RESUMEN
In this study, we irradiated the antioxidant kaempferol in ethanol and methanol solutions with gamma rays at doses ranging from 0.2-20 kGy. NMR and ES-MS spectroscopy were used to identify radiolysis products. Two depsides, [2-[(4'-hydroxybenzoyl)oxy]-4,6-dihydroxyphenyl](oxo) methyl acetate and [2-[(4'-hydroxybenzoyl)oxy]-4,6-dihydroxyphenyl](oxo) ethyl acetate, were the major compounds of kaempferol degradation in methanol and in ethanol, respectively. Other products formed in low concentrations were identified as [4-hydroxyphenyl](oxo) methyl acetate, [4-hydroxyphenyl](oxo) ethyl acetate, and depside [2-[(4'-hydroxybenzoyl)oxy]-4,6-dihydroxyphenyl](oxo) acetic acid. The formation of the latter was observed in both solvents. We propose degradation mechanisms that suggest that (.)CH(2)OH and CH(3)(.)CHOH, produced by solvent radiolysis, react with the 3-OH kaempferol group because of its high H-donor capacity. pi-Electron delocalization in the flavonoxy formed after the first H-transfer leads to C-ring opening and consequently to the formation of depsides. G calculation of the degradation products and of (.)CH(2)OH and CH(3)(.)CHOH radicals confirmed the proposed mechanism of kaempferol radiolysis. The rate constants for the reaction between kaempferol and these free radicals were also calculated. Formation of depside has also been observed in many studies of the oxidation of flavonoids; those studying human metabolism have suggested similar redox transformation of flavonols. The antioxidant activities of radiolysis products were evaluated and compared to those of kaempferol.
Asunto(s)
Antioxidantes/farmacología , Etanol/farmacología , Flavonoides/farmacología , Rayos gamma , Hidroxibenzoatos/química , Quempferoles , Metanol/farmacología , Compuestos de Bifenilo , Cromatografía Líquida de Alta Presión , Depsidos , Relación Dosis-Respuesta en la Radiación , Etanol/química , Radicales Libres , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Metanol/química , Modelos Químicos , Oxígeno/metabolismo , Picratos/química , Superóxidos/química , Factores de Tiempo , Rayos UltravioletaRESUMEN
The flavonol quercetin is one of the most well-known antioxidant flavonoids. Its antioxidant potential has been studied extensively during the last 10 years, but little is known about the metabolites formed in vivo that lead to the formation of depside and small molecules such as benzoic acids. In this study, gamma irradiation of a quercetin methanol solution was used as a model of certain oxidative reactions that occur in vivo. Qercetin at concentrations ranging from 5 x 10(-5) M to 5 x 10(-3) M, was irradiated with gamma rays at doses of 2-14 kGy. Quercetin degradation was evaluated by HPLC analysis. The major radiolytic metabolite was identified as a depside by NMR and LC-MS. Formation of 3,4-dihydroxybenzoic acid was also observed. The presence of CH3O. formed during methanol radiolysis is invoked to explain depside formation. Transformation of the 8-methoxy substituted depside (Q1) to the 8-hydroxyl substituted depside (Q2) is discussed. The antioxidant properties of quercetin metabolites are evaluated according to their capacity to decrease the EPR DPPH signal and to inhibit superoxide radical formed by the enzymatic reaction (xanthine + xanthine oxidase). For both assays, the IC50 of Q2 is twice as high as that of quercetin.
Asunto(s)
Rayos gamma , Quercetina/química , Quercetina/efectos de la radiación , Soluciones/química , Soluciones/efectos de la radiación , Cromatografía Líquida de Alta Presión , Isomerismo , Espectroscopía de Resonancia Magnética , Espectrometría de Masas , Metanol , Estructura Molecular , Oxidación-Reducción/efectos de la radiación , Quercetina/metabolismo , Soluciones/metabolismo , Espectrofotometría Ultravioleta , TermodinámicaRESUMEN
The petrol extract from mace of Myristica argentea Warb. afforded six phenylpropenes, three lignans, three neolignans and a dilignan, bis erythro-argenteane (4) or rel-(8R,8'S,8"S,8"'R)-5',5"'-bis(7-(3,4-methylenedioxyphenyl)-7'-(4'-hydroxy-3'-methoxyphenyl)-8.8'-lignane]. The last-named compound is a new natural product.
Asunto(s)
Lignanos/aislamiento & purificación , Myristicaceae/química , Plantas Medicinales/química , Alquenos/química , Alquenos/aislamiento & purificación , Cromatografía Liquida , Indonesia , Lignanos/química , Conformación Molecular , Estructura Molecular , Resonancia Magnética Nuclear BiomolecularRESUMEN
In an effort to discover new antioxidant natural compounds, seven plants that grow in France (most of them in the Limousin countryside) were screened. Among these plants, was the extensively studied Vitis vinifera as reference. For each plant, sequential percolation was realized with five solvents of increasing polarities (hexane, chloroform, ethyl acetate, methanol, and water). Free radical scavenging activities were examined in different systems using electron spin resonance (ESR) spectroscopy. These assays were based on the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), the hydroxyl radicals generated by a Fenton reaction, and the superoxide radicals generated by the X/XO system. Antiproliferative behavior was studied on B16 melanoma cells. ESR results showed that three plants (Castanea sativa, Filipendula ulmaria, and Betula pendula) possessed, for the most polar fractions (presence of phenolic compounds), high antioxidant activities in comparison with the Vitis vinifera reference. Gentiana lutea was the only one that presented a hydroxyl scavenging activity for the ethyl acetate and chloroform fractions. The antiproliferative test results showed that the same three plants are the most effective, but for the apolar fractions (chloroform and hexane).
Asunto(s)
Antioxidantes/metabolismo , Depuradores de Radicales Libres/metabolismo , Extractos Vegetales/química , Antioxidantes/análisis , Espectroscopía de Resonancia por Spin del Electrón/métodos , Depuradores de Radicales Libres/análisis , Especies Reactivas de OxígenoRESUMEN
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.
Asunto(s)
Flavonoides , Glicósidos/aislamiento & purificación , Quempferoles , Oligosacáridos/aislamiento & purificación , Plantas Medicinales/química , Quercetina/análogos & derivados , Acetilación , Glicósidos/química , Espectroscopía de Resonancia Magnética , Oligosacáridos/química , Quercetina/química , Quercetina/aislamiento & purificación , Espectrofotometría UltravioletaRESUMEN
Curcumin, demethoxycurcumin and bisdemethoxycurcumin are the yellow coloring phenolic compounds isolated from the spice turmeric. This study was part of a program correlating the biological activity and molecular structure of antitumor agents; the effect of these curcuminoids and cyclocurcumin (Cyclocur) was examined on the proliferation of MCF-7 human breast tumor cells. Curcuminoids appeared to be potent inhibitors, whereas Cyclocur was less inhibitory. To contribute to our understanding of the mechanism of antiproliferative activity of curcumin, cell cycle analysis was performed by propidium iodide staining and a flow cytometry technique. Curcumin exerts a cytostatic effect at G2/M which explains its antiproliferative activity. The presence of the diketone moiety in the curcumin molecule seems to be essential for the inhibitory activity.
Asunto(s)
Anticarcinógenos/farmacología , División Celular/efectos de los fármacos , Ácidos Cumáricos/farmacología , Curcumina/análogos & derivados , Curcumina/farmacología , Anticarcinógenos/química , Neoplasias de la Mama/patología , Ciclo Celular/efectos de los fármacos , Ácidos Cumáricos/química , Curcumina/química , Diarilheptanoides , Humanos , Relación Estructura-Actividad , Células Tumorales CultivadasRESUMEN
Juniperoside, a new 9-O[beta- D-glucopyranoside]-3,4,5-trimethoxycinnamyl alcohol has been isolated along with the 9- O-[alpha-L-arabinofuranosyl-(1-->6)-beta- D-glucopyranoside]cinnamyl alcohol (rosarin) and coumarin 7- O-beta- D-glucopyranoside (skimmin) from the acetone extract of the aerial parts of Juniperus phoenicea L. The structure elucidation of these natural products was achieved mainly by mass and NMR spectroscopy.
RESUMEN
Novel isoquinoline alkaloids were evaluated for their effect on the kinetics of a soybean lipoxygenase type I using linoleic acid as substrate. Some of these alkaloids were found to increase the initial reaction velocity, this property seems related to phenolic groups present in the molecule. The effect of these compounds on the soybean lipoxygenase activity was compared to that of others products which are known to affect this reaction. A reaction mechanism is then proposed: it appeared, in this reaction a correlative structure-activity of phenolic compounds we tested.