1,3,4-oxadiazole derivatives as potential antimicrobial agents

Due to the emergence of drug-resistant microbial strains, different research groups are continuously developing novel drug molecules against already exploited and unexploited targets. 1,3,4-Oxadiazole derivatives exhibited noteworthy antimicrobial activities. The presence of 1,3,4-oxadiazole moiety in antimicrobial agents can modify their polarity and flexibility, which significantly improves biological activities due to various bonded and non-bonded interactions viz. hydrogen bond, steric, electrostatic, and hydrophobic with target sites. The present review elaborates the therapeutic targets and mode of interaction of 1,3,4-oxadiazoles as antimicrobial agents. 1,3,4-oxadiazole derivatives target enoyl reductase (InhA), 14α-demethylase in the mycobacterial cell; GlcN-6-P synthase, thymidylate synthase, peptide deformylase, RNA polymerase, dehydrosqualene synthase in bacterial strains; ergosterol biosynthesis pathway, P450-14α demethylase, protein-N-myristoyltransferase in fungal strains; FtsZ protein, interfere with purine and functional protein synthesis in plant bacteria. The present review also summarizes the effect of different moieties and functional groups on the antimicrobial activity of 1,3,4-oxadiazole derivatives.

Synthesis of quinazolinone derivatives containing an acyl hydrazone skeleton as potent anti-urease agents enzyme kinetic studies and anti-oxidant properties

This paper covers the synthesis, in vitro urease inhibition, enzyme kinetic parameters, and anti-oxidant studies of a novel series of quinazolinone derivatives containing an acyl hydrazone skeleton. Compounds 3a, 3b, 5a, and 5b, having IC50 values ranging from 1.86 ± 0.07 to 6.38 ± 0.11 µg mL−1, show greater inhibitory activity than the standard inhibitor, thiourea. Among the products, (2-[2-(3-methoxybenzyl)-4-oxoquinazolin-3(4 H)-yl]acetohydrazide) proves to be the most potent, exhibiting enzyme inhibition activity with an IC50 value of 1.86 ± 0.07 µg mL−1. Kinetic studies involving the Lineweaver–Burk plots reveal that the inhibition mechanism of the most active compounds (3a, 3b, 5a, and 5b) on urease activity are found to be in competitive mode. Also, the anti-oxidant activity and radical-scavenging properties of the synthesized compounds are evaluated using cupric reducing anti-oxidant activity, ferric reducing anti-oxidant capacity, 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid), and 2,2-diphenyl-1-picrylhydrazyl assays. Compounds 3a, b and 5a, b have good anti-oxidant properties and radical-scavenging activity at various final concentrations.

Covalent Inhibition of Bacterial Urease by Bifunctional Catechol-Based Phosphonates and Phosphinates

In this study, a new class of bifunctional inhibitors of bacterial ureases, important molecular targets for antimicrobial therapies, was developed. The structures of the inhibitors consist of a combination of a phosphonate or (2-carboxyethyl)phosphinate functionality with a catechol-based fragment, which are designed for complexation of the catalytic nickel ions and covalent bonding with the thiol group of Cys322, respectively. Compounds with three types of frameworks, including β-3,4-dihydroxyphenyl-, α-3,4-dihydroxybenzyl-, and α-3,4-dihydroxybenzylidene-substituted derivatives, exhibited complex and varying structure-dependent kinetics of inhibition. Among irreversible binders, methyl β-(3,4-dihydroxyphenyl)-β-(2-carboxyethyl)phosphorylpropionate was observed to be a remarkably reactive inhibitor of Sporosarcina pasteurii urease (k_inact/K_I = 10 420 s^-1 M^-1). The high potential of this group of compounds was also confirmed in Proteus mirabilis whole-cell-based inhibition assays. Some compounds followed slow-binding and reversible kinetics, e.g., methyl β-(3,4-dihydroxyphenyl)-β-phosphonopropionate, with K_i* = 0.13 μM, and an atypical low dissociation rate (residence time τ = 205 min).

A Review Exploring Therapeutic Worth of 1,3,4-Oxadiazole Tailored Compounds

1,3,4-Oxadiazole, a five-membered aromatic ring can be seen in a number of synthetic molecules. The peculiar structural feature of 1,3,4-oxadiazole ring with pyridine type of nitrogen atom is beneficial for 1,3,4-oxadiazole derivatives to have effective binding with different enzymes and receptors in biological systems through numerous weak interactions, thereby eliciting an array of bioactivities. Research in the area of development of 1,3,4-oxadiazole-based derivatives has become an interesting topic for the scientists. A number of 1,3,4-oxadiazole based compounds with high therapeutic potency are being extensively used for the treatment of different ailments, contributing to enormous development value. This work provides a systematic and comprehensive review highlighting current developments of 1,3,4-oxadiazole based compounds in the entire range of medicinal chemistry such as anticancer, antifungal, antibacterial, antitubercular, anti-inflammatory, antineuropathic, antihypertensive, antihistaminic, antiparasitic, antiobesity, antiviral, and other medicinal agents. It is believed that this review will be of great help for new thoughts in the pursuit for rational designs for the development of more active and less toxic 1,3,4-oxadiazole based medicinal agents.

F. A review on the development of urease inhibitors as antimicrobial agents against pathogenic bacteria

Ureases are enzymes that hydrolyze urea into ammonium and carbon dioxide. They have received considerable attention due to their impacts on living organism health, since the urease activity in microorganisms, particularly in bacteria, are potential causes and/or factors contributing to the persistence of some pathogen infections. This review compiles examples of the most potent antiurease organic substances. Emphasis was given to systematic screening studies on the inhibitory activity of rationally designed series of compounds with the corresponding SAR considerations. Ureases of Canavalia ensiformis, the usual model in antiureolytic studies, are emphasized. Although the active site of this class of hydrolases is conserved among bacteria and vegetal ureases, the same is not observerd for allosteric site. Therefore, inhibitors acting by participating in interactions with the allosteric site are more susceptible to a potential lack of association among their inhibitory profile for different ureases. The information about the inhibitory activity of different classes of compounds can be usefull to guide the development of new urease inhibitors that may be used in future in small molecular therapy against pathogenic bacteria.

Inhibition of Urease Enzyme Production and some Other Virulence Factors Expression in Proteus mirabilis by N-Acetyl Cysteine and Dipropyl Disulphide

Proteus mirabilis is one of the important pathogens that colonize the urinary tract and catheters resulting in various complications, such as blockage of the catheters and the formation of infective stones.

PURPOSE

In this study we evaluated the effect of N-acetyl cysteine (NAC) and dipropyl disulphide on some virulence factors expressed by a Proteus mirabilis strain isolated from a catheterized patient.

METHODS

Antibacterial activity of both compounds was determined by broth microdilution method. Their effect on different types of motility was determined by LB medium with variable agar content and sub-MIC of each drug. Their effect on adherence and mature biofilms was tested by tissue culture plate assay. Inhibitory effect on urease production was determined and supported by molecular docking studies.

RESULTS

The minimum inhibitory concentration (MIC) of NAC and dipropyl disulphide was 25 mM and 100 mM, respectively. Both compounds decreased the swarming ability and biofilm formation of the tested isolate in a dose-dependent manner. NAC had higher urease inhibitory activity (IC50 249 ±0.05 mM) than that shown by dipropyl disulphide (IC₅₀ 10±0.2 mM). Results were supported by molecular docking studies which showed that NAC and dipropyl disulphide interacted with urease enzyme with binding free energy of -4.8 and -8.528 kcal/mol, respectively. Docking studies showed that both compounds interacted with Ni ion and several amino acids (His-138, Gly-279, Cysteine-321, Met-366 and His-322) which are essential for the enzyme activity.

CONCLUSION

NAC and dipropyl disulphide could be used in the control of P. mirabilis urinary tract infections.

Design, synthesis, molecular docking, anti-Proteus mirabilis and urease inhibition of new fluoroquinolone carboxylic acid derivatives

New hydroxamic acid, hydrazide and amide derivatives of ciprofloxacin in addition to their analogues of levofloxacin were prepared and identified by different spectroscopic techniques. Some of the prepared compounds revealed good activity against the urease splitting bacteria, Proteus mirabilis. The urease inhibitory activity was investigated using indophenol method. Most of the tested compounds showed better activity than the reference acetohydroxamic acid (AHA). The ciprofloxacin hydrazide derivative 3a and levofloxacin hydroxamic acid 7 experienced the highest activity (IC₅₀=1.22μM and 2.20μM, respectively). Molecular docking study revealed high spontaneous binding ability of the tested compounds to the active site of urease.