| Abstract: | Strongly radioactive digitoxin ( 6 ) could be isolated (without dilution) in crystalline form from young plants of Digitalis lanata after their inoculation with D-Glucose-[6-14C] using the wick method. Hydrolytic cleavage of this digitoxin gave digitoxigenin ( 11 ) and D-digitoxose ( 7 ), both being isolated in crystalline form (without dilution). The genin was found to be 4 times more active, pro mole, than the digitoxose. This can be best explained when one assumes that the plant converts 1 mole of D-glucose into 3 moles of acetic acid. After degradation of the digitoxose using NaJO4, acetaldehyde (as the crystalline p-nitrophenylhydrazone) and formic acid (as the Pb salt) could be isolated. The acetaldehyde carried 65% and the formic acid 8,45% of the activity of the digitoxose. This is compatible with the assumption that digitoxose is formed in the plant from D-glucose without re-arrangement of the carbon chain. The appreciable activity of the formic acid could be derived from the relatively large proportion of radioactivity lost (ca. 38,9%), partly in the form of C1-subunits, in the transformation of the intermediary lanosterol into digitoxigenin. This lost activity may be incorporated in unspecifically labelled D-glucose which then re-enters the biosynthetic pathway. |
