Electrophysiological and inotropic effects of natural amino-deoxyglyco-cardenolides

The electrophysiological, inotropic and chronotropic effects of the two first natural amino-dexoyglyco-cardenolides, mitiphylline and holarosine B, were studied. Mitiphylline has qualitatively the same properties as those of common cardiac glycosides but is more potent; holarosine B has a similar action on cardiac electrophysiological parameters of the guinea pig heart but is less potent. The difference in activity between these two compounds could be attributed to the configuration in 5-and 17-positions of the genins. Holarisone B has the particularity of increasing the action potential plateau amplitude and its duration in rat heart; this could be part of the role of the aminosugar moiety.