The identification of cholesterol and other steroids in Euphorbia pulcherimma |
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Authors: | Bernard C Sekula William R Nes |
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Institution: | Department of Biological Sciences, Drexel University, Philadelphia, PA 19104, U.S.A. |
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Abstract: | The 4-desmethyl tetracycles of the whole poinsettia plant (Euphorbia pulcherimma) less roots amounted to 0.07% of the wet wt and were shown by 1H NMR spectroscopy to be steroids and not euphoids. The most abundant component was cholesterol, constituting half the mixture, followed in order of decreasing concentration by 24α-ethylcholesterol (sitosterol), 24α-methylcholesterol (campesterol) and 24β-methylcholesterol (22-dihydrobrassicasterol). The relative amount of cholesterol in this plant is the highest found so far in a tracheophyte. The 4,4-dimethyl compounds (0.1% of wet wt) included lanosterol (5%), 24-dihydrolansterol (5%), β-amyrin (25%), germanicol (50%), an unidentified pentacyclic triterpenoid (8%) and two or more (7%) unidentified components. Both the 4,4-dimethyl- and the 4-desmethylsterols were in the configurational series with a 20α-H-atom. Dihydrolanosterol and lanosterol are the probable intermediates from cycloartenol to cholesterol and 24-alkylcholesterol, respectively. Such a sequence would differ from that operating in most angiosperms, where the alkylation is thought to precede the opening of the 9,19-cyclopropane ring. |
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Keywords: | Euphorbiaceae sterols triterpenoids nuclear magnetic resonance spectroscopy cholesterol sitosterol campesterol dihydrobrassicasterol lanosterol dihydrolanosterol |
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