[Lipophilicity-protein binding relationship in cardenolides (author's transl)]

By equilibrium dialysis the binding of 19 cardenolides and cardenolide conjugates to human plasma proteins has been measured. The binding constants were compared with octanol-water partition coefficients described previously. No correlation was found between the two properties. Glycosides and conjugates of a certain genine show the same extent of protein binding, even if some of the derivatives differ in their physicochemical properties more than by three log units. It is concluded that cardenolide protein binding depends solely on hydrophobic property of the genine involved.