Screening of plant extracts and plant constituents for calcium-channel blocking activity.

Various constituents isolated from plants with described or suggested antihypertensive, spasmolytic or diuretic activity were tested in an in in vitro-guinea pig papillary muscle model for possible calcium-channel blocking activity. Among the isolated compounds some phenylpropanoids of essential oil (e.g. apiol), mono- and sesquiterpene derivatives (e.g. bisabolol-oxide A), naphthoquinones (e.g. juglone, 7-methyljuglone, plumbagin, garlic constituents), some phenolics and alkaloids showed good to moderate activity (IC(50):15-100 μM). Some of the tested compounds caused a prolonged duration of the contraction, suggesting an additional K(+)-channel blocking effect.