Gut microbiota liberate matrix-embedded ellagic acid from strawberry soluble fiber and convert it to urolithins, expanding the celobiotic concept and highlighting microbiota-mediated release of hidden phytochemicals from dietary fibers.
Key Findings
Results
Untargeted metabolomics of in vitro colonic fermentation of strawberry soluble fiber (SSF) identified urolithin C/iso-urolithin C, suggesting microbial liberation of ellagic acid (EA) embedded in the SSF matrix.
SSF was studied as a reservoir of celobiotics (phytochemicals bound to dietary fiber).
Urolithin C/iso-urolithin C is described as a gut microbial metabolite derived exclusively from EA.
Detection of this metabolite implied that EA was released from SSF during fermentation and then metabolized.
Results
Pectinase treatment of SSF increased total EA equivalents by approximately 10-fold, supporting the hypothesis that EA is hidden within the fiber matrix.
Pectinase treatment was used to validate the metabolomics-based hypothesis of matrix-embedded EA.
The abstract reports an increase of approximately 10-fold in total EA equivalents.
Results
Time-course fermentation showed rapid EA liberation from SSF followed by conversion to urolithins.
Fermentation was performed in vitro with gut microbiota.
The sequence observed was release of EA from SSF and then its subsequent urolithin conversion.
Results
EA liberation from SSF and urolithin production were confirmed in vivo in human-microbiota-transplanted mice after SSF consumption.
Mice harbored transplanted human gut microbiota.
The in vivo findings corroborated the in vitro fermentation results.
Results
Human fecal microbiota showed substantial interindividual variation in their capacity to release EA and produce urolithins.
Variation was observed across human fecal microbiota samples in both EA release and urolithin production.
This suggests the microbiota composition influences the extent of celobiotic release and metabolism.
Discussion
EA is widely distributed among plant-derived dietary fibers and is particularly abundant in berry fibers.
This indicates that microbial release of EA is likely not limited to strawberry fiber.
The work expands the celobiotic concept and emphasizes microbiota-mediated release of hidden phytochemicals from dietary fibers.
What This Means
This study looked at the soluble fiber in strawberries and asked whether it carries hidden plant compounds that gut bacteria can release. Using lab models of the human colon, the researchers found a bacterial by-product (urolithin C/iso-urolithin C) that can only come from ellagic acid, a plant compound. This suggested ellagic acid is locked inside the fiber and freed by gut microbes. Treating the fiber with the enzyme pectinase increased measurable ellagic acid about 10-fold, supporting this idea.
Fermentation over time showed that ellagic acid was released quickly from the fiber and then converted by microbes into urolithins. The same process was seen in mice carrying human gut microbiota after they consumed the strawberry fiber. However, people's gut microbiota differed substantially in how well they released ellagic acid and made urolithins.
This research suggests that dietary fibers, especially those from berries, may deliver beneficial compounds that are only unlocked by gut microbes, and that the extent of this may differ from person to person. The findings come from lab and mouse models, so they do not directly show health effects in people.
Zhou Z, Fang Y, Luo M, Du H, Guo X, Chen Y, et al.. (2026). Gut Microbiota-Mediated Liberation of Ellagic Acid from Strawberry Soluble Fiber and Its Metabolism: In Vitro and In Vivo Evidence.. Journal of agricultural and food chemistry. https://doi.org/10.1021/acs.jafc.6c07831