Esters steryl

Note Silica gel, kieselguhr and polyamide layers can be used as stationary phases. Not all acids are stained on RP layers. Amino layers yield a pale blue background. The detection limits are in the pg range for carboxylic acids [1], thioglycolic and dithioglycolic acids [2] and for antithyroid pharmaceuticals [4] they are about 5 ng per chromatogram zone for sterols and steryl esters [6]. 

Although not very commonly used in the separation of nentral hpids, two-dimensional systems have been nsed to separate hydrocarbons, steryl esters, methyl esters, and mixed glycerides that move close to each other in one-dimensional systems. Complex neutral lipids of Biomphalaria glabrata have been first developed in hexane diethyl ether (80 20), dried, and the plates have been turned 90°, followed by the second development in hexane diethyl ether methanol (70 20 10) for complete separation of sterol and wax esters, triglycerides, free fatty acids, sterols, and monoglycerides [54]. 

Three pro-inflammatory steryl esters of furan fatty acids (11-13) have recently been isolated from the Mediterranean sponge Dictyonella incisa [30]. The furan moiety was clearly established by H and 13C NMR signals corresponding to... 

Sterols are minor constituents of most fats. Those of animal origin contain cholesterol and traces of other sterols, whereas plants contain phytosterols, of which p-sitosterol is the most common. Sterols occur in the free form or, after esterification to fatty acids through the 3-OH group, as steryl esters. The presence of sterols in archaeological residues can be a useful indicator of a plant or animal origin or an indicator of both if cholesterol and phytosterols are detected in the same sample. That noted, cholesterol is a potential contaminant of all archaeological samples subjected to handling. 

Saturated hydrocarbons Unsaturated hydrocarbons Wax esters Steryl esters Long chain aldehydes Triacylglycerols Long chain alcohols Free fatty acids Quinones Sterols... 

A similar study has been carried out to separate the steryl esters of pyrophaephorbide-b produced by algae. Typical chromatograms are shown in Fig. 2.129. The chromatographic profiles illustrate that the method separates well the analytes under investigation and allows the detection of differences between the samples of various origins. 

Sterol esterase Steryl-ester acylhydrolase, cholesterol esterase Steryl esters... 

The overall metabolism of vitamin A in the body is regulated by esterases. Dietary retinyl esters are hydrolyzed enzymatically in the intestinal lumen, and free retinol enters the enterocyte, where it is re-esterified. The resulting esters are then packed into chylomicrons delivered via the lymphatic system to the liver, where they are again hydrolyzed and re-esterified for storage. Prior to mobilization from the liver, the retinyl esters are hydrolyzed, and free retinol is complexed with the retinol-binding protein for secretion from the liver [101]. Different esterases are involved in this sequence. Hydrolysis of dietary retinyl esters in the lumen is catalyzed by pancreatic sterol esterase (steryl-ester acylhydrolase, cholesterol esterase, EC 3.1.1.13) [102], A bile salt independent retinyl-palmitate esterase (EC 3.1.1.21) located in the liver cell plasma hydrolyzes retinyl esters delivered to the liver by chylomicrons. Another neutral retinyl ester hydrolase has been found in the nuclear and cytosolic fractions of liver homogenates. This enzyme is stimulated by bile salts and has properties nearly identical to those observed for... 

The intestinal absorption of dietary cholesterol esters occurs only after hydrolysis by sterol esterase steryl-ester acylhydrolase (cholesterol esterase, EC 3.1.1.13) in the presence of taurocholate [113][114], This enzyme is synthesized and secreted by the pancreas. The free cholesterol so produced then diffuses through the lumen to the plasma membrane of the intestinal epithelial cells, where it is re-esterified. The resulting cholesterol esters are then transported into the intestinal lymph [115]. The mechanism of cholesterol reesterification remained unclear until it was shown that cholesterol esterase EC 3.1.1.13 has both bile-salt-independent and bile-salt-dependent cholesterol ester synthetic activities, and that it may catalyze the net synthesis of cholesterol esters under physiological conditions [116-118], It seems that cholesterol esterase can switch between hydrolytic and synthetic activities, controlled by the bile salt and/or proton concentration in the enzyme s microenvironment. Cholesterol esterase is also found in other tissues, e.g., in the liver and testis [119][120], The enzyme is able to catalyze the hydrolysis of acylglycerols and phospholipids at the micellar interface, but also to act as a cholesterol transfer protein in phospholipid vesicles independently of esterase activity [121],... 

Abidi, S. L. (2004). Capillary electrochromatography of sterols and related steryl esters derived from vegetable oils. J. Chromatogr. A 1059, 199—208. 

This enzyme [EC 3.1.1.13] (also known as cholesterol esterase, sterol esterase, cholesterol ester synthase, and triterpenol esterase) catalyzes the hydrolysis of a steryl ester to produce a sterol and a fatty acid anion. This class represents a group of enzymes exhibiting broad specificity. They act on esters of sterols and long-chain fatty acids, and may also bring about the esterification of sterols. These enzymes are typically activated by bile salts. See also Esterases D. P. Hajjar (1994) Adv. Enzymol. 69, 45. 

Pearce, G.E.S. Keely, B.J. Harradine, P.J. Eckardt, C.B. Maxwell, J.R. (1993) Charactaization of naturally occurring steryl esters daived from chtorophyll a. Tetrahedron Lett., 34, 2989-92. 

Figure D1.6.6 latroscan TLC-FID chromatograms of (A) a lipid fraction enriched with neutral lipids isolated from cod flesh and stored in ice (B) neutral lipids spiked with authentic 1 -0-palmityl-glyceryl ether dipalmitate (GE), coinciding in position with authentic highly unsaturated acids such as 22 6n-3 (C) hydrogenated neutral lipids spiked with GE. The solvent system was 97 3 1 (v/v/v) hexane/diethyl ether/formic acid for 40 min. Abbreviations O, origin SF, solvent front FFA, free fatty acid PL, phospholipids SE, steryl ester ST, free sterol TG, triglyceride. Reproduced from Ohshima et al. (1987) with permission from AOCS Press.

The sample is now ready for analysis using the procedures described above (see Basic-Protocol and Alternate Protocol). Figure D1.6.6 shows chromatograms of cod muscle lipids before and after hydrogenation. Note the single peaks for steryl esters and free fatty acids in panel C compared to the double peaks in panels A and B. 

Fig. 4 LC-GC-FID chromatograms for typical olive oils. The nearly complete absence of wax esters (esters 40-esters 46) and very low concentrations of steryl esters indicate a high-quality extra virgin oil. The concentration of free stigmasterol is low. C24-26-OH, fatty alcohols. In lampante oils, more wax esters and steryl esters are found. The concentration of stigmasterol increases more than campesterol if the oil was prepared from olives of low quality. Run at the same sensitivity, chromatograms of solvent-extracted oils are completely overloaded. The refined extraction oil was diluted 1 5 before running the chromatogram shown. Wax ester and steryl ester concentrations are very high. (From Ref. 34, p. 626.)...

The important role of sterol components in the acquisition of freezing tolerance has recently been demonstrated using an Arabidopsis mutant with altered steryl-ester metabolism. Compared with the wild-type the mutant has no visible phenotype at standard growth temperature but exhibits clear symptoms when exposed to low temperatures (Hugly et al.,... 

Hugly, S., McCourt, P., Browse, J., Patterson, G.W. Somerville, C. (1990). A chilling sensitive mutant of Arabidopsis with altered steryl-ester metabolism. Plant Physiology 93, 1053-62. 

Cranwell, P.A., and Volkman, J.K. (1985) Alkyl and steryl esters in a recent lacustrine sediment. J. Chem. Geol. 32, 29 -3. 

King, L.L., and Repeta, D.J. (1994) Novel pyropheophorbide steryl esters in Black Sea... 

Sitosterol and stigmasterol were the major components of celery seed oil. The other components were cholesterol, brassicasterol, campesterol, 97-campesterol, 95-avenasterol, 97-stigmasterol and 9 7-avenasterol (Zlatanov and Ivanov, 1995). Oil bodies isolated from celery cell suspension cultures contained at least 60% of the total steryl ester present in the cells. Free sterols comprised < 0.5% of the total lipid in the oil body. Sterylesters constituted 4.5% of the total lipid of celery oil bodies. The proportion of precursor 4-methylsterols in the free sterol fraction of celery was greater in the oil body (Dyas... 

Kamm el al. (2001) analysed intact steryl esters in the presence of silylated sterols by online transfer from HPLC to a 15 m low-polarity high temperature GC column. Steryl esters were quantified against a cholesteryl laurate internal standard and identified by offline thin layer chromatography-gas chromatography-mass spectrometry. When esters of sitosterol, stigmasterol and campesterol with the major cocoa butter acids were measured in cocoa butters from South America, Asia and Africa, no differences were apparent between cocoa butters of different geographical origin, or between deodorized and non-deodorized butters. 

No comprehensive comparison has been made of the proportions of the free and esterified sterols in cocoa butter with those of fats likely to be used in cocoa butter adulteration. However Gordon and Griffiths (1992) examined the sterol esters of palm kernel oil by isolation with TLC followed by GC and HPLC. They pointed out the problem of co-elution of triacylglycerols with steryl esters with GC. The characterization of esters of triterpene alcohols in CBA fats might well prove useful where the use of fats containing shea is suspected. 

Gordon, M.H. and Griffith, R.E. (1992) A comparison of the steryl esters of coconut and palm kernel oils. FatSci. Technol., 94(6), 218-221. 

Standard methods of analysis of total sterol content of oils involve saponification of the oil, followed by extraction and isolation of total sterols from the unsaponihable fraction by thin layer chromatography (TLC) (AOCS, 1998). Quantification of individual sterols involves silylation of the sterol fraction and analysis by gas chromatography (GC). Sterols and steryl esters in oils and fats can be analysed by LC-GC after silylation or acylation of the free sterols (Artho et al., 1993). An alternative approach to the analysis of intact steryl esters involves separation of sterols and steryl esters by solid phase... 

Ferrari, R., Esteves, W. and Mukherjee, K. (1997) Alteration of steryl ester content and positional distribution of fatty acids in triacylglycerols by chemical and enzymatic interesterification of plant oils. J. Am. Oil Chem. Soc., 74(2), 93—96. 

Gordon, M.H. and Miller, L.A.D. (1997) Development of steryl ester analysis for the detection of admixtures of vegetable oils. J. Amer. Oil Chem. Soc., 74, 505-510. 

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