1,2,3-triazole-thiazole hybrids: Synthesis, in vitro antimicrobial activity and antibiofilm studies.

A new series of triazole-thiazole hybrids were designed, synthesized by the Multi-component reaction approach and evaluated in vitro antimicrobial activity. Most of the tested series of compounds exhibited promising inhibitory activity against the bacterial strains with values in the range of 2.8 to 15.7 µM. The compounds 8i-8l and 8r showed potential-Candida activity against various Candida strains with spectrum values in the range 5.9-14.2 µM. Further, anti-biofilm and toxicity profiles for the potent compounds were also tested, and it was observed that the compounds 8i, 8k, and 8l were found to inhibit the biofilm formation with IC50 values of 6.6, 16.6 and 15.9 µM, respectively against Bacillus subtilis MTCC 121. Besides, 8k and 8l also displayed promising biofilm formation inhibitory activity towards Staphylococcus aureus MTCC 96 with IC50 values of 13.5 and 12.0 µM respectively. In summary, the activity results has emphasized the compounds 8k and 8l as potential leads for further development of antibacterial, anti-Candida, and anti-biofilm agents.

Chumacin-1 and Chumacin-2 from Pseudomonas aeruginosa strain CGK-KS-1 as novel quorum sensing signaling inhibitors for biocontrol of bacterial blight of rice.

The in vitro inhibition of quorum sensing signal, xanthan gum secretion, biofilm formation in different Xanthomonas pathovars and biological control of bacterial blight of rice by the two bioactive extrolites produced by Pseudomonas aeruginosa strain CGK-KS-1 were explored. These extrolites were extracted from Diaion HP-20 resin with methanol and purified by preparative-thin layer chromatography. Further, spectroscopic structural elucidation revealed the tentative identity of these extrolites to be (R,3E,5E,9Z,11E)-13-((3S,5R)-5-acetyl-2,6-dimethylheptan-3-yl)-10-hydroxy-4-methyl-1,8-diazabicyclo[9.3.1]pentadeca-3,5,9,11(15),13-pentaen-2-one and (R,3E,5E,8E,11E)-13-((3S,5R)-5-acetyl-2,6-dimethylheptan-3-yl)-4-methyl-1,8-diazabicyclo[9.3.1]pentadeca-3,5,8,11(15),13-pentaene-2,10-dione, named as Chumacin-1 and Chumacin-2, respectively. Antimicrobial assay showed Chumacin-1 and Chumacin-2 exhibited a strong in vitro growth inhibition against various Xanthomonas pathovars. Quorum sensing overlay assay using a reporter strain Chromobacterium violaceum strain CV026 showed that Chumacin-1 and Chumacin-2 inhibited quorum sensing signaling. The mechanistic studies revealed that these extrolites inhibited the production of quorum sensing signaling factor, cis-11-methyl-2-dodecenoic acid; suppressed the xanthan gum secretion and also inhibited the biofilms formed by various Xanthomonas pathovars. Both Chumacin-1 and Chumacin-2 showed ROS generation in the test Xanthomonas strains, resulting in in vitro cell membrane damage was revealed through CSLM and FE-SEM micrographs. Further, greenhouse experiments using Samba Mashuri (BPT-5204) revealed that seed treatment with Chumacin-1 and Chumacin-2 along with foliar spray groups showed up to ˜80% reduction in bacterial blight disease in rice. To the best of our knowledge, this is the first report on new quorum sensing inhibitors, Chumacin-1 and Chumacin-2 produced by Pseudomonas aeruginosa strain CGK-KS-1 exhibiting DSF inhibition activity in Xanthomonas oryzae pv. oryzae.

Phenazine-1-carboxamide functionalized mesoporous silica nanoparticles as antimicrobial coatings on silicone urethral catheters.

Microbial infections due to biofilms on medical implants can be prevented by antimicrobial coatings on biomaterial surfaces. Mesoporous silica nanoparticles (MSNPs) were synthesized via base-catalyzed sol-gel process at room temperature, functionalized with phenazine-1-carboxamide (PCN) and characterized by UV-visible, FT-IR, DLS, XRD spectroscopic techniques, SEM, TEM, TGA and BET analysis. Native MSNPs, PCN and PCN-MSNPs were evaluated for anti-Candida minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), Candida albicans (C. albicans) biofilms and C. albicans-Staphylococcus aureus (S. aureus) polymicrobial biofilm inhibition. PCN-MSNPs were four-fold effective (MIC 3.9 µg mL-1; 17.47 µM) and MFC (7.8 µg mL-1; 34.94 µM) as compared to pure PCN (MIC 15.6 µg mL-1; 69.88 µM) and MFC (31.2 µg mL-1; 139.76 µM). PCN-MSNPs inhibited in vitro C. albicans MTCC 227-S. aureus MTCC 96 biofilms at very low concentration (10 µg mL-1; 44.79 µM) as compared to pure PCN (40 µg mL-1; 179.18 µM). Mechanistic studies revealed that PCN induced intracellular ROS accumulation in C. albicans MTCC 227, S. aureus MTCC 96 and S. aureus MLS-16 MTCC 2940, reduction in total ergosterol content, membrane permeability, disruption of ionic homeostasis followed by Na+, K+ and Ca2+ leakage leading to cell death in C. albicans MTCC 227 as confirmed by confocal laser scanning micrographs. The silicone urethral catheters coated with PCN-MSNPs (500 µg mL-1; 2.23 mM) exhibited no formation of C. albicans MTCC 227 - S. aureus MTCC 96 and C. albicans MTCC 227 - S. aureus MLS -16 MTCC 2940 biofilms. This is the first report on PCN-MSNPs for use as antimicrobial coatings against microbial adhesion and biofilm formation on silicone urethral catheters.

Na2S-promoted reduction of azides in water: synthesis of pyrazolopyridines in one pot and evaluation of antimicrobial activity.

Reduction of various azides using Na2S has been accomplished in water, and, in situ, the resulting amines on reaction with various ketones lead to pyrazolo[3,4-b]pyridines in one pot. Thus, a number of new trifluoromethyl-substituted pyrazolo[3,4-b]pyridine compounds have been prepared and screened for antimicrobial activity against different Gram-positive and Gram-negative strains. A good number of compounds, 4a, 4b, 4d, 4f, 4i, 4k, 4l, 4m, 4r and 4s, were found to possess promising activity. Notably, Na2S on hydrolysis in water generates H2S and NaOH, which facilitate the reduction of azides followed by intramolecular cyclization leading to the title compounds. To the best of our knowledge, this is the first report of the synthesis of the title compounds in aqueous medium in a one-pot reaction.

Synthesis of new bis-pyrazole linked hydrazides and their in vitro evaluation as antimicrobial and anti-biofilm agents: A mechanistic role on ergosterol biosynthesis inhibition in Candida albicans.

Literature reports suggest that pyrazoles and hydrazides are potential antimicrobial pharmocophores. Considering this fact, a series of nineteen conjugates containing hybrids of bis-pyrazole scaffolds joined through a hydrazide linker were synthesized and further evaluated for their antimicrobial activity against a panel of Gram-positive and Gram-negative bacteria along with Candida albicansMTCC 3017 strain. Although the derivatives exhibited good antibacterial activity, some of the derivatives (13d, 13j, 13l, 13p, and 13r) showed excellent anti-Candida activity with MICs values of 3.9 µg/ml, which was equipotent to that of the standard Miconazole (3.9 µg/ml), which has inspired us to further explore their anti-Candida activity. The same compounds were also tested for anti-biofilm studies against various Candida strains and among them, compounds 13l and 13r efficiently inhibited the formation of fungal biofilms. Field emission scanning electron micrographs revealed that one of the promising compound 13r showed cell damage and in turn cell death of the Candida strain. These potential conjugates (13l and 13r) also demonstrated promising ergosterol biosynthesis inhibition against some of the strains C. albicans, which were further validated through molecular docking studies. In silico computational studies were carried out to predict the binding modes and pharmacokinetic parameters of these conjugates.