[Investigations on the Stability of Proscillaridine, Proscillaridine-3'-methylether and Proscillaridine-4'-methylether in Artificial Gastric and Intestinal Fluids (author's transl)].

The stability of bufadienolides in artificial gastric and intestinal fluids was investigated at different pH-values as a function of incubation time using proscillaridine, proscillaridine-3'-methylether and proscillaridine-4'-methylether. These glycosides were completely stable on pH 3.0--8.5 during the investigated time interval of 1 h. At lower pH-values cleavage of the glycosidic bond occurred. At pH 1.0 73% of proscillaridine, 33% of proscillaridine-3'-methylether and 41% of proscillaridine-4'-methylether were decomposed. At pH 2.0 only about 10% decomposition of these compounds could be detected. These experiments show that the stability of proscillaridine in gastric juice is comparable with the stability of digitalis glycosides and digoxin derivatives. The stability of methylated proscillaridine derivatives in artificial digestion fluids, however, proved to be superior to any orally administered cardiac glycoside.