Synergistic effects of dual antimicrobial combinations of synthesized N-heterocycles or MgO nanoparticles with nisin against the growth of Aspergillus fumigatus: In vitro study.

Introduction of new inhibitory agents such as peptides, heterocyclic derivatives and nanoparticles (NPs) along with preventive proceedings are effective ways to deal with standard and drug-resistant strains of microorganisms. In this regard, inhibitory activities of some recently synthesized 4-thiazolylpyrazoles, imidazolidine- and tetrahydropyrimidine-2-thiones and magnesium oxide (MgO) NPs alone and in combination with nisin have been assessed against Aspergillus fumigatus. Antimicrobial susceptibility tests were done via broth microdilution, disk diffusion and streak plate methods according to the modified Clinical and Laboratory Standards Institute (CLSI) guidelines. Synergistic effects were also determined as fractional inhibitory concentration (FIC) and fractional fungicidal concentration (FFC) values. Inhibitory potentials of all heterocycles and NPs against A. fumigatus were proved based on inhibition zone diameter (IZD) values in the range of 7.72 - 16.85 mm, minimum inhibitory concentration (MIC) values in the range of 64.00 - 512 µg mL-1 and minimum fungicidal concentration (MFC) values in the range of 256 - 2048 µg mL-1. Tetrahydropyrimidine derivative 3f showed the best inhibitory properties. Inhibitory activity was not significant with nisin. While antifungal effects of major derivatives were improved by combination with it. The results indicated that the combined treatment of heterocycles used in the present study with nisin might be efficient for mold prevention and removal in foodstuffs or other products.

Introducing an affordable catalyst for biohydrogen production in microbial electrolysis cells.

This study reports the fabrication of a new cathode electrode assembly using polyaniline (PANI) and graphene on a stainless steel mesh (SSM) as an alternative for the conventional expensive cathode of microbial electrolysis cells (MECs). With respect to the previous efforts to propose an efficient and cost-effective alternative for platinum (Pt) catalysts and cathode electrodes, the present study investigates the assessment of different catalysts to elucidate the potential of the modified SSM cathode electrode for larger-scale MECs. In the case of feeding dairy wastewater to the MEC, the maximum hydrogen production rate and COD removal were obtained by SSM/PANI/graphene cathode and had the values 0.805 m3 H2 m-3 anolyte day-1 and 82%, respectively, at the applied potential of 1 V. These values were only 20% and 7% lower than those of the MEC with Pt on the carbon cloth cathode, respectively. The coulombic efficiencies of SSM/Pt and SSM/PANI/graphene were seen to be 64.48% and 56.67%, respectively. It was also concluded that the fabrication cost of the modified cathode was 50% lower than the conventional cathodes with Pt on the carbon cloth. Finally, the evaluation of the modified cathode performance was achieved based on Fourier transform infrared spectroscopy, linear sweep voltammetry, scanning electron microscopy, and atomic force microscopy.

Green multicomponent synthesis, antimicrobial and antioxidant evaluation of novel 5-amino-isoxazole-4-carbonitriles.

BACKGROUND: Design and synthesis of new inhibitor agents to deal with pathogenic microorganisms is expanding. In this project, an efficient, environmentally friendly, economical, rapid and mild procedure was developed for the synthesis of novel functionalized isoxazole derivatives as antimicrobial potentials. METHODS: Multicomponent reaction between malononitrile (1), hydroxylamine hydrochloride (2) and different aryl or heteroaryl aldehydes 3a-i afforded novel 5-amino-isoxazole-4-carbonitriles 4a-i in good product yields and short reaction times. Deep eutectic solvent K2CO3/glycerol was used as catalytic reaction media. Structure of all molecules were characterized by different analytical tools. In vitro inhibitory activity of all derivatives was evaluated against a variety of pathogenic bacteria including both Gram-negative and Gram-positive strains as well as some fungi. In addition, their free radical scavenging activities were assessed against DPPH. RESULTS: Broad-spectrum antimicrobial activities were observed with isoxazoles 4a, b, d. In addition, antioxidant activity of isoxazole 4i was proven on DPPH. CONCLUSIONS: In this project, compounds 4a, b, d could efficiently inhibit the growth of various bacterial and fungal pathogens. Antioxidant properties of derivative 4i were also significant. These biologically active compounds are suitable candidates to synthesize new prodrugs and drugs due to the presence of different functional groups on their rings.

MgO Nanoparticle-Catalyzed Synthesis and Broad-Spectrum Antibacterial Activity of Imidazolidine- and Tetrahydropyrimidine-2-Thione Derivatives.

The biological properties of imidazolidine- and tetrahydropyrimidine-2-thione derivatives such as antiviral, antitumor, anti-inflammatory, and analgesic activities increase the demand for mild and efficient synthetic routes. In this regard, methods such as reaction of diaminoalkanes with carbon disulfide have been developed. However, this method usually suffers from relatively long reaction times, using excess reagents, vigorous reaction conditions, and emission of pernicious hydrogen sulfide gas. In this project, MgO nanoparticle was used as an efficient, non-toxic, recyclable, and economic catalyst to synthesize cyclic five- or six-membered thioureas 3a-h via reaction of 1:1 molar ratios of 1,2- or 1,3-diaminoalkanes 1a-h and carbon disulfide in ethanol at ambient temperature. More interestingly, no hydrogen sulfide emission was detected during the reaction progress. The in vitro antimicrobial properties of synthesized compounds were investigated against 14 different Gram-positive and Gram-negative pathogenic bacteria according to CLSI (Clinical and Laboratory Standards Institute) broth microdilution and disk diffusion methods. The results were compared to those of penicillin, gentamicin, and ceftriaxone, and reported as inhibition zone diameter (IZD), the minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC) values. The best inhibitory effects were observed with imidazolidine-2-thiones 3c and 3d. They were effective against 14 and 11 pathogens, respectively. The structure-activity relationships of the prepared heterocyclic compounds were also studied.

Evaluation of anti-bacterial effects of some novel thiazole and imidazole derivatives against some pathogenic bacteria.

BACKGROUND AND OBJECTIVES: Bacterial resistance to antibiotics has motivated the researchers to evaluate the novel anti-bacterial compounds such as some thiazole and imidazole derivatives. Thereby, in this work, we investigated the anti-bacterial effects of one new thiazole and two new imidazole derivatives on Bacillus cereus, Listeria monocytogenes, Escherichia coli, Salmonella typhimurium, Proteus mirabilis and Shigella dysenteriae. MATERIALS AND METHODS: The thiazole and imidazole derivatives were dissolved in DMSO. The disk diffusion method was utilized to measure the growth inhibition zone diameter values, and the broth micro-dilution method was applied to determine the minimum inhibitory concentration (MIC) values. RESULTS: The synthesized imidazole derivatives lacked any inhibitory effect against the tested bacteria. On the other hand, although the synthesized thiazole derivative showed no inhibitory effect against Bacillus cereus, Salmonella typhimurium, and Escherichia coli, it inhibited the growth of Proteus mirabilis, Shigella dysenteriae, and Listeria monocytogenes with the MIC values of 1000, 125, and 1000 µg/ml, respectively, and the growth inhibition zone diameter values of 9.3 ± 0.1, 15.6 ± 0.2, and 8.1 ± 0.0 mm, respectively. CONCLUSION: The anti-bacterial effect of the synthesized thiazole derivative on Shigella dysenteriae, Proteus mirabilis and Listeria monocytogenes was proven. However, its inhibition effect against Shigella dysenteriae was more than that against the others. Many in-vitro and in-vivo experiments are required to evaluate the effects of this compound on the bacteria and the human body.