Inhibition of Shiga toxin-converting bacteriophage development by novel antioxidant compounds

Oxidative stress may be the major cause of induction of Shiga toxin-converting (Stx) prophages from chromosomes of Shiga toxin-producing Escherichia coli (STEC) in human intestine. Thus, we aimed to test a series of novel antioxidant compounds for their activities against prophage induction, thus, preventing pathogenicity of STEC. Forty-six compounds (derivatives of carbazole, indazole, triazole, quinolone, ninhydrine, and indenoindole) were tested. Fifteen of them gave promising results and were further characterized. Eleven compounds had acceptable profiles in cytotoxicity tests with human HEK-293 and HDFa cell lines. Three of them (selected for molecular studies) prevent the prophage induction at the level of expression of specific phage genes. In bacterial cells treated with hydrogen peroxide, expression of genes involved in the oxidative stress response was significantly less efficient in the presence of the tested compounds. Therefore, they apparently reduce the oxidative stress, which prevents induction of Stx prophage in E. coli

Development of a series of bis-triazoles as G-quadruplex ligands

Maintenance of telomeres – specialized complexes that protect the ends of chromosomes – is provided by the enzyme complex telomerase, which is a key factor that is activated in more than 80% of cancer cells, but absent in most normal cells. Targeting telomere maintenance mechanisms could potentially halt tumour growth across a broad spectrum of cancer types. Telomeric ends of chromosomes consist of noncoding repeat sequences of guanine-rich DNA. These G-rich ends can fold into structures called G-quadruplexes. Stabilization of G-quadruplexes by small binding molecules called G4 ligands can prevent telomerase enzyme from maintaining telomere integrity in cancer cells. G quadruplexes can exist in other parts of the genome too, especially within promoter sequences of oncogenes, and also be interesting drug targets. Here, we describe the development of a new series of novel bis-triazoles, designed to stabilize G-quadruplex structures selectively as G4 ligands. FRET assays showed two compounds to be moderately effective G4 binders, with particular affinity for the quadruplex formed by the Hsp90a promoter sequence, and good selectivity for G-quadruplex DNA vs. duplex DNA. However, CD spectroscopy failed to provide any information about the folding topology of the human telomeric G-quadruplex resulting from its interaction with one of the ligands. All the new ligands showed potent cell growth inhibitory properties against human colon and pancreatic cancer cell lines, as evidenced by the MTT assay; notably, they were more potent against cancer cells than in fetal lung fibroblasts. Docking studies were performed to rationalize the affinity of these ligands for binding to the telomeric parallel G-quadruplex DNA

Marine Pyrrolocarbazoles and Analogues: Synthesis and Kinase Inhibition

Granulatimide and isogranulatimide are alkaloids obtained from marine sources which have been shown to inhibit cell-cycle G2-checkpoint, targeting more particularly checkpoint 1 kinase (Chk1). At a structural level, they possess a characteristic pyrrolocarbazole framework also shared by the well-known rebeccamycin and staurosporine microbial metabolites which have been described to inhibit topoisomerase I and diverse kinases, respectively. This review reports precisely on the synthesis and kinase inhibitory activities of pyrrolocarbazole-based analogues of granulatimide

Microwave-assisted oxidation of indan-1-ones into ninhydrins

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