Novel synthetic organic compounds inspired from antifeedant marine alkaloids as potent bacterial biofilm inhibitors

Synthesis and in vitro evaluation of antibacterial and antibiofilm activities of novel triphenylphosphonium-functionalized substituted pyrimidines

The increase in the prevalence of antibiotic-resistant pathogens leads to a decrease in the number of antimicrobial agents for the treatment of infections and prompts researchers to search for new effective antimicrobial drugs. This study reports the synthesis of novel triphenylphosphonium-functionalized substituted pyrimidines and in vitro evaluation of their antibacterial and antibiofilm activity. Most of the synthesized derivatives showed high antibacterial activity (MIC = 0.39-1.56 μg/mL) against the methicillin-resistant strain of S. aureus 222. Compounds 2a and 11 exhibited a high level of antibiofilm activity against S. aureus 222 and E. coli 311. The triphenylphosphonium-containing pyrimidines 11 and 2a reduced S. aureus 222 biofilm formation by 99.1% and 95.8%, respectively. In addition, compound 2a was the most active against E. coli 311 biofilm formation (the biomass decreased by 98.4%).

Rapid Assembly of Pyrrole-Ligated 1,3,4-Oxadiazoles and Excellent Antibacterial Activity of Iodophenol Substituents

Pyrrole-ligated 1,3,4-oxadiazole is a very important pharmacophore which exhibits broad therapeutic effects such as anti-tuberculosis, anti-epileptic, anti-HIV, anti-cancer, anti-inflammatory, antioxidant, and antibacterial activities. A one-pot Maillard reaction between D-Ribose and an L-amino methyl ester in DMSO with oxalic acid at 2.5 atm and 80 °C expeditiously produced pyrrole-2-carbaldehyde platform chemicals in reasonable yields, which were utilized for the synthesis of pyrrole-ligated 1,3,4-oxadiazoles. Benzohydrazide reacted with the formyl group of the pyrrole platforms to provide the corresponding imine intermediates, which underwent I₂-mediated oxidative cyclization to the pyrrole-ligated 1,3,4-oxadiazole skeleton. The structure and activity relationship (SAR) of the target compounds with varying alkyl or aryl substituents of the amino acids and electron-withdrawing or electron-donating substituents on the phenyl ring of benzohydrazide were evaluated for antibacterial activity against Escherichia coli, Staphylococcus aureus, and Acinetobacter baumannii as representative Gram(-) and Gram(+) bacteria. Branched alkyl groups from the amino acid showed better antibacterial activities. Absolutely superior activities were observed for 5f-1 with an iodophenol substituent against A. baumannii (MIC < 2 μg/mL), a bacterial pathogen that displays a high resistance to commonly used antibiotics.

A key review on oxadiazole analogs as potential methicillin-resistant Staphylococcus aureus (MRSA) activity: Structure-activity relationship studies

Methicillin-resistant Staphylococcus aureus (MRSA) is becoming dangerous to human beings due to easy transmission mode and leading to the difficult-to-treat situation. The rapid resistance development of MRSA to many approved antibiotics is of major concern. There is a lot of scope to develop novel, efficient, specific, and nontoxic drug candidates to fight against MRSA isolates. The interesting molecular structure and adaptable feature of oxadiazole moiety which are bioisosteres of esters and amides, and these functional groups show improved resistance to esterases mediated hydrolytic cleavage, attracting researchers to develop required novel antibiotics based on oxadiazole core. This review summarizes the developments of oxadiazole-containing derivatives as potent antibacterial agents against multidrug-resistant MRSA strains and discussing the structure-activity relationship (SAR) in various directions. The current survey is the highlight of the present scenario of oxadiazole hybrids on MRSA studies, covering articles published from 2011 to 2020. This collective information may become a good platform to plan and develop new oxadiazole-based small molecule growth inhibitors of MRSA with minimal side effects.

Medicinal Purposes: Bioactive Metabolites from Marine-derived Organisms

The environment of marine occupies about 95% biosphere of the world and it can be a critical source of bioactive compounds for humans to be explored. Special environment such as high salt, high pressure, low temperature, low nutrition and no light, etc. has made the production of bioactive substances different from terrestrial organisms. Natural ingredients secreted by marine-derived bacteria, fungi, actinomycetes, Cyanobacteria and other organisms have been separated as active pharmacophore. A number of evidences have demonstrated that bioactive ingredients isolated from marine organisms can be other means to discover novel medicines, since enormous natural compounds from marine environment were specified to be anticancer, antibacterial, antifungal, antitumor, cytotoxic, cytostatic, anti-inflammatory, antiviral agents, etc. Although considerable progress is being made within the field of chemical synthesis and engineering biosynthesis of bioactive compounds, marine environment still remains the richest and the most diverse sources for new drugs. This paper reviewed the natural compounds discovered recently from metabolites of marine organisms, which possess distinct chemical structures that may form the basis for the synthesis of new drugs to combat resistant pathogens of human life. With developing sciences and technologies, marine-derived bioactive compounds are still being found, showing the hope of solving the problems of human survival and sustainable development of resources and environment.

New Thiazole Nortopsentin Analogues Inhibit Bacterial Biofilm Formation

New thiazole nortopsentin analogues were conveniently synthesized and evaluated for their activity as inhibitors of biofilm formation of relevant Gram-positive and Gram-negative pathogens. All compounds were able to interfere with the first step of biofilm formation in a dose-dependent manner, showing a selectivity against the staphylococcal strains. The most active derivatives elicited IC50 values against Staphylococcus aureus ATCC 25923, ranging from 0.40⁻2.03 µM. The new compounds showed a typical anti-virulence profile, being able to inhibit the biofilm formation without affecting the microbial growth in the planktonic form.