Antifungal activities of fluoroindoles against the postharvest pathogen Botrytis cinerea: In vitro and in silico approaches

Expanding the Structural Diversity of Tubulin-Targeting Agents: Development of Highly Potent Benzimidazoles for Treating Fungal Diseases

Benzimidazoles, the representative pharmacophore of fungicides, have excellent antifungal potency, but their simple structure and single site of action have hindered their wider application in agriculture. In order to extend the structural diversity of tubulin-targeted benzimidazoles, novel benzimidazole derivatives were prepared by introducing the attractive pyrimidine pharmacophore. 2-((6-(4-(trifluoromethyl)phenoxy)pyrimidin-4-yl)thio)-1H-benzo[d]imidazole (A25) exhibited optimal antifungal activity against Sclerotinia sclerotiorum (S. s.), affording an excellent half-maximal effective concentration (EC50) of 0.158 μg/mL, which was higher than that of the reference agent carbendazim (EC50 = 0.594 μg/mL). Pot experiments revealed that compound A25 (200 μg/mL) had acceptable protective activity (84.7%) and curative activity (78.1%), which were comparable with that of carbendazim (protective activity: 90.8%; curative activity: 69.9%). Molecular docking displayed that multiple hydrogen bonds and π-π interactions could be formed between A25 and β-tubulin, resulting in a stronger bonding effect than carbendazim. Fluorescence imaging revealed that the structure of intracellular microtubules can be changed significantly after A25 treatment. Overall, these remarkable antifungal profiles of constructed novel benzimidazole derivatives could facilitate the application of novel microtubule-targeting agents.

Natural terpene-based derivatives to control postharvest sclerotinia rot and the involved potential mechanism

In an effort to develop novel postharvest preservatives of satisfactory environmental compatibility from natural monoterpene, a series of terpene-based derivatives containing oxime ester were designed and prepared. In this research, the inhibitory effect of target compounds against S. sclerotiorum were evaluated though in vitro and in vivo tests. It was investigated that most compounds exhibited promising antifungal activity, especially compound 4k with EC50 value of 3.02 μg/mL, which was significantly superior to commercial fungicide trifloxystrobin. Notably, compound 4k improved the physicochemical quality of carrot including weight loss, contents of titratable acidity, ascorbic acid, carotenoid, malondialdehyde, and enzymes activities, ensuring post-harvest preservation. Simultaneously, the mycelial morphology, ultrastructure, cell wall permeability, and defense/respiration-related enzymes of S. sclerotiorum were destructed. The preliminary toxicity evaluation of target compounds indicated that the prepared target compounds possessed safety and low toxicity. Additionally, the essential chemical features for activity and interaction mode between molecule and cytochrome bc1 complex were inquired by computer-aid technology. The study provided meaningful insight into formulation of natural terpene-based fresh-keeping agent to resist postharvest decay infected by S. sclerotiorum.

Halogenated Antimicrobial Agents to Combat Drug-Resistant Pathogens

Antimicrobial resistance presents us with a potential global crisis as it undermines the abilities of conventional antibiotics to combat pathogenic microbes. The history of antimicrobial agents is replete with examples of scaffolds containing halogens. In this review, we discuss the impacts of halogen atoms in various antibiotic types and antimicrobial scaffolds and their modes of action, structure-activity relationships, and the contributions of halogen atoms in antimicrobial activity and drug resistance. Other halogenated molecules, including carbohydrates, peptides, lipids, and polymeric complexes, are also reviewed, and the effects of halogenated scaffolds on pharmacokinetics, pharmacodynamics, and factors affecting antimicrobial and antivirulence activities are presented. Furthermore, the potential of halogenation to circumvent antimicrobial resistance and rejuvenate impotent antibiotics is addressed. This review provides an overview of the significance of halogenation, the abilities of halogens to interact in biomolecular settings and enhance pharmacological properties, and their potential therapeutic usages in preventing a postantibiotic era. SIGNIFICANCE STATEMENT: Antimicrobial resistance and the increasing impotence of antibiotics are critical threats to global health. The roles and importance of halogen atoms in antimicrobial drug scaffolds have been established, but comparatively little is known of their pharmacological impacts on drug resistance and antivirulence activities. This review is the first to extensively evaluate the roles of halogen atoms in various antibiotic classes and pharmacological scaffolds and to provide an overview of their ability to overcome antimicrobial resistance.

Study on the Antifungal Activity and Potential Mechanism of Natamycin against Colletotrichum fructicola

In this investigation, the antifungal activity, its influence on the quality of apples, and the molecular mechanism of natamycin against Colletotrichum fructicola were systematically explored. Our findings indicated that natamycin showed significant inhibition against C. fructicola. Moreover, it efficaciously maintained the apple quality by modulating the physicochemical index. Research on the antifungal mechanism showed that natamycin altered the mycelial microstructure, disrupted the plasma membrane integrality, and decreased the ergosterol content of C. fructicola. Interestingly, the exogenous addition of ergosterol weakened the antifungal activity of natamycin. Importantly, natamycin markedly inhibited the expression of Cyp51A and Cyp51B genes in C. fructicola, which was contrary to the results obtained after treatment with triazole fungicide flusilazole. All these results exhibited sufficient proof that natamycin had enormous potential to be conducive as a promising biopreservative against C. fructicola on apples, and these findings will advance our knowledge on the mechanism of natamycin against pathogenic fungi.

Encapsulation of tannic acid in polyvinylidene fluoride mediated electrospun nanofibers and its antibiofilm and antibacterial activities

In the past 15 years or more, interest in polymer-mediated nanofibers (NFs), a significant class of nanomaterials, has grown. Although fibers with a diameter of less than 1 mm are frequently commonly referred to as NFs, and are typically defined as having a diameter of less than several hundreds of nanometers. Due to the increased antibiotic resistance of many diseases nowadays, NFs with antibacterial activity are quite important. A flexible technique for creating NFs with the desired characteristics is called electrospinning. This research article describes how to make electrospun NFs of tannic acid (TA) with polyvinylidene fluoride (PVDF) as the template. As a result, the absorbance of the obtained NFs has been raised without forming any additional peaks in the spectral ranges. The obtained NF has a gradual increase in intensity, and the FT-IR data show that the TA is present in the NFs. FE-SEM images show that the NFs are discovered to be completely bead-free. Since TA reduced the viscosity of the spinning solution while marginally increasing solution conductivity, PVDF NFs have a greater average fiber diameter (AFD) than NFs of TA with PVDF, which is likely a result of the TA solutions in it. The findings showed that TA greatly decreased S. aureus and E. coli's ability to attach. The acquired NFs created in this work may have significant potential for reducing the pathogenicity of S. aureus and E. coli as well as their ability to build biofilms.

Synthesis, Antioxidant, and Antifungal Activities of β-Ionone Thiazolylhydrazone Derivatives and Their Application in Anti-Browning of Freshly Cut Potato

In order to develop a new type of antioxidants with high efficiency, a series of β-ionone thiazolylhydrazone derivatives were designed and synthesized from β-ionone, and their structures were characterized by 1H-NMR, 13C-NMR, FT-IR, and HR-MS. The antioxidant test in vitro indicated that most of the target compounds had high biological activity. Among them, compound 1k exhibited very strong DPPH (1,1-diphenyl-2-picrylhydrazyl radical)-scavenging activity with a half-maximal effective concentration (IC50) of 86.525 μM. Furthermore, in the ABTS (2,2-azinobis (3-ethylbenzothiazoline-6-sulfonate) diammonium salt)-scavenging experiment, compound 1m exhibited excellent activity with an IC50 of 65.408 μM. Their biological activities were significantly better than those of the positive control Trolox. These two compounds, which have good free-radical-scavenging activity in vitro, were used as representative compounds in the anti-browning experiment of fresh-cut potatoes. The results showed that 1k and 1m had the same anti-browning ability as kojic acid, and they were effective browning inhibitors. In addition, it is well known that microbial infection is one of the reasons for food oxidation. Therefore, we investigated the antifungal activity of 25 target compounds against eight plant fungi at a concentration of 125 mg/L. The results indicated that these compounds all have some antifungal activity and may become new potential fungicides. Notably, compound 1u showed the best inhibitory effect against Poria vaporaria, with an inhibition rate as high as 77.71%; it is expected to become the dominant structure for the development of new antifungal agents.

Gum Arabic polysaccharide embedded L-cysteine capped copper oxide nanocarriers selectively inhibit fluconazole-resistant C. albicans biofilm and remove the toxic dye from wastewater

Copper oxide nanocarriers have attracted increasing interest in the scientific community, including antimicrobial applications. Candida biofilm developed causes serious clinical problems, leading to drug failure caused by its inherent drug tolerance. Nanocarriers are a good alternative approach to solving this challenge because of their excellent penetration power inside biofilms. Hence, main objectives of this research were to prepare gum arabic-embedded L-cysteine-capped copper oxide nanocarriers (GCCuO NCs) and tested against C. albicans and explore another application. To achieve the main research objectives, GCCuO NCs were synthesized and investigated for antibiofilm potency against C. albicans. Various methods were employed to measure antibiofilm potency such as biofilm assay etc., of NCs. The nano size of GCCuO NCs is advantageous for augmenting penetration power and retention into biofilms. GCCuO NCs at 100 μg/mL exhibited significant antibiofilm activity against the C. albicans DAY185 by switching of yeast-to-hyphae and gene perturbation. The level of CR dye adsorption was 58.96 % using 30 μg/mL of NCs. Based on effective C. albicans biofilm inhibition and CR dye adsorption capacity of NCs, it can be suggested that present research work opens an innovative path to treat biofilm-associated fungal infections, and these NCs can be used for environmental remedies.

4F-Indole Enhances the Susceptibility of Pseudomonas aeruginosa to Aminoglycoside Antibiotics

Infections caused by multidrug-resistant bacteria are becoming increasingly serious. The aminoglycoside antibiotics have been widely used to treat severe Gram-negative bacterial infections. Here, we reported that a class of small molecules, namely, halogenated indoles, can resensitize Pseudomonas aeruginosa PAO1 to aminoglycoside antibiotics such as gentamicin, kanamycin, tobramycin, amikacin, neomycin, ribosomalin sulfate, and cisomicin. We selected 4F-indole as a representative of halogenated indoles to investigate its mechanism and found that the two-component system (TCS) PmrA/PmrB inhibited the expression of multidrug efflux pump MexXY-OprM, allowing kanamycin to act intracellularly. Moreover, 4F-indole inhibited the biosynthesis of several virulence factors, such as pyocyanin, type III secretion system (T3SS), and type VI secretion system (T6SS) exported effectors, and reduced the swimming and twitching motility by suppressing the expression of flagella and type IV pili. This study suggests that the combination of 4F-indole and kanamycin can be more effective against P. aeruginosa PAO1 and affect its multiple physiological activities, providing a novel insight into the reactivation of aminoglycoside antibiotics. IMPORTANCE Infections caused by Pseudomonas aeruginosa have become a major public health crisis. Its resistance to existing antibiotics causes clinical infections that are hard to cure. In this study, we found that halogenated indoles in combination with aminoglycoside antibiotics could be more effective than antibiotics alone against P. aeruginosa PAO1 and preliminarily revealed the mechanism of the 4F-indole-induced regulatory effect. Moreover, the regulatory effect of 4F-indole on different physiological behaviors of P. aeruginosa PAO1 was analyzed by combined transcriptomics and metabolomics. We explain that 4F-indole has potential as a novel antibiotic adjuvant, thus slowing down the further development of bacterial resistance.

Synthesis of Bio-Based Polybenzoxazine and Its Antibiofilm and Anticorrosive Activities

Candida albicans are highly widespread pathogenic fungi in humans. Moreover, its developed biofilm causes serious clinical problems, leading to drug failure caused by its inherent drug tolerance. Hence, the inhibition of biofilm formation and virulence characteristics provide other means of addressing infections. Polymer composites (PCs) derived from natural products have attracted increasing interest in the scientific community, including antimicrobial applications. PCs are a good alternative approach to solving this challenge because of their excellent penetration power inside biofilms. The main objectives of this study were to synthesize a novel curcumin-based polybenzoxazine polymer composite (poly(Cu-A) PC) using Mannich condensation reaction and evaluate their potency as an antibiofilm and anticorrosive candidate against C. albicans. In addition, their anticorrosive efficacy was also explored. PC exhibited significant antibiofilm efficacy versus C. albicans DAY185 by the morphologic changing of yeast to hyphae, and>90% anticorrosive efficacy was observed at a higher dose of PC. These prepared PC were safe in vivo against Caenorhabditis elegans and Raphanus raphanistrum. The study shows that a polybenzoxazine polymer composite has the potential for controlling biofilm-associated fungal infections and virulence by C. albicans, and opens a new avenue for designing PCs as antifungal, anticorrosive agents for biofilm-associated fungal infections and industrial remediation.

Novel Microwave Synthesis of Copper Oxide Nanoparticles and Appraisal of the Antibacterial Application

The exceptional characteristics of bio-synthesized copper oxide nanoparticles (CuO NPs), including high surface-to-volume ratio and high-profit strength, are of tremendous interest. CuO NPs have cytotoxic, catalytic, antibacterial, and antioxidant properties. Fruit peel extract has been recommended as a valuable alternative method due to the advantages of economic prospects, environment-friendliness, improved biocompatibility, and high biological activities, such as antioxidant and antimicrobial activities, as many physical and chemical methods have been applied to synthesize metal oxide NPs. In the presence of apple peel extract and microwave (MW) irradiation, CuO NPs are produced from the precursor CuCl₂. 2H₂O. With the help of TEM analysis, and BET surface area, the average sizes of the obtained NPs are found to be 25-40 nm. For use in antimicrobial applications, CuO NPs are appropriate. Disk diffusion tests were used to study the bactericidal impact in relation to the diameter of the inhibition zone, and an intriguing antibacterial activity was confirmed on both the Gram-positive bacterial pathogen Staphylococcus aureus and Gram-negative bacterial pathogen Escherichia coli. Moreover, CuO NPs did not have any toxic effect on seed germination. Thus, this study provides an environmentally friendly material and provides a variety of advantages for biomedical applications and environmental applications.

Tavaborole-Induced Inhibition of the Aminoacyl-tRNA Biosynthesis Pathway against Botrytis cinerea Contributes to Disease Control and Fruit Quality Preservation

The inhibitory effect of tavaborole on the invasion of Botrytis cinerea in grapes and tomatoes, as well as the potential mechanism involved, was discovered in this study. Our findings showed that tavaborole inhibited Botrytis cinerea spore germination and mycelial expansion in vitro and that the control efficiency in vivo on fruit decay was dose-dependent, which was effective in reducing disease severity and maintaining the organoleptic quality of the fruit, such as reducing weight loss and retaining fruit hardness and titratable acid contents during storage. Furthermore, the precise mechanism of action was investigated further. Propidium iodide staining revealed that Botrytis cinerea treated with tavaborole lost membrane integrity. For further validation, cytoplasmic malondialdehyde accumulation and leakage of cytoplasmic constituents were determined. Notably, the inhibitory effect was also dependent on inhibiting the activities of aminoacyl-tRNA synthetases involved in the aminoacyl-tRNA biosynthesis pathway in Botrytis cinerea. The above findings concluded that tavaborole was effective against Botrytis cinerea infection in postharvest fruit, and a related mechanism was also discussed, which may provide references for the drug repurposing of tavaborole as a postharvest fungicide.

Grafted Chitosan-Hyaluronic Acid (CS-g-poly (MA-co-AN) HA) Complex Inhibits Fluconazole-Resistant Candida albicans Biofilm Formation

Fungal resistance that leads to the failure of drug therapy due to biofilm development is a major clinical challenge. Various polysaccharides have been used to control biofilm formation by drug-resistant fungi, and this study was undertaken to develop chitosan (CS)-modified materials and evaluate their abilities to inhibit Candida biofilm growth. CS was grafted with methacrylamide (MA) and acrylonitrile (AN) and, to improve its application characteristics further, was grafted with hyaluronic acid to produce CS-g-poly (MA-co-AN) HA complex. Grafting and complex formation were confirmed using spectroscopic techniques. CS-g-poly (MA-co-AN) HA was tested to investigate its ability to inhibit Candida albicans biofilm formation and showed significant antibiofilm activity at 200 µg/mL. Additionally, CS-g-poly (MA-co-AN) HA did not have any toxic effect on Caenorhabditis elegans. Thus, this study provides an innovative means of preventing microorganism-associated biofilm formation.

Antibiofilm and Antimicrobial Activities of Chloroindoles Against Uropathogenic Escherichia coli

Uropathogenic Escherichia coli (UPEC) is a nosocomial pathogen associated with urinary tract infections and expresses several virulence factors that cause recurring infections and cystitis of the bladder, which can lead to pyelonephritis. UPEC uses different types of extracellular appendages like fimbriae and pili that aid colonization and adherence to bladder epithelium and can form persistent biofilm-like bacterial communities that aid its survival after the deployment of host immune responses. We investigated the antibiofilm, antimicrobial, and antivirulence properties of three indole derivatives namely, 4-chloroindole, 5-chloroindole, and 5-chloro 2-methyl indole. All the three chloroindoles had MICs of 75 μg/ml and inhibited biofilm formation by an average of 67% at 20 μg/ml. In addition, they inhibited swarming and swimming motilities, which are essential for dissemination from bacterial communities and colonization, reduced cell surface hydrophobicity, and inhibited indole production and curli formation. Gene expression analysis showed all three chloroindoles significantly downregulated the expressions of virulence genes associated with adhesion, stress regulation, and toxin production. A 3D-QSAR analysis revealed substitutions at the fourth and fifth positions of the indole moiety favored antimicrobial activity. Furthermore, these chloroindoles potently inhibited biofilm formation in other nosocomial pathogens and polymicrobial consortia.

Visible Light-induced Phosphine-Catalyzed Perfluoroalkylation of Indoles

A photo-induced, catalytic phosphine-promoted perfluoroalkylation reaction of indole molecules is developed. Inexpensive and readily available PPh3 is used in a catalytic amount as the sole reaction initiator in this protocol....