Impact of plant extract on the gastrointestinal fate of nutraceutical-loaded nanoemulsions: phytic acid inhibits lipid digestion but enhances curcumin bioaccessibility

The impact of phytic acid on lipid digestion and curcumin bioaccessibility in oil-in-water nanoemulsions was investigated using a simulated gastrointestinal tract (GIT). The size, charge, and structural organization of the colloidal particles in the system were measured as the curcumin-loaded emulsions (7 mg curcumin per g lipid) were passed through simulated mouth (pH 6.8, 2 min), stomach (pH 2.5, 2 hours), and small intestine (pH 7.0, 2 hours) stages. After the small intestine stage, the level of free fatty acids (FFAs) generated and the bioaccessibility of curcumin were measured. The total amount of FFAs released significantly decreased with increasing phytic acid level, from 105.7 ± 5.9% (control) to 78.4 ± 6.4% (0.5% phytic acid). Conversely, curcumin bioaccessibility significantly increased from 39.4 ± 3.5% (control) to 74.7 ± 2.6% (0.5% phytic acid). The inverse relationship between lipolysis and curcumin bioaccessibility was ascribed to the impact of phytic acid on droplet flocculation and the level of free calcium ions present, which affected the production of mixed micelles capable of solubilizing the nutraceutical. The knowledge obtained here might prove beneficial for the employment of phytic acid as a multifunctional ingredient that inhibits lipid digestion while boosting nutraceutical bioavailability.