Anti‐inflammatory effects of bay laurel (<i>Laurus nobilis</i> L.) towards the gut microbiome in dextran sodium sulfate induced colitis animal models

Abstract

Bay laurel (<i>Laurus nobilis</i> L.) contains active antioxidative phenolic components that are beneficial to human health. However, none was examined and reported utilizing health effects related to inflammatory bowel diseases (IBD) mainly ulcerative colitis (UC) in correlation to gut microbiota (GM). Thus, the current study aimed to investigate the impacts of bay leaves on UC albino rats targeting on the GM composition and their metabolites production (i.e., short-chain fatty acids; SCFAs) for improving the gut barrier functions. UC models were induced by supplementing 5% DSS into their drinking water. The models were then divided randomly for the diet with 1%, 2%, and 3% of bay leaves, as well as two control studies (positive and negative). Colon-to-body weight ratio was used as an indicator for the presence of edema tissue. From the collected fecal samples at 0, 24 h, and final day, the population changes of gut microbiota (<i>Lactobacillus</i>, <i>Bifidobacteria</i>, <i>Clostridium</i>, and sulfate-reducing bacteria) and SCFAs production were evaluated using fluorescence in situ hybridization (FISH) and gas-liquid chromatography (GC). The colon-to-body weight ratio of the rat models consuming 2% and 3% bay leaves was found to be significantly lower with better recovery of colonic function. Models consuming 3% bay leaves showed the best treatment effects on GM compositions; promoting the growth of <i>Bifidobacteria</i> and <i>Lactobacillus</i> in addition to producing high butyric acid levels<i>.</i> Meanwhile, the number of <i>Clostridium</i> and SRB was significantly reduced. Conclusively, consuming bay leaves brought significant colon health benefits other than stimulating appetite for a better taste.