Enhancement of Ellagic Acid Solubility and Bioaccesibility by Microencapsulation Process and Biotransformation to Urolithins

The aim of this study was to enhance the stability and water solubility of ellagic acid (EA) from pomegranate peel by microencapsulation using various carriers, and to improve its biotransformation into urolithin A (Uro-A) and urolithin B (Uro-B) by a probiotic microorganism. The formulation of carrier materials, comprising maltodextrin, inulin, and gum Arabic, and the inlet air temperature of the spray-drying microencapsulation process were optimized to enhance the stability and water solubility of EA. In addition to the variable ratios of carrier materials, a fixed concentration of β-cyclodextrin (1.1%) was incorporated into carrier formulations to further improve the water solubility of EA. The optimal spray drying conditions were determined as an inlet air temperature of 158°C and a carrier composition ratio of maltodextrin:inulin:gum Arabic at 2:1:0, supplemented with 1.1% β-cyclodextrin. The EA concentration and water solubility of the microcapsules produced under the optimum conditions were 11.39 ± 0.35 g/100 g dry weight and 9.31 ± 0.78%, respectively. The optimized encapsulation process increased the water solubility of EA by 21.54 times compared to free EA. Microcapsules of EA produced under optimal conditions were evaluated through in vitro gastrointestinal digestion and compared with controls. Bifidobacterium pseudocatenulatum was used for microbial fermentation, and the conversion of EA to urolithins A and B was evaluated according to the microbial load and the length of the incubation time. Encapsulation was found to significantly enhance this biotransformation. The microcapsules were also characterized and tested under various storage conditions. PRACTICAL APPLICATIONS: Encapsulation of EA increases its stability and water solubility, making it a more effective bioactive compound. The study found that EA microcapsules produced under optimized spray-drying conditions significantly enhanced biotransformation to Uro-A and Uro-B when incubated with Bifidobacterium pseudocatenulatum. These results support the potential use of encapsulated EA in functional foods and dietary supplements to improve gut health and more effectively deliver bioactive compounds. Obtained results will be useful for science, food, and the nutraceutical industry.