Microencapsulation studies to increase the bioavailability of ellagic acid from pomegranate peels

Pomegranate (Punica granatum L.) is a fruit rich in bioactive substances. Pomegranate is generally consumed as a fresh fruit, mostly by processing into fruit juice. Pomegranate peel, which is the waste of pomegranate juice processing, constitutes approximately 50% of the whole fruit, and there is a higher rate of ellagic acid in this waste compared to the pomegranate itself. It has been determined that ellagic acid, a polyphenolic compound, is an effective component in the treatment of various diseases such as cancer, diabetes, autoimmune and cardiovascular diseases, obesity and neurodegenerative disorders due to oxidative stress. It has been observed that in vivo and in vitro studies with ellagic acid are not compatible with each other, and the reasons for this compound's low solubility in water, limited absorption, and differences in biological activity depending on the difference in microflora between individuals have been stated. Studies have shown that ellagic acid is metabolized by colonic microflora into compounds called urolithin, and it has been suggested that urolithin and its derivatives are responsible for its potential health effects. As a matter of fact, it has been determined that urolithins have effects against neurodegenerative and cardiovascular disorders, including antioxidant, estrogenic, anti-inflammatory and anticarcinogenic properties. In this study, it was aimed to increase the water solubility of pomegranate-derived ellagic acid by microencapsulation with carriers of different polarities and emulsion capacities, and to increase its bioavailability by metabolizing it by probiotic microorganisms in the lower digestive tract and converting it to urolithins. In order to increase the bioavailability of ellagic acid, carrier material concentration and inlet air temperature were chosen as independent variables in the optimization of the microencapsulation process performed with the spray drying system. A mixture of arabic gum, maltodextrin and inulin was used as carrier material. The limit values of the air inlet temperature were determined as 130-190 °C and powder microcapsules were produced. The optimum carrier concentrations to be used and the inlet temperature were calculated and verified based on the percent water solubility and ellagic acid concentration of the microcapsules. As a result, the optimum carrier materials and ratios were found to be 20% maltodextrin and 10% inulin, and the optimum inlet temperature was 158°C. In addition, it was concluded that the presence of β-cyclodextrin (β-SD) at a rate of 1.5% should be within optimum conditions. Microcapsules produced in the determined optimum formulation were subjected to in vitro digestion tests in the gastrointestinal tract together with control samples, and microbial fermentation of Bifidobacterium pseudocatenulatum and ellagic acid was performed. Conversion and post-conversion concentrations of commercial ellagic acid and microencapsulated ellagic acid to urolithin A and urolithin B were compared. In addition, ellagic acid microcapsules in powder form produced under optimum conditions were stored at two different temperatures, 4ºC and 25ºC for 45 days, and changes in the physicochemical properties of the product (moisture, water activity, solubility) were analyzed on the 0th, 15th, 30th and 45th days of storage. , bulk density, compacted density, total phenolic substance, antioxidant activity, ellagic acid, color). The ellagic acid content and percent solubility values of ellagic acid microcapsules produced under optimum conditions were determined as 12.77 g/100g DM and 10.77%, respectively. The ellagic acid amounts of the microcapsules varied between 12.77-10.40 g/100g and their solubility ratios varied between 10.77% and 7.11% during storage at two different storage temperatures. According to the results of the research, it was observed that the water solubility value of the ellagic acid microcapsules obtained by the encapsulation technique applied under optimized conditions in order to increase the bioavailability of ellagic acid increased 21.54 times compared to the commercial ellagic acid. It was determined that this solubility increase increased the release of encapsulated ellagic acid in the model stomach and intestinal system 1.74 times compared to commercial ellagic acid. As a result of incubation with ellagic acid microcapsules produced under optimum conditions in the presence of commercial ellagic acid in the presence of B. pseudocatenulatum, ellagic acid was transformed into urolith A and urolith B at different levels, depending on the incubation time and the microbial load of B. pseudocatenulatum. With the encapsulation approach of ellagic acid, which supports its water solubility, this conversion is markedly increased.