RESUMO
Protection-deprotection steps, which are usually needed for regioselective alkylation of pyrimidine deoxynucleosides, can be avoided by choosing the appropriate solvent. The combined effects of low dielectric constant and possible sodium chelation by pyrimidine nucleosides may account for the unexpected regioselectivity observed in THF.
Assuntos
Quelantes/química , Nucleosídeos de Pirimidina/química , Alquilação , Éteres de Coroa/química , Desoxicitidina/química , Desoxiuridina/química , Impedância Elétrica , Solventes/química , Estereoisomerismo , Especificidade por Substrato , Timidina/químicaRESUMO
Natural polyphenols are known to exhibit a lot of different biological properties, including antioxidant activity. For some polyphenols these activities are attributed to the presence of a guaiacol moiety. In the present paper we focus on the role of this moiety. For this purpose nine different compounds were enzymatically synthesized from guaiacol. To elucidate the structure-activity relationship of these polyphenols, DFT-(PCM)B3P86/6-311+G(2d,3pd)//(PCM)B3P86/6-31+G(d,p) calculations supported the experimental DPPH free radical scavenging activities. The antioxidant activities were correlated to (i) O-H BDEs (bond dissociation enthalpies), (ii) BDE(D) (BDE of a second H atom abstraction from the phenoxyradicals), (iii) spin density, (iv) HOMO (highest occupied molecular orbital) distribution, (v) IPs (ionization potentials), (vi) DeltaG and DeltaG(#) free energies of HAT (H atom transfer), and (vii) HAT rate constants. BDE(D) appeared to be the most important descriptor to understand the free radical scavenging ability of these compounds.
Assuntos
Sequestradores de Radicais Livres/química , Guaiacol/química , Polímeros/química , Teoria Quântica , Compostos de Bifenilo/química , Espectroscopia de Ressonância de Spin Eletrônica , Enzimas/metabolismo , Sequestradores de Radicais Livres/síntese química , Sequestradores de Radicais Livres/metabolismo , Guaiacol/síntese química , Guaiacol/metabolismo , Radical Hidroxila/química , Cinética , Modelos Moleculares , Conformação Molecular , Peróxidos/química , Picratos/química , TermodinâmicaRESUMO
This paper describes an efficient procedure for selective 3'-O- or 3-N-protection of 5'-O-tert-butyldimethylsilylthymidine, depending on the use of aprotic polar solvents with low or high dielectric constant, respectively. These syntheses were activated by either ultrasound or microwaves. Several alkyl bromides offer a convenient route to prepare 3'-O- or 3-N-protected and functionalized thymidine derivatives.
Assuntos
Solventes/química , Timidina/química , Brometos/química , Micro-Ondas , Estrutura Molecular , EstereoisomerismoRESUMO
Syntheses of new glycosylated neutral and cationic porphyrin dimers linked at the meso-position via a flexible hydrocarbon chain are described. A detailed 1H and 13C NMR study allows their complete structural elucidation. The UV-visible, fluorescence and MALDI mass spectra are also presented. Photocytotoxicities of these compounds against K562 leukaemia cell line are compared to those of Photofrin II.
Assuntos
Fotoquimioterapia/métodos , Porfirinas/síntese química , Porfirinas/farmacologia , Sobrevivência Celular/efeitos dos fármacos , Éter de Diematoporfirina , Dimerização , Glicosilação , Humanos , Células K562 , Espectroscopia de Ressonância Magnética , Estrutura Molecular , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Análise Espectral , Relação Estrutura-AtividadeRESUMO
Three flavonol triglycosides kaempferol 3-[2Gal-(4-acetylrhamnosyl)robinobioside], kaempferol 3-(2Gal-rhamnosylrobinobioside) and quercetin 3-(2G-rhamnosylrutinoside) have been isolated from a methanolic extract of Galega officinalis aerial parts. They are reported for the first time in the genus Galega; moreover, the acetylated triglycoside is a new natural product.
Assuntos
Flavonoides , Glicosídeos/isolamento & purificação , Quempferóis , Oligossacarídeos/isolamento & purificação , Plantas Medicinais/química , Quercetina/análogos & derivados , Acetilação , Glicosídeos/química , Espectroscopia de Ressonância Magnética , Oligossacarídeos/química , Quercetina/química , Quercetina/isolamento & purificação , Espectrofotometria UltravioletaRESUMO
The few well-characterized fungal growth-regulating substances include 10-oxo-trans-8-decenoic acid (ODA) and hercynine. This report deals with production and tissue location of ODA. It also describes some biological activities of addition of ODA, hercynine, and cytokinins on growth and postharvest morphogenesis of Agaricus bisporus. Production of ODA in sporophore extracts was limited mainly by oxygen availability and the possible occurrence of a competitive metabolic pathway. Presumably synthesized within the stipe and skin tissues, ODA accumulated in the gills. Mycelium growth rate on a potato-based medium was significantly increased in the presence of ODA. Moreover, stipe lengthening was slightly stimulated by 10 or 100 µM ODA. Although these findings were similar to previous ones (Mau JL, Beelman RB, Ziegler GR. Phytochemistry 1992;31:4059-64), ODA appeared poorly active in our assays and mycelium growth on asparagine-glucose medium was strongly inhibited by 200 µM ODA. In contrast with cytokinins or hercynine, ODA did not speed up cap opening. Finally, tests carried out on animal cells suggested a dose-dependent cytotoxic effect of ODA.
RESUMO
Isoflavones and others phytoestrogens have been suggested to be anticarcinogenic. Anti-aromatase, antiestrogenic or antiproliferative actions of these compounds have been postulated and related to the observation that there is a reduced incidence of breast cancer associated with diet. In this study, we explored some mechanisms by which they can exert cancer-preventive effects. Phytoestrogens were tested for estimating anti-aromatase, anti-3beta-hydroxysteroid dehydrogenase delta5/delta4 isomerase (3beta-HSD) and anti-17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities in human placental microsomes. We found that isoflavonoids and compounds which presented the phenolic B ring in the 3 position on the pyran ring preferentially inhibited 3beta-HSD and/or 17beta-HSD activities than aromatase activity. We also evaluated their interactions with the estrogen receptor using a stably transfected human breast cancer cell line (MVLN). On the other hand phytoestrogens were evaluated for their effects on the proliferation in estrogen-dependent (MCF-7) and independent (MDA-MB231) human breast cancer cells. We established a relationship structure-activity and determined regions or/and substituents essential for these different activities. However, at high concentrations it seems that some phytoestrogens exert their protection against breast cancer through other estrogen-independent mechanisms.