Abstract
5-Pregnen-3β-ol-20-one (pregnenolone), 4-pregnene-3,20-dione (progesterone), 5-pregnene-3β,21-diol-20-one
(21-hydroxypregnenolone), 4-pregnen-21 -ol-3,20-dione (cortexone), 5β-pregnane-3,20-dione,
5α-pregnane-3,20-dione, 5β-pregnan-3α-ol-20-one, 5β-pregnan-3β-ol-20-one, 5β-pregnane-3β,14β,
21-triol-20-one 3-acetate, 23-nor-5-cholenic acid-3β,20ξ-diol, and 23-nor-3,20(22)E-choladienic acid-3β-ol were administered to photomixotrophic shoot cultures of Digitalis lanata Ehrh. capable of synthesizing cardenolides, as well as to cardenolide-free tissue
cultures, such as auxotrophic, dark-grown shoot cultures and cell suspension cultures
of the same plant species. None of the pregnane precursors was qualified to restore
cardenolide biosynthesis in the cardenolide-free tissues. The cardenolide content
of light-grown shoot cultures, on the other hand, increased by 161%, 240%, 30%, 430%
and 80% when l00 mg l-1 of 21-hydroxypregnenolone, 5β-pregnane-3,20-dione, 5β-pregnan-3β-ol-20-one, 5β-pregnane-3β,14β,21-triol-20-one,
23-nor-5,20 (22)E-choladienic acid-3β-ol, respectively, were administered. Pregnenolone, progesterone,
cortexone, 5α-pregnanes, 5β -pregnan-21-ols, and 23-nor-5-cholenic acid-3β,20ξ-diol,
on the other hand, had no visible effect. Two different types of cardenolides (termed
fucose-type cardenolides and digitoxose-type cardenolides) were identified which may
be formed via different biosynthetic routes. The “norcholanic acid pathway” seems
to be operative in D. lanata shoot cultures only in the formation of fucose-type cardenolides.
key words
Digitalis lanata
- Scrophulariaceae - cardiac glycosides - shoot culture - biosynthesis
