Improved photostability of Vitamin A palmitate originating from self-assembled supramolecular gels

Retinyl palmitate (RP) is a derivative of Vitamin A and widely applied as the active component in the fields of cosmetic and pharmaceutics. RP can easily lose its physiological activity under UV irradiation due to its photosensitivity. In this work, it was found that the activity of RP remained 75% after 80 min of UVA irradiation when RP was entrapped in supramolecular gels formed by self-assembly of sorbitol-based gelators. By contrast, the activity of RP in conventional hydroxyethyl cellulose gels only remained 10% under the same conditions. These results showed that the supramolecular gels exhibited a significant protective effect on the photostability of RP. UV spectra of RP in supramolecular gels and corresponding solutions showed no distinct differences, indicating no change of the physicochemical properties of RP. The images of field-emission scanning electron microscopy and fluorescent optical microscopy suggested that the protection by supramolecular gels on the photostability of RP may be attributed to the three-dimensional network structure formed by the self-assembly of the gelators, which reduced the molecular collisions and the degradation process of the photoactivated RP. The present results showed that this protection can be influenced by the structures and the concentration of gelators as well as by the solvent composition.