Spasmolytic activity of Artemisia copa aqueous extract and isolated compounds.

Artemisia copa Phil. (Compositae) is used in popular medicine as a digestive and for gastric pains. The effects of A. copa aqueous extract and its isolated compounds were evaluated on isolated rat jejunum. The extract inhibited non-competitively the cumulative concentration-response curves induced by acetylcholine and CaCl2. The tonic jejunum contractions induced by 80 mM KCl were inhibited by A. copa. Relaxant effects of A. copa on the tonic contraction induced by 25 mM KCl, [EC50: 0.94 mg mL(-1) (0.64-1.39)], was not inhibited by glibenclamide, TEA, l-NAME or methylene blue. Chrysoeriol, spinacetin and luteolin (30 µg mL(-1)), produced an antagonism on the CaCl2 concentration-response curve, showing an inhibition of the maximum contractions (70.0% ± 5.0%, 49.1% ± 4.5% and 77.0% ± 3.5% of E max, respectively), whereas tricin did not inhibit when the same concentration was used. A. copa exerts spasmolytic activity by blocking calcium channels and three isolated compounds could be, at least partly, responsible for the effect.