Gas and liquid chromatography-mass spectrometry of aldehydic products from lipid peroxidation

Abstract

Reactive species, especially those deriving from oxygen, produced during either physiological enzymatic reactions or particular conditions involving xenobiotics metabolism and pathological disorders, generate oxidative stress when physiological antioxidant defense mechanisms are overloaded. Oxidative stress leads to damages of biomolecules, such as lipids, proteins and nucleic acids. Lipid peroxidation is a degradation chain reaction of polyunsaturated fatty acids, which are easy targets of free radical attack. It further leads to conjugated dienes, hydroperoxides and aldehydes [1]. Aldehydes are secondary products of peroxidation, more stable and diffusible than hydroperoxides. Their composition is very complex and depends on the fatty acid content of the lipids and on the free radical generating system [2]. Aldehydes act as "second toxic messengers", responsible for damage of targets which are distant from the initial free radical event [3,4]. Among them, 4-hydroxyalkenals, in particular 4-hydroxynonenal, were found to have high toxic effects on cell membranes and on numerous cell functions, being involved in the aetiology of many human diseases, e.g. atherosclerosis and cancer [3,5].The present study is focused on the development of methods devoted to the identification of aldehydes resulting from polyunsaturated fatty acids oxidation. Lipid peroxidation is usually monitored by colorimetric reaction of thiobarbituric acid with malondialdehyde, a dicarbonyl compound produced in relatively high amount during autoxidation of fatty acids. Nevertheless, the thiobarbituric acid-reactive substances assay is criticized because of many interfering side reactions [6]. Moreover, major products of lipid peroxidation, such as alkanals and 4-hydroxyalkenals, are not detected by the thiobarbituric acid-reactive substances assay; thus, it is not a reliable index of peroxidation and toxicity [7].Further, analysis of 4-hydroxynonenal has been performed by HPLC [8] or by GC/MS after derivatization [8,9,10]. As a result, 4-hydroxynonenal being a better indicator than malondialdehyde, it was assumed as a model molecule for oxidative stress [3,5].Characterization of individual breakdown products of lipid peroxidation requires high sensitive derivatization methods of carbonyl groups and the use of mass spectrometry (MS) techniques for their identification. Among various derivatization techniques, reaction with 1,3-cyclohexanedione produces fluorescent dehydroacridine derivatives which are separated by HPLC. Such a method is sensitive, but has a low specificity [11]. Oxime derivatives, obtained with either hydroxylamine or pentafluorobenzylhydroxylamine, were successfully used for carbonyl products identification by GC/MS, directly or after trimethylsilylation [12,13]. However, these derivatives are colourless and some difficulties arise for their specific detection during the preliminary thin layer chromatography (TLC) step. 2,4-dinitrophenylhydrazine (DNPH) derivatization presents several advantages: high reaction specificity, se...

Phytochemical study of the headspace volatile organic compounds of fresh algae and seagrass from the Adriatic Sea (single point collection)

“…For example, the formation of hexanal is proposed via linoleic acid cascade and arachidonic acid cascade through their hydroperoxides as intermediates by the lipoxygenase/fatty acid hydroperoxide lyase pathway. It could also be provided by oxidation from other polyunsaturated fatty acids, as well as heptanal [ 54 ]. Lower aliphatic alcohols may be formed by decomposition of secondary hydroperoxides of fatty acids by the reduction of the corresponding aldehydes [ 55 ].…”

Optimization of Dynamic Headspace Extraction of the Edible Red Algae Palmaria palmata and Identification of the Volatile Components

“…These aldehydes are widespread, as they have already been found in many other sea products, such as green and brown macroalgae (refs 5 and 13, respectively), lobsters (28) and oysters (12,29). When studying by GC-MS and LC-MS, the aldehydes produced by lipid peroxidation, Enoiu et al (30) demonstrated that hexanal and 2-(E)-hexenal could come from linolenic acid, a ω3 PUFA. They also could arise from other ω3 PUFAs such as C20:5ω3 (31), which have been reported as the most likely substrates for enzymatic oxidation, producing mainly aldehydes and alcohols.…”

“…Thus, we could conclude that eicosapentaenoic acid was probably the precursor of these two volatile compounds. Hexanal could also be provided by oxidation from linoleic acid (30) or other ω6 PUFAs, as well as heptanal. As Palmaria palmata contains both linoleic and arachidonic acids (32,33), the detection of these compounds was not surprising.…”

“…As Palmaria palmata contains both linoleic and arachidonic acids (32,33), the detection of these compounds was not surprising. Octanal and nonanal, which were the major aldehydes extracted (2430 and 1130 ng ‚ kg -1 ), could originate from ω9 monounsaturated fatty acids (MUFAs) (12), among which C18:1ω9 was the only one present in the alga and also from ω6 PUFAs such as linoleic acid (30).…”

Carbon isotope analysis of acetaldehyde emitted from leaves following mechanical stress and anoxia

“…The rapid increase in the concentrations of reactive oxygen species (ROS) such as superoxide, hydrogen peroxide, singlet oxygen and the hydroxyl radical may have direct and indirect roles in the stress response, such as acting as an antibiotic agent and controlling gene expression (Kotchoni & Gachomo 2006). Many oxygenated VOCs important in atmospheric chemistry such as formaldehyde, acetone and acetaldehyde are major products of lipid peroxidation by ROS (Dennis & Shibamoto 1990;DeZwart et al 1997;Enoiu et al 2000;Orhan et al 2006;Shibamoto 2006). Although extensively used as biomarkers for lipid oxidation in animals, including humans, their production in stressed plants via this mechanism has not previously been demonstrated.…”