Introduction and objective:
Irritable bowel syndrome (IBS) is a chronic functional gastrointestinal disorder characterized by recurrent disturbances in bowel habits and abdominal discomfort. Modulation of the gut microbiota and oxidative balance using plant-derived metabolites represents a promising supportive strategy for functional gastrointestinal disorders. The aim of this study is to evaluate the in vitro biological activity and cytocompatibility of the herbal mixture B9 supplemented with whey protein in the context of intestinal health.

Material and methods:
The phenolic profile of the B9 extract was characterized using UHPLC-ESI-MS/MS and included ellagic acid, gallic acid, chebulanin, chebulic acid, corilagin, and quercetin. Antioxidant activity was assessed using the DPPH assay; the B9 preparation exhibited strong radical scavenging activity (EC50 = 4.13 µg/mL), nearly six times higher than butylated hydroxytoluene (BHT) and comparable to Trolox. Antioxidant effects were further evaluated by measuring protein carbonyl group levels in Enterococcus faecalis ATCC 29212. Cytocompatibility was assessed by measuring the metabolic activity of normal intestinal epithelial cells (CCD 841 CoTr) using the MTT assay.

Results:
The B9 preparation significantly reduced protein carbonyl levels in E. faecalis, indicating antioxidative activity. Co-treatment with whey increased metabolic activity of intestinal epithelial cells, with the strongest effects observed at 3.0% and 5.0% (v/v) of the B9 extract combined with 7.5% (v/v) of whey, indicating good cytocompatibility.

Conclusions:
In conclusion, the B9 herbal preparation enriched with whey exhibits pronounced antioxidant activity and favourable cytocompatibility toward normal intestinal epithelial cells in vitro, supporting its further investigation in the context of intestinal health and functional gastrointestinal disorders such as IBS.