RESUMEN
Cholesterol homeostasis is tightly controlled process that involves a variety of regulators including liver X receptors (LXR). Agonists of LXR are expected to increase cholesterol efflux, lower LDL, and raise HDL levels. Screening of a natural product library of microbial extracts using a LXR-scintillation proximity assay (SPA) binding assay and bioassay-guided fractionation of a number of fungal extracts led to the isolation of five ergostane and a cycloartane derivative. These compounds exhibited IC50 value ranging 0.5 approximately 9 microM in the binding assay for a-receptor and a number of these showed in vitro agonist activity in the coactivator association assays but lacked the cell based LXR activation. The isolation and LXR activity of these compounds are described.
Asunto(s)
Proteínas de Unión al ADN/agonistas , Hongos/metabolismo , Receptores Citoplasmáticos y Nucleares/agonistas , Esteroides/aislamiento & purificación , Triterpenos/aislamiento & purificación , Proteínas de Unión al ADN/metabolismo , Hongos/química , Concentración 50 Inhibidora , Ligandos , Hígado/metabolismo , Receptores X del Hígado , Receptores Nucleares Huérfanos , Receptores Citoplasmáticos y Nucleares/metabolismo , Esteroides/química , Esteroides/farmacología , Triterpenos/química , Triterpenos/farmacologíaRESUMEN
Liver X receptors (LXR) are nuclear hormone receptors that play a critical role in cholesterol homeostasis. They regulate the expression of the ABCA1 gene, which mediates the efflux of cholesterol out of cells. LXR agonists are expected to increase cholesterol efflux, lower LDL, and raise HDL levels. Screening of a natural product library of microbial extracts using a LXR-SPA binding assay and bioassay-guided fractionation of an active extract of a Streptomyces sp. (MA6657) led to the discovery of two new hexacyclic aromatic ketones, (-)-anthrabenzoxocinone [(-)-ABX (1)], an enantiomer of BE-24566B, and (-)-bischloroanthrabenzoxocinone [(-)-BABX (2)]. The IC50 values of LXRalpha-SPA binding are 2 microM for (-)-ABX and 10 microM for (-)-BABX. This extract was also found to inhibit type II fatty acid synthesis, and its active component, (-)-BABX, was responsible for the majority of the inhibition. All three compounds showed good Gram-positive antibacterial activity (MIC 0.5-2 microg/mL). Details of the isolation, structure elucidation, LXR ligand binding, antibacterial activity, and selectivity of inhibition of 1 and 2 are described.
Asunto(s)
Antibacterianos/aislamiento & purificación , Proteínas de Unión al ADN/metabolismo , Compuestos Heterocíclicos de 4 o más Anillos/aislamiento & purificación , Receptores Citoplasmáticos y Nucleares/metabolismo , Streptomyces/química , Antraquinonas/aislamiento & purificación , Antibacterianos/química , Antibacterianos/farmacología , Compuestos Heterocíclicos de 4 o más Anillos/química , Compuestos Heterocíclicos de 4 o más Anillos/farmacología , Concentración 50 Inhibidora , Ligandos , Receptores X del Hígado , Estructura Molecular , Receptores Nucleares Huérfanos , EstereoisomerismoRESUMEN
It has been demonstrated that liver X receptors (LXR) play a significant role in cholesterol homeostasis. Agonists of LXR are expected to increase cellular cholesterol efflux, lower LDL, and raise HDL levels. Screening of a natural product library of plant extracts using a LXR-SPA binding assay and bioassay-guided fractionation of a number of plant and marine gorgonian extracts led to the isolation of a number of active compounds. These included acanthoic acid (1) and alcohol (2), viperidone (3), polycarpol (4), rosacea acid (5), a cycloartane derivative (6), a new cycloartane analogue (7), betulinic acid (8), and gorgostane derivatives (9, 10, and 11). Of these compounds, 1, 4, and 11 exhibited potent binding affinity for alpha-receptor with IC(50) values of 0.25, 0.12, and 0.07 microM, respectively. Functionally they also showed strong coactivator association stimulation for LXRalpha receptor with EC50 values of 0.18, 0.03, and 0.05 microM, respectively. They also exhibited 15-, 8-, and 13-fold induction of the alpha-receptor in a transactivation assay in HEK-293 cells, respectively. In general these compounds were selective for the LXR alpha-receptor over the beta-receptor in all assays and were much better stimulators of the alpha-receptor than the endogenous steroid ligands.
Asunto(s)
Proteínas de Unión al ADN/agonistas , Diterpenos/aislamiento & purificación , Plantas Medicinales/química , Hidrocarburos Policíclicos Aromáticos/aislamiento & purificación , Receptores Citoplasmáticos y Nucleares/agonistas , Esteroides/aislamiento & purificación , Triterpenos/aislamiento & purificación , Animales , Annonaceae/química , Antozoos/química , Bahamas , Cactaceae/química , Campanulaceae/química , Células Cultivadas , Costa Rica , Diterpenos/química , Diterpenos/farmacología , Guyana , Humanos , Concentración 50 Inhibidora , Receptores X del Hígado , Estructura Molecular , Olacaceae/química , Receptores Nucleares Huérfanos , Triterpenos Pentacíclicos , Perú , Pinaceae/química , Hidrocarburos Policíclicos Aromáticos/química , Hidrocarburos Policíclicos Aromáticos/farmacología , Esteroides/química , Esteroides/farmacología , Triterpenos/química , Triterpenos/farmacología , Estados Unidos , Ácido BetulínicoRESUMEN
Liver X receptors (LXR) have been implicated in cholesterol homeostasis. Agonists of LXR are expected to increase cholesterol efflux, lower LDL, and raise HDL levels. Screening of a natural product library of plant extracts using a LXR-SPA binding assay and bioassay-guided fractionation of the bark and stem extract of Garcinia humilis led to the discovery of a new polyisoprenylated benzophenone named guttiferone I (1). The IC(50) value for this compound in the LXRalpha-SPA binding assay was 3.4 muM. Details of the isolation, structure elucidation, and ligand binding activity of 1 are described.
Asunto(s)
Benzofenonas/aislamiento & purificación , Proteínas de Unión al ADN/metabolismo , Garcinia/química , Receptores Citoplasmáticos y Nucleares/metabolismo , Benzofenonas/química , Benzofenonas/farmacología , Concentración 50 Inhibidora , Ligandos , Hígado/metabolismo , Receptores X del Hígado , Estructura Molecular , Receptores Nucleares HuérfanosRESUMEN
HIV-1 protease is one of several key enzymes required for the replication and maturation of HIV-1 virus. An almost two-decade research effort by academic and pharmaceutical institutions resulted in the successful commercialization of seven drugs that are potent inhibitors of HIV-1 protease activity and which, if used correctly, are highly effective in managing viral load. However, identification of clinical viral isolates that are resistant to these drugs indicates that this is a significant problem and that new classes of inhibitors are continually needed. Screening of microbial extracts followed by bioassay-guided isolation led to the discovery of a natural hinnuliquinone, a C(2)-symmetric bis-indolyl quinone natural product that inhibited the wild-type and a clinically resistant (A44) strain of HIV-1 protease with K(i) values of 0.97 and 1.25microM, respectively. Crystallographic analysis of the inhibitor-bound HIV-1 protease helped explain the importance of the C(2)-symmetry of hinnuliquinone for activity. Details of the isolation, biological activity, and crystallographic analysis of the inhibitor-bound protease are herein described.