Cardiac effects of six actodigin (AY-22,241)-related semisynthetic glycosides.

Six actodigin (AY-22,241)-related semisynthetic glycosides (with the C-3 natural linkage of the lactone ring to the steroid nucleus, transposed to C-2) were assayed in failing hearts of canine heart-lung preparations. Two compounds, with additional small modifications in the steroid nucleus, were incapable of reversing heart failure. Two others, an isodigoxigenin and an isogitoxigenin derivative, were only slightly active. However, the two other actodigin-derived compounds, with methyl groups at the lactone C-4, were very active. Compound 5 had the methyl group in beta position and was 2.5 times more potent than actodigin. Compound 6, with the methyl group in alpha position, had a potency similar to that of actodigin. In the anesthetized and vagotomized dog, their toxic effects (to the point of atrioventricular dissociation) were short lasting and completely reversible. Both of these agents had a wide margin of safety (relationship between the minimal therapeutic, irregularity and lethal doses).