RESUMO
From the aerial parts of Laennecia sophiifolia (Kunth) G.L. Nesom, a neo-clerodane and an acyclic furano diterpene were isolated, along with four known compounds, 2beta-hydroxyhardwickiic acid, hawtriwaic acid, apigenin, and beta-sitosterol. Their structures were established as 12-epi-bacchotricuneatin A and (2E,6E)-9-(3-furyl)-6-methyl-2-(4-methylpent-3-enyl)-nona-2,6-dienoic acid, by analysis of spectral evidence. The absolute structure of 12-epi-bacchotricuneatin A was determined by a circular dichroism spectral comparison with that of bacchotricuneatin A.
Assuntos
Asteraceae/química , Diterpenos/isolamento & purificação , Diterpenos/química , Estrutura Molecular , Análise EspectralRESUMO
A novel compound, 1 beta-hydroxydehydroabietic acid has been obtained by the microbial transformation of dehydroabietic acid, using cultures of Fusarium oxysporum and F. moniliforme. Its antibacterial activity was also tested.
Assuntos
Abietanos , Anti-Infecciosos/isolamento & purificação , Diterpenos/isolamento & purificação , Diterpenos/metabolismo , Fusarium/metabolismo , Anti-Infecciosos/química , Anti-Infecciosos/farmacologia , Diterpenos/química , Diterpenos/farmacologia , Hidroxilação , Espectroscopia de Ressonância Magnética , Testes de Sensibilidade Microbiana , Estrutura MolecularRESUMO
15N NMR spectroscopy was used to explore the interactions between natural polyamines and Escherichia coli tRNA. It was found that when tRNA is added to solutions of 15N-labeled spermine or spermidine, there is a considerable decrease in the relative heights of the -NH(2+)--resonances with respect to the signals arising from the -NH3+ groups. The presence of tRNA was also found to reduce the longitudinal relaxation times T1 of the nitrogens, mainly those of the -NH(2+)- groups. The longitudinal relaxation times of the nitrogens were used to characterize the temperature dependence of the binding, and they allowed us to calculate the activation energies that determine the correlation times of amino groups in the presence of tRNA. Both the thermodynamic and the relaxation results indicate that (i) spermine binds more strongly to tRNA than spermidine does and (ii) within each of these molecules the -NH(2+)- groups bind more strongly to tRNA than the more electropositive -NH3+ moieties. This specificity suggests that the interaction between polyamines and tRNA cannot be described exclusively in terms of electrostatic forces and that other interactions (most likely, hydrogen bonding) are very important for establishing the polyamine-tRNA link. Some of the factors that may conspire against the binding of -NH3+ groups to tRNA are briefly discussed.
