Steryl Ester Fraction Research Articles

Esterified sterols and their contribution to the total sterols in edible mushrooms

Mushrooms are a valued source of sterols, which can be present in free form and esterified to fatty acids. In addition to the principal ergosterol, several minor sterols occur. Ergosterol and ergosteryl ester were determined directly by gas chromatography coupled to mass spectrometry (GC/MS) in the trimethylsilylated lipid extract of each six samples of button mushrooms, oyster mushrooms, king trumpet mushrooms and shiitake. Free ergosterol was highest in button mushrooms 415–544mg/100g dry matter (d.m.) and lowest in oyster and king trumpet mushrooms (<350mg/100g d.m.). On the other hand, concentrations of ergosteryl esters were significantly lower (5–26mg/100g d.m.) in all mushroom samples. The distribution of minor sterols (most importantly ergosta-7,22-dienol, ergosta-5,7-dienol, ergosta-7-enol) between free and esterified form was determined after group separation with solid phase extraction. Higher proportions of the minor sterols were found esterified to fatty acids and ergosta-7-enol was found predominantly (70%) in this form in oyster mushrooms and shiitake. The minor sterols ergosta-8,24(241)-dienol, ergosta-8-enol and 7-dehydro-poriferasterol could be tentatively identified in the samples based on GC/MS data. In addition, four sterols were found only in the steryl ester fraction of the mushroom samples.

Method Development for the Determination of Free and Esterified Sterols in Button Mushrooms (Agaricus bisporus).

Ergosterol is the major sterol in button mushrooms (Agaricus bisporus) and can occur as free alcohol or esterified with fatty acids (ergosteryl esters). In this study, gas chromatography with mass spectrometry in the selected ion monitoring mode (GC/MS-SIM) was used to determine ergosterol and ergosteryl esters as well as other sterols and steryl esters in button mushrooms. Different quality control measures were established and sample preparation procedures were compared to prevent the formation of artifacts and the degradation of ergosteryl esters. The final method was then used for the determination of ergosterol (443 ± 44 mg/100 g dry matter (d.m.)) and esterified ergosterol (12 ± 6 mg/100 g d.m.) in button mushroom samples (n = 4). While the free sterol fraction was vastly dominated by ergosterol (∼90% of five sterols in total), the steryl ester fraction was more diversified (nine sterols in total, ergosterol ∼55%) and consisted primarily of linoleic acid esters.

Identification of fatty acid steryl esters in margarine and corn using direct flow injection ESI-MSn ion trap-mass spectrometry

An approach for identification of steryl esters using flow injection ESI-MS2 and ESI-MS3 ion trap mass spectrometry has been developed. Sterols and other lipids extracted from samples of margarine and corn using hexane were subjected to solid phase extraction. The steryl ester fraction was eluted with hexane:diethyl ether (98:2, v/v). In ESI-MS experiments fatty acid steryl esters were easily detected as ammoniated adducts [M+NH4]+ using ammonium acetate as dopant. Steryl esters including molecular isomers could be identified using ESI-QIT MS2 by the facile ester cleavage whereby the charge resides with the steryl moiety. For positive confirmation of the sterol group, ESI-QIT MS3 was carried out on the intact steryl fragmentation cation. The resulting CID spectra of the steryl cation were found to be unique and similar to those from APCI-QIT MS2 CID of free sterol standards. All major steryl esters were identified in both margarine (12 esters) and corn (7 esters) extracts. Based on the ion intensity of the ESI-MS spectra the major steryl esters in margarine were: β-sitosteryl stearate, β-sitosteryl oleate, β-sitosteryl linoleate, campesteryl stearate and campesteryl linoleate. In corn they were: β-sitosteryl oleate, campesteryl stearate, campesteryl oleate and stigmasteryl linoleate. This method can be very useful for rapid and complete identification of fatty acid steryl esters extracted from other biological samples.

Steryl esters of Digitalis purpurea L. herb.

Abstract The non-polar fraction sterols of Digitalis purpurea flowering plants were separated into a steryl ester and free sterol fraction. The ester fraction consisted of cycloeucalenol, obtusifoliol, 24-methylenelophenol, 24-ethylenelophenol, cholesterol, campesterol, stigmasterol, sitosterol, isofucosterol and 24-methylenecholesterol. These compounds were esterified with an αβ-unsaturated C10 fatty acid, whereas the glycerides from the same plant consisted of a complex of acids predominated by C18 and C16 types. The free sterols consisted of cycloartenol, 24-methylenecycloartenol, cholesterol, campesterol, stigmasterol, sitosterol, fucosterol and 24-methylenecholesterol. The relative proportions of each of these steroids in the two fractions were recorded.

Comparison of the lipid profiles from wild caught eggs and unfed larvae of two scombroid fish: northern bluefin tuna (Thunnus thynnus L., 1758) and Atlantic bonito (Sarda sarda Bloch, 1793)

Lipids and essential fatty acids are determinants of the reproductive process in marine fish, affecting fecundity, egg quality, hatching performance, pigmentation and larval malformation. We have analyzed and characterized the lipids of eggs and unfed larvae of two wild caught scombroid fish, the Atlantic northern bluefin tuna (Thunnus thynnus) and Atlantic bonito (Sarda sarda). Dry matter and total lipid contents, polar and neutral lipid classes and total lipid fatty acid contents were determined in the eggs of bluefin tuna and eggs and unfed larvae during the development of Atlantic bonito. Bluefin tuna eggs had slightly but significantly more dry mass than bonito eggs but very similar lipid content. However, bluefin tuna eggs presented a higher polar lipid content due to increased proportions of phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI). Bonito eggs and larvae showed increasing dry mass and decreasing lipid content with development. The proportion of polar lipids increased due to increased PE, PS and PI, whereas choline-containing polar lipids (phosphatidylcholine and sphingomyelin) remained relatively constant. Free cholesterol also increased, whereas the levels of other neutral lipids, especially triacylglycerol and steryl ester fractions, decreased, presumably due to utilization for energy to drive development. Bluefin tuna eggs had higher levels of n - 3 and n - 6 highly unsaturated fatty acids due to higher docosahexaenoic and arachidonic acid contents, respectively, than bonito eggs. The results are discussed in relation to the lipid and fatty acid requirements of larval scombroid fish in comparison to those of other larval marine finfish species under culture conditions.

Ferrous, But Not Ferric, Iron Maintains Homeostasis in Histoplasma capsulatum Triacylglycerides

Iron is an indispensable micronutrient for virtually all microorganisms, where it acts as a cofactor of many enzymes involved in regulation of multiple cellular and physiological functions. This metal is also considered an important determinant contributing to the pathogenesis of fungal infectious diseases, and therefore the identification of iron-regulated metabolic processes occurring within the invading fungal cell can help the development of new antifungal therapeutic strategies. In this study, we examined relationships between iron availability and neutral storage lipids in Histoplasma capsulatum, a dimorphic fungus responsible for the most common respiratory and systemic mycosis in humans. Yeast cells were grown in a defined minimal medium supplemented with or without iron. Lipids were extracted from cells at the log and late stationary growth phases, then separated by thin-layer chromatography, and fatty acids were analyzed by gas chromatography. A culture age-related decrease in the unsaturated fatty acid content was observed in all four neutral lipid classes examined. Iron-related alterations could be seen in relation to triacylglycerol and free fatty acid pools, whereas no iron-dependent effects were detected in diacylglycerol and steryl ester fractions. Regarding triacylglycerols, the presence of iron positively affected the content of unsaturated fatty acids, and this stabilizing action of iron was notably increased when ferrous ions were added. Subsequent iron uptake studies showed a definite preference of H. capsulatum to acquire iron in its reduced, more soluble, ferrous form, and therefore, the availability of iron may be the underlying reason for the observed iron-maintained homeostasis in H. capsulatum triacylglycerols.

Seasonal and within-stem variations of neutral lipids in silver birch (Betula pendula) wood.

Neutral lipids were analyzed in stem wood of a 7-year-old clone and in five 35-70-year-old mature trees of silver birch (Betula pendula Roth). In young trees and in mature wood of old trees, the free fatty acid fraction comprised less than 5% of the concentration of triacylglycerols (TG). The concentration of free linoleic acid was lowest in March when the young trees were dormant and highest during midsummer and September. In mature trees, the TG concentration increased toward the pith, indicating that living parenchyma cells close to the pith have a large TG storage capacity. The TG concentration (mean 0.51 +/- 0.02% of wood dry mass) remained constant throughout the year in young trees, whereas the concentration of beta-sitosterol, the dominant free sterol (mean 82.5 +/- 0.4% of total free sterols), decreased during spring and early summer when the temperature gradually increased, and increased during autumn when the trees became dormant. In young trees, we detected a seasonal interconversion between the free and esterified forms of beta-sitosterol and campesterol, and within the steryl ester fraction between squalene and betulaprenol-7. The concentration of esterified sterols/isoprenoids was exceptionally high, especially in the inner regions of mature stem wood (mean 0.6 +/- 0.03% of wood dry mass). No heartwood formation was detected.

Influence of the vegetable oil refining process on free and esterified sterols

AbstractThe influence of the refining process on the distribution of free and esterified phytosterols in corn, palm, and soybean oil was studied. Water degumming did not affect the phytosterol content or its composition. A slight increase in the content of free sterols was observed during acid degumming and bleaching due to acid‐catalyzed hydrolysis of steryl esters. A significant reduction in the content of total sterols during neutralization was observed, which was attributed to a reduction in the free sterol fraction. Free sterols probably form micelles with soaps and are transferred into the soapstock. The steryl ester content remained constant during all neutralization experiments, indicating that hydrolysis of steryl esters did not take place during neutralization. During deodorization, free sterols are distilled from the oil, resulting in a gradual reduction in the total sterol content as a function of the deodorization temperature (220–260°C). A considerable increase in the steryl ester fraction was found during physical refining, probably owing to a heat‐promoted esterification reaction between free sterols and FA.

Identification and quantification of important steryl esters in aspen wood

AbstractSteryl esters make up a major portion of the total lipids in aspen wood, and contribute significantly to pitch deposit problems during pulping. Fungal treatment of aspen is an attractive method for removing these compounds because it is inexpensive and environmentally acceptable; however, the mechanism of steryl ester removal remains unclear. Identification of the steryl esters will lead to a better understanding of how they are removed by fungi. The steryl ester fraction from aspen wood was obtained by acetone extraction then further purified by silica gel column chromatography and argentation‐silica gel column chromatography. This led to the isolation of three major fractions: fraction I, fraction II, and fraction III. The major steryl esters of fractions I and II were identified by gas chromatography, gas chromatography‐mass spectroscopy, and proton nuclear magnetic resonance analysis of the intact fraction as well as sterol and fatty acid moieties obtained after base hydrolysis. Identification of the steryl esters was carried out by mass spectra comparisons with steryl ester standards synthesized in the laboratory and comparison with mass spectra libraries (Wiley and NIST) by mass fragmentography. Fraction I contained primarily the palmitate, stearate, and eicosanoate esters of α‐ and β‐amyrin. Fraction II consisted mainly of the palmitate, stearate, and eicosanoate esters of tirucalla‐7,24‐dien‐3β‐ol and lupeol.

Temperature of water heat treatments influences tomato fruit quality following low-temperature storage

Abstract Mature-green tomato fruit (Lycopersicon esculentum Mill. cv. Sunbeam) were treated in water for 1 h at 27 (ambient), 39, 42, 45, or 48°C, and then either ripened at 20°C (nonchilled) or stored at 2°C (chilled) for 14 days before ripening at 20°C. Treatment at 42°C reduced decay by 60%, whereas the other water temperatures were less effective. Heat treatment had no effect on time required to ripen the fruit, with 11 days required for nonchilled and 27 days required for chilled fruit (including storage time). Ripe, nonchilled tomatoes had higher respiration rates and evolved more ethylene than did chilled fruit. The 48°C treatment increased respiration and ethylene evolution compared with the other treatment temperatures. Red color development was enhanced by heat treatment, and inhibited by chilling. At red ripe, fruit were firmer as a result of storage at the chilling temperature, while heat treatment had no effect on firmness. With the exception of the 45°C treatment, chilled as well as nonchilled fruit previously treated at 39, 42, or 45°C were preferred in terms of taste and texture in informal taste tests over fruit treated at 27 or 48°C. Storage at 2°C led to an increase in electrolyte leakage, particularly in the 48°C treated fruit. Of the 15 flavor volatiles analyzed, the levels of five were decreased and two were increased with increasing temperature of heat treatment. Storage at the chilling temperature reduced the levels of five flavor volatiles. Heat treatments decreased sterols in the steryl ester fraction, several sterols in the free sterol, steryl glycoside, and acylated steryl glycoside fractions. Prestorage heat treatments, with the possible exception of the 48°C temperature, can reduce decay with only minimal adverse effects on tomato fruit quality.

Occurrence of Potential Brassinosteroid Precursor Steroids in Seeds of Wheat and Foxtail Millet

L.) and foxtail millet (Setaria italica Beauv.) were found by GC-MS to contain, in addition to bulk sterols, 4-en-3-one steroids including 24-ethylcholesta-4,24(28)Z- dien-3-one (a new steroid), 24-methylcholest-4-en-3-one, 24-ethylcholesta-4,22E-dien-3-one and 24-ethylcholest-4-en-3-one, as well as 5α-steroidal 3-one compounds including 24-methyl-5α-cholestan-3-one, 24-ethyl-5α-cholestan-3-one and 24-ethyl 5α-cholest-22E-en-3-one (in S. italica only). Analysis of free sterol and steryl ester fractions indicated that campestanol and sitostanol were present at high levels in both seeds. These results suggest that the seeds of T. aestivum and S. italica synthesize campestanol from campesterol via 24-methylcholest-4-en-3-one and 24-methyl-5α-cholestan-3-one as has already been demonstrated in Arabidopsis thaliana L., and also produce sitostanol from sitosterol via 24-ethylcholest-4-en-3-one and 24-ethyl-5α-chotestan-3-one. Biosynthetic relationships of campestanol and sitostanol with C28 and C29 brassinosteroids are discussed.

Liver lipids and fatty acids of the sting ray Dasyatis bleekeri (Blyth)

AbstractThe sting ray, Dasyatis bleekeri (Blyth), has been studied for lipids and fatty acids of its liver. The neutral lipids identified were hydrocarbons, wax esters, steryl esters, 1‐O‐alkyl‐2,3‐diacylglycerols, triacylglycerols, and sterols. Neutral lipids were predominant (91.8%), major components being triacylglycerols (92.7%). Polyenoic fatty acids of n‐3 series, viz. eicosapentaenoic acid and docosahexaenoic acid, were high in the phospholipid and neutral lipid fractions. Cholesterol was the major component (67.9%) in the steryl ester fraction. Glyceryl ethers, with chainlengths up to 30 carbons, were recorded with unsaturated, anteiso, iso, and normal chains. In wax ester alcohols, up to 32‐carbon chains were recorded. Hydrocarbons were up to 36‐carbon chains with anteiso, iso, and normal chains. Among branched chain hydrocarbons, pristane was the major component (6.7%) and squalene was present at the level of 3.5%. Chimyl and batyl alcohol backbones were the major components found in 1‐O‐alkyl‐diacylglycerols.

Rapid separation of microbial lipids using solid phase extraction columns

A method was developed to rapidly separate lipid classes commonly found in microorganisms. The method is based on the use of aminopropyl solid phase extraction columns to separate polyhydroxyalkanoates (PHA), phospholipids, sterols, triglycerides, diglycerides, monoglycerides, and steryl esters. Recoveries of all lipid classes, with the exception of PHA and sterols, ranged from 91% to greater than 99%. PHA were recovered at 69% of the standard, and sterols from 82–84% of the standard. When applied to the analysis of lipids extracted from the cyanobacterium Spirulina platensis, the method afforded excellent recovery and separation of phospholipids and diglycerides including saturated, monounsaturated and polyunsaturated fatty acids. The S. platensis lipids also contained hydrocarbons and phytol recovered in the steryl ester and diglyceride fractions, respectively. This method provided a high yield, specific and rapid separation of microbial lipids with little contamination from other lipid groups, and will be useful for the characterization of microbial communities in environmental samples.

Development of steryl ester analysis for the detection of admixtures of vegetable oils

AbstractThe steryl ester content and composition of 28 samples from 10 vegetable oil types have been determined by isolation of the steryl esters by high‐performance liquid chromatography and analysis by gas chromatography. The oils can be classified into oils with a high content (&gt;4000 mg/kg) of steryl esters (corn and rapeseed); oils with a medium content (1400–2400 mg/kg) of steryl esters (sunflower oil and high‐oleic sunflower oil); and oils with a low content (&lt;1200 mg/kg) of steryl esters (safflower, soybean, cottonseed, groundnut, olive, and palm oils). The composition of the steryl ester fraction varies to a greater extent for different oil types than for different varieties of the same oilseed. The developed method is promising for authentication of some oils, and is particularly suitable for detecting admixtures of low levels of corn or rapeseed oils.

Effect of Steryl Cinnamic Acid Derivatives from Corn Bran on Aspergillus flavus, Corn Earworm Larvae, and Driedfruit Beetle Larvae and Adults

Steryl esters of ferulic and p-coumaric acids were tested for their effect on corn fungal pathogens and insects. The steryl ester fraction from corn bran had no effect on corn earworm larvae or driedfruit beetle adults, but driedfruit beetle larvae showed a significant increase in weight and the triglyceride fraction was active. Bioassays of pure ferulate esters and the ester fraction from both corn and rice showed no appreciable effect at 100 ppm on spore germination or germ tube growth of Aspergillus flavus, Fusarium moniliforme, or Diplodia maydis. Sclerotinia sclerotiorum was inhibited 75−90% by the total steryl ester fraction from corn and approximately 50% by the ester fraction from rice bran oil. Stigmastanyl and campestanyl ferulate showed little or no inhibition. The steryl ester fraction increased aflatoxin B1 level in A. flavus NRRL 6536 significantly at 0.33 and 1.0 mg/mL. However, the esters had no effect on A. flavus NRRL 3357. The steryl ferulate and p-coumarate ester fraction from corn was...

Sterol and fatty acid composition of neutral lipids of Paratenuisentis ambiguus and its host eel.

The sterol composition of free sterol and steryl ester fractions of the fish parasite Paratenuisentis ambiguus was determined. In addition, the fatty acid composition of various neutral lipid classes, i.e., wax esters, steryl esters, triacylglycerols and free fatty acids, as well as the composition of the 1-O-alkyl moieties of total ether glycerolipids of the parasite, were investigated. The results of these studies were compared with those obtained on the intestinal tract tissue of its host, the eel (Anguilla anguilla). Cholesterol is the major sterol in both P. ambiguus and A. anguilla. However, the sterols of P. ambiguus contain high proportions (> 20%) of other sterols, such as campesterol and various dehydrosterols. [e.g., 7-dehydrocholesterol and cholesta-5,22(E)-dienol]. The presence of these minor sterols agrees with the known biotransformations of exogenous sterols in various helminths. Considerable differences are found in the fatty acid composition of neutral lipid fractions, as well as the total lipid extract from the endoparasite as compared to the host tissue. In particular, eicosapentaenoic acid (20:5n-3), other polyunsaturated fatty acids, such as 20:4n-6, 22:5n-3 and 22:6n-3, as well as long-chain saturated fatty acids, such as 20:0, are generally enriched in the neutral lipid fractions of the parasite as compared to those of infected eel intestine.(ABSTRACT TRUNCATED AT 250 WORDS)

The sterol composition of five plant species grown as cell suspension cultures

The free sterols, steryl esters, steryl glycosides and acylated steryl glycosides were examined from five plant species grown as cell suspension cultures, i.e. Apium graveolens, Morinda citrifolia, Nicotiana tabacum, Solanum tuberosum and Tabernaemontana divaricata. The amount and composition of the various steryl lipid classes varied between plant species, but some features previously reported in suspension cultures of A. graveolens were common to other species. Firstly, stigmasterol, which represented between 3 and 44% of the free sterols of the cultures, was either undetected or contributed very little to the steryl ester fraction. Secondly, the precursor sterols (cycloartenol, obtusifoliol) were esterified in greater proportion to palmitic acid than to the C 18 fatty acids. There did not appear to be a simple relationship between the amount of free sterol and the extent of esterification in the various cultures, as the free sterol: esterified sterol ratio varied from 0.39 to 79.25. The composition of the steryl lipids of S. tuberosum differed markedly from that of the other cultures. The steryl glycosides of this species contained both pyranosides and furanosides, which were separable under the GC conditions employed. The steryl lipids of N. tabacum and S. tuberosum were also at variance with reported lipid analyses of the whole plant tissue of these species.

The steryl ester and phospholipid fatty acids of the spongeAgelas conifera from the Colombian Caribbean

AbstractThe steryl ester and phospholipid fractions of the marine spongeAgelas conifera were isolated and analyzed. The fatty acyl components of the steryl ester and phospholipid fractions as determined by gas chromatography and gas chromatography/mass spectrometry were very similar and consisted of 56.8 and 62.7% of C14−C20 acids (normal; branched, especiallyiso andanteiso; and monounsaturated, particularly Δ9 and Δ11 acids) and of 43.1 and 35.5% of C24−C26 acids (Δ5,9 diunsaturated acids), respectively. The major constituent fatty acids detected were 13‐methyltetradecanoic,n‐hexadecanoic, 10‐methylhexadecanoic, 11‐octadecenoic, 12‐methyloctadecanoic, 5,9‐pentacosadienoic and 5,9‐hexacosadienoic acids. The phospholipids isolated were identified as phosphatidylcholine (37%), phosphatidylserine (34%), phosphatidylethanolamine (16%) and phosphatidylinositol (11%). The distribution of fatty acids within the phospholipid classes was also determined.

Temperature Preconditioning Increases Tolerance to Chilling Injury and Alters Lipid Composition in Zucchini Squash

Temperature preconditioning at 15°C for 2 d effectively delayed the development of chilling injury in zucchini squash (Cucurbita pepo L., cv. ‹Ambassador›) storage at 5°C. Chilling at 5°C resulted in loss of phospholipids, including PC, PE, PG, and PI. These losses were reduced by temperature preconditioning treatment. The degree of fatty-acid unsaturation of phospholipids declined during storage, but was higher in treated squash than in the controls. Temperature preconditioning treatment also reduced losses of the galactolipids MGDG and DGDG during the cold storage. Spinasterol and Δ7-stigmastenol were the two predominant sterols, constituting more than 75 % of both the free sterol and steryl ester fractions. The ratio of free sterol/total phospholipids increased during the cold storage. The increase of this ratio was suppressed by the temperature preconditioning treatment. These results may indicate that acclimation to chilling storage temperatures involves protection of membranes from chilling-induced degradation of glycerolipids.

A Comparison of the Steryl Esters of Coconut and Palm Kernel Oils

AbstractThe steryl ester fraction of coconut and palm kernel oils has been separated and analysed by gas chromatography (GC) and high performance liquid chromatography (HPLC). The gas chromatograms of the steryl ester fractions of the oils are rather similar, but the liquid chromatograms show important differences which may represent a basis for distinguishing between the two oils.