# Probiotic-Driven Metabolic Transformation in Dark Tea: Enhanced Bioactives and Gut Microbiota Modulation Underlie Its Alleviation Effect Against Constipation

## TL;DR

Fermented dark tea with a probiotic helps relieve constipation better than regular dark tea by changing gut bacteria and boosting helpful compounds.

## Contribution

The study reveals that probiotic fermentation enhances dark tea's anti-constipation effects through gut microbiota modulation and bioactive compound transformation.

## Key findings

- Fermented dark tea (FDT) improved constipation symptoms more effectively than non-fermented dark tea (DT) in mice.
- FDT increased beneficial gut bacteria like Lactobacillus and reduced harmful Prevotellaceae_UCG-001.
- FDT's fermentation enriched bioactive compounds like cyclic dipeptides and hydroxylated linoleic acid derivatives.

## Abstract

Constipation is a widespread gastrointestinal condition with complex causes and limited therapeutic efficacy of current treatments. Probiotics and natural-function foods like dark tea (DT) have emerged as promising alternatives. We investigated the protective effects of dark tea (DT) and Lactiplantibacillus paracasei K34-fermented dark tea (FDT) against constipation induced by loperamide (LOP) in mice. FDT exhibited a superior effect over DT in alleviating constipation, as evidenced by increased fecal water content, reduced defecation time, and accelerated small intestinal transit. FDT also restored serum gastrointestinal neurotransmitters and repaired intestinal barrier damage more effectively. FDT intervention significantly increased the richness and altered the composition of gut microbiota, notably elevating Lactobacillus, Ligilactobacillus, and Actinobacteria, while reducing Prevotellaceae_UCG-001. Correlation analysis linked these microbial shifts with improved motility and anti-inflammatory responses. Untargeted metabolomics indicated that fermentation drastically enriched key bioactive compounds in FDT compared to DT, including cyclic dipeptide (cyclo-(Gly-Pro), 132.4-fold) and hydroxylated linoleic acid derivatives (N-(17-hydroxy-9,12-octadecadienoyl)-glutamine, 123.8-fold). KEGG pathway analysis suggested fermentation upregulated tryptophan metabolism and branched-chain amino acid biosynthesis, while downregulating flavone biosynthesis. Collectively, probiotic fermentation enhances the anti-constipation efficacy of DT, which is achieved via a synergistic mechanism involving neuroendocrine modulation, intestinal barrier repair, gut microbiota composition, and transformation of bioactive metabolites.