Sterol conjugate interconversions during germination of white mustard (Sinapis alba)

Changes in the content of free sterols (FS), steryl esters (SE), steryl glucosides (SG) and acylated steryl glucosides (ASG) in germinating seeds of white mustard (Sinapis alba) were studied together with parrallel changes in specific activities of some enzymes involved in sterol conjugate transformation. It has been found that a distinct increase in the net SE content and a similar, but less pronounced, increase in SG content at the beginning of germination can be correlated with a distinctly earlier appearance of SE and SG synthesizing enzymes, i.e. triacylglycerol: sterol acyltransferase and UDPG: sterol glucosyltransferase in comparison with hydrolytic activities, i.e. SE hydrolase and SG hydrolase. Our results suggest that metabolism of SG and ASG takes place mainly in the cotyledons while SE metabolism takes place mainly in the roots.     

Sterols,steryl esters and fatty acids in some Vicia faba seeds

Free and esterified sterol levels in seeds of five cultivars of Vicia faba were determined. Sitosterol was the most abundant free sterol, followed by stigmasterol and campesterol. Cholesterol could not be detected. Esters were generally present in greater quantities than the free form of the sterols. The fatty acid content of the plants is also reported.     

Acyl donors for sterol esterification by cell-free preparations from Sinapis alba roots

Homogenates or crude 300-16 000 g membrane fractions from Sinapis alba roots catalysed esterification of [4-¹⁴C]cholesterol with utilization of endogenous acyl sources. With acetone powder preparations cholesterol esterification was distinctly stimulated by a neutral lipid fraction isolated from S. alba roots. Among neutral lipids triacylglycerols were the most active in this process. Experiments with various acyl-labelled acylglycerols as acyl donors and non-labelled sterols as acceptors confirmed that triacylglycerols are directly utilized as the source of fatty acids for sterol esterification. Di- and mono-acylglycerols were much less effective.     

Sterols in relation to ageing of seeds of Helianthus annuus and Cicer arietinum

Under accelerated ageing at high relative humidity and high temperature for 4 days germination and membrane permeability remained unaffected both in sunflower and chick pea seeds. However, the steryl glycoside concentration in the pooled leachate increased progressively with ageing. Total sterols, as well as steryl glycosides and free sterols of the seeds, increased with a concomitant decline in steryl esters under accelerated ageing. Pretreatment with the sterol biosynthesis inhibitor SK & F 7997A₃ prevented the increase of total sterols under accelerated ageing conditions but there were increases in the amounts of steryl glycosides and free sterols and a decrease in steryl ester after such treatment, therefore, indicating interconversions of the various sterol types. Accelerated ageing also caused increases in free amino acids and soluble carbohydrate. Low relative humidity-high temperature and high relative humidity-low temperature failed to produce such effects.     

Changes in the levels and composition of sterols in different tissues of Lolium temulentum plants during floral development

Free, esterified and glycosylated sterols were analysed separately from the shoot apices, leaves, leaf sheaths and stems of Lolium temulentum L. (strain Ceres) plants during floral development. Short-day grown plants (50 days old) were induced to flower by exposure to a single long day. The four major sterols found by GC-MS analysis were sitosterol, cholesterol, campesterol and stigmasterol. The sterol levels in the shoot apex were much higher than those in the leaf, leaf sheath and stem. A much greater proportion of cholesterol was found in the shoot apex than in other tissues and this may reflect a specific association of cholesterol with meristematic and/or reproductive tissues.
During the inductive treatment, the sterol levels decreased in all four tissues. The major effect during early differentiation was the occurrence of transient increases in the free and esterified sterol levels in the leaf and the stem tissues. The steryl ester content peaked 24 h before the appearance of double ridges, followed by a peak in free sterol content at the double ridge stage. Similar changes could not be detected in the shoot apices. This is the first report of the sterol composition of developing shoot apices, and the results emphasize the dynamic nature of sterol metabolism during reproductive growth of L. temulentum.     

Biosynthesis and metabolism of steryl glycosides in Sinapis alba seedlings

With ¹⁴CO₂, d-glucose-[U-¹⁴C] and dl-mevalonate-[4R-4-³H₁] used as precursors, a study was made of the labelling dynamics of the steryl glucosides (SG) and steryl acylglucosides (ASG) in Sinapis alba seedlings. The radioactivity of the sterol and sugar moieties, as well as of the fatty acid moieties in the case of ASG, was analysed separately. The course of incorporation of ¹⁴C from ¹⁴ CO₂ and glucose-[U-¹⁴C] into the sugar part of SG and ASG indicated that about $\text{2}\text{3}$ of the whole pool of the newly synthesized sterol glycosides of both types underwent rapid deglucosylation. Likewise, fatty acids in the ASG pool were rapidly exchanged. The present results point to a high metabolic activity of the sterol glycoside derivatives in plant cells.     

Steryl glycosides and acyl steryl glycosides from Musa paradisiaca

From peeled fruits of Musa paradisiaca (banana, vegetable variety), two new acyl steryl glycosides, sitoindoside-III and sitoindoside-IV, and two new steryl glycosides, sitosterol gentiobioside and sitosterol myo-inosityl-β-D-glucoside, have been isolated by gradient solvent extraction and extensive chromatography (CC, prep. TLC, GC and HPLC). The compounds have been characterized by comprehensive spectroscopic analyses (IR, ¹H NMR, GC, mass spectra, [α]_D) and crucial chemical transformation. Additionally, seasonal variations of the total sterols, free sterols, steryl esters, steryl glycosides and acyl steryl glycosides in the active samples of banana have been analysed. The results provide a basis for the observed fluctuations in the anti-ulcerogenic activity of the extracts, in different seasons, and the importance of appropriate formulation of the pure principles to optimize the activity.     

Evidence for the Presence of "Metabolic Sterols" in Pneumocystis: Identification and Initial Characterization of Pneumocystis carinii Sterols

Mixed life cycle stages of rat-derived Pneumocystis carinii were isolated from host lungs and their sterols were compared with those present in lungs from normal and immunosuppressed uninfected rats. Gas-liquid chromatography consistently detected, resolved, and quantified 9, 10, and 20 sterol components in the total nonsaponifiable neutral lipid fraction of lungs from normal rats, lungs from immunosuppressed uninfected rats, and P. carinii preparations, respectively. In all samples, cholesterol was the most abundant sterol present, comprising 97%, 93%, and 78% of total sterols in lungs from normal rats, lungs from immunosuppressed uninfected rats, and P. carinii , respectively. Tentative identifications of several rat lung and P. carinii minor sterols were made based on gas-liquid chromatogram retention times and fragmentation patterns from mass spectral analyses. Campesterol (ergost-5-en-3-ol), cholest-5-en-3-one, and β -sitosterol (stigmast-5-en-3-ol) were among the minor components present in both types of lung controls, and were also components of P. carinii sterols. In contrast to lung controls, the sterols of P. carinii were enriched in C₂₈ and C₂₉ sterols with one or two double bonds, and a hydroxyl group at C-3 (ergost-5-en-3-ol, ergost-7-en-3-ol, ergosta-dien-3-ol, stigmast-5-en-3-ol, stigmast-7-en-3-ol and stigmasta-dien-3-ol). Steryl esters of P. carinii , probably stored in cytoplasmic lipid droplets, were dominated by those present in the host lung. In separate studies. 3-hydroxy-3-methylglutaryl coenzyme A activity, a key enzyme in the regulation of sterol biosynthesis, was detected in purified P. carinii preparations and incorporation of radiolabeled squalene and mevalonate was observed. Together, these results suggest that the parasite readily takes up and incorporates host sterols, and that the organism synthesizes some of its own "metabolic sterols"     

Free sterols,steryl esters,glucosides, acylated glucosides and water-soluble complexes in Calendula officinalis

In 3- and 14-day-old seedlings and in the leaves of Calendula officinalis the following sterols were identified: cholestanol, campestanol, stigmastanol, cholest-7-en-3-β-ol, 24-methylcholest-7-en-3β-ol, stigmast-7-en-3β-ol, cholesterol, campesterol, sitosterol, 24-methylcholesta-5,22-dien-3β-ol, 24-methylenecholesterol, stigmasterol and clerosterol. Sitosterol was predominant in young and stigmasterol in old tissues. Young tissues contained relatively more campesterol but in old tissues a C₂₈Δ^5,22 diene was present suggesting transformation of campesterol to its Δ^5,22 analog, similar to that of sitosterol to stigmasterol. All the identified sterols were present as free compounds and also in the steryl esters, glucosides, acylated glucosides and water-soluble complexes. The variations in the amounts of these fractions in the embryo axes and cotyledons of 3- and 14-day-old seedlings and the distribution of individual sterols among the fractions are discussed.     

Partial purification and specificity of triacylglycerol: Sterol acyltransferase from Sinapis alba

Triacylglycerol: sterol acyltransferase is present in roots of Sinapis alba seedlings. The enzyme is located predominantly in the cell membrane structures sedimenting at 300–16 000 g but can be solubilized by acetone treatment and buffer extraction. During gel filtration on Sephadex G-100 the acyltransferase activity was separated into two peaks corresponding to MW 1.8 × 10¹⁴ and MW ? 10⁵, respectively. A number of natural 3β-hydroxysterols can be esterified by the solubilized acyltransferase. The rate of esterification is much higher for sterols containing a planar ring system. The number and position of double bonds, as well as the structure of the side chain at C- 17 of the sterol molecule, are of secondary importance. Triacylglycerols containing fatty acids C, C₆-C₂₂ can be utilized as acyl donors. Among triacylglycerols containing saturated fatty acids, tripalmitoylglycerol (C_16:0) is the best acyl donor. For triacylglycerols containing C₁₈-fatty acids the following sequence was observed: trioleoylglycerol (C_18:1) > trilinoleoylglycerol (C_18:2) > trilinolenoylglycerol (C_18:3) > tristearoylglycerol (C_18:0).     

Occurrence of steryl glycosides and acylated steryl glycosides in some marine algae

There is some controversy concerning the presence of steryl glycosides and acylated steryl glycosides in eucaryotic algae. These two classes of sterol compounds were investigated in species belonging to the three major groups of eucaryotic algae: green algae (Ulva gigantea, Cladophora rupestris), brown algae (Fucus vesiculosus, Ascophyllum nodosum), and red algae (Rhodymenia palmata, Porphyridium sp.). All these algae contain both steryl glycosides and acylated steryl glycosides. The sterol components of these compounds vary according to the alga but they are always the same as the free sterols of the alga in question. The most common sugar moiety is glucose. In the acylated steryl glycosides, the fatty acid is mainly palmitic acid. The percentage of these compounds (as a percentage of the total sterol content) is often low.     

Separation and analysis of steryl and wax esters from Dicranum elongatum

Abstract Complete separation of the steryl and wax esters in the subarctic moss Dicranum elongatum was achieved on MgO thin-layer plates without any notable alteration of the acyl and alkyl moieties of the esters. Gas chromatography-mass spectrometry of the hydrolyzed fraction showed that the sterols (campesterol, stigmasterol, sitosterol, cycloartenol, 24-methylene cycloartanol and an unidentified sterol) were primarily esterified with unsaturated fatty acids 18:2 ω 6, 18:3 ω 3 and 20:4 ω 6. In contrast, the wax alcohols (l-octadecanol, phytol and geranylgeraniol) were mainly esterified with saturated fatty acids with 16:0, 18:0 and 20:0 as major components. No great differences were found in the fatty acid pattern of the steryl esters between different portions of the shoot. Slight differences, however, were found in the proportions of ω 3 and ω 6 fatty acids. In the wax esters a clear decrease was found in the proportions of 18:0 and 20:0 acids with increased shoot age accompanied by a slight increase in the proportions of 14:0, 20:4 ω 6 and phytenic acid.     

Hexane soluble non-volatiles in flowering to fruiting stages of Fatsia japonica

The n-hexane soluble non-volatile fraction of the acetone extracts from the flower buds, the flowers and the immature and the mature fruits of Fatsia japonica were all found to contain fatty acids, fatty acid methyl esters, squalene, β-amyrin and sterols. At all the stages between budding to the mature fruit, the major fatty acids were palmitic and linoleic acids and the major phytosterol was stigmasterol. In addition steryl and β-amyrenyl esters were found in the flowers and the immature and the mature fruits, but these esters were not present in the flower buds. Sitosteryl ester was the major constituent of the steryl ester fraction in the fruiting stages. Phytol was found in only the flowering stage and triglycerides in only the mature fruits. The variations in the lipid constituents is discussed in relation to the stages from budding to the mature fruit.     

Free and conjugated desmethylsterol composition of Zea mays hybrids exposed to mild osmotic stress

Five hybrids of Zea mays (A619 × H60, B73 × MO17, B73 × PA91, B73 × VA17. A632 × H96) were grown hydroponically at osmotic potentials of -0.1 (control), -0.4 and -0.6 MPa. Dry weights of hybrids B73 × VA17 and A632 × H96 decreased significantly at -0.4 and -0.6 MPa. Few changes were observed in the free sterol, steryl glycoside and steryl ester fractions. However, steryl esters of the roots and stems of osmotically treated plants declined in most of the hybrids. The stigmasterol to sitosterol ratio increased in all three steryl fractions in the roots of B73×VA17 and A632×H96 as a result of the osmotic treatments. B73×VA17 and A632×H96 also exhibited the greatest initial electrolyte leakage when leaf dises were subjected to osmotic stress. A632×H96 and possibly B73×VA17 were less tolerant to osmotic treatments than the other hybrids. Modification of sterols may reflect initial events that lead to the stabilization or destabilization of cellular membrances which in turn may affect the tolerance of plants to stressful environments.     

Steryl chlorin esters in sediments of the southern Baltic Sea

Sediments of the southern Baltic Sea were analysed for content of steryl chlorin esters, the chlorin compounds discovered recently in the marine environment. The chlorin esters occur in the Baltic sediments in substantial amounts and form a considerable fraction of the total chlorin content. Among the physicochemical parameters studied the highest correlation with the steryl chlorins showed organic carbon content in sediments and the content of fraction of sediments smaller than 10 μm. A significant correlation was observed between the steryl chlorins content and other chlorins as chlorophylla, phaeophytina, pyrophaeophytina as well as with β-carotene, the distinctly less significant correlation was with phaeophorbidea. This indicates an other way of formation of the steryl chlorins from algae than zooplankton grazing.     

Purification and some properties of steryl β-d-glucoside hydrolase from Sinapis alba seedlings

Homogenates of 7-day-old S. alba seedlings hydrolysed cholesteryl[4-H¹⁴C] β-d-glucoside or sitosteryl β-d-glucoside-[6-³H]. Activity was located predominantly in the cell membrane structures sedimenting at 1000–15 000 g and was solubilized by acetone treatment. Partially purified enzyme preparation, with an about 1500 times higher specific activity with respect to the crude homogenate, was obtained by repeated acetone precipitation and subsequent chromatography on DEAE-Sephadex and Sephadex G-100. During this procedure a considerable separation from other enzymes with β-glucosidase activity was achieved. The enzyme had MW 65 000 daltons, pH optimum at 5.2–5.6. Two observations suggested that the enzyme was a specific steryl β-d-glucoside hydrolase. Firstly, there was no substrate competition between steryl glucosides and several other β-d-glucosides. Secondly, enzyme activity wasstrongly inhibited by low concentrations of various 3β-OH sterols with a planar ring system and an intact side chain.     

Die zusammensetzung der samen und schoten von sommerraps “Erglu” während der reifung

Changes in the water and lipid content, in the nonsaponifiable matter and total sterols, as well as in the composition of the fatty acids and stero