ReviewArtifact generation and monitoring in analysis of cholesterol oxide products
Section snippets
Defining artifacts and sampling
Cholesterol with its single double bond is vulnerable to oxidation, including enzymatic oxidation, autoxidation, and photooxidation [2], [10], [46]. The resulting oxidation products are COPs. During autoxidation, cholesterol can break down in a series of reactions. Primary products are various cholesterol hydroperoxides (CHPs), which can react to yield epoxy-cholesterols or can be converted to cholesterol-diols and keto-cholesterols. These secondary products can be further altered by
Artifact generation
How are artifacts generated? The same factors that initiate autoxidation and photooxidation contribute to artifact generation. Exposure to air, light, or metals propagates oxidation of cholesterol and COPs and these oxidative factors may be limited during analysis. Artifacts are also generated by experimental conditions which compromise the stability of cholesterol and existing COPs. Experimental conditions such as elevated saponification and evaporation temperatures or the alkaline
Is total artifact prevention possible?
Can artifacts be prevented? Are they truly inherent since artifacts can be generated by both oxidative processes and experimental conditions? Artifact generation can be limited through careful measures to control oxidative processes and experimental conditions; but, several investigators acknowledge that it may be impossible to entirely prevent them. For Rose-Sallin and colleagues, the belief that artifacts from cholesterol are “essentially impossible to avoid” led to the development of an
Artifact monitoring
Artifact monitoring is important and should be addressed in COP papers as many investigators do not monitor artifacts or report monitoring methods. There are several methods in use for artifact monitoring: using unlabeled/labeled cholesterol and multiple individually labeled COPs.
Reports on artifacts in the literature
Despite all of the controversy surrounding artifact generation during saponification and other causes, articles involving unrecognized artifacts are still being published. As COPs become better understood and their ubiquitous presence acknowledged, they are being studied or used as markers/measures of oxidative damage in various disease states. Use of COPs as markers/measures is relatively new in some disease conditions, indicating that the complex history of artifact generation methodology is
Application of knowledge of COPs to phytosterol oxidation products
Recently, phytosterols have become commercial nutraceutical ingredients present in several types of foods and as a result, phytosterol oxidation and analysis of its products (POPs) are an emerging, rapidly growing field of investigation. Because phytosterols share a similar structure with cholesterol, they, too, are subject to oxidation leading to the same spate of oxidation products. Fig. 3 compares the structure of the most common phytosterol, β-sistosterol, to cholesterol. The similarities
Future of sterol oxide products analysis
One of the many challenges scientist face is ensuring that newcomers to the field and clinicians know about artifact generation during analysis. Investigators who specialize in disease states and are looking for new markers may come to the field of SOPS unaware of artifact issues. COPs are now under investigation in several new areas, such as for antifungal activity and the questionable oxidation of cholesterol in arterial plaques by ozone [99], [100], [101]. Many aspects of POPs and their
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