Self-emulsifying Transparent Nanoemulsion to Improve 9'-cis-Bixin Photo Stability in Aqueous Solution by Tween 20 and Lecithin

Aqueous and photo stability of bixin are challenges in practical applications. Herein, transparent nanoemulsion can be self-emulsified to improve 9'- cis -bixin aqueous and photo stability. The 0.25 g carvacrol with 0.5% w/w 9'- cis -bixin, 2.08 g 12-% soybean lecithin, 2.25 g Tween 20, and 0.42 g water were mixed and stored overnight to fabricate transparent oil-in-water (O/W) nanoemulsion. The O/W nanoemulsion droplets had an average dimeter of 12.03 nm and equivalent spherical diameter of 6.78 nm. Photo stability of 9'- cis -bixin was improved after encapsulating in nanoemulsion droplets, demonstrated by significant improvement of 9'- cis -bixin degradation rate constant under ultraviolet. Nanoemulsion droplets significantly improved cell uptake of 9'- cis -bixin especially at the first 15 min after cocultivation of Caco-2 cells and 9'- cis -bixin encapsulated nanoemulsion. This study provides a comprehensive understanding of bixin protection by nanoemulsion fabricated by a self-emulsification method with potential cellular uptake.