Activities of novel polyhydroxylated cardiotonic steroids purified from nuchal glands of the snake, Rhabdophis tigrinus.

Seven novel polyhydroxylated steroids were isolated from the nucho-dorsal glands of the snake, Rhabdophis tigrinus. Biological activities of these steroids in inhibiting (Na+ + K+)ATPase and in producing positive inotropic action were examined in comparison with those of ouabain and gamabufotalin. Gamabufotalin was approximately 10 times more potent than ouabain in inhibiting (Na+ + K+)ATPase. Two compounds, compounds III and XIII, of the seven, produced nearly equipotent enzyme inhibitory activity to ouabain. The activity of the remaining five was relatively low among the compounds tested. All compounds exhibited more or less positive inotropic action in the papillary muscle preparations. The ranking order of the potency was: gamabufotalin greater than ouabain and compound IV greater than compound III and XIII greater than compound I, II, XII and XIV.