Progesterone: its possible role in the biosynthesis of cardenolides in Digitalis lanata.

The incorporation of progestrone-7alpha-(3)H and pregnenolone-7alpha-(3)H into digitoxigenin, gitoxigenin, and digoxigenin in isolated, surviving leaves of Digitalis lanata was demonstrated. In addition, the conversion of pregnenolone to progesterone in the same system was proved. The results tend to indicate that progesterone is as good a precursor of cardenolides as pregnenolone It is suggested that the biosynthesis of cardenolides might proceed through the intermediacy of progesterone.