Rosmarinic acid alleviates colitis and repairs mucus barrier damage in a gut microbiota-dependent manner, as transplanting fecal microbiota from RA-pretreated donors alleviated colitis while direct oral administration to pseudo-germ-free mice did not produce protective effects.
Key Findings
Results
Fecal microbiota transplantation (FMT) from RA-pretreated donor mice into pseudo-germ-free colitis recipients significantly reduced disease activity.
FMT from high-dose RA-treated donors produced a 52% reduction in the disease activity index (DAI) score compared to DSS controls.
Recipient mice showed improved histological scores alongside the reduction in DAI.
Serum pro-inflammatory cytokines IL-6 and TNF-α were markedly lower in FMT recipients.
mRNA expression of anti-inflammatory cytokines IL-10 and IL-25 was upregulated in recipient mice.
Pseudo-germ-free mouse models and FMT methodology were used to isolate the role of gut microbiota.
Results
The colonic mucus barrier was substantially restored in pseudo-germ-free mice receiving FMT from RA-pretreated donors.
Goblet cell numbers increased approximately 5-fold in the RH-FMT group compared to the DSS group.
Mucus coverage rose from 5.24% in the DSS group to 35.4% in the RHF (high-dose RA FMT) group.
mRNA levels of tight junction proteins and mucins, including ZO-1 and MUC1, were elevated in recipient mice.
These mucus barrier improvements were observed following microbiota transfer rather than direct RA administration.
Results
Short-chain fatty acid (SCFA) levels were substantially recovered in FMT recipient mice.
Total SCFAs increased by approximately 130.77% in FMT recipient mice compared to DSS controls.
SCFA recovery was associated with microbiota transfer from RA-pretreated donors.
SCFA levels were positively correlated with expression of genes involved in mucus barrier and tight junction function.
Results
Gut microbiota composition was remodeled in FMT recipient mice, with increases in beneficial bacteria and decreases in harmful bacteria.
Beneficial bacteria including Akkermansia and Limosilactobacillus increased in recipient mice following RA-donor FMT.
Harmful bacteria including Proteobacteria and Klebsiella decreased in recipient mice.
Abundance of SCFA-producing beneficial genera—including Akkermansia, Limosilactobacillus, and Blautia_A—was significantly positively correlated with mucus barrier gene expression and SCFA levels.
Results
Direct oral administration of rosmarinic acid to pseudo-germ-free mice did not produce protective effects against colitis.
Neither high nor low doses of RA administered orally to pseudo-germ-free mice produced the anti-colitis protective effects seen with FMT.
This finding demonstrates that the gut microbiota is critically required for RA's protective mechanism.
The pseudo-germ-free model was used specifically to isolate the contribution of gut microbiota from direct drug effects.
This result establishes that RA's benefits are microbiota-dependent rather than a direct action of the compound on host tissues.
Conclusions
Rosmarinic acid alleviates colitis through mucus barrier repair and modulation of SCFA metabolism in a process that critically depends on gut microbiota.
The study used both pseudo-germ-free models and FMT to establish microbiota dependency.
Correlation analysis linked SCFA-producing beneficial genera with mucus barrier gene expression and SCFA levels.
The mechanism involves remodeling of gut microbiota composition, restoration of SCFA production, and subsequent repair of the colonic mucus barrier.
RA's protective effects were transferable via microbiota transplantation but not reproducible by direct drug administration in the absence of a normal microbiome.
What This Means
This research suggests that rosmarinic acid (RA), a natural compound found in herbs like rosemary and basil, can protect against colitis (colon inflammation) — but only when the gut's community of bacteria (the microbiome) is present. Using mice with antibiotic-depleted gut bacteria, researchers showed that giving RA directly to these mice did not reduce colitis symptoms. However, when fecal bacteria from RA-treated healthy mice were transplanted into sick mice with depleted microbiomes, the colitis was significantly reduced, inflammation markers dropped, and the protective mucus lining of the colon was largely restored.
The transplanted microbiota produced several measurable benefits: goblet cells (which produce protective mucus) increased nearly five-fold, mucus coverage of the colon rose from about 5% to over 35%, and levels of short-chain fatty acids (SCFAs) — beneficial compounds produced by gut bacteria that help maintain gut health — increased by over 130%. Beneficial bacterial species like Akkermansia and Limosilactobacillus became more abundant, while harmful bacteria like Klebsiella decreased. The abundance of these SCFA-producing bacteria was strongly correlated with improved gut barrier function.
This research suggests that rosmarinic acid does not act directly on the gut lining to provide its anti-inflammatory benefits; instead, it works by reshaping the gut microbiome into a healthier composition, which in turn produces the compounds and signals needed to repair the intestinal mucus barrier. These findings have implications for understanding how dietary compounds influence gut health through the microbiome rather than through direct biological action, and may inform future strategies using diet or natural compounds to manage inflammatory bowel conditions.
Liang S, Peng S, Zhao Y, Liang W, Yu J, Zhang L, et al.. (2026). Rosmarinic acid alleviates colitis and repairs mucus barrier damage in a gut microbiota-dependent manner.. Food & function. https://doi.org/10.1039/d6fo03083a