N-cholesteryl amino acid conjugates and their antimicrobial activities

Unlocking the bacterial membrane as a therapeutic target for next-generation antimicrobial amphiphiles

Gram-positive bacteria like Enterococcus faecium and Staphylococcus aureus, and Gram-negative bacteria like Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter Spp. are responsible for most of fatal bacterial infections. Bacteria present a handful of targets like ribosome, RNA polymerase, cell wall biosynthesis, and dihydrofolate reductase. Antibiotics targeting the protein synthesis like aminoglycosides and tetracyclines, inhibitors of RNA/DNA synthesis like fluoroquinolones, inhibitors of cell wall biosynthesis like glycopeptides and β-lactams, and membrane-targeting polymyxins and lipopeptides have shown very good success in combating the bacterial infections. Ability of the bacteria to develop drug resistance is a serious public health challenge as bacteria can develop antimicrobial resistance against newly introduced antibiotics that enhances the challenge for antibiotic drug discovery. Therefore, bacterial membranes present a suitable therapeutic target for development of antimicrobials as bacteria can find it difficult to develop resistance against membrane-targeting antimicrobials. In this review, we present the recent advances in engineering of membrane-targeting antimicrobial amphiphiles that can be effective alternatives to existing antibiotics in combating bacterial infections.

Design, synthesis, and characterization of 2,2-bis(2,4-dinitrophenyl)-2-(phosphonatomethylamino)acetate as a herbicidal and biological active agent

The present study was designed to synthesize the bioactive molecule 2,2-bis(2,4-dinitrophenyl)-2-(phosphonatomethylamino)acetate (1), having excellent applications in the field of plant protection as a herbicide. Structure of newly synthesized molecule 1 was confirmed by using the elemental analysis, mass spectrometric, NMR, UV-visible, and FTIR spectroscopic techniques. To obtain better structural insights of molecule 1, 3D molecular modeling was performed using the GAMESS programme. Microbial activities of 1 were checked against the pathogenic strains Aspergillus fumigatus (NCIM 902) and Salmonella typhimurium (NCIM 2501). Molecule 1 has shown excellent activities against fungal strain A. fumigates (35 μg/l) and bacterial strain S. typhimurium (25 μg/l). To check the medicinal significance of molecule 1, interactions with bovine serum albumin (BSA) protein were checked. The calculated value of binding constant of molecule 1-BSA complex was 1.4 × 10⁶ M^-1, which were similar to most effective drugs like salicylic acid. More significantly, as compared to herbicide glyphosate, molecule 1 has exhibited excellent herbicidal activities, in pre- and post-experiments on three weeds; barnyard grass (Echinochloa Crus), red spranglitop (Leptochloa filiformis), and yellow nuts (Cyperus Esculenfus). Further, effects of molecule 1 on plant growth-promoting rhizobacterial (PGPR) strains were checked. More interestingly, as compared to glyphosate, molecule 1 has shown least adverse effects on soil PGPR strains including the Rhizobium leguminosarum (NCIM 2749), Pseudomonas fluorescens (NCIM 5096), and Pseudomonas putida (NCIM 2847).

Stereoselective synthesis of 3,7-diarylaminocholestanes by titanium-mediated reductive amination

An efficient method for the synthesis of aryl aminocholestanes, using a chlorotriisopropoxytitanium(IV)-mediated reductive amination reaction of 5α-cholestane-3,7-dione, is reported. A series of 3,7-diarylaminocholestane derivatives were prepared according to this methodology in up to 98% yield. These compounds were primarily characterized by (1)H NMR, (13)C NMR, and mass spectrometry.