Identification of cholesterol-bound aldehydes in copper-oxidized low density lipoprotein.

Lipid-soluble cholesteryl ester core aldehydes (aldehydes still bound to the cholesterol ring) were identified among the products of copper-catalyzed peroxidation of human low density lipoprotein (LDL). The LDL was exposed to oxygenated buffer and 5 microM CuSO4 for 24 h. The core aldehydes were isolated as the dinitrophenylhydrazones, and were identified by reverse-phase HPLC with mass spectrometry. The major components were the C4-C10 oxoalkanoyl esters of cholesterol and 7-ketocholesterol, and accounted for 1-2% of the cholesteryl linoleate and arachidonate consumed.