Partition of tocopheryl glucopyranoside into liposome membranes studied by fluorescence methods

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.