Synthesis and Cytotoxic Evaluation of Arimetamycin A and Its Daunorubicin and Doxorubicin Hybrids

The arimetamycin A glycan governs the compound's cytotoxicity (IC50). To study this branched, deoxy-amino disaccharide, we designed and synthesized a modified acyl donor that underwent glycosylation with three anthracycline aglycones: steffimycinone, daunorubicinone, and doxorubicinone. The result of the approach was a synthesis of arimetamycin A and two novel hybrid anthracyclines. Each molecule exhibited enhanced cytotoxicity in comparison to the parent anthracyclines, steffimycin B, daunorubicin, and doxorubicin. An orienting mechanistic evaluation revealed that the daunorubicin hybrid inhibits the ability of human topoisomerase IIα to relax negatively and positively supercoiled DNA.

Synthesis and Antimicrobial Evaluation of 1,4-Naphthoquinone Derivatives as Potential Antibacterial Agents

1,4-Naphthoquinones are an important class of compounds present in a number of natural products. In this study, a new series of 1,4-naphthoquinone derivatives were synthesized. All the synthesized compounds were tested for in vitro antimicrobial activity. In this present investigation, two Gram-positive and five Gram-negative bacterial strains and one pathogenic yeast strain were used to determine the antibacterial activity. Naphthoquinones tested for its antibacterial potencies, among seven of them displayed better antimicrobial activity against Staphylococcus aureus (S. aureus; 30-70 μg/mL). Some of the tested compounds showed moderate to low antimicrobial activity against Pseudomonas aeruginosa (P. aeruginosa) and Salmonella bongori (S. bongori; 70-150 μg/mL). In addition, most active compounds against S. aureus were evaluated for toxicity to human blood cells using a hemolysis assay. For better understanding, reactive oxygen species (ROS) generation, time-kill kinetic study, and apoptosis, necrosis responses were investigated for three representative compounds.

1,4-Naphthoquinone Analogues: Potent Antibacterial Agents and Mode of Action Evaluation

1,4-Naphthoquinones have antibacterial activity and are a promising new class of compound that can be used to treat bacterial infections. The goal was to improve effective antibacterial agents; therefore, we synthesized a new class of naphthoquinone hybrids, which contain phenylamino-phenylthio moieties as significant counterparts. Compound 4 was modified as a substituted aryl amide moiety, which enhanced the antibacterial activity of earlier compounds 3 and 4. In this study, five bacterial strains Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Escherichia coli (E. coli), Pseudomonas aeruginosa (P. aeruginosa) and Klebsiella pneumoniae (K. pneumoniae) were used to evaluate the antibacterial potency of synthesized naphthoquinones using the minimal inhibitory concentration (MIC) method. Most of the studied naphthoquinones demonstrated major antibacterial activity with a MIC of 15.6 µg/mL–500 µg/mL. Selected compounds (5a, 5f and 5x) were studied for the mode of action, using intracellular ROS generation, determination of apoptosis by the Annexin V-FITC/PI assay, a bactericidal kinetic study and in silico molecular modelling. Additionally, the redox potentials of the specified compounds were confirmed by cyclic voltammetry (CV).

Synthesis of Glycosides of Glucuronic, Galacturonic and Mannuronic Acids: An Overview

Uronic acids are carbohydrates present in relevant biologically active compounds. Most of the latter are glycosides or oligosaccharides linked by their anomeric carbon, so their synthesis requires glycoside-bond formation. The activation of this anomeric center remains difficult due to the presence of the electron-withdrawing C-5 carboxylic group. Herein we present an overview of glucuronidation, mannuronidation and galacturonidation reactions, including syntheses of prodrugs, oligosaccharides and stereochemical aspects.