Solubilization of lycopene in jojoba oil microemulsion

The unique properties of jojoba oil make it an essential raw material in the manufacture of cosmetics. New, totally dilutable U-type microemulsions of water, jojoba oil, alcohols, and the nonionic surfactant polyoxyethylene-10EO-oleyl alcohol (Brij 96V) have been formulated recently. Here, these microemulsions are shown to be capable of solubilizing lycopene, a nutraceutical insoluble in water and/or oil, much more effectively than the solvent (or a solvent and surfactant blend) can dissolve them. In water-in-oil (W/O) and oil-in-water (O/W) microemulsions with 10 and 90 wt% water, respectively, the normalized maximal solubilization efficiency alpha is ca. 20-fold larger than its solubility. The solubilization capacity of the system is mainly surfactant-concentration dependent. The lycopene resides at the interfaces of the W/O and O/W microemulsions and engenders significant structural changes in the organization of the microemulsion droplets. In the absence of lycopene, the droplets are spherical; when lycopene is added, compaction of the droplets and formation of threadlike droplets are observed. On further addition of lycopene, the bridging effect wanes and the droplets revert to a spherical shape. The enhanced solubilization demonstrated for lycopene opens up new options for formulators interested in making liquid and transparent products for cosmetic or pharmaceutical uses.