Bioavailiability of L. nobilis leaf polyphenols encapsulated by spray-drying

In recent times, increasing evidence has demonstrated that polyphenols, secondary plant metabolites, can be utilized by the gut microbiota which results in promising effects in the prevention and treatment of various diseases such as diabetes, obesity, autoimmune diseases, inflammatory bowel disease, colorectal cancer and other. Laurus nobilis L. is an evergreen Mediterranean shrub whose leaves have traditionally been used in folk medicine due to their beneficial health effects that can largely be attributed to the presence of polyphenols which include flavonoids, phenolic acids, tannins and lignans. Since polyphenols are unstable which limits their biological activities and aggravates the process of studying their association with gut microbiota, encapsulation technologies focused on protection against unfavorable conditions in the stomach are emerging. Microencapsulation by spray- drying is the most commonly used method for encapsulating bioactive molecules in which the liquid extract with the dissolved carrier is passed through a stream of hot air during which the solvent evaporates and a powder with bioactive molecules encapsulated in the protective coating of the carrier is formed. In the present study, hydroalcoholic (70% ethanol) extract of L. nobilis leaf polyphenols was encapsulated by spray-drying on Büchi Mini Spray-Dryer B-290 at 180°C using three different carriers (β-cyclodextrin ; β- cyclodextrin:maltodextrin (50:50) ; β- cyclodextrin:gum arabic (50:50)) at a ratio 1:2 (extract dry matter:carrier). The obtained powders were subjected to in-vitro simulated digestion and three phases (gastric, absorbed and intestinal) were analyzed by Folin-Ciocalteu spectrophotometric method for total phenolic content (TPC). The TPC in the intestinal phase, which is considered as bioavailable for the gut microbiota, ranged from 46.9–54.5% compared to the TPC in initial powders prior to digestion. β- cyclodextrin:maltodextrin (50:50) resulted in highest, and β-cyclodextrin:gum arabic in lowest bioavailability. The integrity of individual polyphenols present in the intestinal phase was confirmed by ultra-high performace liquid chromatography tandem mass spectrometry (UPLC/MS- MS).