Sterol Metabolism X: Epimeric 23-Hydroxycholesterols

Lier, Johan E. van; Smith, Leland L.

doi:10.1002/jps.2600590535

Cited by 12 publications

(4 citation statements)

References 25 publications

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“…The 22R-and 22S-isomers can be nicely separated by partition chromatography on columns of Celite 545 (149). The 23R-and 23S-isomers of 23-OH-Chol have been reported to have been cleanly separated by simple TLC of their dibenzoate derivatives (1159) and, as the free sterols, by silica gel column chromatography or by TLC (1158,1159) but not by GC as the free sterols or as their diacetate derivatives on SE-30 or QF-1 columns (1158). As noted previously, the 20R,22Rand 20S,22S-isomers of 20,22-dihydroxycholesterol have been separated, as their 3␤-acetate derivatives, by Ag ϩ -HPLC (872).…”

Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

“…24R-and 24S-24-OH-Chol, as their TMS derivatives, can be resolved by capillary GC (592,596). The 24R-and 24S-isomers of 24-OH-Chol can be separated with difficulty by TLC in the form of their 3␤-benzoate derivatives (856,1039,1159) or more readily by HPLC of the 3␤,24-dibenzoate derivatives (501). The 24R-and 24Sisomers of 24-OH-Chol can also be resolved, as their diacetate derivatives, by reverse-phase HPLC (521).…”

Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

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Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

872

687

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Oxygenated derivatives of cholesterol (oxysterols) present a remarkably diverse profile of biological activities, including effects on sphingolipid metabolism, platelet aggregation, apoptosis, and protein prenylation. The most notable oxysterol activities center around the regulation of cholesterol homeostasis, which appears to be controlled in part by a complex series of interactions of oxysterol ligands with various receptors, such as the oxysterol binding protein, the cellular nucleic acid binding protein, the sterol regulatory element binding protein, the LXR nuclear orphan receptors, and the low-density lipoprotein receptor. Identification of the endogenous oxysterol ligands and elucidation of their enzymatic origins are topics of active investigation. Except for 24, 25-epoxysterols, most oxysterols arise from cholesterol by autoxidation or by specific microsomal or mitochondrial oxidations, usually involving cytochrome P-450 species. Oxysterols are variously metabolized to esters, bile acids, steroid hormones, cholesterol, or other sterols through pathways that may differ according to the type of cell and mode of experimentation (in vitro, in vivo, cell culture). Reliable measurements of oxysterol levels and activities are hampered by low physiological concentrations (approximately 0.01-0.1 microM plasma) relative to cholesterol (approximately 5,000 microM) and by the susceptibility of cholesterol to autoxidation, which produces artifactual oxysterols that may also have potent activities. Reports describing the occurrence and levels of oxysterols in plasma, low-density lipoproteins, various tissues, and food products include many unrealistic data resulting from inattention to autoxidation and to limitations of the analytical methodology. Because of the widespread lack of appreciation for the technical difficulties involved in oxysterol research, a rigorous evaluation of the chromatographic and spectroscopic methods used in the isolation, characterization, and quantitation of oxysterols has been included. This review comprises a detailed and critical assessment of current knowledge regarding the formation, occurrence, metabolism, regulatory properties, and other activities of oxysterols in mammalian systems.

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Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

Section: Chromatographic Separations Of Oxysterol Isomersmentioning

confidence: 99%

Oxysterols: Modulators of Cholesterol Metabolism and Other Processes

Schroepfer

2000

Physiological Reviews

872

687

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“…The solid was filtered and air-dried to give 34.9 g (100%). Recrystallization from CH3CN-Et20 gave yellow needles: mp 101-102.5°; ir (mull) 3375 b, 1656 (C= N+<);' nmr (DMSO-dn) 2.1-2.5 (m, 4, ß CH2's), 3.8-4.4 (m, 4, a CH/s), 6.67 (9, 1, Jza = 4.1, Jt," = 2.5 Hz, 4 H), 7.37 (d, \,J = 4.1 Hz, 3 H), 7.77 (bs, 1, 5 H), 8.78 The crude salt was stirred into a mixture of water, ether, and a slight excess of NaHCOa to convert it to the aldehyde. After 5 min the layers were separated, and the organic solid was isolated in the usual way.…”

Section: Methodsmentioning

confidence: 99%

Synthesis of .beta.-substituted pyrroles via 1-(pyrrol-2-ylmethylene)pyrrolidinium salts

Sonnet¹

1971

J. Org. Chem.

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rapidly to resemble those characteristic of the disulfide, indicate that 2-nitro-5-mercaptobenzoic acid is exceedingly sensitive to aerial oxidation.Since it was not practical to prepare a sample of pure 2-nitro-5-mercaptobenzoic acid, its molar absorptivity was calculated from the absorbance of a solution of the disulfide in aqueous phosphate buffer to which sufficient aqueous solution of sodium thioglycolate had been added to produce maximal absorbance (Table II). A solution of exactly the same Table II Absorption Spectral Constants for Certain Aromatic Disulfides and the Corresponding Thiols Compd Registry no. Xmaxi nm am 2,2 '-Dinitro-5,5'-dithiodibenzoate" 552-24-9 325 17,500 748 2,800 2-N itro-5

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“…It had also been isolated from brain of different animal species including cattle and rabbit with a general conclusion that it presents universally in all mammals (Dhar et al, 1973). Chromatographic studies revealed that human brain contains only one epimer of 24-OHC (Van Lier and Smith, 1970). 24-OHC was then isolated from different human brain parts including cortex, white matter, midbrain, pons and cerebellum (Smith et al, 1972).…”

Section: Discovery and Early Researchesmentioning

confidence: 99%