No abstract

Methanolic extracts from dried fruits, roots and nutgalls of Piper longum, P. sarmentosum, Quercus infectoria respectively, were examined for their spasmolytic activities using isolated rat or guinea pig ileums and compared with a reference antidiarrheal drug (loperamide) and an L-type calcium channel blocker (verapamil). Isolated rat ileums were contracted by acetylcholine (ACh, 10 µM) and serotonin (5HT, 3 µM), while guinea pig ileums were contracted by histamine (Hist, 1 µM). Prior application of P. longum, P. sarmentosum and Q. infectoria extracts into the bathing solution, the contraction-induced by ACh, 5HT and Hist were concentration-dependently inhibited with the IC 50 of 91, 6, 54 µg/mL; 88, 13, 44 µg/mL and 343, 36, 377 µg/mL, respectively. Loperamide and verapamil exhibited similar pattern of inhibitions with IC 50 of 0.61, 0.89, 0.42 µg/mL and 0.44, 0.15, 0.70 µg/mL respectively. All extracts and both drugs also suppressed the contractionevoked by KCl (30 mM) in rat ileums and caused the rightward shift of concentration-response curves of CaCl 2-induced contractions of guinea pig ileums in a concentration-dependent manner. It is known that the contraction-induced by agonists and KCl are mainly due to calcium influx through L-type calcium channels which opened indirectly and directly by agonist-receptor activation and KCl respectively. Thus, it is concluded that the spasmolytic activities of all extracts may occur mainly through interruption of calcium influx via voltage-gated channels. The order of potency is P. longum = P. sarmentosum > Q. infectoria. However, they are less potent than loperamide and verapamil.