Relaxant effects of Hydrastis canadensis L. and its major alkaloids on guinea pig isolated trachea

Hydrastis or goldenseal, one of the most popular medicinal herbs in the U.S .A., is used in mild pathological conditions Like cold and flu, based on th e pharmacological properties of its active components, berberine (anticholi nergic, antisecretory, and antimicrobial) and P-hydrastine (astringent). We previously reported the relaxant effect of a total ethanolic extract of hy drastis on carbachol precontracted isolated guinea pig trachea, and with th e present study, using the same experimental model, we aimed at evaluating the contribution of its major alkaloids, berberine, P-hydrastine, canadine and; canadaline to the total effect. Furthermore, using specific pharmacolo gical tools, like timolol and xanthine amine congener, we attempted to eluc idate its mechanism of action. The ECS, of berberine, beta -hydrastine, can adine and canadaline, went 34.2+/-0.6, 72.8+/-0.6, 11.9+/-1.2 and 2.4+/-0.8 mug/ml, respectively. Timolol effectively antagonized the effect of canadi ne (EC50=19.7+/-3.0 mug/ml) and canadaline (EC50=17.1+/-1.2 mug/ml) but not that of berberine and P-hydrastine, while xanthine amine congener antagoni zed the effect of beta -hydrastine (EC50=149.9+/-35.3 mug/ml) and canadalin e (EC50= 26.1+/-3.0 mug/ml) but not that of berberine and canadine. Besides , the hydrastis extract, at concentrations between 0.01 and 0.1 mug/ml, pot entiated the relaxant effect of isoprenaline on carbachol-precontracted iso lated guinea pig trachea. These data, which are insufficient to draw defini te mechanistic conclusions, indicate that the aforementioned alkaloids may act by interacting with adrenergic and adenosinic receptors.