Effect of Digestion on Ursolic Acid Self-Stabilized Water-in-Oil Emulsion: Role of Bile Salts

Abstract

Exploring the effect of bile salts on the properties of emulsion carriers containing hydrophobic bioactive compounds is particularly critical to understanding the stability and bioavailability of these hydrophobic bioactive compounds in the digestive process. In this study, the effects of bile salts on the stability and digestive characteristics of the ursolic acid (UA) self-stabilized water-in-oil (W/O) emulsion were investigated via static and dynamic (with or without enzyme) in vitro simulated digestive systems. The results showed that under the static system, the basic conditions had less interference, while the bile salts had a significant effect on the appearance and microstructure of the emulsion. The primary mechanism of emulsion instability is hydrophobic binding and depletion flocculation. Under the dynamic condition, it was found that the low concentrations of bile salts can promote the release amount and the rate of free fatty acids via displacement, while high concentrations of bile salts inhibit the decomposition of lipid, which may be related to the secondary coverage formed at the interface by the bile salts. These findings provide a theoretical basis for understanding the digestive behavior of the UA emulsion and its interaction with bile salts, which are conducive to developing and designing new emulsions to improve the bioaccessibility of UA.