Ethanol Extract of Glycyrrhiza uralensis Fisch: Antidiarrheal Activity in Mice and Contraction Effect in Isolated Rabbit Jejunum.

Objective: To evaluate the antidiarrheal effect of ethanol extract of Glycyrrhiza uralensis Fisch root (GFR) in vivo and jejunal contraction in vitro. Methods: In vivo, 50 mice were divided into negative control, positive control (verapamil), low-, medium- and high-dose GFR (250, 500, 1,000 mg/kg) groups by a random number table, 10 mice in each group. The antidiarrheal activity was evaluated in castor oil-induced diarrhea mice model by evacuation index (EI). In vitro, the effects of GFR (0.01, 0.03, 0.1, 0.3, 1, 3, and 10 g/L) on the spontaneous contraction of isolated smooth muscle of rabbit jejunum and contraction of pretreated by Acetylcholine (ACh, 10 µmol/L) and KCl (60 mmol/L) were observed for 200 s. In addition, CaCl₂ was accumulated to further study its mechanism after pretreating jejunal smooth muscle with GFR (1 and 3 g/L) or verapamil (0.03 and 0.1 µmol/L) in a Ca²⁺-free-high-K⁺ solution containing ethylene diamine tetraacetic acid (EDTA). Results: GFR (500 and 1,000 mg/kg) significantly reduced EI in castor oil-induced diarrhea model mice (P<0.01). Meanwhile, GFR (0.01, 0.03, 0.1, 0.3, 1, 3, and 10 g/L) inhibited the spontaneous contraction of rabbit jejunum (P<0.05 or P<0.01). Contraction of jejunums samples pretreated by ACh and KCl with 50% effective concentration (EC₅₀) values was 1.05 (0.71–1.24), 0.34 (0.29–0.41) and 0.15 (0.11–0.20) g/L, respectively. In addition, GFR moved the concentration-effect curve of CaCl₂ down to the right, showing a similar effect to verapamil. Conclusions: GFR can effectively against diarrhea and inhibit intestinal contraction, and these antidiarrheal effects may be based on blocking L-type Ca²⁺ channels and muscarinic receptors. [ABSTRACT FROM AUTHOR]