Abstract
Praeruptorin C and E isolated from Peucedanum praeruptorum Dunn. decreased the maximum contractile effect of Ca 2+ in potassium-depolarized swine coronary strips and shifted the concentration-response curve to the right in a non-parallel manner. The calcium antagonistic activity of praeruptorin C and E expressed as pD 2 ′ value was 5.7 and 5.2, respectively. Nifedipine, with a pD 2 ′ value of 6.88, was used as a known calcium antagonistic drug to compare the potency of the drugs studied. The relaxation induced by praeruptorin C was concentration-dependent and the IC 50 value was 79 μM. Praeruptorin C also reduced the maximum contractile response and shifted the concentration-response curve for calcium to the right in a non-parallel manner in potassium-depolarized guinea-pig left atria (pD 2 ′ = 5.52) but its potency was much less than that of nifedipine (pD 2 ′ = 7.19). The results suggest that praeruptorin C and E relaxed swine coronary artery and decreased contractility in guinea-pig left atria. These affects are similar in many respects to those displayed by drugs that have calcium entry blocking activity.
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