Characterisation of an extract from the leaves of Cissampelos sympodials Eichl. on the spontaneous tone of isolated trachea

An aqueous fraction of the ethanol extract of the leaves (AFL) of Cissampelos sympodialis Eichl. (Menispermaceae) was shown to relax the spontaneous tone of guinea-pig tracheal smooth muscle rings with an IC50 of 20.5 μg/mL. The AFL inhibited cyclic nucleotide phosphodiesterase activity in isolated smooth muscle homogenates and stimulated an increase in intracellular cAMP synthesis in intact cultured smooth muscle cells. A complete inhibition of phosphodiesterase activity in isolated homogenates was almost achieved. These studies indicate that the AFL contains a substance which is a non-selective, but highly potent inhibitor of phosphodiesterase activity. This probably accounts for its effect on the spontaneous tone of guinea-pig tracheal smooth muscle.