RESUMO
Five stilbenoids, E-resveratrol, E-piceatannol, (+) E-(epsilon)-viniferin, (+)-ampelopsin A and vitisin C were isolated from methyl tert-butyl ether (MtBE) stem extract of Vitis vinifera (Chardonnay cv). Their purification on a preparative scale was obtained by centrifugal partition chromatography (CPC) using quaternary Arizona solvent systems composed of n-heptane/ethyl acetate/methanol/water. We tested 23 Arizona solvent systems to partition the extract and found that systems K and M (Hept/EtOAc/MeOH/water, 1:2:1:2 and 5:6:5:6, respectively; v/v) were the best to separate the stilbenes mentioned above. This support-free liquid-liquid chromatographic procedure made it possible to isolate ampelopsin A from V. vinifera for the first time. The antiamyloidogenic activity of the isolated stilbenes was evaluated versus beta-amyloid fibrils. E-resveratrol and (+)-ampelopsin A were found to be the most active compounds with 63 and 46% inhibition at 10microM, respectively. These findings suggest that E-resveratrol and (+)-ampelopsin A may function as attractive new candidates for protecting against brain cell dysfunction in vivo in AD by inhibiting the aggregation of Abeta.
Assuntos
Centrifugação/métodos , Cromatografia Líquida/métodos , Caules de Planta/química , Estilbenos/isolamento & purificação , Vitis/química , Extratos Vegetais/química , Extratos Vegetais/isolamento & purificação , Estilbenos/químicaRESUMO
The metabolism of labelled pyruvate followed by 13C NMR and the measure of glutamine synthetase (GS) showed, according to previous results, a high activity of this enzyme in suspension cells of Nicotiana plumbaginifolia. This activity could derive glutamate from the alkaloid synthesizing pathways. However, a recent work showed that the rate of the GS gene transcription was inversely proportional to the Gln/Glu ratio. The measures of Gln and Glu concentrations in Nicotiana plumbaginifolia cells revealed that high GS activity correlates with the weak value of Gln/Glu ratio. Therefore, the hypothesis of GS dysfunctioning for the non-biosynthesis of alkaloids in N. plumbaginifolia suspension cells can be discarded. This conclusion is strengthened by the results obtained when using a GS inhibitor.
Assuntos
Alcaloides/biossíntese , Datura stramonium/metabolismo , Glutamato-Amônia Ligase/metabolismo , Ácido Glutâmico/biossíntese , Glutamina/biossíntese , Nicotiana/metabolismo , Proteínas de Plantas/metabolismo , Plantas Medicinais , Plantas Tóxicas , Ácido gama-Aminobutírico/biossíntese , Células Cultivadas , Datura stramonium/genética , Indução Enzimática , Inibidores Enzimáticos/farmacologia , Regulação da Expressão Gênica de Plantas , Glutamato-Amônia Ligase/antagonistas & inibidores , Glutamato-Amônia Ligase/genética , Espectroscopia de Ressonância Magnética , Metionina Sulfoximina/farmacologia , Proteínas de Plantas/antagonistas & inibidores , Proteínas de Plantas/genética , Especificidade da Espécie , Suspensões , Nicotiana/genéticaRESUMO
We measured the spin-lattice and spin-spin relaxation times (T1 and T2, respectively) and the nuclear Overhauser effect (NOE) of 31P nuclei of 2,3-diphosphoglycerate (2,3-DPG) in living erythrocytes. The relaxation of water protons was also studied. Phosphorus relaxation is pH-dependent due to a modification of the binding of 2,3-DPG to hemoglobin. We compared the results obtained with normal and uremic erythrocytes. In uremic erythrocytes the 31P relaxation rates are increased, but the intraerythrocytic pH variation in uremic erythrocytes cannot itself explain this increase. A possible role of dialysable substances may explain the increased relaxation rate.