Antidiarrheal effect of the ethanol extract from Scutellaria barbata and its effect on the contraction of jejunum smooth muscles

Scutellaria barbata (S. barbata), a traditional herbal medicine used in southern China, possesses anti-inflammatory, antitumor, spasmolytic and expectorant effects. However, there are not many recent studies on its gastrointestinal effects. This study aimed to evaluate the antidiarrheal effect of the ethanol extract of S. barbata (SBE) and its effect on the isolated jejunum smooth muscle.

Methods: The antidiarrheal effect of SBE (doses: 125, 250 and 500 mg/kg) on castor oil-induced diarrhea was investigated in vivo. The effect of SBE (0.01-10 mg/mL) on spontaneous or acetylcholine chloride (ACh, 10μM)/KCl (60mM)-induced contraction of isolated rabbit jejunum smooth muscle was examined in vitro. The possible spasmolytic mechanism of SBE (1 and 3mg/mL) was analyzed by accumulating CaCl₂ in a Ca²⁺-free high-K⁺ (60mM) solution.

Results: SBE (125, 250 and 500mg/kg) could delay the initial semi-solid onset time of mice and also reduce the diarrhea index in vivo. Furthermore, SBE (0.01-10mg/mL) could alleviate the spontaneous or ACh/KCl-induced contraction in vitro. SBE (1 and 3mg/mL) also inhibited the contraction induced by CaCl₂, and the concentration-response curves of CaCl₂ moved downward and to the right, similar to those of verapamil (0.01 and 0.1μM).

Conclusions: SBE exerts antidiarrheal and spasmolytic effects, which provides a pharmacological basis for its use in functional gastrointestinal disorders.