Isolation of cholesterol oxidation products from animal fat using aminopropyl solid-phase extraction

Excipient-related impurities in liposome drug products

Liposomes are widely used in the pharmaceutical industry as drug delivery systems to increase the efficacy and reduce the off-target toxicity of active pharmaceutical ingredients (APIs). The liposomes are more complex drug delivery systems than the traditional dosage forms, and phospholipids and cholesterol are the major structural excipients. These two excipients undergo hydrolysis and/or oxidation during liposome preparation and storage, resulting in lipids hydrolyzed products (LHPs) and cholesterol oxidation products (COPs) in the final liposomal formulations. These excipient-related impurities at elevated concentrations may affect liposome stability and exert biological functions. This review focuses on LHPs and COPs, two major categories of excipient-related impurities in the liposomal formulations, and discusses factors affecting their formation, and analytical methods to determine these excipient-related impurities.

Dietary cholesterol oxidation products: Perspectives linking food processing and storage with health implications

Dietary cholesterol oxidation products (COPs) are heterogeneous compounds formed during the processing and storage of cholesterol-rich foods, such as seafood, meat, eggs, and dairy products. With the increased intake of COPs-rich foods, the concern about health implications of dietary COPs is rising. Dietary COPs may exert deleterious effects on human health to induce several inflammatory diseases including atherosclerosis, neurodegenerative diseases, and inflammatory bowel diseases. Thus, knowledge regarding the effects of processing and storage conditions leading to formation of COPs is needed to reduce the levels of COPs in foods. Efficient methodologies to determine COPs in foods are also essential. More importantly, the biological roles of dietary COPs in human health and effects of phytochemicals on dietary COPs-induced diseases need to be established. This review summarizes the recent information on dietary COPs including their formation in foods during their processing and storage, analytical methods of determination of COPs, metabolic fate, implications for human health, and beneficial interventions by phytochemicals. The formation of COPs is largely dependent on the heating temperature, storage time, and food matrices. Alteration of food processing and storage conditions is one of the potent strategies to restrict hazardous dietary COPs from forming, including maintaining relatively low temperatures, shorter processing or storage time, and the appropriate addition of antioxidants. Once absorbed into the circulation, dietary COPs can contribute to the progression of several inflammatory diseases, where the absorbed dietary COPs may induce inflammation, apoptosis, and autophagy in cells in the target organs or tissues. Improved intake of phytochemicals may be an effective strategy to reduce the hazardous effects of dietary COPs.

Desarrollo de un método analítico de preparación de muestras de alimentos para determinar óxidos de colesterol (COP) mediante cromatografía

Las transformaciones surgidas durante los procesos de limpieza de los alimentos grasos para determinar productos de oxidación de colesterol (COP) limitan los resultados reales en un estudio. Por tanto, el objetivo de este estudio fue comparar los COP obtenidos por distintos métodos de extracción: fase sólida (SPE) y cromatografía líquida en fase normal y reversa, comparando sus perfiles de elución. Adicionalmente, se tuvo como objetivo optimizar los procesos de limpieza para reducir las transformaciones de COP. Se usaron muestras de lomo de cerdo crudo, jamón serrano y salmón ahumado. Las transformaciones de COP se determinaron por SPE y GC–FID y se optimizaron los métodos de limpieza con la técnica SPE. Los cartuchos apolares no mostraron transformación de COP durante el tratamiento de muestras y los cambios de pH generaron transformaciones del triol a 6 ceto epóxido. Debido a que la limpieza del cartucho suele ser deficiente y genera coelución de compuestos indeseables (ácidos grasos) implicados en la transformación de epóxidos α y β en triol, estas transformaciones se evitaron con la técnica SPE, uso de cartuchos C18, con ajuste del volumen de elución de MeOH y ajustes del pH. La reducción de los pasos de la limpieza de muestras optimizó el proceso en un 73%.

Identification of Vitamin D3 Oxidation Products Using High-Resolution and Tandem Mass Spectrometry

In a successful fortification program, the stability of micronutrients added to the food is one of the most important factors. The added vitamin D3 is known to sometimes decline during storage of fortified milks, and oxidation through fatty acid lipoxidation could be suspected as the likely cause. Identification of vitamin D3 oxidation products (VDOPs) in natural foods is a challenge due to the low amount of their contents and their possible transformation to other compounds during analysis. The main objective of this study was to find a method to extract VDOPs in simulated whole milk powder and to identify these products using LTQ-ion trap, Q-Exactive Orbitrap and triple quadrupole mass spectrometry. The multistage mass spectrometry (MSⁿ) spectra can help to propose plausible schemes for unknown compounds and their fragmentations. With the growth of combinatorial libraries, mass spectrometry (MS) has become an important analytical technique because of its speed of analysis, sensitivity, and accuracy. This study was focused on identifying the fragmentation rules for some VDOPs by incorporating MS data with in silico calculated MS fragmentation pathways. Diels-Alder derivatization was used to enhance the sensitivity and selectivity for the VDOPs' identification. Finally, the confirmed PTAD-derivatized target compounds were separated and analyzed using ESI(+)-UHPLC-MS/MS in multiple reaction monitoring (MRM) mode. Graphical Abstract ᅟ.

Current knowledge on the mechanism of atherosclerosis and pro-atherosclerotic properties of oxysterols

Due to the fact that one of the main causes of worldwide deaths are directly related to atherosclerosis, scientists are constantly looking for atherosclerotic factors, in an attempt to reduce prevalence of this disease. The most important known pro-atherosclerotic factors include: elevated levels of LDL, low HDL levels, obesity and overweight, diabetes, family history of coronary heart disease and cigarette smoking. Since finding oxidized forms of cholesterol – oxysterols – in lesion in the arteries, it has also been presumed they possess pro-atherosclerotic properties. The formation of oxysterols in the atherosclerosis lesions, as a result of LDL oxidation due to the inflammatory response of cells to mechanical stress, is confirmed. However, it is still unknown, what exactly oxysterols cause in connection with atherosclerosis, after gaining entry to the human body e.g., with food containing high amounts of cholesterol, after being heated. The in vivo studies should provide data to finally prove or disprove the thesis regarding the pro-atherosclerotic prosperities of oxysterols, yet despite dozens of available in vivo research some studies confirm such properties, other disprove them. In this article we present the current knowledge about the mechanism of formation of atherosclerotic lesions and we summarize available data on in vivo studies, which investigated whether oxysterols have properties to cause the formation and accelerate the progress of the disease. Additionally we will try to discuss why such different results were obtained in all in vivo studies.

Current Knowledge about Oxysterols: A Review

For years food consumers have been warned that a cholesterol-rich diet may result in atherosclerosis. It is also well known that consumption of large amounts of phytosterols decreases concentration of low-density lipoproteins (LDLs) in blood (LDLs are regarded a key risk factor in development of cardiovascular diseases). However, no scientific evidence has unambiguously proved any direct connection between amount of consumed cholesterol and LDL level in blood. On the other hand, concentration of cholesterol oxidation products, oxysterols, seems to be indeed relevant; for example, they significantly impact appearance of atherosclerotic lesions (plaques). Phytosterols (like sitosterol or campasterol) decrease LDL level in blood, but on the other hand products of their oxidation are toxic. Therefore, it is worth to know influence of phytosterols on living organisms, processes which lead to their formation, and their levels in popular foodstuffs. This paper is an attempt to review literature data on the above aspects, as well as on impact on living organisms of oxidation products of popular sterols.

A new SPE/GC-fid method for the determination of cholesterol oxidation products. Application to subcutaneous fat from Iberian dry-cured ham

A new method for the isolation and analysis of cholesterol oxidation products (COPs) using solid phase extraction (SPE) and silica columns was developed using gas chromatography-flame ion detection (GC-FID). The method comprises of saponification and liquid-liquid extraction of the unsaponifiable fraction prior to the isolation and derivatization of the COPs to trimethylsilyl ethers. The COPs used in this study are cholestane-5α-6α-epoxide, cholestane-3β-5α-6β-triol, 25-hydroxycholesterol and 5-cholesten-3β-ol-7-one. In order to identify the COPs fraction a GC-ion-trap-mass spectrometry experiment were conducted using authentic standards to verify the presence of the COPs. The method was effective at rapidly separating the COPs (25 min run). Calibration curves were linear with the LODs and LOQs bellow 0.03 and 0.07 mgkg(-1) for all cases, respectively. This methodology gave a total recovery for every compound that was used in the study. Betulin was used as an internal standard to monitor the recovery. The method was validated with a standard mixture of COPs. The method has been applied to characterize the COP fraction of subcutaneous fat from Iberian dry-cured ham. Cholestane-5α-6α-epoxide, cholestane-3β-5α-6β-triol, 25-hydroxycholesterol and 5-cholesten-3β-ol-7-one have been identified for the first time in these samples.

Determination of thermo-oxidation products of plant sterols

Plant sterols are subjected to oxidation when exposed to air and, especially, when heated at high temperatures. We developed a method to study thermo-oxidation of plant sterols. The method consisted of cold saponification, purification of oxides by solid-phase extraction and gas chromatography analysis. To compensate for losses during the procedure, an internal standard was added before saponification. The method showed good recovery of added cholesterol oxides, separation of plant sterol oxides and reproducibility in detecting thermo-oxidation products of stigmasterol and rapeseed oil. Based on this study, the major products are 7-hydroxy, 5,6-epoxy and 7-keto compounds and oxides are formed faster in bulk stigmasterol than in rapeseed oil.

Determination of cholesterol oxides in processed food using high-performance liquid chromatography-mass spectrometry with atmospheric pressure chemical ionisation

The present work describes the development and application of an on-line atmospheric pressure ionisation (APCI) LC-MS interface for the simultaneous determination of seven toxicologically relevant cholesterol oxides (7alpha-hydroxycholesterol, 7beta-hydroxycholesterol, 25-hydroxycholesterol, 7-ketocholesterol, 5,6alpha-, 5,6beta-epoxycholesterol and cholestan-3beta,5alpha,6beta-triol). The HPLC method has been optimised to reach better separation of all tested compounds. The influences of APCI parameters (nebulising temperature, cone voltage, source temperature) on signal intensity and fragmentation pattern were investigated for all tested cholesterol oxides compounds. This is the first report on optimisation and determination of two compounds 7alpha-hydroxycholesterol and 5,6beta-epoxycholesterol in processed food using LC-MS. After extraction with hexane, clean-up was carried out using solid-phase extraction on a silica column. For the chromatographic separation of cholesterol oxides an Aquasil C18 column was used with acetonitrile-methanol (60:40) as mobile phase. For the first time we report the use of such a C18 column with a relatively hydrophilic nature for the separation of cholesterol oxides. APCI-MS detection was then applied in selected ion monitoring and positive ion modes by using the molecular ions and the main fragments. The developed method shows good linearity, high repeatability and good recovery for all tested cholesterol oxides. The method was applied for determination of seven selected cholesterol oxidation products in different foodstuffs such as butter, butteroil, lard and egg powder.

Update on solid-phase extraction for the analysis of lipid classes and related compounds

This article provides information on the different procedures and methodologies developed when solid-phase extraction (SPE) is used for lipid component separation. The analytical systematics, established by different authors and designed to separate groups of compounds and also specific components by using a combination of chromatographic supports and solvents are presented. The review has been divided into three parts, which we consider well defined: edible fats and oils, fatty foods and biological samples. Separations of non-polar and polar lipids is the most extensive systematic, although many other published methods have been established to isolate specific components or a reduced number of components from edible fats and oils, fatty foods or biological samples susceptible to further analysis by other quantitative techniques.