RESUMEN
A novel nortriterpene, termed correolide, purified from the tree Spachea correae, inhibits Kv1.3, a Shaker-type delayed rectifier potassium channel present in human T lymphocytes. Correolide inhibits 86Rb+ efflux through Kv1.3 channels expressed in CHO cells (IC50 86 nM; Hill coefficient 1) and displays a defined structure-activity relationship. Potency in this assay increases with preincubation time and with time after channel opening. Correolide displays marked selectivity against numerous receptors and voltage- and ligand-gated ion channels. Although correolide is most potent as a Kv1.3 inhibitor, it blocks all other members of the Kv1 family with 4-14-fold lower potency. C20-29-[3H]dihydrocorreolide (diTC) was prepared and shown to bind in a specific, saturable, and reversible fashion (Kd = 11 nM) to a single class of sites in membranes prepared from CHO/Kv1.3 cells. The molecular pharmacology and stoichiometry of this binding reaction suggest that one diTC site is present per Kv1.3 channel tetramer. This site is allosterically coupled to peptide and potassium binding sites in the pore of the channel. DiTC binding to human brain synaptic membranes identifies channels composed of other Kv1 family members. Correolide depolarizes human T cells to the same extent as peptidyl inhibitors of Kv1.3, suggesting that it is a candidate for development as an immunosuppressant. Correolide is the first potent, small molecule inhibitor of Kv1 series channels to be identified from a natural product source and will be useful as a probe for studying potassium channel structure and the physiological role of such channels in target tissues of interest.
Asunto(s)
Activación del Canal Iónico/efectos de los fármacos , Bloqueadores de los Canales de Potasio , Canales de Potasio con Entrada de Voltaje , Linfocitos T/metabolismo , Triterpenos/química , Triterpenos/farmacología , Animales , Sitios de Unión/efectos de los fármacos , Células CHO , Línea Celular , Caribdotoxina/farmacología , Cricetinae , Humanos , Inmunosupresores/antagonistas & inhibidores , Inmunosupresores/química , Inmunosupresores/metabolismo , Inmunosupresores/farmacología , Canal de Potasio Kv1.3 , Potenciales de la Membrana/efectos de los fármacos , Neurotoxinas/farmacología , Canales de Potasio/metabolismo , Radioisótopos de Rubidio/metabolismo , Venenos de Escorpión/farmacología , Membranas Sinápticas/efectos de los fármacos , Membranas Sinápticas/metabolismo , Linfocitos T/efectos de los fármacos , Triterpenos/antagonistas & inhibidores , Triterpenos/metabolismoRESUMEN
A resorcylic acid lactone, L-783,277, isolated from a Phoma sp. (ATCC 74403) which came from the fruitbody of Helvella acetabulum, is a potent and specific inhibitor of MEK (Map kinase kinase). L-783,277 inhibits MEK with an IC50 value of 4 nM. It weakly inhibits Lck and is inactive against Raf, PKA and PKC. L-783,277 is an irreversible inhibitor of MEK and is competitive with respect to ATP. L-783,290, the trans-isomer of L-783,277, was isolated from the same culture and evaluated together with several semi-synthetic resorcylic acid lactone analogs. A preliminary structure-activity relationship is presented. Several independent cell-based assays have been carried out to study the biological activities of these resorcylic acid lactone compounds and a brief result summary from these studies is presented.
Asunto(s)
Inhibidores Enzimáticos/farmacología , Lactonas/farmacología , Quinasa 1 de Quinasa de Quinasa MAP , Proteínas Serina-Treonina Quinasas/antagonistas & inhibidores , Resorcinoles/farmacología , Adenosina Trifosfato/farmacología , Humanos , Proteína Tirosina Quinasa p56(lck) Específica de Linfocito/antagonistas & inhibidoresRESUMEN
We have identified a novel nonsteroidal ecdysteroid agonist. This compound was isolated from a methanol extract of Ajuga reptans L. (Lamiaceae) and the structure was identified by spectroscopic methods as 8-O-acetylharpagide. We have characterised this compound as an ecdysteroid agonist in a transactivation assay using beta-galactosidase as the reporter gene regulated by ecdysteroid response elements. In this assay, 8-O-acetylharpagide has an EC50 of 22 microM. The compound also competes with tritiated-ponasterone A for binding to the Drosophila ecdysteroid receptor. Finally, it induces differentiation of Drosophila Kc cells as would be expected of an ecdysteroid agonist. This iridoid glycoside is common to several plant species and may play a role in the natural defense mechanisms of plants.
Asunto(s)
Ecdisterona/agonistas , Plantas/metabolismo , Piranos/metabolismo , Animales , Drosophila/metabolismo , Ecdisterona/metabolismo , Hormonas de Insectos , Estructura Molecular , Extractos Vegetales , Piranos/química , Receptores de Esteroides/metabolismoRESUMEN
Cytosporin A, B and C, three antagonists of [125I]-angiotensin II binding to rat adrenal glands were discovered in fermentations of an endophytic Cytospora sp. during routine screening using semi-automated procedures. The most potent of these displayed an IC50 of 1.5-3 microM and was specific for angiotensin II AT2.
Asunto(s)
Angiotensina II/antagonistas & inhibidores , Benzopiranos/farmacología , Hongos Mitospóricos/química , Glándulas Suprarrenales/metabolismo , Angiotensina II/metabolismo , Animales , Benzopiranos/química , Fermentación , Espectrometría de Masas , RatasRESUMEN
A novel oleic acid ester of the carotane sesquiterpene 14-hydroxy CAF-603 was isolated from Trichoderma virens grown in a solid brown rice-based medium, a solid millet-based medium, or a mannitol-based liquid medium. Its structure was determined on the basis of ms and nmr analysis. It retains distinct biological activity on the high conductance calcium-activated potassium channel, unlike its analogues 14-hydroxy CAF-603, CAF-603 3-oleate, or CAF-603 3-linoleate.
Asunto(s)
Canales de Potasio/agonistas , Sesquiterpenos/farmacología , Trichoderma/química , Animales , Aorta/efectos de los fármacos , Aorta/metabolismo , Calcio/fisiología , Bovinos , Cristalografía por Rayos X , Técnicas In Vitro , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Músculo Liso Vascular/efectos de los fármacos , Músculo Liso Vascular/metabolismo , Canales de Potasio/efectos de los fármacos , Sesquiterpenos/aislamiento & purificaciónRESUMEN
Pneumocandin D0 (9), a new member of the echinocandin class of antifungal agents, has been isolated as a minor constituent from fermentation broths of the filamentous fungi Zalerion arboricola (ATCC 20957). The structure of 9 has been determined mainly on the basis of spectroscopic analysis and by comparison with published data for similar compounds. To date, pneumocandin D0 has been found to be the most potent inhibitor of Pneumocystis carinii development in vivo within the natural-occurring echinocandin family of antifungal agents.
Asunto(s)
Antibacterianos/aislamiento & purificación , Antibacterianos/farmacología , Antifúngicos/aislamiento & purificación , Antifúngicos/farmacología , Péptidos , Pneumocystis/efectos de los fármacos , Secuencia de Aminoácidos , Animales , Antibacterianos/biosíntesis , Antifúngicos/biosíntesis , Candidiasis/tratamiento farmacológico , Equinocandinas , Fermentación , Ratones , Ratones Endogámicos , Hongos Mitospóricos/metabolismo , Datos de Secuencia Molecular , Estructura Molecular , Péptidos Cíclicos/biosíntesis , Péptidos Cíclicos/aislamiento & purificación , Péptidos Cíclicos/farmacología , Neumonía por Pneumocystis/tratamiento farmacológico , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
gamma-Pyrone-3-acetic acid (L-741,494) is a novel metabolite produced by a culture of the fungal genus Xylaria. This substance is a water-soluble, competitive, irreversible inhibitor of Interleukin-1 beta Converting Enzyme that is inactive against papain and trypsin. It has a mol wt of 154 and an empirical formula of C7H6O4. We propose the name xylaric acid for this compound.
Asunto(s)
Acetatos/farmacología , Cisteína Endopeptidasas/química , Metaloendopeptidasas/química , Pironas/farmacología , Xylariales/metabolismo , Acetatos/química , Acetatos/aislamiento & purificación , Secuencia de Aminoácidos , Caspasa 1 , Cromatografía por Intercambio Iónico , Espectroscopía de Resonancia Magnética , Datos de Secuencia Molecular , Pironas/química , Pironas/aislamiento & purificaciónRESUMEN
Detailed structure determination of the major and minor base-catalyzed degradation products of the chromophore of the enediyne anticancer antibiotic neocarzinostatin in the absence of DNA demonstrates that the enolate Michael addition reaction leading to a spirolactone cumulene intermediate is a spontaneous, stereoselective process. The implications of these findings for the mechanism of the thiol-independent, site-specific cleavage by the so-generated radical species of the drug at a DNA bulge are described.
Asunto(s)
ADN/química , Cinostatina/química , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Conformación Molecular , Estructura Molecular , Conformación de Ácido Nucleico , Espectrometría de Masa Bombardeada por Átomos Veloces , Cinostatina/análogos & derivadosRESUMEN
Three closely related fungal metabolites, zaragozic acids A, B, and C, that are potent inhibitors of squalene synthase have been isolated and characterized. Zaragozic acids A, B, and C were produced from an unidentified sterile fungal culture, Sporormiella intermedia, and Leptodontium elatius, respectively. The structures of the zaragozic acids and their trimethyl esters were determined by a combination of physical and chemical techniques. The zaragozic acids are characterized by a novel 2,8-dioxobicyclo[3.2.1]octane-4,6,7- trihydroxyl-3,4,5-tricarboxylic acid core and differ from each other in the structures of the 6-acyl and 1-alkyl side chains. They were found to be potent competitive inhibitors of rat liver squalene synthase with apparent Ki values of 78 pM, 29 pM, and 45 pM, respectively. They inhibited cholesterol synthesis in Hep G2 cells, and zaragozic acid A was an inhibitor of acute hepatic cholesterol synthesis in the mouse (50% inhibitory dose of 200 micrograms/kg of body weight). Inhibition of squalene synthase in cells and in vivo was accompanied by an accumulation of label from [3H]mevalonate into farnesyl diphosphate, farnesol, and organic acids. These data indicate that the zaragozic acids are a previously unreported class of therapeutic agents with potential for the treatment of hypercholesterolemia.
Asunto(s)
Ascomicetos/metabolismo , Compuestos Bicíclicos Heterocíclicos con Puentes , Compuestos Bicíclicos con Puentes/farmacología , Farnesil Difosfato Farnesil Transferasa/antagonistas & inhibidores , Lípidos/biosíntesis , Hígado/metabolismo , Hongos Mitospóricos/metabolismo , Ácidos Tricarboxílicos/farmacología , Animales , Compuestos Bicíclicos con Puentes/aislamiento & purificación , Compuestos Bicíclicos con Puentes/metabolismo , Colesterol/biosíntesis , Cromatografía Líquida de Alta Presión , Femenino , Fermentación , Humanos , Cinética , Hígado/efectos de los fármacos , Ratones , Estructura Molecular , Ácidos Tricarboxílicos/aislamiento & purificación , Ácidos Tricarboxílicos/metabolismo , Células Tumorales CultivadasRESUMEN
Pneumocandin B0 (6) and six related lipopeptides are antifungal and anti-Pneumocystis carinii agents from mutants of Zalerion arboricola, whose structures were determined mainly on the basis of spectroscopic analysis. They belong, along with pneumocandin A0 (L-671,329) previously isolated from these laboratories, to the echinocandin class of antifungal agents. The product from base-catalyzed ring opening involving the hemiaminal position of the dihydroxyornithine residue of B0, has been clearly defined as 6b. Modifications were limited to the 3-hydroxy-4-methylproline, 3,4-dihydroxyhomotyrosine and 4,5-dihydroxyornithine residues of pneumocandin A0.
Asunto(s)
Antibacterianos , Antifúngicos/química , Hongos Mitospóricos/química , Péptidos , Antifúngicos/farmacología , Antivirales/química , Candida albicans/efectos de los fármacos , Cristalografía , Equinocandinas , Espectroscopía de Resonancia Magnética , Péptidos Cíclicos/química , Péptidos Cíclicos/farmacología , Pneumocystis/efectos de los fármacos , Estereoisomerismo , Relación Estructura-ActividadAsunto(s)
Antibacterianos , Antifúngicos/biosíntesis , Glutamatos/metabolismo , Leucina/metabolismo , Hongos Mitospóricos/metabolismo , Péptidos , Prolina/metabolismo , Antifúngicos/química , Isótopos de Carbono , Equinocandinas , Ácido Glutámico , Hidroxiprolina/análogos & derivados , Hidroxiprolina/biosíntesis , Espectroscopía de Resonancia Magnética , Isótopos de Nitrógeno , Péptidos Cíclicos/biosíntesis , Péptidos Cíclicos/químicaRESUMEN
Cochinmicins I, II, and III are competitive endothelin antagonists produced by Microbispora sp. ATCC 55140. The cochinmicins are cyclic depsipeptides containing six alpha-amino acids and a pyrrolecarboxylic acid. Based upon MS, 1D and 2D NMR, and LC data, the structures and absolute stereochemistries of the cochinmicins have been assigned. All three components have the same basic sequence and contain one equivalent each of D-allo-threonine, D-alanine, L-phenylalanine, D-phenylalanine, 5-chloropyrrole-2-carboxylic acid (or pyrrole-2-carboxylic acid in cochinmicin I), plus two equivalents of 3,5-dihydroxyphenylglycine (DHPG). The phenylalanine residues were differentiated via a methanolysis product which contained only one of the phenylalanine residues. Both DHPG residues have the D configuration in the more active cochinmicins I and III. Cochinmicin II contains both D- and L-DHPG and these residues have been differentiated in the sequence based upon 1H NMR data.
Asunto(s)
Endotelinas/antagonistas & inhibidores , Micromonosporaceae/metabolismo , Péptidos Cíclicos/química , Secuencia de Aminoácidos , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Conformación Molecular , Datos de Secuencia Molecular , Estructura Molecular , Peso Molecular , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
A novel HIV-1 protease inhibitor, L-696,474 (C30H39NO4, 477), was isolated from the fermentations of the fungus Hypoxylon fragiforme (ATCC 20995, MF5511) and purified by silica gel chromatography followed by crystallization. Spectroscopic studies have shown the competitive inhibitor L-696,474 to be a novel cytochalasin. Two related novel cytochalasins were also isolated and had no effect on the enzyme.
Asunto(s)
Ascomicetos/química , Citocalasinas/aislamiento & purificación , Inhibidores de la Proteasa del VIH , Citocalasinas/química , Citocalasinas/farmacología , IsoindolesRESUMEN
The conversion of [2-deutero-3-fluoro-D-Ala8]cyclosporin A (1) to a dehydroalanine analog [delta-Ala8]cyclosporin A (2) was achieved with lithium diisopropylamide in THF at low temperature. This dehydro compound is a useful intermediate for the preparation of position 8 analogs of cyclosporin A formed from it by the conjugate addition of thiol compounds. NMR conformational studies have provided evidence for the restoration of D-stereochemistry in the modified Ala8 residues. The preparation of several of these cyclosporin analogs and their bioactivities are described.
Asunto(s)
Ciclosporinas/química , Inmunosupresores/química , Activación de Linfocitos , Linfocitos T/efectos de los fármacos , Animales , Cromatografía Líquida de Alta Presión , Cromatografía en Capa Delgada , Ciclosporinas/farmacología , Femenino , Inmunosupresores/farmacología , Espectroscopía de Resonancia Magnética , Ratones , Ratones Endogámicos C57BL , Conformación Molecular , Espectrometría de Masa Bombardeada por Átomos VelocesRESUMEN
The antibiotic heneicomycin (1), C44H62N2O11, was isolated from cultures of Streptomyces filipinensis as an amorphous yellow powder. Mass spectral and NMR analysis showed the compound to be a deoxy modification of aurodox (2), a member of the elfamycin antibiotic family. A marked change in mass spectral fragmentation compared to aurodox and 1H NMR couplings indicated the absence of the hydroxyl at position 30 of aurodox (position 3 of the tetrahydropyran).
Asunto(s)
Antibacterianos/aislamiento & purificación , Streptomyces/química , Antibacterianos/farmacología , Aurodox/farmacología , Fenómenos Químicos , Química , Piridonas/aislamiento & purificación , Piridonas/farmacología , Relación Estructura-ActividadRESUMEN
The discovery and physico-chemical characterization of three novel and minor virginiamycin M1 analogs as potent gastrin antagonists from a culture of a strain of Streptomyces olivaceus are described. These analogs are L-156,586, L-156,587 and L-156,588. They are, respectively, 15-dihydro-13,14-anhydro-, 13,14-anhydro- and 13-desoxy-analogs of virginiamycin M1. We also chemically converted virginiamycin M1 (via L-156,587) to L-156,586 and its unnatural epimer, L-156,906. These analogs are competitive and selective antagonists of gastrin and brain cholecystokinin binding at nanomolar concentrations. These are the most potent gastrin/brain cholecystokinin antagonists from natural products. The same compounds showed poor Gram-positive antibiotic activity versus virginiamycin M1. Structurally related Gram-positive antibiotics, griseoviridin and madumycin I, were inactive in gastrin and brain cholecystokinin binding at up to 100 microM.