Configuration at C-24 of sterols from the marine phanerogames Posidonia oceanica and Cymodocea nodosa

Sterols were extracted from two marine phanerogames, Posidonia oceanica and Cymodocea nodosa. The two plants contain 24α-ethyl sterols, while the 24α-methyl sterols are accompanied by 24β-epimers. The most abundant components are sitosterol, cholesterol and stigmasterol.     

The sterols and triterpenes of Sorghum vulgare grains

A complex mixture containing more than 20 4-demethylsterols, 4-monomethylsterols and triterpenes was isolated from the grains of Sorghum vulgare. Seventeen of these compounds were identified using a combination of GLC, GC-MS, IR and NMR.     

Sterols of the brown alga Sargassum fluitans

The sterol composition of the warm-water brown alga Sargassum fluitans Børgesen of the Gulf of Mexico was determined by TLC, GLC and IR measurements. The presence of over ten sterols was suggested, of which four (fucosterol, cholesterol, 24-methylenecholesterol, and trans- 22-dehydrocholesterol) were identified and four (a 24-methylcholesterol, a 24-ethylcholesterol, a 24-methyl-trans-22-dehydrocholestero 1 and a 24-ethyl-trans-22-dehydrocholesterol) were recognized but not definitively identified. Saringosterol and 24-ketocholesterol were not found. The crude sterol mixture from S. fluitans was oxidized by osmium tetroxide to 24-ketocholesterol in poor yield.     

Influence du milieu de culture sur la composition en sterols de Leptosphaeria typhae

C₂₇, C₂₈ and C₂₉ sterols have been isolated from a Leptosphaeria typhae culture grown in vitro in light on a synthetic medium. These products were characterized by GLC and MS. Saturated and mono-, di- and tri-unsaturated sterols are present, both free and esterified. There are significant differences between these sterols and those in the same fungus grown on “oat water”. Unexpectedly, cholesterol was detected in the latter case.     

Sterols,sterol esters and fatty acids of Botrydium granulatum, Tribonema aequale and Monodus subterraneus

The composition of the sterols, sterol esters and fatty acids has been determined in 8-, 11- and 14-day cultures of three members of the Xanthophyceae, Botrydium granulatum, Tribonema aequale and Monodus subterraneus. The main sterols, whether esterified or unesterified, were cholesterol and clionasterol, whose proportions do not vary with age of culture. Much smaller quantities of cycloartenol and 24-methylenecycloartanol were also found in all three algae. The C₁₆ fatty acids are the most common fatty acids in all three algae with C_16:1 being particularly abundant. B. granulatum and T. aequale, however, differ from M. subterraneus in having polyunsaturated C₁₆ fatty acids and a smaller proportion of C_20:5.     

Les sterols de l'Ascomycete Leptosphaeria typhae

A mixture of C₂₈ and C₂₉ sterols have been isolated from Leptosphaeria typhae grown in vitro on “oat water” and characterized by GLC and MS. Mono-, di- and tri-unsaturated sterols are present in the extracts of fungi cultivated both in the dark and in the light but the sterol composition is different. The influence of “oat water” on sterol structure has been determined by comparison with the sterols of the same fungus grown on synthetic medium in the dark.     

The conversion of 24-ethylidene sterols into poriferasterol by the alga Ochromonas malhamensis

A convenient method is described for the preparation of fucosterol-[7-³H₂] and 28-isofucosterol-[7-³H₂]. Both of these 24-ethylidene sterols, as well as 5α-stigmasta-7,Z-24(28)-diene-3β-ol-[2,4-³H₄], were converted into the 24β-ethyl sterol, poriferasterol, by cultures of the chrysophyte alga Ochromonas malhamensis. However, fucosterol-[7-³H₂] was not so efficiently incorporated as the other two compounds thus indicating that the configuration of the 24-ethylidene group is of some importance. It is suggested that a 24-ethylidene sterol of the Z-configuration is produced in de novo poriferasterol synthesis and that a Δ^22,24(28)-diene may be an important subsequent intermediate.     

Distribution of different forms of sterols in three cellular subfractions of Calendula officinalis leaves

From Calendula officinalis leaves three cellular subtractions (mitochondrial, Golgi membranes and microsomal) were obtained and enzymatically characterized. The contents of Δ⁰, Δ⁵, Δ⁷, Δ^{5, 22} sterols, as well as those of 24-methylenecholesterol and clerosterol, in the free and bound in the form of esters, glucosides and acylated glucosides were determined in these fractions. The results revealed the predominance of free sterols in the microsomal fraction, of esters in the mitochondrial fraction and of steryl glucosides and acylated glucosides in the Golgi fraction.     

The occurrence of C28 sterols in red algae

Lenormandia prolifera and Amansia glomerata contain large amounts of 24-methylenecholesterol. These two algae belong to the Amansia group of Rhodomelaceae as do Rytiphloea tinctoria and Vidalia volubilis, which are already known to be able to alkylate sterols at C-24. Halopythis pinastroides is an exception in the Amansia group, no C-28 sterols being present in this alga.     

Free and bound sterols in seedlings of Cucumis sativus

Free sterols, sterol esters, sterol monoglucosides and sterol acylmonoglucosides have been obtained from 10 days old seedlings of Cucumis sativus. Free sterols and sterol esters consist mainly of Δ⁷ di- and triunsaturated sterols, whereas Δ⁷ mono-unsaturated and Δ⁵ mono- and diunsaturated sterols predominate in the glucosides and acylglucosides. Both acetates and derivatives of higher fatty acids, mainly linoleic and linolenic acids, have been found in the sterol esters. Sterol acylglucosides contain mostly saturated fatty acids, palmitic and stearic acids being the main components.     

Complex formation between solanaceous steroidal glycoalkaloids and free sterols in vitro

Both the steroidal glycoalkaloid mixture from potato (α-solanine and α-chaconine) and pure α-tomatine are able to complex with the sterols cholesterol, sitosterol, stigmasterol, campesterol and ergosterol in vitro. The sterol-complexing ability of tomatine was greater than that of the potato alkaloids and more akin to that of the steroidal saponin, digitonin. With all three compounds, cholesterol was the least-readily bound sterol while binding to other sterols was of a similar order. Complex formation with tomatine was not markedly influenced by temperature, and with the aglycone tomatidine did not appear to occur at all.     

Intracellular distribution and origin of sterols in Calendula officinalis leaves

In Calendula officinalis leaves 66% of all steryl forms are present in the ‘microsomal fraction’ (IV), 24% in the mitochondrial and Golgi membranes (III), 5% in the ‘chloroplast’ (II), 4% in the ‘cell wall and membrane’ (I) fraction and 1%. in the cytosol. Free sterols, their esters, glycosides and acylated glycosides are present in varying proportions in all cellular subtractions. Mevalonate-[2¹⁴C] labelling of sterols derived from various steryl forms showed that free sterols and all their derivatives, i.e. steryl esters and glucosides, are formed in fraction IV and are then translocated to other organelles. Fraction III is the main site of glycosylation of transported sterols as well as of acylation of steryl glycosides.     

Sterols of roots and nitrogen fixing root nodules of vicia faba

Sterols of both roots and nodules of Vicia faba were found to be mainly 24-methylcholesterol, 24-ethyl-5,22-cholestadien-3β-ol and 24-ethylcholesterol. Nodules contained nearly twice the quantity of sterols present in roots, mainly due to an increase in 24-ethylcholesterol from about 40–60% of the total sterol content of root extract to over 80% of nodule extracts. Insignificant amounts of sterol were detected in nodule bacteroid fractions and in free-living Rhizobium leguminosarum.     

Dehydrodinosterol,dinosterone and related sterols of a non-photosynthetic dinoflagellate, Crypthecodinium cohnii

The heterotrophic dinoflagellate Crypthecodinium cohnii contained the 4α-methyl sterols, dinosterol, dehydrodinosterol (4α,23,24-trimethylcholesta-5,22-dien-3β-ol) and the tentatively identified 4α,24-dimethyl-cholestan-3β-ol and 4α,24-dimethylcholest-5-en-3β-ol. The major 4-demethyl sterol was cholesta-5,7-dien-3β-ol which was accompanied by a smaller amount of cholesterol and traces of several other C₂₇,C₂₈ and C₂₉ sterols. In addition, a 3-oxo-steroid fraction was isolated and the major component identified as dinosterone (4α,23,24-trimethylcholest-22-en-3-one). The possible biosynthetic relationships of these compounds are discussed.     

The structure of elasterol from Ecballium elaterium

The structure of elasterol, the major sterol of Ecballium elaterium, is revised to (24S)-24-ethyl-5α-cholesta- 7,22,25-trien-3β-ol from 24-ethyl-5α-cholesta-7,16,25-trien-3β-ol.     

Free sterols of citrus roots

Free 4-desmethylsterols from fibrous roots of 6 citrus rootstocks were identified by combined gas chromatography and mass spectrometry as campesterol, stigmasterol, sitosterol and cholesterol (minor component). No isofucosterol was present.     

Inhibitors of sterol synthesis. Chemical syntheses and activities of new derivatives of 15-oxygenated sterols

The chemical syntheses of 5α-cholestane-3β,14α,15β-triol, 5α-cholestane-14α-ol-3,15-dione, 5α-cholestane-3β,14α-diol-15-one, 14α,15α-epoxy-5α-cholestan-3β-ol, and 5α-cholest-8(14)-en-3β-ol-15-one oxime are described. All of these compounds were found to be potent inhibitors of sterol synthesis in cultured mouse L cells. However, the former three compounds had little or no effect on the levels of 3-hydroxy-3-methylgutaryl (HMG)-CoA reductase in the same cells. In contrast, in the case of the latter two compounds, the concentrations required to cause a 50% inhibition of the synthesis of digitonin-precipitable sterols were comparable to those required to cause a 50% reduction in the levels of HMG-CoA reductase in the same cells. 5α-Cholest-8(14)-en-3β-ol-15-one oxime had no effect on serum cholesterol levels when administered to male rats at a level of 0.15% in a cholesterol-free diet.     

NMR spectra of C-24 isomeric sterols

Cholesterol and four pairs of C-24 isomeric sterols, campesterol-22,23-dihydrobrassicasterol, α-spinasterol-chondrillasterol, stigmasterol-poriferasterol, and sitosterol-22,23-dihydroporiferasterol were studied by NMR spectroscopy and their spectra are presented. The NMR spectra of three of the pairs of isomeric sterols recorded at 100 MHz could be differentiated from each other, although at 60 MHz only the spectra of campesterol (24α-methylcholesterol) and 22,23-dihydrobrassicasterol (24β-methylcholesterol) showed differences. Sitosterol and 22,23-dihydroporiferasterol, the pair of sterols that showed no differences in their NMR spectra are readily differentiated by the physical properties of their acetates. The practical application of NMR spectroscopy to several problems concerning the C-24 isomeric sterols is demonstrated.     

Sterol utilization in honey bees fed a synthetic diet: Analysis of prepupal sterols

The sterols of prepupal honey bees, Apis mellifera L., from brood reared by workers fed chemically-defined synthetic diets containing cholesterol, campesterol, sitosterol, stigmasterol, 24-methylenecholesterol, or no sterol over a 12-week period were isolated, identified, and quantified. The major sterol present in each prepupal sample was 24-methylenecholesterol, but significant levels of sitosterol and isofucosterol were also present in every case, as was a very small percentage of desmosterol (usually < 1%). This is the first report of isofucosterol being identified in the sterols of the honey bee. A considerably larger percentage of each dietary sterol was found in prepupae reared by workers fed that particular sterol in the diet. This was most dramatic in the case of the cholesterol diet in which case cholesterol content increased to as much as 17.2% of the prepupal sterols, whereas cholesterol had not exceeded 2.2% in samples from other diet regimens. However, stigmasterol comprised no more than 6.3% of the total sterols in any sample from prepupae fed the stigmasterol diet. The preponderance of 24-methylenecholesterol in all prepupae, regardless of the dietary sterol provided to the workers, as well as the lesser quantities of sitosterol and isofucosterol present in all samples, suggest a unique system of utilization and metabolism of these dietary sterols by the worker bees. Apparently they make available to the brood varying amounts of unchanged dietary sterol plus considerable and fairly constant portions of 24-methylenecholesterol, sitosterol, and isofucosterol drawn from their own sterol pools.