Effect of Lactobacillus casei fermented Senna tora L. seeds and its active compound via muscarinic M3 signaling on the improvement of intestinal function in rats

We previously reported the potential of Senna tora L. seeds fermented by Lactobacillus casei (FSL) as a laxative agent in a loperamide-induced constipation rat model. Here, we examine the mechanism of action of FSL and its bioactive compound, revealed herein, on loperamide-induced constipation Sprague Dawley rat model. We identified the compound aurantio-obtusin (AO) using HPLC quantitative analysis. Rats were randomly assigned to six experimental groups (eight rats each)-normal and constipated groups (loperamide, FSL [100, 300, 500 mg/kg], and AO [1 mg/kg]). The FSL and AO-treated group showed an increase in the frequency, amount, and water content of feces in the constipated rat. Moreover, FSL and AO increased the intestinal transit speed in the constipated rat. Histological analysis revealed that FSL and AO recovered the intestinal mucus, the number of goblet cells, as well as thickness of the mucosa layer and muscle. Furthermore, the protein levels of the muscarinic acetylcholine receptor M3, which is involved in intestine contraction, were recovered in the FSL and AO-treated group. Its downstream signaling pathway (p-protein kinase C) was recovered by FSL and AO treatment. In conclusion, fermentation of S. tora L. seeds increases AO, which improves intestinal function, indicating that FSL is effective for treating constipation.