A consists of berberine chloride and an extract from geranium herb. To clarify mechanisms of the antidiarrheal effect of Phelloberin-A, we investigated the astringent action by determining its binding activity to rabbit hemoglobin and effects on active transport, which was indicated by short-circuit current (Isc), in rat jejunum by the Ussing chamber technique. The effects of berberine chloride and geranium herb on both the binding activity to hemoglobin and the electrophysiological parameters such as Isc were compared with those of the antidiarrhoeicas, tannic acid, albumin tannate and bismuth subnitrate. Geranium herb, tannic acid and bismuth subnitrate increased significantly the binding activity to hemoglobin at concentrations of > 1 mg/ml, > 0.3 mg/ml and 10 mg/ml, respectively, but berberine or albumin tannate did not. Geranium herb and tannic acid dose-dependently and moderately increased Isc in rat jejunal mucosa and the increase became significant at a concentration of 10 mg/ml. Neither berberine chloride, albumin tannate nor bismuth subnitrate affected Isc. In contrast, cholera toxin, which increases the secretion from intestinal mucosa to the lumen and induces diarrhea, decreased Isc at a concentration of 0.1 mg/ml. The decrease of Isc induced by cholera toxin was antagonized by pretreatment with geranium herb (10 mg/ml), indicating that geranium herb inhibited the toxin-induced increase in secretion. These results suggest that geranium herb possesses an astringent action and moderately increases Isc across the intestinal mucosa. Therefore, the effects may support an antidiarrheal effect of both geranium herb and Phelloberin-A.
