Biogenetic mechanisms. I. Incorporation of 4-14C-progesterone into gitoxigenin by Digitalis purpurea

In vivo administration of 4-14C-progesterone to a 6-month-old Digitalis purpurea species over a period of 4 weeks resulted in 0.477% incorporation of the radioactivity into gitoxigenin. The identity of the crystalline cardenolide isolated was established by thin-layer and gas chromatography, infrared spectroscopy, as well as isotope dilution with authentic carrier material and crystallization to constant specific activity. The role which progesterone may play as an active precursor in the biogenesis of steroid cardenolides is discussed.