Pharmacological basis for the use of peach leaves in constipation

The aqueous crude extract (PPL.Cr) of peach leaves (Prunus persica) was studied for the possible presence of gut stimulatory constituent(s) to rationalize the folkloric use of the plant in constipation. PPL.Cr at the dose of 1-10 mg/ml caused a moderate degree of spasmogenic effect in isolated guinea-pig ileum. Pretreatment of the tissue with atropine (1 M) completely abolished the contractile effect of the plant extract similar to that of acetylcholine which is suggestive of a cholinergic mechanism. In isolated rabbit jejunum preparations, PPL.Cr produced a week spasmogenic effect followed by relaxation of the spontaneous contractions at higher doses. Bioassay-directed fractionation revealed that the spasmogenic activity was separated in the aqueous fraction, while the spasmolytic activity was concentrated in the ethyl acetate fraction. When tested against K(+)-induced contraction, both PPL.Cr and its ethyl acetate fraction (PPL.EtAc) caused a dose-dependent inhibition, suggesting calcium channel blockade (CCB). The presence of CCB in peach leaves was confirmed when pretreatment of the tissue with PPL.EtAc caused a dose-dependent rightward shift in the Ca(2+) dose-response curves, similar to that produced by verapamil. These data indicate that the plant contains spasmogenic (cholinomimetic) and spasmolytic (calcium antagonist) constituents, which are concentrated in the aqueous and ethyl acetate fractions, respectively. Furthermore, the laxative effect of the plant reported in the traditional system of medicine may be partially due to the cholinergic action, which was dominant over the spasmolytic component.