oxepins and stictic-acid

The phytochemical study of Stereocaulon montagneanum harvested in Sumatra (Indonesia) led to the isolation of 11 known compounds including two metabolites not previously described in the genus Stereocaulon, peristictic acid (8) and menegazziaic acid (10). The complete 1H and 13C NMR spectral assignments of stictic acid derivatives are reported with some revisions. Five depsidones belonging to the stictic acid chemosyndrome were superoxide anion scavengers as potent as ascorbic acid and with no toxicity on two human cell lines.

Topics: Animals; Antioxidants; Cell Line; Drug Evaluation, Preclinical; Free Radical Scavengers; Heterocyclic Compounds, 4 or More Rings; Humans; Indonesia; Keratinocytes; Lichens; Melanoma, Experimental; Mice; Molecular Structure; Nuclear Magnetic Resonance, Biomolecular; Oxepins; Radiation-Protective Agents; Solvents; Superoxides; Ultraviolet Rays

The bacterial system for fatty acid biosynthesis (FAS) contains several enzymes whose sequence and structure are highly conserved across a vast array of pathogens. This, coupled with their low homology and difference in organization compared to the equivalent system in humans, makes the FAS pathway an excellent target for antimicrobial drug development. To this end, we have cloned, expressed, and purified the β-hydroxyacyl-acyl carrier protein dehydratase (FabZ) from both Francisella tularensis (FtFabZ) and Yersinia pestis (YpFabZ). We also solved the crystal structures and performed an enzymatic characterization of both enzymes and several mutant forms of YpFabZ. Additionally, we have discovered two novel inhibitors of FabZ, mangostin and stictic acid, which show similar potencies against both YpFabZ and FtFabZ. Lastly, we selected several compounds from the literature that have been shown to be active against single homologues of FabZ and tested them against both YpFabZ and FtFabZ. These results have revealed clues as to which scaffolds are likely to lead to broad-spectrum antimicrobials targeted against FabZ as well as modifications to existing FabZ inhibitors that may improve potency.

Topics: Amino Acid Substitution; Bacterial Proteins; Biocatalysis; Catalytic Domain; Crystallography, X-Ray; Dimerization; Enzyme Inhibitors; Francisella tularensis; Heterocyclic Compounds, 4 or More Rings; Histidine; Hydro-Lyases; Hydrophobic and Hydrophilic Interactions; Models, Molecular; Molecular Docking Simulation; Molecular Weight; Oxepins; Point Mutation; Protein Conformation; Recombinant Proteins; Xanthones; Yersinia pestis

The guardian of the genome, p53, is the most mutated protein found in all cancer cells. Restoration of wild-type activity to mutant p53 offers promise to eradicate cancer cells using novel pharmacological agents. Several molecules have already been found to activate mutant p53. While the exact mechanism of action of these compounds has not been fully understood, a transiently open pocket has been identified in some mutants. In our study, we docked twelve known activators to p53 into the open pocket to further understand their mechanism of action and rank the best binders. In addition, we predicted the absorption, distribution, metabolism, excretion and toxicity properties of these compounds to assess their pharmaceutical usefulness. Our studies showed that alkylating ligands do not all bind at the same position, probably due to their varying sizes. In addition, we found that non-alkylating ligands are capable of binding at the same pocket and directly interacting with Cys124. The comparison of the different ligands demonstrates that stictic acid has a great potential as a p53 activator in terms of less adverse effects although it has poorer pharmacokinetic properties.

Topics: Alkylation; Amifostine; Aza Compounds; Bridged Bicyclo Compounds, Heterocyclic; Drug Evaluation, Preclinical; Ellipticines; Heterocyclic Compounds, 4 or More Rings; Humans; Kinetics; Ligands; Mercaptoethylamines; Molecular Dynamics Simulation; Mutagenesis, Site-Directed; Mutation; Oxepins; Protein Binding; Pyrimidines; Quinuclidines; Tumor Suppressor Protein p53

The tumour suppressor p53 is the most frequently mutated gene in human cancer. Reactivation of mutant p53 by small molecules is an exciting potential cancer therapy. Although several compounds restore wild-type function to mutant p53, their binding sites and mechanisms of action are elusive. Here computational methods identify a transiently open binding pocket between loop L1 and sheet S3 of the p53 core domain. Mutation of residue Cys124, located at the centre of the pocket, abolishes p53 reactivation of mutant R175H by PRIMA-1, a known reactivation compound. Ensemble-based virtual screening against this newly revealed pocket selects stictic acid as a potential p53 reactivation compound. In human osteosarcoma cells, stictic acid exhibits dose-dependent reactivation of p21 expression for mutant R175H more strongly than does PRIMA-1. These results indicate the L1/S3 pocket as a target for pharmaceutical reactivation of p53 mutants.

Topics: Apoptosis Regulatory Proteins; Aza Compounds; Binding Sites; Bridged Bicyclo Compounds, Heterocyclic; Cell Line, Tumor; Computational Biology; Cyclin-Dependent Kinase Inhibitor p21; Cysteine; Heterocyclic Compounds, 4 or More Rings; Humans; Molecular Dynamics Simulation; Mutant Proteins; Oxepins; Protein Stability; Protein Structure, Secondary; Protein Structure, Tertiary; Proto-Oncogene Proteins; Reproducibility of Results; Structure-Activity Relationship; Transcription, Genetic; Tumor Suppressor Protein p53

A chromatographic method is described for the purification and characterization of secondary lichen substances with biological activity. A simple reversed-phase high-performance liquid chromatography method with gradient elution has been developed that allows the determination and isolation of salazinic, usnic and stictic acids from lichen samples in a single run and the quantification of every acid in the tested extracts. The antioxidant activity of both the isolated compounds and the respective lichen belonging to Xanthoparmelia genus was determined by the Oxygen Radical Absorbance Capacity (ORAC) assay; their effect as free radical scavengers, effect on cell survival by the 3(4,5-dimethyltiazol-2-yl)-2,5-diphenyltetrazolium reduction assay and 2',7'-dichlorofluorescin diacetate method were tested on U373 MG human astrocytome cell line. Both lichens extracts and all isolated compounds protected U373 MG cells from hydrogen peroxide-induced damage, suggesting that they could act as antioxidant agents in those neurodegenerative disorders associated with oxidative damage, such as Alzheimer's disease and Parkinson's disease.

Topics: Antioxidants; Benzofurans; Cell Line, Tumor; Cell Survival; Chromatography, Reverse-Phase; Drug Screening Assays, Antitumor; Free Radical Scavengers; Heterocyclic Compounds, 4 or More Rings; Humans; Lactones; Lichens; Oxepins; Plant Extracts; Salicylates

Two new beta-orcinol depsidones, 1 and 2, together with 13 known compounds were isolated from the lichen Usnea articulata. The structures of 1 and 2 were elucidated by spectroscopic analyses and those of known compounds by comparison of their spectroscopic data with literature values or by direct comparison with authentic standards. Compounds 1, 2, and 5 exhibited moderate antiradical activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The depsidones 4 and 5 showed better superoxide anion scavenging activity (IC50 = 566 and 580 microM, respectively) than quercetin (IC50 = 754 microM).

Topics: Antioxidants; Biphenyl Compounds; Depsides; Free Radical Scavengers; Heterocyclic Compounds, 4 or More Rings; Indonesia; Inhibitory Concentration 50; Lactones; Molecular Structure; Oxepins; Picrates; Quercetin; Superoxides; Usnea