Fermented licorice extract alleviates ulcerative colitis by inhibiting the TLR4/NF-κB pathway and rebuilding intestinal microbiota in mice

Abstract

There was limited research on investigating the suitable lactic acid bacteria genera for fermentation of on licorice extract and studying the effects of the fermentation products on ulcerative colitis (UC). The purpose of this study was to preliminarily investigate the therapeutic effects of licorice extract fermented by probiotic Lactobacillus plantarum ZKLp100 on UC and its underlying mechanisms. Therefore, time-of-flight mass spectrometer (TOF-MS), Western blot, immunohistochemical and 16S rRNA sequencing were performed. Results shown that Lactobacillus plantarum ZKLp100 exhibited strong tolerance to acid and bile salts and antibacterial capabilities. The optimal conditions for fermenting licorice extract involved an inoculum of ZKLp100 at 3.2 × 108 CFU/mL, licorice extract concentration of 75%, yeast extract addition of 0.4%, fermentation duration of 20 h, resulting in a viable bacterial count of 4.0 × 108 CFU/mL. Fermentation by Lactobacillus plantarum ZKLp100 significantly enhanced the proportion of beneficial components in licorice extract. Fermented licorice extract significantly alleviated clinical symptoms (P < 0.05), inflammation (P < 0.05), oxidative stress (P < 0.05), and intestinal damage (P < 0.05), while rebuilt the intestinal microbiota in UC mice. Mechanistic study revealed that fermented licorice extract significantly inhibited the activation of toll-like receptor 4 (TLR4)/nuclear factor-κB (NF-κB) pathway in colon tissues (P < 0.05). Additionally, under equivalent concentrations, the therapeutic efficacy of fermented licorice extract was significantly superior to that of licorice extract (P < 0.05). In conclusion, licorice extract fermented by Lactobacillus plantarum ZKLp100 alleviated UC by inhibiting the TLR4/NF-κB pathway and rebuilding intestinal microbiota in mice.