Quantification Of Cholesterol Oxidation Products Research Articles

Analysis, Formation and Inhibition of Cholesterol Oxidation Products in Foods: An Overview (Part I)

Cholesterol oxidation products (COPs) formed in cholesterol-containing foods during heating or illumination have been found to impart a potential hazard to health. Numerous studies have indicated that COPs may have several adverse biological effects, such as mutagenicity, carcinogenicity, angiotoxicity, cytotoxicity, atherogenicity, atherosclerosis, cell membrane damage and inhibition of cholesterol biosynthesis. Therefore, the safety of COPs has become a major concern for the public. This paper is an overview of analysis, formation and inhibition of COPs in foods. COPs are routinely extracted by organic solvents, followed by saponification and solid phase extraction for enrichment of COPs, and separation and identification by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS). The identification and quantification of COPs using the GC-MS technique was found to be rapid and sensitive, however, the formation of artifacts is a major drawback. The HPLC method failed to resolve several geometrical isomers, and double bond-free COPs such as isomeric 5,6-epoxides and triol could not be detected with UV. The oxidation of cholesterol can be accelerated by heating, pH, storage conditions, the presence of food components and other factors. Several COPs are commonly present in food systems, including 7α-OH, 7β-OH, 5,6α-EP, 5,6β-EP, 7-keto, 20α-OH, 25-OH and triol. Of these COPs, 5,6α-EP, 5,6β-EP, 7-keto, 20α-OH and 25-OH are primary oxidation products, while 7α-OH, 7β-OH and triol are secondary products. Some antioxidants have been found to reduce the formation of COPs in an appropriate concentration. Also, adequate packaging is necessary to provide a physical barrier for air and light, and thus minimize cholesterol oxidation. Further research is necessary to study how to inhibit COPs formation in foods.

Comparison of Cholesterol Oxidation Product Preparation Methods for Subsequent Gas Chromatographic Analysis

An evaluation was made of the stability of cholesterol hydroperoxides (CHPs) under the analytical conditions and preparation methods commonly used for determination and quantification of cholesterol oxidation products (COPs). CHPs were prepared by photoxidation and separated by silica thin-layer chromatography. CHPs were individually collected by normal-phase liquid chromatography and then subjected either to reduction or to cold saponification. The corresponding hydroxyl derivatives were generated by reduction, whereas cold saponification gave rise predominantly to 7-ketocholesterol. In another test, silylated and non-silylated CHPs were separately injected into a gas chromatograph at 310 degrees C, collected, and re-injected into a gas chromatography-mass spectrometry system. The silylated CHPs were more stable than the non-silylated ones, giving 7-ketocholesterol, 7alpha- and 7beta-hydroxycholesterol as main degradation products. Two unknown degradation peaks were detected in both silylated and nonsilylated CHPs, having 384 as main m/z fragment. The study of their mass spectra led to the conclusion that peaks A and B correspond to 6alpha- and 6beta-hydroxycholesterol, respectively.

Identification and quantification of cholesterol oxidation products in canned tuna

AbstractCholesterol oxidation in tuna canned in brine was studied. Gas chromatography‐mass spectrometry was used for the detection of the seven major cholesterol oxidation products originating from both direct and indirect oxidation. The total amount of cholesterol oxidation products in the analyzed samples varied considerably, ranging between 40 and 350 μg/g lipids, with the exception of an anomalous sample, that reached a 1600 μg/g level. The lipid content ranged between 0.5 and 1 g/100 g wet product. As most samples did not exceed 100 μg/g lipids, it is possible to assume that the total content of cholesterol oxidation products can be kept below this value if good manufacturing conditions are used, together with a careful choice of the best tuna cuts. The application of principal component analysis to the detected variables confirmed that 7‐ketocholesterol is a useful index of the whole oxidation process.

Comparative analysis of plasma and erythrocyte 7-ketocholesterol as a marker for oxidative stress in patients with diabetes mellitus

Objectives: To reveal increased lipid peroxidation in diabetics by quantification of cholesterol oxidation products (COPs) not only in plasma, but also in erythrocytes. Design and methods: We quantified 7-ketocholesterol (7-kCho) by gas chromatography-mass spectrometry as a surrogate measure for COPs. These assays were performed on both plasma and erythrocytes in 20 control subjects and 20 treated patients with relatively poorly controlled Type 2 diabetes. Results: Both plasma and erythrocyte 7-kCho levels in diabetics were significantly higher than those in control subjects. Although neither plasma nor erythrocyte 7-kCho levels were associated with markers for glucose tolerance in diabetics, a negative correlation of serum HDL-cholesterol levels with erythrocyte, but not plasma, 7-kCho levels was found. Conclusion: Increased oxidative stress in diabetics affects oxidation of cholesterol. Assays of COPs not only in plasma, but also in erythrocytes, may yield complementary information in lipid peroxidation.

Quantification of cholesterol oxidation products in commercial fish meals and their formation during storage

Twenty-two samples of commercial fish meals from Norway, Chile and Peru were analysed for cholesterol and oxysterols using gas chromatography. Cholesterol content ranged from 25.2 to 64.8 g kg−1 total lipids. Detectable levels of the oxysterols 7β-hydroxycholesterol and 7-ketocholesterol were found and their identity was confirmed by gas chromatography-mass spectrometry. Samples of fish meal exhibited wide variability in oxysterols content, 7β-hydroxycholesterol ranging from 3.9 to 105.6 mg kg−1 total lipids (0.4–9.4 mg kg−1 dry matter) and 7-ketocholesterol from 2.0 to 56.2 mg kg−1 total lipids (0.2–5.0 mg kg−1 dry matter). The formation of 7β-hydroxycholesterol and 7-ketocholesterol in one sample of Norse LT94 fish meal stored at room temperature was also studied. Oxysterol content increased during the first 42 days of storage by about 350% and then decreased with further storage. The low amount of oxysterols measured indicates a limited degree of cholesterol oxidation in commercially available fish meals.

Comparison of Solid-Phase Extraction Methods for the Cleanup of Cholesterol Oxidation Products

Cholesterol oxidation products (COPs) may accumulate in foods of animal origin during processing or storage. As they represent a potential health risk, a need exists for rapid and efficient methods to monitor the occurrence of COPs in the human diet. Methods involving saponification to remove triacylglycerols suffer from artifact formation; therefore, alternatives involving solid-phase extraction (SPE) cartridges have been proposed. The efficiencies of several SPE methods for the cleanup of COPs were compared, and a combination of a silica cartridge followed by an NH 2 cartridge was found to be optimal for the removal of matrix components. COPs added at the 150 ppb level to milk fat were recovered by the method proposed ≥90% except cholestanetriol, for which the recovery rate was only 52%. Separation and quantification of COPs were done by GC/MS in full-scan mode. Splitless injection of COPs at a concentration of 0.3 ng/μL produced signal-to-noise ratios between 1:10 and 1:200 for epoxycholesterol and 7β-hydroxycholesterol, respectively.

Evaluation of Solid Phase Extraction and Gas Chromatography for Determination of Cholesterol Oxidation Products in Spray-Dried Whole Egg

A method using solid phase extraction (SPE) and capillary gas chromatography (GC) was developed for the rapid quantification of cholesterol oxidation products (COPS) in egg powders. Total lipid extracts were fractionated on disposable silica SPE tubes to isolate COPS from triacylglycerols, phospholipids, and cholesterol. The COPS (α- and β-epoxides, 7α- and 7β-hydroxycholesterols, 7-ketocholesterol) were resolved as their trimethylsilyl ether derivatives on a nonpolar capillary column. Combined GC-mass spectrometry was used to confirm the identities of the trimethylsilyl ethers of COPS. Homogeneous and consistently high recoveries of COPS standards as well as 6-ketocholestanol (internal standard), approximately 86%, were achieved with this analytical technique.

Quantification of Cholesterol Oxidation Products in Milk Powders Using [2H7]Cholesterol To Monitor Cholesterol Autoxidation Artifacts

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTQuantification of Cholesterol Oxidation Products in Milk Powders Using [2H7]Cholesterol To Monitor Cholesterol Autoxidation ArtifactsChristine Rose-Sallin, Anthony C. Huggett, Jacques O. Bosset, Raffaele Tabacchi, and Laurent B. FayCite this: J. Agric. Food Chem. 1995, 43, 4, 935–941Publication Date (Print):April 1, 1995Publication History Published online1 May 2002Published inissue 1 April 1995https://doi.org/10.1021/jf00052a017RIGHTS & PERMISSIONSArticle Views365Altmetric-Citations96LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (2 MB) Get e-Alerts Get e-Alerts

Isolation and quantification of cholesterol oxides in dairy products by selected ion monitoring mass spectrometry.

A method for isolation, detection and quantification of cholesterol oxidation products based on solid phase extraction in combination with preparative HPLC and gas chromatography-mass spectrometry selected ion monitoring has been developed for dairy products. The isolation procedure had a high recovery and artifact formation was minimal, as shown by isotope labelling. The limits of detection ranged from 0.3 to 35 pg/microliters of the isomeric forms of 7-hydroxycholesterol, 20 alpha-hydroxycholesterol, the isomeric forms of cholesterol-5,6-epoxides, cholestanetriol, 25-hydroxycholesterol and 7-ketocholesterol corresponding to a limit of quantification of 2-6 ng oxysterol/g lipid in the dairy product, depending on the nature of the cholesterol oxidation product.

Quantification of Cholesterol Oxidation Products In Egg Yolk Powder Spray‐dried with Direct Heating

ABSTRACTA direct‐heated spray dryer with an evaporative capacity of up to 7 kg H2O/hr was used to identify processing conditions responsible for formation of cholesterol oxidation products (COPS) in spray‐dried egg yolk. Outlet air temperature and nitrogen oxides (NOx) in the combustion gases were the only conditions that affected COPS levels. At outlet temperature 150°C, total COPS concentrations in the spray‐dried product were 75 ppm at 5 ppm NOx and 213 ppm at 300 ppm NOx. In products dried at 75°C outlet temperature, total COPS concentrations were 21 ppm at 5 ppm NOx and 58 ppm at 300 ppm NOx. In general, individual COPS responded to outlet temperature and NOx in the same manner as total COPS.

Wide‐Bore Capillary Gas Chromatographic Method for Quantification of Cholesterol Oxidation Products in Egg Yolk Powder

ABSTRACTA wide‐bore capillary gas chromatographic (GC) method was developed for quantification of cholesterol oxidation products in egg yolk powder. Baseline separations were achieved between 7α‐ and 7β‐hydroxycholesterol, cholesterol, cholesterol‐5α,6α‐epoxide, cholesterol‐5β,6β‐epoxide and 7‐ketocholesterol chromatographed as the trimethylsilylated sterols. Excellent response linearity was obtained for each cholesterol oxidation product, permitting reliable quantification. Recoveries from freeze‐dried egg yolk spiked with various levels of cholesterol oxidation products ranged from 78.2 to 95.1%. The coefficients of variation compared favorably to those for packed column GC methods.

Quantification of Cholesterol Oxidation Products in a Variety of Foods

Cholesterol oxidation products (COPS) were estimated in a variety of foods by gas chromatography. Substantial quantities of α- and β-epoxide (2 to 46 and 0 to 111 ppm, respectively) and lesser quantities of 7β-hydroxy- and 7-ketocholesterol were found in powdered egg products. Other foods found to contain COPS included dehydrated chicken, turkey and beef (0 to 43 ppm); and Cheddar, Blue, Romano and Parmesan cheese powders (0 to 17 ppm). Powdered infant formulas and dehydrated baby foods displayed several peaks coinciding to COPS but none were confirmed by mass spectroscopy. COPS were either not detected or noted at < 15 ppm in fresh dairy products.

7α and 7β‐Hydroxycholesterols Formed in a Dry Egg Nog Mix Exposed to Fluorescent Light

ABSTRACTLight‐induced generation of two cholesterol oxidation products, 7α‐ and 7β‐hydroxycholesterol, was measured in an egg nog mix using an improved isolation procedure and high performance liquid chromatography (HPLC). Dry egg nog mix was exposed continuously to fluorescent light at room temperature for 90 days. The 7α‐hydroxycholesterol was formed in consistently greater amounts than the 7β‐form. Amounts of both forms increased for up to 80 days (23 ± 2°C), then declined. Mix stored in the dark did not contain detectable amounts of 7α‐ or 7β‐hydroxycholesterol. Purification techniques enabled HPLC quantification of cholesterol oxidation products in a food.