Biosynthesis of stigmasterol from sitosterol in Digitalis Lanata

The composition of phytosterols in first and second year Digitalis purpurea L

The phytosterols of Digitalis purpurea occur as lipids and as glucosides. Gas-liquid chromatography and mass-spectrometry indicated that both fractions contained sitosterol as the major component, and also varying proportions of stigmasterol, campesterol and cholesterol. Certain of the lipid fractions contained 24-methylenecholesterol. The phytosterol concentrations and relative proportions were determined at monthly intervals during the first year of growth, and also in various morphological units of second year plants. The composition of the phytosterol fractions depended upon the plant organ examined and also upon the phase of growth of the plant.

The sterols and tetracyclic triterpenoids of Digitalis purpurea L. seeds

Three types of sterols were isolated from the non-saponified fraction of D. purpurea seed oil. These were the 4,4′-dimethylsterols, the 4α-methylsterols and the 4-desmethylsterols. By combination of t.l.c., g.l.c. and mass spectrometry, the first group were found to consist of cycloartenol and 24-methylenecycloartenol, the second group of 24-methyl-lophenol, 24-ethyl-lophenol, 24-methylenelophenol, 24-ethylidenelophenol, obtusifoliol, 4α-methylzymosterol and cycloeucalenol. The third group of true phytosterols consisted of cholesterol, campesterol, stigmasterol, β-sitosterol, fucosterol, 28-isofucosterol and 24-methylenecholesterol. Possibly present also in this group were 7-ene-cholestenol, 7-ene-campestenol, 7-ene-22-dihydrostigmastenol, 7-ene-24-methylenecholestenol and 7-ene-isofucostenol.

Relative sterol composition in the genus Nicotiana

Stigmasterol, β-sitosterol, campesterol, and cholesterol are the predominant sterols identified by gasliquid chromatographic techniques in the mature leaves of 50 Nicotiana species. The relative composition pattern of the four sterols varies significantly among the subgenera as well as within the subgenus. However, six N. tabacum cultivars showed a similar pattern, of which as an average stigmasterol represents the highest proportion (43%) followed by β-sitosterol (30%), campesterol (19%), and cholesterol (8%) in total sterol content. Negative correlations were obtained for the composition of stigmasterol vs. β-sitosterol, cholesterol vs. campesterol, and cholesterol vs. β-sitosterol. Some correlations between geographic distribution of Nicotiana species and sterol composition were evident. In evaluating phylogenetic relationship between amphiploid species and the possible diploid progenitors, the results of sterol composition are in favor of N. undulata and N. paniculata being the ancestors of N. rustica and the N. sylvestris X N. tomentosiformis as the hybrid combination from which N. tabacum was evolved.