Abstract:

The solubilization of four bioactive mols. with different polarities, in three reverse hexagonal (HII) systems has been investigated. The three HII systems were a typical reverse hexagonal composed of glycerol monooleate (GMO)/tricaprylin/water and two fluid hexagonal systems contg. either 2.75 wt. % Transcutol or ethanol as a fourth component. The phase behavior of the liq. cryst. phases in the presence of ascorbic acid, ascorbyl palmitate, D-$\alpha$-tocopherol and D-$\alpha$-tocopherol acetate were detd. by small-angle X-ray scattering (SAXS) and optical microscopy. Differential scanning calorimetry (DSC) and Fourier-transform IR (FT-IR) techniques were utilized to follow modifications in the thermal behavior and in the vibrations of different functional groups upon solubilizing the bioactive mols. The nature of each guest mol. (in both geometry and polarity) together with the different HII structures (typical and fluids) detd. the corresponding phase behavior, swelling or structural transformations and its location in the HII structures. Ascorbic acid was found to act as a chaotropic guest mol., localized in the water-rich core and at the interface. The AP was also a chaotropic guest mol. with its head located in the vicinity of the GMO headgroup while its tail embedded close to the surfactant tail. D-$\alpha$-tocopherol and D-$\alpha$-tocopherol acetate were incorporated between the GMO tails; however, the D-$\alpha$-tocopherol was located closer to the interface. Once Transcutol or ethanol was present and upon guest mol. incorporation, partial migration was detected. [on SciFinder(R)]