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14 pages, 1280 KiB

Open AccessArticle

Antifungal Activity of Volatile Organic Compounds Produced by Bacillus methylotrophicus and Bacillus thuringiensis against Five Common Spoilage Fungi on Loquats

by Chao-Nan He, Wan-Qiong Ye, Ying-Ying Zhu and Wen-Wen Zhou

Molecules 2020, 25(15), 3360; https://doi.org/10.3390/molecules25153360 - 24 Jul 2020

Cited by 42 | Viewed by 4789

Abstract

Loquat fruit is one of the most perishable fruits in China, and has a very limited shelf life because of mechanical injury and microbial decay. Due to an increasing concern about human health and environmental security, antagonistic microorganisms have been a potential alternative [...] Read more.

Loquat fruit is one of the most perishable fruits in China, and has a very limited shelf life because of mechanical injury and microbial decay. Due to an increasing concern about human health and environmental security, antagonistic microorganisms have been a potential alternative for fungicides to control postharvest diseases. In this work, the antifungal effect of volatile organic compounds (VOCs) produced by Bacillus methylotrophicus BCN2 and Bacillus thuringiensis BCN10 against five postharvest pathogens isolated from loquat fruit, Fusarium oxysporum, Botryosphaeria sp., Trichoderma atroviride, Colletotrichum gloeosporioides, and Penicillium expansum were evaluated by in vitro and in vivo experiments. As a result, the VOCs released by BCN2 and BCN10 were able to suppress the mycelial growth of all targeted pathogens according to inhibition ratio in the double petri-dish assay as well as disease incidence and disease diameter on loquat fruits. The main volatile compounds were identified by solid-phase microextraction (SPME)-gas chromatography. These VOCs produced by the two strains played complementary roles in controlling these five molds and enabled loquat fruits to keep fresh for ten days, significantly. This research will provide a theoretic foundation and technical support for exploring the functional components of VOCs applicable in loquat fruit preservation. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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14 pages, 1727 KiB

Open AccessArticle

Concentrated Bioshell Calcium Oxide (BiSCaO) Water Kills Pathogenic Microbes: Characterization and Activity

by Shingo Nakamura, Masayuki Ishihara, Yoko Sato, Tomohiro Takayama, Sumiyo Hiruma, Naoko Ando, Koichi Fukuda, Kaoru Murakami and Hidetaka Yokoe

Molecules 2020, 25(13), 3001; https://doi.org/10.3390/molecules25133001 - 30 Jun 2020

Cited by 10 | Viewed by 3369

Abstract

Bioshell calcium oxide (BiSCaO) exhibits deodorizing properties and broad microbicidal activity. In this study, we examined possible utility of BiSCaO Water for that purpose. BiSCaO Water was prepared by adding 10 wt% BiSCaO to clean water and gently collecting the supernatant in a [...] Read more.

Bioshell calcium oxide (BiSCaO) exhibits deodorizing properties and broad microbicidal activity. In this study, we examined possible utility of BiSCaO Water for that purpose. BiSCaO Water was prepared by adding 10 wt% BiSCaO to clean water and gently collecting the supernatant in a bottle. The same volume of clean water was gently poured onto the BiSCaO precipitate and the supernatant was gently collected in a bottle; this process was repeated fifty times. The produced BiSCaO Water contained nanoparticles (about 400–800 nm) composed of smaller nanoparticles (100–200 nm), and was colorless and transparent, with a pH > 12.7. In vitro assays demonstrated that BiSCaO Water eliminated more than 99.9% of influenza A (H1N1) and Feline calicivirus, Escherichia coli such as NBRC 3972 and O-157:H7, Pseudomonas aeruginosa, Salmonella, and Staphylococcus aureus within 15 min. We compared BiSCaO Water with the other microbicidal reagents such as ethanol, BiSCaO, BiSCa(OH)₂ suspensions, povidone iodine, NaClO, BiSCaO dispersion and colloidal dispersion with respect to deodorization activity and microbicidal efficacy. The results showed that BiSCaO Water was a potent reagent with excellent deodorization and disinfection activities against pathogenic bacteria and viruses (including both enveloped and nonenveloped viruses). Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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20 pages, 9660 KiB

Open AccessArticle

Synthesis of a Small Library of Nature-Inspired Xanthones and Study of Their Antimicrobial Activity

by Diana I. S. P. Resende, Patrícia Pereira-Terra, Joana Moreira, Joana Freitas-Silva, Agostinho Lemos, Luís Gales, Eugénia Pinto, Maria Emília de Sousa, Paulo Martins da Costa and Madalena M. M. Pinto

Molecules 2020, 25(10), 2405; https://doi.org/10.3390/molecules25102405 - 21 May 2020

Cited by 25 | Viewed by 3789

Abstract

A series of thirteen xanthones 3–15 was prepared based on substitutional (appendage) diversity reactions. The series was structurally characterized based on their spectral data and HRMS, and the structures of xanthone derivatives 1, 7, and 8 were determined by [...] Read more.

A series of thirteen xanthones 3–15 was prepared based on substitutional (appendage) diversity reactions. The series was structurally characterized based on their spectral data and HRMS, and the structures of xanthone derivatives 1, 7, and 8 were determined by single-crystal X-ray diffraction. This series, along with an in-house series of aminated xanthones 16–33, was tested for in-vitro antimicrobial activity against seven bacterial (including two multidrug-resistant) strains and five fungal strains. 1-(Dibromomethyl)-3,4-dimethoxy-9H-xanthen-9-one (7) and 1-(dibromomethyl)-3,4,6-trimethoxy-9H-xanthen-9-one (8) exhibited antibacterial activity against all tested strains. In addition, 3,4-dihydroxy-1-methyl-9H-xanthen-9-one (3) revealed a potent inhibitory effect on the growth of dermatophyte clinical strains (T. rubrum FF5, M. canis FF1 and E. floccosum FF9), with a MIC of 16 µg/mL for all the tested strains. Compounds 3 and 26 showed a potent inhibitory effect on two C. albicans virulence factors: germ tube and biofilm formation. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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16 pages, 2974 KiB

Open AccessArticle

Wide-Antimicrobial Spectrum of Picolinium Salts

by Sarka Salajkova, Marketa Benkova, Jan Marek, Radek Sleha, Lukas Prchal, David Malinak, Rafael Dolezal, Kristina Sepčić, Nina Gunde-Cimerman, Kamil Kuca and Ondrej Soukup

Molecules 2020, 25(9), 2254; https://doi.org/10.3390/molecules25092254 - 11 May 2020

Cited by 10 | Viewed by 3634

Abstract

Nosocomial infections, which greatly increase morbidity among hospitalized patients, together with growing antibiotic resistance still encourage many researchers to search for novel antimicrobial compounds. Picolinium salts with different lengths of alkyl chains (C₁₂, C₁₄, C₁₆) were prepared [...] Read more.

Nosocomial infections, which greatly increase morbidity among hospitalized patients, together with growing antibiotic resistance still encourage many researchers to search for novel antimicrobial compounds. Picolinium salts with different lengths of alkyl chains (C₁₂, C₁₄, C₁₆) were prepared by Menshutkin-like reaction and evaluated with respect to their biological activity, i.e., lipophilicity and critical micellar concentration. Picolinium salts with C₁₄ and C₁₆ side chains achieved similar or even better results when in terms of antimicrobial efficacy than benzalkoniums; notably, their fungicidal efficiency was substantially more potent. The position of the methyl substituent on the aromatic ring does not seem to affect antimicrobial activity, in contrast to the effect of length of the N-alkyl chain. Concurrently, picolinium salts exhibited satisfactory low cytotoxicity against mammalian cells, i.e., lower than that of benzalkonium compounds, which are considered as safe. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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12 pages, 1471 KiB

Open AccessArticle

Antifungal Activity of an Original Amino-Isocyanonaphthalene (ICAN) Compound Family: Promising Broad Spectrum Antifungals

by Miklós Nagy, Gábor Szemán-Nagy, Alexandra Kiss, Zsolt László Nagy, László Tálas, Dávid Rácz, László Majoros, Zoltán Tóth, Zsuzsa Máthéné Szigeti, István Pócsi and Sándor Kéki

Molecules 2020, 25(4), 903; https://doi.org/10.3390/molecules25040903 - 18 Feb 2020

Cited by 6 | Viewed by 3076

Abstract

Multiple drug resistant fungi pose a serious threat to human health, therefore the development of completely new antimycotics is of paramount importance. The in vitro antifungal activity of the original, 1-amino-5-isocyanonaphthalenes (ICANs) was evaluated against reference strains of clinically important Candida species. Structure-activity [...] Read more.

Multiple drug resistant fungi pose a serious threat to human health, therefore the development of completely new antimycotics is of paramount importance. The in vitro antifungal activity of the original, 1-amino-5-isocyanonaphthalenes (ICANs) was evaluated against reference strains of clinically important Candida species. Structure-activity studies revealed that the naphthalene core and the isocyano- together with the amino moieties are all necessary to exert antifungal activity. 1,1-N-dimethylamino-5-isocyanonaphthalene (DIMICAN), the most promising candidate, was tested further in vitro against clinical isolates of Candida species, yielding a minimum inhibitory concentration (MIC) of 0.04–1.25 µg/mL. DIMICAN was found to be effective against intrinsically fluconazole resistant Candida krusei isolates, too. In vivo experiments were performed in a severly neutropenic murine model inoculated with a clinical strain of Candida albicans. Daily administration of 5 mg/kg DIMICAN intraperitoneally resulted in 80% survival even at day 13, whereas 100% of the control group died within six days. Based on these results, ICANs may become an effective clinical lead compound family against fungal pathogens. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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15 pages, 817 KiB

Open AccessArticle

Synthesis and Antimicrobial Activity of Methoxy- Substituted γ-Oxa-ε-lactones Derived from Flavanones

by Witold Gładkowski, Monika Siepka, Tomasz Janeczko, Edyta Kostrzewa-Susłow, Jarosław Popłoński, Marcelina Mazur, Barbara Żarowska, Wojciech Łaba, Gabriela Maciejewska and Czesław Wawrzeńczyk

Molecules 2019, 24(22), 4151; https://doi.org/10.3390/molecules24224151 - 16 Nov 2019

Cited by 18 | Viewed by 3399

Abstract

Six γ-oxa-ε-lactones, 4-phenyl-3,4-dihydro-2H-1,5-benzodioxepin-2-one (5a) and its five derivatives with methoxy groups in different positions of A and B rings (5b–f), were synthesized from corresponding flavanones. Three of the obtained lactones (5b,c, [...] Read more.

Six γ-oxa-ε-lactones, 4-phenyl-3,4-dihydro-2H-1,5-benzodioxepin-2-one (5a) and its five derivatives with methoxy groups in different positions of A and B rings (5b–f), were synthesized from corresponding flavanones. Three of the obtained lactones (5b,c,f) have not been previously described in the literature. Structures of all synthesized compounds were confirmed by complete spectroscopic analysis with the assignments of signals on ¹H and ¹³C-NMR spectra to the corresponding atoms. In most cases, lactones 5a–f exerted an inhibitory effect on the growth of selected pathogenic bacteria (Escherichia coli, Bacillus subtilis, and Staphylococcus aureus), filamentous fungi (Fusarium graminearum, Aspergillus niger, and Alternaria sp.), and yeast (Candida albicans). The broadest spectrum of activity was observed for unsubstituted lactone 5a, which was particularly active against filamentous fungi and yeast. Lactones with methoxy groups in the 3′ (5c) and 4′ (5d) position of B ring were more active towards bacteria whereas lactone substituted in the 7 position of the A ring (5e) exhibited higher antifungal activity. In most cases, the introduction of lactone function increased the activity of the compound compared to its flavonoid precursors, chalcones 3a–e, and flavanones 4a–f. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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16 pages, 2663 KiB

Open AccessArticle

Identification of New Antifungal Agents Targeting Chitin Synthesis by a Chemical-Genetic Method

by Yan Li, Hongmin Sun, Xiaohong Zhu, Cong Bian, Yanchang Wang and Shuyi Si

Molecules 2019, 24(17), 3155; https://doi.org/10.3390/molecules24173155 - 29 Aug 2019

Cited by 22 | Viewed by 4509

Abstract

Fungal infection is a leading cause of mortality in immunocompromised population; thus, it is urgent to develop new and safe antifungal agents. Different from human cells, fungi have a cell wall, which is composed mainly of polysaccharide glucan and chitin. The unique cell [...] Read more.

Fungal infection is a leading cause of mortality in immunocompromised population; thus, it is urgent to develop new and safe antifungal agents. Different from human cells, fungi have a cell wall, which is composed mainly of polysaccharide glucan and chitin. The unique cell wall structure is an ideal target for antifungal drugs. In this research, a chemical-genetic method was used to isolate antifungal agents that target chitin synthesis in yeast cells. From a compound library, we isolated two benzothiazole compounds that showed greater toxicity to yeast mutants lacking glucan synthase Fks1 compared to wild-type yeast cells and mutants lacking chitin synthase Chs3. Both of them inhibited the activity of chitin synthase in vitro and reduced chitin level in yeast cells. Besides, these compounds showed clear synergistic antifungal effect with a glucan synthase inhibitors caspofungin. Furthermore, these compounds inhibited the growth of Saccharomyces cerevisiae and opportunistic pathogen Candida albicans. Surprisingly, the genome-wide mass-spectrometry analysis showed decreased protein level of chitin synthases in cells treated with one of these drugs, and this decrease was not a result of downregulation of gene transcription. Therefore, we successfully identified two new antifungal agents that inhibit chitin synthesis using a chemical-genetic method. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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Review

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25 pages, 962 KiB

Open AccessReview

Towards Robust Delivery of Antimicrobial Peptides to Combat Bacterial Resistance

by Matthew Drayton, Jayachandran N. Kizhakkedathu and Suzana K. Straus

Molecules 2020, 25(13), 3048; https://doi.org/10.3390/molecules25133048 - 3 Jul 2020

Cited by 67 | Viewed by 5904

Abstract

Antimicrobial peptides (AMPs), otherwise known as host defence peptides (HDPs), are naturally occurring biomolecules expressed by a large array of species across the phylogenetic kingdoms. They have great potential to combat microbial infections by directly killing or inhibiting bacterial activity and/or by modulating [...] Read more.

Antimicrobial peptides (AMPs), otherwise known as host defence peptides (HDPs), are naturally occurring biomolecules expressed by a large array of species across the phylogenetic kingdoms. They have great potential to combat microbial infections by directly killing or inhibiting bacterial activity and/or by modulating the immune response of the host. Due to their multimodal properties, broad spectrum activity, and minimal resistance generation, these peptides have emerged as a promising response to the rapidly concerning problem of multidrug resistance (MDR). However, their therapeutic efficacy is limited by a number of factors, including rapid degradation, systemic toxicity, and low bioavailability. As such, many strategies have been developed to mitigate these limitations, such as peptide modification and delivery vehicle conjugation/encapsulation. Oftentimes, however, particularly in the case of the latter, this can hinder the activity of the parent AMP. Here, we review current delivery strategies used for AMP formulation, focusing on methodologies utilized for targeted infection site release of AMPs. This specificity unites the improved biocompatibility of the delivery vehicle with the unhindered activity of the free AMP, providing a promising means to effectively translate AMP therapy into clinical practice. Full article

(This article belongs to the Special Issue Recent Advances in the Development of Antimicrobial Agents)

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