The presence of cholinomimetic and calcium channel antagonist constituentsin Piper betle Linn.

The crude aqueous extract of Piper betle leaves (Pb.Cr) was studied for the possible presence of cholinomimetic and calcium channel antagonist constit uents. Pb.Cr at doses of 1-10 mg/mL, caused a moderate spasmogenic effect i n isolated guinea-pig ileum and this activity was concentrated in the aqueo us fraction, which was found to be about 5 times more potent. Pretreatment of the tissue with atropine (1 mu M) but not hexamethonium (100 mu M) compl etely abolished the contractile effect of the aqueous fraction indicating a cholinergic (muscarinic) mechanism. In isolated rabbit jejunum preparation s Pb.Cr did not produce a significant increase in the spontaneous contracti ons, but instead produced a dose-dependent (0.03-3.0 mg/mL) inhibition of s pontaneous activity. Activity-directed fractionation revealed that the spas molytic action was concentrated in the ethyl acetate fraction. When tested against K+-induced contractions, both Pb.Cr and its ethyl acetate fraction (Pb.EtAc) caused a dose-dependent inhibition, suggesting calcium channel bl ockade (CCB). The potent CCB effect of the crude extract and its ethyl acet ate fraction was confirmed when pretreatment of the tissue with Pb.Cr or Pb .EtAc shifted the Ca++ dose-response curves to the right in a dose-dependen t manner. These data indicate that the plant contains cholinomimetic and po ssible calcium channel antagonist constituents, which are concentrated in t he aqueous and ethyl acetate fractions respectively. It is suggested that s ome of the traditional uses of this plant may be explained on the basis of these activities. Copyright (C) 2000 John Wiley & Sons, Ltd.