Digitonin is produced from seeds of Digitalis pupurea and other Digitalis species. It is a steroid glycoside consistingof the aglycon digitogenin linked to five sugar residues. Digitonin reacts hemolytic and is toxic to humans. Reaction of naturally occurring steroids carrying a 3b-hydroxyl groupwith digitonin results in an insoluble precipitate. Determination of cholesterol and ergosterol. Digitonin permeabilizes plasma membranes of eukaryotic cells by complexing with membrane cholesterol and other unconjugated beta-hydroxysterols. Used for solubilization of membrane proteins and permeabilization of cellular and nuclear membranes.