Studies on phytosterol biosynthesis. The presence of 4-alpha,14-alpha-dimethyl-delta-8,24(28)-ergostadien-3-beta-ol in grapefruit peel and its co-occurrece with cycloeucalenol in higher plant tissues

A sterol database: GC/MS data and occurrence of 150 sterols in seventy-four oils

Comprehensive data on the occurrence of sterols in plant oils is currently hardly available since only a few sterols are obtainable as standard compounds. Accordingly, many peaks are rarely labeled in gas chromatograms due to missing or outdated information. This lack of information hampers the progress in sterol research. For this reason, gas chromatography with mass spectrometry in selected ion monitoring mode (GC/MS-SIM) was used to create a database that summarizes the occurrence and semi-quantitative levels of 150 sterols with 27-32 carbon atoms and 0-4 double bonds in 66 different vegetable oils and eight other matrices. The highest number of sterols was detected in rice bran and tamanu oil (40 sterols), eggplant (39 sterols), moringa, chili seed, and amaranth oil (37 sterols). Several sterols were detected in >60 of the 74 matrices. This detailed information in the database will serve users working in food authentication and the biosynthesis of sterols.

Usefulness of the 1H NMR Multisuppression Approach for the Global Characterization of Monovarietal Extra-Virgin Olive Oils

Extra-virgin olive oil (EVOO) is one of the most appreciated vegetable oils worldwide, but its high price makes it prone to suffer adulteration with lower quality oils. Therefore, it is important to have methodologies able to study EVOO composition as a whole in a simple and fast way, in order to guarantee its quality and safety. For this purpose, in this study, commercial samples of five Spanish olive cultivars (Arbequina, Arroniz, Cornicabra, Hojiblanca, Picual) were studied by Proton Nuclear Magnetic Resonance (1H NMR) spectroscopy, using standard and multisuppression pulses. The aim was to explore the possibility of 1H NMR use to characterize in a single run and in a global way the composition of these monocultivar oils, regarding not only their main components (fatty acids supported on triglycerides) but also minor ones (squalene, sterols, diterpenic wax esters of phytol and geranylgeraniol, phenolic and secoiridoid derivatives, like tyrosol, hydroxytyrosol, oleacein, oleocanthal, and lignans, among others, and aldehydes). The use of univariate and multivariate statistical analyses confirmed the presence of compositional features that were specific to some olive varieties. The Arbequina and Arroniz oils showed the most characteristic features that allowed for clearly differentiating them from the others. In contrast, the discrimination between the Cornicabra, Hojiblanca and Picual oils was not so easily achieved.

Gas chromatography with mass spectrometry analysis of 4,4-dimethylsterols and 4-methylsterols in edible oils after their enrichment by means of solid phase extraction

4-Methylsterols (4-M-sterols) and 4,4-dimethylsterols (4,4-D-sterols) are a group of underexplored minor sterols that occur in almost all living organisms. Here, we developed a strategy for the determination of the biochemical precursors of the predominant 4-desmethylsterols in edible oils. Due to their low contribution to the sterol content in the samples, a solid phase extraction (SPE) method was developed for the enrichment of 4-M- and 4,4-D-sterols in the hexane extracts of saponified oils. In a two-fold SPE procedure, the bulk of 4,4-D-sterols was collected in one fraction. The residual sample was subjected to a second SPE step which targeted all 4-M-sterols and low shares of 4,4-D-sterols in one fraction and the predominant 4-desmethylsterols in another one. After silylation of the SPE fractions, gas chromatography with mass spectrometry (GC/MS) was used to analyze 4,4-D- and 4-M-sterols. The results were used to define eight subgroups whose characteristic structural features could be linked with the presence of specific m/z values. These m/z values were measured sensitively by GC/MS operated in selected ion monitoring (SIM) mode. Application of the GC/MS method to eighteen edible oils enabled the detection of 55 mostly very low abundant 4-M- and 4,4-D-sterols. Twenty-four of the 4-M- and 4,4-D-sterols could be assigned and the remaining 31 unknown sterols could be traced back to their basic structures.

Sterol synthesis. Chemical synthesis, structure determination and metabolism of 14 alpha-methyl-5 alpha-cholest-7-en-3 beta, 15 beta-diol and 14 alpha-methyl-5 alpha-cholest-7-en-3 beta, 15 alpha-diol

14alpha-Methyl-5alpha-cholest-7-en-3beta,15beta-diol and 14alpha-methyl-5alpha-cholest-7-en-3beta,15alpha-diol have been prepared by chemical synthesis. Unequivocal establishment of these structures was based upon X-ray crystallographic analysis of 3beta-p-bromobenzoyloxy-14alpha-methyl-5alpha-cholest-7-en-15beta-ol and was supported by other spectroscopic data. Spectroscopic data were presented for the following compounds prepared in this study: 3beta-benzoyloxy-5alpha-cholest-8(14)-en-15-one, 3beta-benzoyloxy-14alpha-methyl-5alpha-cholest-7-en-15-one, 3beta-benzoyloxy-14alpha-methyl-5alpha-cholest-7-en-15beta-ol, 14alpha-methyl-5alpha-cholest-7-en-3beta, 15beta-diol, 14alpha-methyl-5alpha-cholest-7-en-3beta, 15alpha-cholest-7-en-15beta-diol, 14alpha-methyl-5alpha-cholest-7-en-3beta, 15alpha-diol, 3beta, 15alpha-bis-benzoyloxy-14alpha-methyl-5alpha-cholest-7-ene, 3beta-p-bromobenzoyloxy-14alpha-methyl-5alpha-cholest-7-en-15beta-ol and 3beta, 15beta-bis-p-bromobenzoyloxy-14alpha-methyl-5alpha-cholest-7-ene. Studies of the metabolism of [16-3H]-14alpha-methyl-5alpha-cholest-7-en-3beta, 15beta-diol and [16-3H]-14 alpha-methyl-5 alpha-cholest-7-en-3beta, 15alpha-diol in liver homogenates of female rats indicated that only the 3beta, 15beta-diol was convertible to cholesterol.

Chemical synthesis, spectral properties, and chromatography of 4alpha-methyl and 4beta-methyl isomers of (24R)-24-ethyl-5alpha-cholestan-3beta-ol and (24S)-24-ethyl-cholesta-5,22-dien-3beta-ol

Described herein are chemical syntheses of the following compounds: 4-methyl-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4,4-dimethyl-(24S)-24-ethyl-cholesta-5,22-dien-3-one, 4beta-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24R)-24-ethyl-5alpha-cholestan-3beta-ol, 4alpha-methyl-(24S)-24-ethyl-5alpha-cholest-22-en-3beta-ol, 4-methyl-6beta-bromo-(24S)-24-ethyl-cholesta-4,22-dien-3-one, 4alpha-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol, 4alpha,5alpha-epoxy-(24S)-24-ethyl-cholesta-4,22-dien-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholest-22-en-3beta,5alpha-diol, 4beta-methyl-5alpha-hydroxy-(24S)-24-ethyl-cholest-22-en-3beta-yl acetate, 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-yl acetate and 4beta-methyl-(24S)-24-ethyl-cholesta-5,22-dien-3beta-ol. Chromatographic, nuclear magnetic resonance, and mass spectral data are presented for the compounds under consideration.

24-Methylenelanost-9(11)-en-3beta-ol, new triterpene alcohol from shea butter

A new triterpene alcohol was isolated fron shea butter and its structure was shown to be 24-methylenelanost-9(11)-en-3beta-ol. Gas chromatographic correlations between this triterpene alcohol and other related compounds are discussed.

The sterols of the echinoderm Asterias rubens

1. Twenty-two sterols were identified in the starfish Asterias rubens (Phylum, Echinodermata; Class, Asteroidea). 2. The major 4-demethyl sterols had a Delta(7) bond and the C(27) compound 5alpha-cholest-7-en-3beta-ol predominated over other mono- and di-unsaturated sterols belonging to the C(26), C(27), C(28) and C(29) series. 3. Small amounts of cholest-5-en-3beta-ol and 5alpha-cholestan-3beta-ol were also present. 4. The minor sterols identified all contained either one or two methyl groups at C-4 and are considered to be potential biosynthetic precursors of 5alpha-cholest-7-en-3beta-ol. 5. Three sterols possessing a 9beta,19-cyclopropane ring were also isolated and were probably derived by the starfish from a dietary source.

Biosynthesis of carotenoids and plant triterpenes

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[Biosynthesis of sterols in tobacco tissues cultivated in vitro. Kinetics of the formation of sterols and their precursors]

Tobacco tissues grown in vitro were fed with labelled acetic acid during 5, 30 and 150 min, respectively. 4, 4‐Dimethylsterols, 4‐methylsterols and sterols were extracted and purified and their specific activities were determined by acetylation of biosynthetically labelled alcohols with [3H]acetic anhydride of known specific activity.

On the basis of the measured specific activities, a tentative scheme for plant sterol biosynthesis is proposed. In particular, cycloartenol appears to play a direct role in this biosynthesis. The conversion of cycloartenol into sterols appears to be a non‐specific process with several possible parallel routes. The linear scheme previously proposed, involving the following transformations : cycloartenol → methylene‐24 cycloartanol → cycloeucalenol → obtusifoliol →“lophenols”, etc., appears to be only one of the pathways followed in our material.