Stability of Sumac (Rhus coriaria) Polyphenolic Extract during Simulated Gastrointestinal Digestion and Colonic Fermentation
Abstract
The effects of Sumac (Rhus coriaria) polyphenolic extract were evaluated against common pathogenic and probiotic bacteria. The bacteria were individually treated with free sumac (free Su) and encapsulated sumac (NPSu) polyphenols. It was hypothesized that the encapsulated particles would have a higher engagement and interaction potential with the chemical constituents within the bacteria cell wall structure. The factors influencing the disruption of the membrane and eventually death of the bacteria were investigated. To assess the antibacterial properties attributed to sumac polyphenols, three Gram-positive and three Gram-negative bacteria were chosen and treated with free Su and NPSu ethanolic extracts. The antibacterial activity against all tested bacteria was increased as the concentration of polyphenols elevated; however, the samples exhibited different antibacterial properties. While free sumac extract showed a higher bacterial growth inhibition property against Gram-positive bacteria compared to that of Gram-negative bacteria, the encapsulated extract exhibited an opposite trend and behavior. The antibacterial activity in encapsulated samples was also higher against all tested bacteria compared to that of free samples. The stability and release profile of encapsulated samples were evaluated under different pH conditions to simulate the pH in the oral, gastric, and intestinal environments. The stability of encapsulated particles was increased with lowering the pH values. The stability was tested using a membrane dialyzing assay followed by UV-V analysis. pH 2.5 exhibited the highest stability compared to other pH conditions being tested. The samples were also exposed to different gastric juices with similar chemical compositions as the human gastrointestinal tract. In addition to the gastrointestinal chemically simulated conditions, the samples were used as treatments for probiotic bacteria as a representative of human gut microbiota. The results indicated that the Lactobacillus plantarum strain was able to produce low molecular weight tannin metabolites. However, the production of metabolites was higher when the tested bacteria were treated with nanoparticle sumac extracts. Encapsulation of sumac polyphenolic extracts may lower the rate of tannin degradation during simulated gastrointestinal digestion. The Pluronic-based nanoparticles’ lower stability to the pH prevailing intestinal compartment may dissociate the chemical binding between galloylated compounds with Pluronic polymers.
Citation
Hashemi, Mehdi (2022). Stability of Sumac (Rhus coriaria) Polyphenolic Extract during Simulated Gastrointestinal Digestion and Colonic Fermentation. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /197279.