ISSN print edition: 0366-6352 ISSN electronic edition: 1336-9075 Registr. No.: MK SR 9/7 Published monthly

Oscillopolarographic observation of the cleavage of the lactone rings and isomerization of cardioactive glycosides. I. Cardenolides

L. Molnár and K. Molnárová

Pharmakologisches Institut, Tschechosloivakische Akademie der Wissenschaften, Bratislava

Abstract: Helveticoside, convallatoxin, and strophanthidine were studied in M NaOH. Immediately after mixing of the glycoside with NaOH, a cathodic peak at -1.6 v. vs. S.C.E. is formed, which diminishes with time and a new peak at - 1.4 v. appears at the same time. This is ascribed to the cleavage of the 5-membered lactone ring under the formation of the salt of a hydroxy acid. After acidification to pH 2 with HCl and alkalization with M NaOH, the peak at -1.6 v. appears again, which shows that a reversible relactonization occurs. At higher temps. or in M NaOH in MeOH, the glycosides undergo irreversible isomerization. This method is suitable for anal. control of the stability of cardenolides solns. The possibility of the quant. evaluation of oscillograms for kinetic measurements is mentioned.

Full paper in Portable Document Format: 185-6a355.pdf (in German)

Chemical Papers 18 (5-6) 355–362 (1964)