Gut microbe fermentation of Moringa oleifera leaf extract increases measurable polyphenols and improves barrier function in a cell culture model

Authors: Kable, Mary; Storms, David; Alkan, Zeynep; MURIKI, MANEESHA - University Of California, Davis; DEVRIES, DANA - University Of California, Davis; WATERMAN, CARRIE - University Of California, Davis; Lemay, Danielle

Submitted to: MicrobiologyOpen
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/5/2025
Publication Date: 11/24/2025
Citation: Kable, M.E., Storms, D.H., Alkan, Z., Muriki, M., Devries, D., Waterman, C., Lemay, D.G. 2025. Gut microbe fermentation of Moringa oleifera leaf extract increases measurable polyphenols and improves barrier function in a cell culture model. MicrobiologyOpen. 14(6). Article e70068. https://doi.org/10.1002/mbo3.70068.
DOI: https://doi.org/10.1002/mbo3.70068

Interpretive Summary: We investigated the growth, ability to metabolize available sugars, and release of phenolic compounds from Moringa leaf water extract during fermentation by three common gut bacteria, Bifidobacterium longum, Bacteroides thetaiotaomicron, and E. coli. Our results showed that B. longum had the largest increase in total growth, the highest carbohydrate consumption, and highest production of soluble phenolic compounds out of the three bacteria tested. Further, B. longum M. oleifera fermentation products caused the greatest increase in intestinal cell barrier function in a cell culture model.

Technical Abstract: Background: Moringa oleifera (M. oleifera) is purported to mediate several nutritional and therapeutic benefits. However, there is limited research on whether these health benefits are mediated directly by the plant or through fermentation with intestinal microbes. Therefore, we set out to study the interaction between M. oleifera leaves and the human gut microbiota by focusing on three organisms, the abundance of which was previously shown to be affected by M. oleifera consumption in intervention studies. Methods: The three organisms of focus were Escherichia coli, Bifidobacterium longum, and Bacteroides thetaiotaomicron. Kinetic growth curves of E. coli, B. longum, and B. thetaiotaomicron were examined in the presence of increasing concentrations of M. oleifera in YCFA media with and without carbohydrates and short chain fatty acids (SCFAs). Anthrone and Fast Blue BB assays were conducted on spent media to measure carbohydrate and phenolic content, respectively, after fermentation by each microbe. Sterile fermentation supernatants were applied to an in vitro gut barrier model consisting of differentiated Caco-2 monolayers on permeable cell culture inserts and the transepithelial resistance (TEER) was measured. M. oleifera fermentations significantly increased TEER compared to glucose fermentations. Results: While it was hypothesized that components of M. oleifera, particularly phenolic acids, have inhibitory effects on E. coli, kinetic growth curve analysis demonstrated that all three bacterial isolates tested can grow in the presence of M. oleifera. However, B. longum had a greater increase in total growth, consumed more soluble carbohydrates, and produced more soluble polyphenols than the other two microbes in carbohydrate limited media, using M. oleifera extract as a sole carbohydrate source. Additionally, B. longum fermentation of both glucose and M. oleifera increased TEER in Caco-2 monolayers significantly more than E. coli fermentation of both carbohydrate sources (p=0.0007). Conclusion: Overall, these results suggest a potential mechanism through which consumption of M. oleifera promotes the growth of probiotic organisms within the human gut and influences health through interactions with the gut microbiome.