Identification of core aldehydes amongin vitro peroxidation products of cholesteryl esters

Abstract

Synthetic cholesteryl 5-oxovalerate and 9-oxononanoate were used as reference standards for the isolation and identification of cholesteryl ester core aldehydes from tert-butyl hydroperoxide/Fe++ oxidation of synthetic and natural cholesteryl esters. The core aldehydes were recovered from the peroxidation products by thin-layer chromatography as the free aldehydes or the 2,4-dinitrophenylhydrazones and were identified, respectively, by gas-liquid chromatography (GLC) and by GLC combined with mass spectrometry (GC/MS) or by reverse-phase high-performance liquid chromatography (HPLC) and by HPLC with MS (LC/MS). The core aldehydes produced by peroxidation of cholesteryl linoleate were identified as mainly 9-oxononanoates of cholesterol and oxycholesterols, with smaller amounts of the 8-oxooctenoates, 10-oxodecenoates, 11-oxoundecenoates and 12-oxododecenoates. Peroxidation of cholesteryl arachidonate yielded 5-oxovalerates of cholesterol and the oxycholesterols as the main products with smaller amounts of the 4-oxobutyrates, 6-oxohexenoates, 7-oxoheptenoates, 8-oxooctenoates, 9-oxononenoates, 9-oxononadienoates and 10-oxodecadienotes. The oxycholesterols resulting from the peroxidation of the steroid ring were identified as mainly 7-keto-, 7 alpha-hydroxy- and 7 beta-hydroxy-cholesterols and 5 alpha,6 alpha- and 5 beta,6 beta-epoxy-cholestanols. Cholesteryl palmitate and oleate did not yield core aldehydes in the present peroxidation system. In these esters, the sterol and linoleic acid moieties appeared to be oxygenated at about the same rate, while the arachidonic acid moiety reacted more rapidly than did the sterol moiety.

Effect of platelet activating factor-acetylhydrolase on the formation and action of minimally oxidized low density lipoprotein.

“…Work is currently under way to identify the molecular structure of these phospholipids. It has previously been shown that Ox-LDL contains cholesterolbound aldehydes, the carbonyl function of which is predominately associated with the most proximal carbon involved in a double bond (i.e., cholesteryl-arachidonate results in cholesteryl-5-oxovalerate and cholesteryl-linoleate results in cholesteryl-9-oxononanoate) (47). If this is a general phenomenon of esterified PUFA, one might expect the predominate phospholipid-bound aldehydes in LDL to be l-acyl-2(5)-oxovaleroylsn-glycero-3-phosphorylcholine and 1-acyl-2 (9) -oxononanoylsn-glycero-3-phosphorylcholine.…”

Oxidized Low Density Lipoprotein Induces Apoptosis in Cultured Human Umbilical Vein Endothelial Cells by Common and Unique Mechanisms

“…The oxLDL and acetylated LDL had 2-3-fold higher R f values on agarose gel electrophoresis compared with the native LDL. Gas chromatography (45) revealed that a typical preparation of ox LDL contained 4.0 g of 7␣-hydroxycholesterol/mg of LDL protein, 13.1 g of epoxide/mg of LDL protein, 14.9 g of 7-keto-cholesterol/mg of LDL protein, and 1.1 mg of unidentified oxycholesterol/mg of LDL protein.…”

Isolation and identification of glycated aminophospholipids from red cells and plasma of diabetic blood

“…We have previously reported on the identification of high molecular weight secondary products of peroxidation of standard lipids and lipoproteins during in vitro incubation with tert-butyl hydroperoxide [1,2] or copper ions [3,4]. Using these products as reference standards we have identified lipid ester hydroperoxides and core aldehydes in plasma and atheromas of patients with atherosclerosis and diabetes [5].…”

“…All chemicals were of reagent grade quality, while the solvents were of chromatographic purity and were obtained from local suppliers. The purity of the reference compounds was ascertained by thin-layer chromatography (TLC) [3,7]. …”