Cholesteryl palmitate

Chromatographic Separation of Lipids A mixture of lipids is applied to a silica gel column, and the column is then washed with increasingly polar solvents. The mixture consists of phosphatidylserine, phosphatidylethanolamine, phosphatidylcholine, cholesteryl palmitate (a sterol ester), sphingomyelin, palmitate, -re-tetradecanol, triacylglycerol, and cholesterol. In what order do you expect the lipids to elute from the column Explain your reasoning. 

Atherosclerosic aortic sinuses from ApoE knockout mice Cholesterol esters (cholesteryl palmitate and cholesteryl oleate) markers of atherosclerosis progression ... 

Answer Because silica gel is polar, the most hydrophobic lipids elute first, the most hydrophilic last. The neutral lipids elute first cholesteryl palmitate and triacylglycerol. Cholesterol and %-tetradecanol, neutral but somewhat more polar, elute next. The neutral phospholipids phosphatidylcholine and phosphatidylethanolamine follow. Sphingomyelin, neutral but slightly more polar, elutes after the neutral phospholipids. The negatively charged phosphatidylserine and palmitate elute last—phosphatidylserine first because it is larger and has a lower charge-to-mass ratio. 

Figure 4. Normal phase high-pressure liquid chromatography of cholesterol esters isolated from atherosclerotic lesions of human aorta (I), free cholesterol (II), oxygenated cholesterol esters (III), cholesteryl arachidonate (IV), cholesteryl linoleate (V), cholesteryl oleate and cholesteryl palmitate.

The formation of plasma lipoprotein CE begins in cells of the intestinal mucosa and liver (Fig. 2B). ACAT activity in these cells leads to the formation of cholesteryl palmitate and cholesteryl oleate, which can be included in nascent chylomicrons, VLDL, and apparently also small spherical HDL [15,80-82], These esters presumably accumulate when more than enough UC is present in the cells to provide for the requirements of cell membranes and lipoprotein surfaces. (For a more detailed discussion of ACAT activity in intestinal epithelial cells, see Chapter 5.)... 

Figure 9.35 Sensitivities of LC-MS and LC-FID systems, (a) Response of a neutral lipid standard mixture (CE, cholesteryl palmitate TG, tripalmitin) injected on a 3.2 x 250mm column packed with lOjum silicic acid. Detector LC-MS interface system, methane chemical ionization, single ion monitors at m/e 211. (b) Response of neutral lipid standard mixture (CE = cholesteryl oleate, TG = triolein) injected on a 2.1 X 250mm column packed with 6-8//m Zorbax-Sil, Detector LC-FID system (Privett and Erdahl, 1978).

Figure 9.37 Methane chemical ionization spectra at 2.8Torr. (A) Cholesterol reactor 380 C. (B) Cholesterol reactor 430 °C. (C) Cholesteryl palmitate reactor 330 C. (D) Cholesteryl palmitate reactor 430 °C. Samples were applied to the belt continuously (Privett and Erdahl, 1978).

Grunwald (1968, 1971) found that the ethanol- and methanol-induced leakage of plant tissues can be prevented by sterols. While free cholesterol was effective even at 0.1 ftM, concentrations of cholesteryl palmitate and cho-lesteryl glucoside at 0.1-100 ftM had no effect on the leakage. The actual penetration of these substances into the plasma membranes of plant cells would be worthy of study. 

Fig. 94. Test of the resolution of thin-layer chromatographic separations [725]. Layer silica gel G solvent petrol ether (BP 60—70° C)-diethyl ether-acetic acid (80 + 20 + 1) time of run 1 h indicator A iodine vapour B autoradiography amounts about 200 (ig of each of the naturally occurring lipids 1 cholesteryl palmitate-l- C, tripalmitin-l- C and palmitic acid-l- C 2 human depot fat and tripalmitin-l-i C 3 dogfish shark liver oil and tripalmitin-l- C 4 lipid extract of the calcification of a human aorta and cholesteryl palmitate-l- C...

Some Na-ethoxide mixed with cholesteryl acetate and methyl palmitate, flushed with Ng, and heated 1 hr. at 80-90°/20-30 mm with occasional gentle shaking and distillation of the resulting methyl acetate cholesteryl palmitate. Y 77%. F. e. s. V. Mahadevan and W. O. Lundberg, J. Lipid Research 3, 106 (1962). 

FIGURE 9.10 Separation of lipid class representatives. (1) PAR (paraffin, liquid), (2) WE (n-hexyldecyl palmitate), (3) CE (cholesteryl palmitate), (4) FAME (stearic acid methyl ester), (5) TAG (glycerol tripalmitate), (6) FOH (hexadecyl alcohol), (7) FEA (stearic add), (8) CHOL (cholesterol), (9) 1>DAG (glycerol-1,3-dipalmitate), (10) 1,2-DAG (glyc-erol-l,2-dipalmitate), (11) MAG (glycerol monopalmitate) and (12) FAA (erucylamide). For chromatographic conditions, see Section 9.2.5 concentrations 20—50 mg/1, except CHOL 100 mg/1. Source Reprinted from R. [41] with permission from Elsevier. 

C7-C9 alkanes (3) benzene, toluene, ethylbenzene, xylenes 4-methylcyclohexyl alkanoates (10) cholesteryl palmitate (Sm, Ch, I) [546]... 

SCDs are a family of microsomal Fe-based metalloenzymes. They act on long-chain saturated acyl CoAs and introduce a ds-double bond at the C-9 or C-10 position. For example, SCDs convert stearic acid into oleic acid, and palmitic acid into palmitoleic acid. Monounsaturated FAs constitute a major component of TGs, cholesteryl esters, and phospholipids. The reaction requires molecular 02 and NADH and generates H20 in the process [3,4]. 

Physical Barriers. Wu et al (46) observed that the inclusion of palmitic acid or cholesteryl acetate in linoleic acid monolayers on silica, exerted a protective effect against oxidation. They suggested that these compounds act as a spacer keeping the linoleic acid molecules farther apart while being only slowly oxidized themselves. Similarly, our recent work with cholesterol oxidation appears to indicate that carbohydrates do not change the pathway of cholesterol oxidation but rather act as a physical barrier against the migration of reactive species. 

Ceramides Cholesterol Palmitic acid Cholesteryl sulfate ... 

Clindamycin Palmitate Hydrochloride Clindamycin Palmitate Hydrochloride for oral solution Glass, 0.6 M x 3 mm I.D. 1% G36/S1AB (80-100 mesh) Helium 290 FID Cholesteryl Benzoate USP (24, pp. 431 and 432)... 

A very different type of reaction is represented by the conjugation of xenobiotic alcohols with fatty acids, yielding highly lipophilic metabolites accumulating in tissues. Thus, ethanol and haloethanols form esters with palmitic acid, oleic acid, linoleic acid, and lin-olenic acid enzymes catalyzing such reactions are cholesteryl ester synthase (EC 3.1.1.13) and fatty-acyl-ethyl-ester synthase (EC 3.1.1.67) (71). Larger xenobiotics such as tet-rahydrocannabinols and codeine are also acy-... 

The levels of palmitic acid, palmitoleic acid, stearic acid and oleic acid increased in both groups, after 4 h of copper-oxidation. While concentrations of cholesteryl oleate, cholesteryl linoleate, cholesteryl arachidonate and cholesteryl docosahexanoate were reduced, following copper stimulated oxidation, in both groups [85]. 

Cholesteryl oleate was probably a component of the mixture of steryl esters described in fine-cured tobacco by Rowland and Latimer (3358) and in tobacco smoke by Rodgman et al. (3296). The steryl esters included sterols esterified with a series of saturated (palmitic, stearic, etc) and unsaturated (oleic, linoleic, etc.) acids. 

The inert beta layers of the cell membrane complex are Upid-protein-type structures [78]. Sakamoto et al. [83] claim that fatty acids and wax esters are the main components of the internal lipids of human hair. Hilter-haus-Bong and Zahn [84] also find fatty acids, cholesteryl esters, and wax esters as main components however, they find polar lipids as major components. The fatty acids of this important component of human hair are predominately palmitic, stearic, and oleic acids. 

Fig. 11.6.1. HPLC separation of cholesterol and cholesteryl ester standards. Chromatographic conditions column, Supelcosil LC-18 (250x4.6 mm I.D.) mobile phase, acetonitrile-methanol-chloroform (1 1 1, v/v/v) flow rate, 1.0 ml/min temperature, ambient detection, differential refractometer. Peaks 1, cholesterol, 2, acetate 3, propionate 4, butyrate 5, nonanoate 6, decanoate 7, arachidonate 8, laurate 9, linoleate 10, oleate 11, elaidate 12, palmitate 13, stearate. The average mass of lipid chromatographed was 20-40 ng. Reproduced from Perkins et al. (1981), with...

Cl 8-20 glycol isostearate C20-30 glycol isostearate C14-16 glycol palmitate Chimyl alcohol Chimyl stearate Chloro-2-hydroxypropyl trimonium chloride Cholesterol Cholesteryl stearate Choleth-5 Choleth-10 Choleth-15 Choleth-20 Choleth-24... 

Bovine milk fat is made up of 97-98 (wt% of total lipids) triacylglycerols accompanied by much smaller amounts of diacylglycerols (0.36%) and monoacylglyc-erols (0.03%), free cholesterol (0.31%), trace amounts of cholesteryl esters, phospholipids (0.60%), and minor amounts of free fatty acids. For reviews of the composition of bovine milk lipids, the reader is referred to Christie (4) and Jensen and Clarke (5). More than 400 fatty acids have been identified in milk fat, although it is generally accepted that 15 major and 12 minor fatty acids dominate the fatty acid spectrum. The major fatty acids found in milk are long chain (Cj. , myristic Ci6-o. palmitic Cjg., stearic Cjg.j, oleic) and the minor fatty acids are short chain... 

Fig. 151. Calibration curves for the colorimetric estimation of lipids [3]. Ch cholesterol and cholesteryl esters, Tp Tripalmitin and palmitic acid, Le lecithin. Changes in absorbance of the dichromate reagent are plotted against amounts of lipid...

St. Clair et al. (1968) described the fatty acids synthesized from acetate by perfused pigeon aortas and incorporated into three lipid classes (phospholipids, glycerides, cholesteryl esters). The major newly synthesized fatty acids were stearic acid in the phospholipid fraction stearic, palmitic, and oleic acids in the glycerides and oleic acid in the cholesteryl esters. The synthesis of all the fatty acids in all the lipid classes was increased in the atherosclerotic aortas. Especially noteworthy was the finding that the synthesis of oleic acid and its esterification to cholesterol was stimulated to the greatest extent. 

There are two forms of the hydrolytic enzyme, one of which is specific for short chain esters like retinyl acetate, even though this ester does not occur naturally The other has maximum activity with retinyl palmitate as substrate but also hydrolyses other long chain esters. As in the hydrolysis of cholesteryl esters, the enzyme is not just a non-specific esterase, but has quite definite specificity for retinyl esters. In vitamin A deficiency, the activity of the enzyme increases one hundred fold. The esterification enzyme resembles the low energy cholesteryl esterase in that neither ATP nor coenzyme A appear to take part in the reaction nor are free fatty acids or acyl-CoA thiolesters incorporated into retinyl esters. One of the major problems in this area of research is to identify the acyl donor, which may be, as in plasma cholesteryl ester biosynthesis, a phospholipid. 

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