Biosynthesis of plant sterols. Conversion of cholesterol to pregnenolone inDigitalis purpurea

The role of deoxycorticosterone in the biosynthesis of cardenolides in Digitalis lanata

“…This view is fortified by the demonstration of the biosynthesis of cholesterol from mevalonic acid in Digitalispurpurea (Jacobsen & Frey, 1967). In accordance with this, the transformation of cholesterol into pregnenolone (I) (Caspi, Lewis, Piatak, Thimann & Winter, 1966) and the conversion of the latter into cardenolides (Tschesche & Lilienweiss, 1964;Tschesche & Brassat, 1966) and bufadienolides (Tschesche & Brassat, 1965) in plants has been demonstrated. Further studies on the metabolism of pregnenolone (I) in Digitali8 lanata have revealed that this homallylic alcohol is converted into progesterone (II) and that the formation of a 3-ketone is an obligatory step in the biosynthesis of cardenolides (Caspi & Lewis, 1967;Caspi & Hornby, 1968).…”

“…Co., Toms River, N.J. 08753, U.S.A. digitoxigenin (III). As mentioned above, in the route from pregnenolone to cardenolides progesterone is formed and is incorporated to the extent of about 2% into digitoxigenin (Caspi & Lewis, 1967;Caspi & Hornby, 1968). Therefore, as a first approximation, it was expected that the relative importance of the biosynthetic roles of the two steroids could be defined from changes in the 3H/14C ratio of the biosynthesized products.…”

“…The sequence of events leading from the C21 precursors pregnenolone (I) and progesterone (II) to cardenolides must include the introduction of two oxygen functions, namely at C-14 and C-21. Studies on the mechanism of hydroxylation at C-14 are in progress in this Laboratory (Caspi & Lewis, 1968). The present paper deals with the question of C-21 hydroxylation and the possible involvement of deoxycorticosterone (V) in the biosynthesis of cardenolides.…”

“…1 were used for paper chromatography. With 'Bush systems' the papers were pretreated before development (Caspi & Lewis, 1967;Bush & Crowshaw, 1965). Radioactivity measurement.…”

Steroidogenesis in plants – Biosynthesis and conversions of progesterone and other pregnane derivatives

“…It could be shown that administered 14 Ccholesterol could serve as precursor of pregnenolone or progesterone in Digitalis purpurea [23]. The predominant sterols of higher plants are C29 compounds, e.g.…”