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... 

Research has also been conducted in which steryl phosphonic acid (SPA) was examined in place of benzyl arsonic acid (BAA), which was used in an operating plant in China [5], In this study, several collectors were examined, including sodium laurate, sodium dodecyl sulphate, amino acids, diphosphonic acid (SPA). It was discovered that SPA was the most effective and that aliphatic alcohol (i.e. octanol) was required to maintain the effectiveness of SPA. The use of emulsifier in the mixture was required to provide a suitable emulsion of the composite collector. 

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... 

Another RP-HPLC procedure was applied for the study of the distribution and stability of steryl chlorin esters in copepod faecal pellets from diatom grazing. Pigments were sonicated for 15 min with acetone at 0°C and the procedure was repeated until the extract became colourless. The organic phase was evaporated and the fraction containing the free alcohols was separated by TLC (silica stationary and dichloromethane mobile phases) and analysed by gas chromatography. RP-HPLC measurements were performed in an ODS... 

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. 

Steryl choline esters (SCEs) found in the samples are listed in Table 2.102. It can be concluded from the data that the method is suitable for the investigation of the fate of chlorophylls in algae [294],... 

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],... 

Another enzyme in this class is steryl sulfatase (steroid sulfatase, steryl-sulfate hydrolase, EC 3.1.6.2). The typical substrate of this enzyme is the endogenous metabolite 3/3-hydroxyandrost-5-en-17-one 3-sulfate, but the enzyme also hydrolyzes some related steryl sulfates. 

A number of enzymes known as sulfuric ester hydrolases (EC 3.1.6) are able to hydrolyze sulfuric acid esters. They comprise arylsulfatase (sulfatase, EC 3.1.6.1), steryl-sulfatase (steroid sulfatase, steryl-sulfate sulfohydrolase, arylsulfatase C, EC 3.1.6.2), choline-sulfatase (choline-sulfate sulfohydrolase, EC 3.1.6.6), and monomethyl-sulfatase (EC 3.1.6.16). Whereas mono-methyl-sulfatase is highly specific and does not act on higher homologues, arylsulfatase has a broad substrate specificity and is of particular significance in the hydrolysis of sulfate conjugates of phenols, be they endogenous compounds, drugs, or their metabolites [167-169],... 

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

Arylsulfatase [EC 3.1.6.1 ], also known simply as sulfatase, catalyzes the hydrolysis of a phenol sulfate, thereby producing a phenol and sulfate. This enzyme classification represents a collection of enzymes with rather similar specificities. (1) Steryl-sulfatase [EC3.1.6.2],also referred to as arylsulfatase C and steroid sulfatase, catalyzes the hydrolysis of 3-j8-hydroxyandrost-5-en-17-one 3-sulfate to 3-j8-hydroxyandrost-5-en-17-one and sulfate. The enzyme utilizes other steryl sulfates as substrates. (2) Cere-broside-sulfatase [EC 3.1.6.8], or arylsulfatase A, catalyzes the hydrolysis of a cerebroside 3-sulfate to yield a cerebroside and sulfate. The enzyme will also hydrolyze the galactose 3-sulfate bond present in a number of lipids. In addition, the enzyme will also hydrolyze ascorbate 2-sulfate and other phenol sulfates. 

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. 

Norton, R. A. Quantitation of steryl ferulate and p-coumarate esters from corn and rice. Lipids 1995 30(3) 269-274. 

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. 

Cell suspension cultures of Gypsophila paniculata and Saponaria officinalis produce very closely related triterpenoid saponins. Pretreatment of cell suspension cultures of G. paniculata with gypsogenin 3,0-glucuxonide (a triterpenoid saponin precursor in G. paniculata) followed by administration of [ C] acetate resulted in a marked reduction in incorporation of radioactivity into saponins and their precursors, but not into sterols and steryl glycosides [26]. Measurements of OSC activities revealed that there was no effect of elicitor treatment on CS levels in either species, but in G. paniculata AS levels went down while in S. officinalis they increased. This suggests that in these two species OSCs are regulating steps in the isoprenoid pathway and control the flux to sterols and triter-penes. 

Ciclopiroxolamine Loprox Cetyl alcohol, steryl alcohol, polysorbate 60 NF, sorbitan monostearate Benzyl alcohol NF... 

The main problem in this approach is the very low permeability of mevalonic acid to membranes, resulting in very low incorporation. Positive results have been obtained by the use of cell-free systems incubated with [14C]-mevalonic acid,26,27 [14C]isopentenyl diphosphate,28 or [32P]orthophos-phate.29 Incubation of these radioactive lipids with glycosyl nucleotides labelled in the glycosyl group with a different isotope, followed by extraction and cochromatography in different solvent systems, may indicate that both compounds are present in the same molecule. When the lipid moiety becomes labelled from mevalonic acid or isopentenyl diphosphate, chromatography on DEAE-cellulose columns should be performed, in order to avoid confusion with steryl glycosides. 

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. 

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