Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)

Research

Jump to: Editorial

13 pages, 4469 KiB  
Article
Luteolin 4′-Neohesperidoside Inhibits Clinically Isolated Resistant Bacteria In Vitro and In Vivo
by Riham A. El-Shiekh, Mai A. Elhemely, Ibrahim A. Naguib, Sarah I. Bukhari and Rana Elshimy
Molecules 2023, 28(6), 2609; https://doi.org/10.3390/molecules28062609 - 13 Mar 2023
Cited by 3 | Viewed by 1433
Abstract
Multidrug resistance (MDR) pathogens are usually associated with higher morbidity and mortality rates. Flavonoids are good candidates for the development of new potential antimicrobials. This research investigated whether luteolin 4′-neohesperidoside (L4N) has antibacterial and synergistic activities against four antibiotic-resistant pathogens: methicillin-resistant Staphylococcus aureus [...] Read more.
Multidrug resistance (MDR) pathogens are usually associated with higher morbidity and mortality rates. Flavonoids are good candidates for the development of new potential antimicrobials. This research investigated whether luteolin 4′-neohesperidoside (L4N) has antibacterial and synergistic activities against four antibiotic-resistant pathogens: methicillin-resistant Staphylococcus aureus (MRSA), Klebsiella pneumoniae, fosA-positive shiga toxin producing the Escherichia coli serogroup O111 (STEC O111), and Bacillus cereus. In vitro antimicrobial susceptibility testing revealed highly potent anti-MRSA (MIC of 106.66 ± 6.95 µg/mL), anti-K. pneumoniae (MIC of 53.33 ± 8.47 µg/mL) and anti-STEC O111 (MIC of 26.66 ± 5.23 µg/mL) activities. Significant synergistic combination was clearly noted in the case of gentamycin (GEN) against Gram-negative bacteria. In the case of B. cereus, the combination of vancomycin (VAN) with L4N could efficiently inhibit bacterial growth, despite the pathogen being VAN-resistant (MIC of 213.33 ± 7.9 µg/mL). In vivo evaluation of L4N showed significant decreases in K. pneumoniae and STEC shedding and colonization. Treatment could significantly diminish the levels of pro-inflammatory markers, tumor necrosis factor-alpha (TNF-α), and immunoglobulin (IgM). Additionally, the renal and pulmonary lesions were remarkably enhanced, with a significant decrease in the bacterial loads in the tissues. Finally, this study presents L4N as a potent substitute for traditional antibiotics with anti-STEC O111 and anti-K. pneumoniae potential, a finding which is reported here for the first time. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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19 pages, 7691 KiB  
Article
In Silico Identification of 1-DTP Inhibitors of Corynebacterium diphtheriae Using Phytochemicals from Andrographis paniculata
by Jameel M. Al-Khayri, Sakshi Dubey, Gopishankar Thirumoorthy, Praveen Nagella, Adel Abdel-Sabour Rezk and Wael Fathi Shehata
Molecules 2023, 28(2), 909; https://doi.org/10.3390/molecules28020909 - 16 Jan 2023
Cited by 1 | Viewed by 1370
Abstract
A number of phytochemicals have been identified as promising drug molecules against a variety of diseases using an in-silico approach. The current research uses this approach to identify the phyto-derived drugs from Andrographis paniculata (Burm. f.) Wall. ex Nees (AP) for the treatment [...] Read more.
A number of phytochemicals have been identified as promising drug molecules against a variety of diseases using an in-silico approach. The current research uses this approach to identify the phyto-derived drugs from Andrographis paniculata (Burm. f.) Wall. ex Nees (AP) for the treatment of diphtheria. In the present study, 18 bioactive molecules from Andrographis paniculata (obtained from the PubChem database) were docked against the diphtheria toxin using the AutoDock vina tool. Visualization of the top four molecules with the best dockscore, namely bisandrographolide (−10.4), andrographiside (−9.5), isoandrographolide (−9.4), and neoandrographolide (−9.1), helps gain a better understanding of the molecular interactions. Further screening using molecular dynamics simulation studies led to the identification of bisandrographolide and andrographiside as hit compounds. Investigation of pharmacokinetic properties, mainly ADMET, along with Lipinski’s rule and binding affinity considerations, narrowed down the search for a potent drug to bisandrographolide, which was the only molecule to be negative for AMES toxicity. Thus, further modification of this compound followed by in vitro and in vivo studies can be used to examine itseffectiveness against diphtheria. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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5 pages, 226 KiB  
Communication
Xylityl Sesquicaprylate Efficacy as an Antiseptic Ingredient for Oral Care Products (Mouthwash): An In Vitro Screening Investigation against Eight Microorganisms
by Cecília Nogueira, Liliam Mussi, André Rolim Baby, Roseli Zupeli and Wagner Vidal Magalhães
Molecules 2023, 28(1), 28; https://doi.org/10.3390/molecules28010028 - 21 Dec 2022
Cited by 1 | Viewed by 1673
Abstract
For dental caries and periodontal diseases initiated by dental plaque (as bacterial communities) and to inhibit the growth of oral pathogenic bacteria, oral care products containing antiseptic active ingredients are highly recommended, nonetheless, side effects of such actives are a concern (teeth discoloration/staining [...] Read more.
For dental caries and periodontal diseases initiated by dental plaque (as bacterial communities) and to inhibit the growth of oral pathogenic bacteria, oral care products containing antiseptic active ingredients are highly recommended, nonetheless, side effects of such actives are a concern (teeth discoloration/staining and taste perception, for example). In this context, we challenged xylityl sesquicaprylate, an antiseptic compound from natural resources, as an active ingredient to be used in an alcohol-free mouthwash formulation. The xylityl sesquicaprylate sample was compared to a respective blank mouthwash formulation and one containing triclosan. The in vitro efficacy was screened by the time-kill assay against eight microorganisms. The xylityl sesquicaprylate-containing mouthwash (0.45% w/w) presented a particularly interesting profile of efficacy against Actinomyces viscosus, Fusobacterium nucleatum, Porphyromonas gingivalis, and Tannerella forsythia, with results of greater magnitude to reduce the log10 of those microorganisms in comparison with the triclosan sample. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
18 pages, 3118 KiB  
Article
Indonesian Mangrove Sonneratia caseolaris Leaves Ethanol Extract Is a Potential Super Antioxidant and Anti Methicillin-Resistant Staphylococcus aureus Drug
by Kholis Abdurachim Audah, Jufendi Ettin, Jason Darmadi, Norma Nur Azizah, Amalda Siti Anisa, Tedi Dwi Fauzi Hermawan, Conny Riana Tjampakasari, Rudi Heryanto, Intan Safinar Ismail and Irmanida Batubara
Molecules 2022, 27(23), 8369; https://doi.org/10.3390/molecules27238369 - 30 Nov 2022
Cited by 8 | Viewed by 2424
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) is an S. aureus strain that has developed resistance against ß-lactam antibiotics, resulting in a scarcity of a potent cure for treating Staphylococcus infections. In this study, the anti-MRSA and antioxidant activity of the Indonesian mangrove species Sonneratia caseolaris [...] Read more.
Methicillin-resistant Staphylococcus aureus (MRSA) is an S. aureus strain that has developed resistance against ß-lactam antibiotics, resulting in a scarcity of a potent cure for treating Staphylococcus infections. In this study, the anti-MRSA and antioxidant activity of the Indonesian mangrove species Sonneratia caseolaris, Avicennia marina, Rhizophora mucronata, and Rhizophora apiculata were studied. Disk diffusion, DPPH, a brine shrimp lethality test, and total phenolic and flavonoid assays were conducted. Results showed that among the tested mangroves, ethanol solvent-based S. caseolaris leaves extract had the highest antioxidant and anti-MRSA activities. An antioxidant activity assay showed comparable activity when compared to ascorbic acid, with an IC50 value of 4.2499 ± 3.0506 ppm and 5.2456 ± 0.5937 ppm, respectively, classifying the extract as a super-antioxidant. Moreover, S. caseolaris leaves extract showed the highest content of strongly associated antioxidative and antibacterial polyphenols, with 12.4% consisting of nontoxic flavonoids with the minimum inhibitory concentration of the ethanol-based S. caseolaris leaves extract being approximately 5000 ppm. LC-MS/MS results showed that phenolic compounds such as azelaic acid and aspirin were found, as well as flavonoid glucosides such as isovitexin and quercitrin. This strongly suggested that these compounds greatly contributed to antibacterial and antioxidant activity. Further research is needed to elucidate the interaction of the main compounds in S. caseolaris leaves extract in order to confirm their potential either as single or two or more compounds that synergistically function as a nontoxic antioxidant and antibacterial against MRSA. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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14 pages, 2174 KiB  
Article
Brazilian Red Propolis Presents Promising Anti-H. pylori Activity in In Vitro and In Vivo Assays with the Ability to Modulate the Immune Response
by Mariana B. Santiago, Luis Fernando Leandro, Rafael B. Rosa, Murilo V. Silva, Samuel C. Teixeira, João Paulo S. Servato, Sérgio Ricardo Ambrósio, Rodrigo Cassio S. Veneziani, Jennyfer A. Aldana-Mejía, Jairo K. Bastos and Carlos Henrique G. Martins
Molecules 2022, 27(21), 7310; https://doi.org/10.3390/molecules27217310 - 27 Oct 2022
Cited by 4 | Viewed by 1922
Abstract
Helicobacter pylori is a Gram-negative, microaerophilic, curved-rod, flagellated bacterium commonly found in the stomach mucosa and associated with different gastrointestinal diseases. With high levels of prevalence worldwide, it has developed resistance to the antibiotics used in its therapy. Brazilian red propolis has been [...] Read more.
Helicobacter pylori is a Gram-negative, microaerophilic, curved-rod, flagellated bacterium commonly found in the stomach mucosa and associated with different gastrointestinal diseases. With high levels of prevalence worldwide, it has developed resistance to the antibiotics used in its therapy. Brazilian red propolis has been studied due to its biological properties, and in the literature, it has shown promising antibacterial activities. The aim of this study was to evaluate anti-H. pylori from the crude hydroalcoholic extract of Brazilian red propolis (CHEBRP). For this, in vitro determination of the minimum inhibitory and bactericidal concentration (MIC/MBC) and synergistic activity and in vivo, microbiological, and histopathological analyses using Wistar rats were carried out using CHEBRP against H. pylori strains (ATCC 46523 and clinical isolate). CHEBRP presented MIC/MBC of 50 and 100 μg/mL against H. pylori strains (ATCC 43526 and clinical isolate, respectively) and tetracycline MIC/MBC of 0.74 µg/mL. The association of CHEBRP with tetracycline had an indifferent effect. In the stomach mucosa of rats, all treatments performed significantly decreased the number of H. pylori, and a concentration of 300 mg/kg was able to modulate the inflammatory response in the tissue. Therefore, CHEBRP showed promising anti-H. pylori in in vitro and in vivo assays. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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16 pages, 6680 KiB  
Article
Date Fruit (Phoenix dactylifera L.) Cultivar Extracts: Nanoparticle Synthesis, Antimicrobial and Antioxidant Activities
by Abdulghani Ashraf Halabi, Bassma H. Elwakil, Mohamed Hagar and Zakia A. Olama
Molecules 2022, 27(16), 5165; https://doi.org/10.3390/molecules27165165 - 13 Aug 2022
Cited by 3 | Viewed by 1395
Abstract
The pharmaceutical research sector’s inability to produce new drugs has made it difficult to keep up with the rate at which microbial resistance is developing. Recently, nanotechnology and its combinations with natural products have been the saviors against multidrug resistant bacteria. In the [...] Read more.
The pharmaceutical research sector’s inability to produce new drugs has made it difficult to keep up with the rate at which microbial resistance is developing. Recently, nanotechnology and its combinations with natural products have been the saviors against multidrug resistant bacteria. In the present investigation, different Egyptian and Saudi date cultivars were extracted and then phytochemically analyzed and tested for possible antimicrobial activities against multidrug resistant (MDR) microbes. The results revealed that extract of the flesh of fresh “Hayany” fruit (Egyptian date) showed the highest antimicrobial activity, with high levels of phenolic, flavonoid, and tannin concentrations (538.578 µg/mL, 28.481 µg/mL, and 20.888 µg/mL, respectively) and high scavenging activity, with an IC50 reaching 10.16 µg/mL. The highest synergistic activity was found between fresh “Hayany” fruit extract and amikacin. Novel nano-fresh fruit of “Hayany” date extract was synthesized using a ball-milling technique. The vesicle size was 21.6 nm, while the PDI and zeta potential were 0.32 and +38.4 mV, respectively. The inhibition zone diameters of nano-fresh fruit of “Hayany” date extract/amikacin reached 38 mm and 34 mm, with complete microbial eradication after 9 h and 6 h, against Candida albicans and Staphylococcus aureus, respectively. In conclusion, date fruit extract could be used as a candidate bioactive compound in the fight against infectious diseases. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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16 pages, 3364 KiB  
Article
The Derived Components of Gnaphalium hypoleucum DC. Reduce Quorum Sensing of Chromobacterium violaceum
by Yu-Long Li, Zi-Yong Chu, Gui-Min Liu, Sheng-Qiang Yang and Hong Zeng
Molecules 2022, 27(15), 4881; https://doi.org/10.3390/molecules27154881 - 30 Jul 2022
Cited by 4 | Viewed by 1329
Abstract
Gnaphalium hypoleucum DC. was first recorded in the Chinese National Pharmacopoeia “Yi Plant Medicine”. There is no detailed report on its main components’ activity in suppressing the quorum sensing activity (QS) of bacteria. Our study aimed to screen the main components in extracts [...] Read more.
Gnaphalium hypoleucum DC. was first recorded in the Chinese National Pharmacopoeia “Yi Plant Medicine”. There is no detailed report on its main components’ activity in suppressing the quorum sensing activity (QS) of bacteria. Our study aimed to screen the main components in extracts of G. hypoleucum DC. in order to measure their effects on bacterial QS activity and to explore specific quorum sensing mechanisms that are affected by G. hypoleucum DC. extracts. Crude extracts of G. hypoleucum DC. contained significant amounts of two compounds shown to inhibit bacterial QS activity, namely apigenin and luteolin. Apigenin and luteolin in crude extracts of G. hypoleucum DC. showed substantial inhibition of pigment formation, biofilm production, and motility in Chromobacterium violaceum ATCC 12472 compared to the effects of other phytochemicals from G. hypoleucum DC. Apigenin and luteolin exhibited a strong QS inhibitory effect on C. violaceum, interfering with the violacein pigment biosynthesis by downregulating the vioB, vioC, and vioD genes. In the presence of signal molecules, the QS effect is prevented, and the selected compounds can still inhibit the production of the characteristic purple pigment in C. violaceum. Based on qualitative and quantitative research using genomics and bioinformatics, we concluded that apigenin and luteolin in crude extracts of G. hypoleucum DC can interfere with the generation of QS in C. violaceum by downregulating the vioB, vioC, and vioD genes. Indeed, G. hypoleucum DC. is used for the treatment of bacterial infections, and this research provides new ideas and potential alternative uses for medicinal plants. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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14 pages, 943 KiB  
Article
Boswellic Acids as Effective Antibacterial Antibiofilm Agents
by Petr Jaroš, Elizaveta Timkina, Jana Michailidu, Dominik Maršík, Markéta Kulišová, Irena Kolouchová and Kateřina Demnerová
Molecules 2022, 27(12), 3795; https://doi.org/10.3390/molecules27123795 - 13 Jun 2022
Cited by 4 | Viewed by 1849
Abstract
Boswellic acids are biologically active pentacyclic terpenoid compounds derived from Boswellia sp. plants. Extracts containing these acids have a number of positive effects on human health, especially in the treatment of inflammation, arthritis, or asthma. With increasing resistance to common antibiotics, boswellic acid-containing [...] Read more.
Boswellic acids are biologically active pentacyclic terpenoid compounds derived from Boswellia sp. plants. Extracts containing these acids have a number of positive effects on human health, especially in the treatment of inflammation, arthritis, or asthma. With increasing resistance to common antibiotics, boswellic acid-containing extracts could serve as an alternative or work in synergy with commonly available preparations. This study aims to determine the effect of boswellic acids on suspension cells and biofilms of Staphylococcus epidermidis, Enterococcus faecalis, and Escherichia coli. The antimicrobial and antibiofilm effect found was compared with commonly available antibiotics to control these undesirable microorganisms. The synergistic effect of boswellic acids and common antibiotics on the growth of these microorganisms was also determined. All tested microorganisms showed a positive additive effect of antibiotics and boswellic acid extract. The most significant effect was found in Enterococcus faecalis ATCC 29212 in a combination of 0.2 × MIC80 erythromycin (0.2 mg/L) and 0.8 × MIC80 boswellic acid extract (16 mg/L). Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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21 pages, 2562 KiB  
Article
From Monographs to Chromatograms: The Antimicrobial Potential of Inula helenium L. (Elecampane) Naturalised in Ireland
by Ciara-Ruth Kenny, Anna Stojakowska, Ambrose Furey and Brigid Lucey
Molecules 2022, 27(4), 1406; https://doi.org/10.3390/molecules27041406 - 18 Feb 2022
Cited by 8 | Viewed by 3763
Abstract
With antimicrobial resistance rising globally, the exploration of alternative sources of candidate molecules is critical to safeguard effective chemotherapeutics worldwide. Plant natural products are accessible, structurally diverse compounds with antimicrobial potential. The pharmacological applications of plants in medicine can be guided by the [...] Read more.
With antimicrobial resistance rising globally, the exploration of alternative sources of candidate molecules is critical to safeguard effective chemotherapeutics worldwide. Plant natural products are accessible, structurally diverse compounds with antimicrobial potential. The pharmacological applications of plants in medicine can be guided by the attestation of traditional use, as demonstrated in this study. In Irish ethnomedical literature, Inula helenium L. (elecampane) is often indicated for respiratory and dermal ailments. This is the first assessment of antimicrobial sesquiterpene lactones from the roots of elecampane, naturalised in Ireland. Traditional hydro-ethanolic extracts were prepared from multi-origin elecampane roots. A novel clean-up strategy facilitated the bioactivity-guided fractionation of a subset of anti-staphylococcal fractions (the compositions of which were investigated using HPLC-DAD, supported by 1H NMR). The natural products attributing to the antimicrobial activity, observed in vitro, were identified as alantolactone (1), isoalantolactone (2), igalan (3), and an unseparated mixture of dugesialactone (4) and alloalantolactone (5), as major compounds. The findings suggest that the geographical origin of the plant does not influence the anti-bacterial potency nor the chemical composition of traditional elecampane root. Considering the prevalence of staphylococci-associated infections and associated broad spectrum resistance in Irish hospitals, currently, further research is warranted into the usage of the identified compounds as potential candidates in the control of staphylococcal carriage and infection. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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15 pages, 2243 KiB  
Article
Bioactive Compounds of Ganoderma boninense Inhibited Methicillin-Resistant Staphylococcus aureus Growth by Affecting Their Cell Membrane Permeability and Integrity
by Yow-San Chan and Khim-Phin Chong
Molecules 2022, 27(3), 838; https://doi.org/10.3390/molecules27030838 - 27 Jan 2022
Cited by 9 | Viewed by 3049
Abstract
Some species of Ganoderma, such as G. lucidum, are well-known as traditional Chinese medicine (TCM), and their pharmacological value was scientifically proven in modern days. However, G. boninense is recognized as an oil palm pathogen, and its biological activity is scarcely [...] Read more.
Some species of Ganoderma, such as G. lucidum, are well-known as traditional Chinese medicine (TCM), and their pharmacological value was scientifically proven in modern days. However, G. boninense is recognized as an oil palm pathogen, and its biological activity is scarcely reported. Hence, this study aimed to investigate the antibacterial properties of G. boninense fruiting bodies, which formed by condensed mycelial, produced numerous and complex profiles of natural compounds. Extract was cleaned up with normal-phase SPE and its metabolites were analyzed using liquid chromatography–mass spectrometry (LCMS). From the disc diffusion and broth microdilution assays, strong susceptibility was observed in methicillin-resistant Staphylococcus aureus (MRSA) in elute fraction with zone inhibition of 41.08 ± 0.04 mm and MIC value of 0.078 mg mL−1. A total of 23 peaks were detected using MS, which were putatively identified based on their mass-to-charge ratio (m/z), and eight compounds, which include aristolochic acid, aminoimidazole ribotide, lysine sulfonamide 11v, carbocyclic puromycin, fenbendazole, acetylcaranine, tigecycline, and tamoxifen, were reported in earlier literature for their antimicrobial activity. Morphological observation via scanning electron microscope (SEM), cell membrane permeability, and integrity assessment suggest G. boninense extract induces irreversible damage to the cell membrane of MRSA, thus causing cellular lysis and death. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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20 pages, 2050 KiB  
Article
The Untargeted Phytochemical Profile of Three Meliaceae Species Related to In Vitro Cytotoxicity and Anti-Virulence Activity against MRSA Isolates
by Leilei Zhang, Maha M. Ismail, Gabriele Rocchetti, Nesrin M. Fayek, Luigi Lucini and Fatema R. Saber
Molecules 2022, 27(2), 435; https://doi.org/10.3390/molecules27020435 - 10 Jan 2022
Cited by 8 | Viewed by 1882
Abstract
Background: A high mortality rate is associated with about 80% of all infections worldwide, mainly due to antimicrobial resistance. Various antimicrobial and cytotoxic activities have been proposed for Meliaceae species. This study aimed to evaluate the in vitro anti-virulence and cytotoxic effect of [...] Read more.
Background: A high mortality rate is associated with about 80% of all infections worldwide, mainly due to antimicrobial resistance. Various antimicrobial and cytotoxic activities have been proposed for Meliaceae species. This study aimed to evaluate the in vitro anti-virulence and cytotoxic effect of the leaf extracts of Aphanamixis polystachya, Toona ciliata and Melia azedarach against five MRSA strains and on three cancer cell lines, followed by biological correlation to their encompassed phytoconstituents. Material and Methods: We explored three plants of this family against a panel of Methicillin-resistant Staphylococcus aureus (MRSA) strains and several cancer cell lines to select the most promising candidates for further in vivo and preclinical studies. The phytochemical composition was evaluated by UHPLC–QTOF–MS untargeted profiling. Cell viability was assessed by SRB assay. Minimum Inhibitory Concentration was carried out by using the agar micro-dilution technique. Inhibition of biofilm formation and preformed biofilm disruption were assessed spectrophotomertically, according to the Sultan and Nabil method (2019). Results: A total of 279 compounds were putatively annotated to include different phytochemical classes, such as flavonoids (108), limonoids/terpenoids (59), phenolic acids (49) and lower-molecular-weight phenolics (39). A. polystachya extract showed the most potent cytotoxic activity against Huh-7, DU-145 and MCF-7 cell lines (IC50 = 3, 3.5 and 13.4 µg mL−1, respectively), followed by M. azedarach, with no effect recorded for T. ciliata extract. Furthermore, both A. polystachya and M. azedarach extracts showed promising anti-virulence and antimicrobial activities, with A. polystachya being particularly active against MRSA. These two latter extracts could inhibit and disrupt the biofilm, formed by MRSA, at sub-lethal concentrations. Interestingly, the extracts inhibited hemolysin-α enzyme, thus protecting rabbit RBCs from lysis. A. polystachya extract reduced the pigmentation and catalase enzyme activity of tested pigmented strains better than M. azedarach at both tested sub-MICs. Consequently, susceptibility of the extract-treated cells to oxidant killing by 200 mM H2O2 increased, leading to faster killing of the cells within 120 min as compared to the extract-non-treated cells, likely due to the lower antioxidant-scavenging activity of cells exhibiting less staphyloxanthin production. Conclusion: These findings suggested that both A. polystachya and M. azedarach natural extracts are rich in bioactive compounds, mainly limonoids, phenolics and oxygenated triterpenoids, which can combat MRSA biofilm infections and could be considered as promising sources of therapeutic cytotoxic, antibiofilm and anti-virulence agents. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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14 pages, 32944 KiB  
Article
Comparison of Phytochemical Contents, Antioxidant and Antibacterial Activities of Various Solvent Extracts Obtained from ‘Maluma’ Avocado Pulp Powder
by Thi-Van-Linh Nguyen, Quoc-Duy Nguyen, Nhu-Ngoc Nguyen and Thi-Thuy-Dung Nguyen
Molecules 2021, 26(24), 7693; https://doi.org/10.3390/molecules26247693 - 20 Dec 2021
Cited by 4 | Viewed by 3355
Abstract
Although avocado is a superfood rich in phytochemicals with high antioxidant activities, studies on the antibacterial properties of its pulp are limited, except for seed and peel portions. In this study, three types of solvent (acetone, methanol, and diethyl ether) were used to [...] Read more.
Although avocado is a superfood rich in phytochemicals with high antioxidant activities, studies on the antibacterial properties of its pulp are limited, except for seed and peel portions. In this study, three types of solvent (acetone, methanol, and diethyl ether) were used to obtain the extracts from “Maluma” avocado pulp powder prepared by infrared drying. The extracts were analyzed for total polyphenols, phytopigments (total chlorophylls and carotenoids), antioxidant activities (ferric-reducing antioxidant power (FRAP), 2,2-Diphenyl-1-picrylhydrazyl (DPPH), and 2,2-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) assays), and antibacterial activities against seven pathogens (Shigella sonnei ATCC 9290, Escherichia coli ATCC 8739, Salmonella typhi ATCC 6539, Vibrio parahaemolyticus ATCC 17802, Proteus mirabilis ATCC 25933, Staphylococcus aureus ATCC 6538, and Bacillus cereus ATCC 11778). The results showed that the acetone solvent could extract the highest polyphenols and chlorophylls with the highest antioxidant activity in terms of ABTS and DPPH assays. In contrast, diethyl ether exhibited the most significant content of carotenoids and FRAP values. However, the methanol extract was the best solvent, exerting the strongest antibacterial and meaningful antioxidant activities. For the bacterial activities, Gram-positive pathogens (Bacillus cereus and Staphylococcus aureus) were inhibited more efficiently by avocado extracts than Gram-negative bacteria. Therefore, the extracts from avocado powder showed great potential for applications in food processing and preservation, pharmaceuticals, and cosmetics. Full article
(This article belongs to the Special Issue Antibacterial Agents from Natural Source)
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