RESUMEN
Vitamin E is poorly soluble in aqueous solutions. Enhanced physiological activity is expected from synthesized glycosidic tocopherol derivatives. We investigated binding, location and interactions of newly synthesized DL-alpha-tocopheryl beta D glucopyranoside (II) in phosphatidylcholine liposomes using fluorescence emission, anisotropy and lifetime methods. In liposomes emission maximum and fluorescence lifetime of glucoside were similar to those observed in methanol. High fluorescence anisotropy value indicates that tocopheryl glucoside is located in restricted mobility region of the membrane. Thermodynamic calculation indicated efficient partition of (II) into membrane. The energy minimization calculations of electrostatic potential distribution of (II) and solvation energies performed with Gaussian program confirmed strong affinity of glucosidic moiety for ionic interactions and supported proposed model of interactions. The all obtained data indicate that DL-alpha-tocopheryl beta-glucoside is embedded into the membrane interior whereas sugar moiety protrudes above the water/lipid interface of the membrane surface.
Asunto(s)
Glucósidos/metabolismo , Liposomas/metabolismo , Tocoferoles/metabolismo , 1,2-Dipalmitoilfosfatidilcolina/química , 1,2-Dipalmitoilfosfatidilcolina/metabolismo , Absorción , Membrana Celular/química , Membrana Celular/metabolismo , Polarización de Fluorescencia , Glucósidos/química , Liposomas/química , Modelos Moleculares , Conformación Molecular , Teoría Cuántica , Solventes/química , Espectrometría de Fluorescencia , Tocoferoles/químicaRESUMEN
In this study we estimated how conjugation with a sugar moiety influences the spectral properties of tocopherol and relate the spectroscopic properties of glycosides to solvent properties such as viscosity and polarity. Spectroscopic properties (absorption, fluorescence, fluorescence anisotropy and fluorescence lifetime) of three dl-alpha-tocopheryl glycosides (dl-alpha-tocopheryl orthoacetate derivative and glycosides of dl-alpha-tocopherol model compounds: 2,2,5,7,8-pentamethyl-6-chromanol and Trolox) were studied in DMSO/water solution. In all investigated compounds dissolved in DMSO/water mixture the absorption and emission maxima were blue-shifted. The fluorescence lifetimes were longer compared with those obtained for the parent compounds, except for the Trolox glucoside, in which it was shorter. The observed effect is connected with an increase in the electronic energy in the ground state due to electron rearrangement in the chromanol system caused by interaction with the sugar moiety. The extent of the spectral shift is related to the sugar moiety substituted at the phenolic oxygen rather than to substitution at the 2a position in the chromanol ring. The fluorescent properties of dl-alpha-tocopheryl glucoside in organic solvents were measured. The Stokes shift was related to the orientational polarizability of the solvents. The study of viscosity suggested two different mechanisms explaining the results observed in a low- and high-viscosity environment. The results indicated the fundamental role of interactions between the chromophore and sugar moiety in a low-viscosity environment. The results obtained at high values of viscosity are discussed in terms of a frictional boundary solvent-solute interaction model.
Asunto(s)
Antioxidantes/química , Dimetilsulfóxido/química , Glicósidos/química , Solventes/química , Agua/química , alfa-Tocoferol/química , Humanos , Estructura Molecular , Espectrometría de Fluorescencia , ViscosidadRESUMEN
The stability of alpha-tocopheryl beta-galactoside in the presence of endogenous galactosidases in selected tissue homogenates (liver, kidney, ileum and brain) was estimated. High degree release of alpha-tocopherol from alpha-tocopheryl beta-galactoside in tissues of ileum, kidney and brain was observed (82%, 75% and 72%, increase above endogenous alpha-tocopherol, respectively). A possible enzymatic mechanism of the galactoside decomposition was proposed.
Asunto(s)
Galactósidos/química , Vitamina E/análogos & derivados , Vitamina E/química , Animales , Química Encefálica , Galactósidos/metabolismo , Íleon/química , Técnicas In Vitro , Riñón/química , Hígado/química , Conformación Molecular , Especificidad de Órganos , Ratas , Vitamina E/metabolismo , alfa-Galactosidasa/químicaRESUMEN
13C NMR CP MAS data for three glycosyl alpha-tocopherol derivatives are reported. The values of delta = delta(solution) - delta(solid state) provided information about rigid and conformationally flexible fragments of alpha-tocopherol molecule and the sugar moieties.
