Abstract
Lipid hydroperoxides (LOOH) are the initial products of the peroxidation of unsaturated lipids and play a crucial role in lipid oxidation due to their ability to decompose into free radicals and cause adverse effects on human health. Thus, LOOHs are commonly considered biomarkers of oxidative stress-associated pathological conditions. Despite their importance, the sensitive and selective analytical method for determination is limited, due to their low abundance, poor stability, and low ionizing efficiency. To overcome these limitations, in this study, we chemically synthesized eight fatty acid hydroperoxides (FAOOH), including FA 18:1-OOH, FA 18:2-OOH, FA 18:3-OOH, FA 20:4-OOH, FA 20:5-OOH, FA 22:1-OOH, FA 22:6-OOH as analytes, and FA 19:1-OOH as internal standard. Then, they were chemically labeled with 2-methoxypropene (2-MxP) to obtain FAOOMxP by one-step derivatization (for 10 min). A selected reaction monitoring assisted targeted analytical method was developed using liquid chromatography/tandem mass spectrometry (LC-MS/MS). The MxP-labelling improved the stability and enhanced the ionization efficiency in positive mode. Application of reverse-phase chromatography allowed coelution of analytes and internal standards with a short analysis time of 6 min. The limit of detection and quantification for FAOOH ranged from 0.1–1 pmol/µL and 1–2.5 pmol/µL, respectively. The method was applied to profile total FAOOHs in chemically oxidized human serum samples (n = 5) and their fractions of low and high-density lipoproteins (n = 4). The linoleic acid hydroperoxide (FA 18:2-OOH) and oleic acid hydroperoxide (FA 18:1-OOH) were the most abundant FAOOHs in human serum and lipoproteins. Overall, our validated LC-MS/MS methodology features enhanced detection and rapid separation that enables facile quantitation of multiple FAOOHs, therefore providing a valuable tool for determining the level of lipid peroxidation with potential diagnostic applications.
Highlights
Lipid peroxidation has attracted much attention in determining the nutritional value of foods and potentially influences pathophysiological processes, including sarcopenia, aging, and inflammatory diseases [1,2,3]
The FAOOH and their 2-MxP derivatives (FAOOMxP) were prepared and purified as described in the experimental section. The authentic standards such as FA 18:1-OOH, FA 18:2-OOH, FA 18:3-OOH, FA 19:1-OOH, FA 22:1-OOH, FA 20:4-OOH, FA 20:5-OOH, and FA 22:6-OOH were obtained from their respective FAs as starting materials by the hematoporphyrin catalyzed photochemical oxidation
The FAOOHs were further derivatized with excess 2-MxP in the presence of the catalytic amount of Pyridinium p-Toluene sulfonate (PPTS) and purified the products
Summary
Lipid peroxidation has attracted much attention in determining the nutritional value of foods and potentially influences pathophysiological processes, including sarcopenia, aging, and inflammatory diseases [1,2,3]. Lipid hydroperoxides (LOOHs) are the primary products of unsaturated lipid oxidation, with -OOH moiety is generally being allylic to Antioxidants 2022, 11, 229. Both clinical and animal studies have shown a positive association between. Lipid oxidation products are responsible for off-flavor foods and cause diseases, such as inflammation, cancer, atherosclerosis, and aging in humans [7,8,9]. Accurate determination of LOOHs is essential for finding and thereby control of the oxidation process in disease conditions
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