Milk thistle extract showed antioxidant properties and protective effect on the gut barrier function in a porcine in vitro model

Milk thistle (Silybum marianum) is known for its broad range of positive properties in human and animal health and especially as hepatoprotective substance [1].

In our study, we investigated an ethanolic (70%) milk thistle (MT) extract for its effect on gut barrier integrity and against the formation of reactive oxygen species (ROS) in a porcine intestinal epithelial cell line (IPEC-J2). Differentiated IPEC-J2 were grown in non-coated Transwell® membrane inserts (1.12 cm²; 0.4 µm pore size) for 7 days, allowing the formation of tight junctions (TJs) and the build-up of a representative intestinal monolayer. On day 7, cells were pre-treated with an ethanolic MT extract, followed by addition of a stressor substance on day 8. The barrier integrity was examined by measuring the transepithelial electrical resistance (TEER) by a Volt-Ohm-Meter after 24h, 48h, and 72h of incubation. With the help of a fluorescence assay (DCFH-DA assay), the cellular ROS amount, which is indicative for increased oxidative stress, was determined. Therefore, hydrogen peroxide (H₂O₂) was used to increase the ROS amount. Then the MT extract was added to counteract the negative effect of H₂O₂.

The non-toxic concentration of 500 µg/mL MT extract increased the stressor-impaired TEER value by 11% (24h incubation) and 7% (48h incubation), respectively. Even compared to the cell control, MT could increase the TEER value by 3 – 10%. In the DCFH-DA assay, 4 µg/mL MT extract reduced the H₂O₂-induced (set to 100%) ROS amount by 12% after 1h of incubation.

MT extract has been shown to act positively on the gut barrier integrity and the antioxidant status. The latter was the most effective parameter considering the applied low concentration in the DCFH-DA assay.