Solanum agrarium Sendtn. is popularly known in Northeastern Brazil as "gogóia". Previous work has verified the presence of the flavonoid kaempferol and showed the crude ethanolic extract from aerial parts of S. agrarium (SA-EtOH) to have non-selective antispasmodic effect on guinea-pig ileum. The aim was to isolate and identify the special metabolites and to investigate antispasmodic mechanism of SA-EtOH on guinea-pig ileum. From their aerial parts was isolated the flavonoid myricetin-3,7,3'-trimethyl ether. SA-EtOH shifted to the right cumulative concentration-response curves to carbachol or histamine in a reversible and non-competitive manner. SA-EtOH relaxed the ileum precontracted with 40 mM KCl (EC 50 =17.4±3.5 µg/ml), 10-6 M carbachol (EC 50 =119.4±24.3 µg/ml) or 10-6 M histamine (EC 50 =18.7±4.6 µg/ml). This is most likely due to the inhibition of calcium influx through voltage-gated calcium channels (Ca V). It was confirmed by SA-EtOH antagonizing CaCl 2-induced contractions in depolarizing medium nominally without Ca 2+ , with non-parallel shift of the concentrationresponse curves to the right and reduction of E max. The uncovering of SA-EtOH (EC 50 =187.2±27.3 µg/ml) inhibiting tonic contractions induced by S-(-)-BayK8644 suggests that Ca 2+ channel subtype involved is Ca V-L. In conclusion, SA-EtOH shows antispasmodic effect on guinea-pig ileum due, in part, to blockade of calcium influx through Ca V channels.
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