Cholesterol ethers

Lipids are of special concern in comparing plastic metabolism between the two groups of fish. Triacyl-glycerols, cholesterol ethers and non-esterified fatty acids, which are the direct sources of energy, have already been discussed in the previous section. We now turn to phospholipids and cholesterol, which are essential to the structure of cell membranes, and to polyunsaturated fatty acids, which determine to a large extent the functional activity of these membranes. 

Phase Transitions Within Po/yfoxyethy/enej Cholesterol Ethers-Based Systems 95... 

Rodriguez, C., Naito, N., and Kunieda, H. (2001) Structure of vesicles in homogeneous short-chain polyoxyethylene cholesterol ether systems. Colloids Surf. A, 181, 237-246. 

Lopez-Quintela, M.A., Akahane, A., Rodriguez, C., and Kunieda, H. (2002) Thermotropic behavior of poly(oxyefhylene) cholesterol ether surfactants. J. Colloid Interface Sci., 247, 186-192. 

N HCl, EtOH, reflux, 90% yield for cholesterol. Although a direct stability comparison was not made, this group should be more stable than the THP group for the same reasons that the anomeric ethers of carbohydrates are more stable than their 2-deoxy counterparts. 

Cholesterol [57-88-5] M 386.7, m 148.9-149.4 , [a]D -35 (hexane). Crystd from ethyl acetate, EtOH or isopropyl ether/MeOH. [Hiromitsu and Kevan J Am Chem Soc 109 4501 I987. For extensive details of purification through the dibromide, see Fieser [J Am Chem SoclS 5421 1953] and Schwenk and Werthessen [Arch Biochem Biophys 40 334 7952], and by repeated crystn from acetic acid, see Fieser [J Am Chem Soc 75 4395 1953]. 

Dihydrocholesterol has been prepared by the reduction of cholestenone with sodium and amyl alcohoP and by the hydrogenation of cholesterol. In the presence of platinum black or platinum oxide, yields varying from 6.5 per cent to 40 per cent have been obtained in ether, acetone, ethyl acetate, and acetic acid. ... 

Chromatography of Nonsaponifiable Lipids. The nonsaponifiable residue plus 4.5 mg. of carrier cholesterol was applied to the top of a 7.5 X 1.7 cm. column containing 20 grams of Merck alumina (suitable for chromatographic adsorption) which had been previously deactivated by mixing with 7% aqueous acetic acid (10% glacial acetic acid in distilled water) (18). The column was packed in petroleum ether (redistilled, b.p. 60-70° C.) and 10 ml. fractions were collected. The eluting solvents are shown in Table II. 

The actual characteristics of REV produced depend on a number of factors such as choice of lipids (% cholesterol and charged lipids), lipid concentration used in the organic solvent, rate of evaporation, and ionic strength of the aqueous phase (Szoka and Papahadjopoulos, 1980). Modifications of this REV technique were proposed by several groups. The SPLV (stable plurilamellar vesicles) method consists of bath-sonicating an emulsion of the aqueous phase in an ether solution of lipid while evaporating the ether (Griiner et al., 1985). 

Kunz and Sager also demonstrated the effectiveness of this procedure. Under BFj catalysis, reactions (in CH2CI2) of 18,20a, and 45a with alcohols [including benzyl alcohol, cholesterol, their silyl ethers, and A-(benzyloxy-... 

The enzymes in peroxisomes do not attack shorter-chain fatty acids the P-oxidation sequence ends at oc-tanoyl-CoA. Octanoyl and acetyl groups are both further oxidized in mitochondria. Another role of peroxisomal P-oxidation is to shorten the side chain of cholesterol in bile acid formation (Chapter 26). Peroxisomes also take part in the synthesis of ether glycerolipids (Chapter 24), cholesterol, and dolichol (Figure 26-2). 

Members of the family Amaranthaceae are known to produce ecdysteroids such as 8-ecdysone (19) and inocosterone (20). From petroleum ether extracts of Amaranthus splnosus Linn. Behari and Andhiwal (21) obtained 8-sitosterol (4), stigmasterol (3), campesterol and cholesterol. From the roots of the same species, Banerji (22) isolated two new saponins, a diglucoside and a triglucoside of o-spinasterol. More recently, Roy et al. (23)... 

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