The calcium channel blocking and phosphodiesterase inhibitory activities of the extract of Andropogon muricatus explains its medicinal use in airways disorders

The present work was carried out to provide a pharmacological base for the medicinal use of Andropogon muricatus in airways disorders, such as asthma. In isolated guinea‐pig tracheal strips, the crude extract of Andropogon muricatus exhibited a non‐specific relaxant effect against carbachol (1 µ m ) and high K⁺ precontractions, with EC₅₀ values of 0.10 (0.07–0.11) and 0.15 mg/mL (0.11–0.18), respectively, similar to papaverine, while verapamil was more potent against high K⁺. This suggests the involvement of a non‐specific relaxant effect, mediated possibly through Ca⁺⁺ channel blockade and phosphodiesterase inhibition. The functional nature of the relaxant effect was further confirmed through indirect evidence when pretreatment of the tissues with the plant extract caused potentiation of the isoprenaline inhibitory response curves, similar to papaverine, while the effect of verapamil remained unchanged. These data indicate that the crude extract of Andropogon muricatus contains constituent(s) that mediate the tracheal relaxant effect, possibly through dual inhibition of Ca⁺⁺ channels and phosphodiesterase and provide pharmacological evidence for its medicinal use in airways disorders, particularly asthma. Copyright © 2011 John Wiley & Sons, Ltd.