Analysis of Polar Cholesterol Oxidation Products:  Evaluation of a New Method Involving Transesterification, Solid Phase Extraction, and Gas Chromatography

Abstract

Monitoring cholesterol oxidation products is important in the evaluation of the potential health risks associated with lipid oxidation. In the present study, a method allowing quick and reliable analysis of polar cholesterol oxidation products was evaluated. After Soxhlet-lipid extraction, the fat was transesterified under mild conditions, thereby minimizing degradation and allowing determination of the free and esterified cholesterol oxides. Sample fractionation was achieved with aminopropyl solid phase extraction cartridges and a stepwise elution with hexane, hexane/methyl tert-butyl ether, and acetone to separate polar cholesterol oxides from cholesterol and other lipid products. Further analysis of the trimethylsilyl derivatives was performed by gas chromatography with detection by flame ionization or mass spectrometry. A phytosterol oxide such as sitosterol R-epoxide (24R-ethyl-5R,6R-epoxycholestan-3β-ol) was employed for the first time as an internal standard for the quantification of cholesterol oxides in foodstuffs of animal origin.

Lipid fraction quality evaluation of Brazilian meat-based products

“…19,[24][25][26][27][28] However, some samples have no addition of antioxidants and others do not indicate whether antioxidants were present in the formulation. Table 2 shows the cholesterol and total lipid contents in the samples of meatballs, hamburger and jerked beef of the different brands.…”

Effect of dietary rapeseed oil and humus-containing mineral preparation on cholesterol and cholesterol oxidation products content in pork

“…The quantification of cholesterol in the sample was calculated by comparing the peak areas of cholesterol and 5α-cholestane. Analysis of cholesterol oxidation products was performed by a modified method given by Schmarr et al [21]. Calibration curve was plotted for eight oxysterols (7α-hydroxycholesterol; 7β-hydroxycholesterol; 5,6α-epoxycholesterol; 5,6β-epoxycholesterol, 20α-hydroxycholesterol; cholestantriol, 7-ketocholesterol, 25-hydroxycholesterol) purchased from Sigma-Aldrich Inc. (St. Louis, MO, USA).…”

Dietary vitamin E supplementation on cholesterol and cholesterol oxides of pig meat and cooked ham

“…The cholesterol oxide cholesta-4,6-dien-3-ona has been observed in different food products, such as butter (Roderbourg and Kudzl-Savoie, 1979): bovine and swine fat (Ryan et al, 1981;Chen et al, 1994), eggs (Penock et al, 1962), milk powder (Flanagan et al, 1975;Chan et al, 1993), bovine meat (Vajdi and Nawar, 1979;Hwang and Maerker, 1993), swine meat (Hwang and Maerker, 1993), and fish (Adachi et al, 1996), with values varying from 0.36 to 5.9 µg/g, depending on the processing and storage. The cholesterol oxide 20 α-hydroxycholesterol was reported in butter and eggs (Pie et al, 1991), swine and bovine meat (Pie et al, 1991;Schmarr et al, 1996), salami and parmesan cheese (Schmarr et al, 1996) in concentrations varying from 0.14 to 10.88 µg/g. 25-hydroxycholesterol is considered as the most cytotoxic of cholesterol oxides, therefore, it inhibits the activity of 3-hydroxy-3-methylglutanyl-coenzyme A-reductase (HMGCoA), leading to the reduction of the endogenous synthesis of the cholesterol Kubow, 1990;Kumar and Singhal, 1991).…”