Structure-activity relationship of cardiac steroids having a doubly linked sugar and related compounds for the inhibition of Na+,K+-adenosine triphosphatase.

Forty-three different cardiac steroids having a doubly linked sugar and related compounds were tested for inhibition of Na+,K+-adenosine triphosphatase from guinea pig heart, and the structure-activity relationship has been discussed. The doubly linked glycosides showed higher activities than the respective genins. The inhibitory activities of these compounds were also dependent upon the presence of ring C substituents. The bufadienolide rhamnosides exhibited greater than three times the inhibitory activity of the parent genin, while the glucosyl residue exerted no significant activity.