At NIZO we have been working on the optimization of our in vitro technologies for the assessment of potential health benefits of plant extracts. In parallel, a small number of olive leaf extracts and pure polyphenols have already been tested.

We applied our Gut Health Discovery Platform (GHDP), starting with fecal batch fermentations in our MicroColon technology (Figure 1). Effects of extracts on gut microbiota composition and metabolism has been studied, as well as the potential of extracts to inhibit growth of the intestinal pathogen Clostridiodes difficile.

Figure 1

Overview of the Gut Health Discovery Platform (GHDP) aiming to contribute to the knowledge on, and selection of microbiome modulators.

So far, results show that microbial metabolism can be modulated as shown by pH and short-chain fatty acid (SCFA) analysis. Further, microbiota composition can be modulated as assessed by qPCR and microbiome analysis, and extracts/pure polyphenols are being metabolized as determined with our targeted UHPLC-MS/MS method (Figure 2). Notably, growth of the intestinal pathogen C. difficile was shown to be inhibited by the OPA 20% extract, while beneficial bifidobacteria were not affected.

Figure 2

Example of a UHPLC-MS/MS chromatogram, showing polyphenols (metabolites) peak assignments.

The connection to the host (Figure 1) was made by applying MicroColon spent culture medium (supernatant after microbial fermentation, containing all metabolites) to our in vitro cell culture model (Figure 3). So far, preliminary results showed protective effects of some extracts and pure polyphenols, and of MicroColon spent supernatant, on the recovery of intestinal barrier function.

Figure 3

Schematic representation of the in vitro cell culture model that combines immune cells with a tight intestinal epithelial layer, allowing to study effects of extracts and ferments on intestinal epithelial barrier integrity and immune responses.

In summary, a small selection of extracts and pure polyphenols shows potential beneficial effects on gut microbial fermentation, on intestinal epithelial barrier integrity, and on suppression of the intestinal pathogen C. difficile.

Within the consortium, more extracts and modifications thereof will become available soon, of which many will be assessed in these models.