Determination of free aliphatic aldehydes in plasma by high-performance liquid chromatography of the 1,3-cyclohexanedione derivatives

A sensitive chemiluminescence detection approach for determination of 2,4-dinitrophenylhydrazine derivatized aldehydes using online UV irradiation - luminol CL reaction. Application to the HPLC analysis of aldehydes in oil samples

Aldehydes are toxic carbonyl compounds that are identified in various matrices surrounding us. For instance, aldehydes could be formed during the cooking and frying of foods which affects the food quality and safety. Derivatization is a must for the determination of aldehydes as they lack intrinsic chromophoric groups. 2,4-Dinitrophenyl hydrazine (DNPH) is the most used derivatizing reagent for aldehydes and the formed hydrazones could be determined by either HPLC-UV or LC-MS. However, UV detection is non-sensitive, and the MS equipment is expensive and not widely available. Thus, herein we report a smart chemiluminescence (CL) detection method for the DNPH aldehydes derivatives. These derivatives are supposed to possess photosensitization ability due to the presence of strong chromophoric structures; nitrobenzene and phenyl hydrazone. Upon their UV irradiation, singlet oxygen is found to be produced which then converts the DNPH-aldehyde derivative into hydroperoxide. Next, the hydroperoxide reacts with luminol in an alkaline medium producing a strong CL. An HPLC system with online UV irradiation and online reaction with luminol followed by CL detection was constructed and used for the determination of aldehydes after their derivatization with DNPH. The developed method showed excellent sensitivity with detection limits down to 1.5-18.5 nM. The achieved sensitivity is superior to that obtained by HPLC-UV and LC-MS detection methods for DNPH-aldehydes derivatives. Additionally, our approach is an chemiluminogenic where the DNPH reagent itself does not produce CL which is an excellent advantage. The method was applied successfully for the determination of aldehydes in canola oil samples using simple liquid-liquid extraction showing good recovery (87.0-106.0%), accuracy (87.2-106.6), and precision (RSD≤10.2%). After analysis of fresh and heated oil samples, it was demonstrated that heating of oil, even for short time, strongly elevated the level of their aldehydes' content. At last, it was found that the results of the analysis of aldehydes in oil samples using the proposed method perfectly matched those obtained by a reference LC-MS method.

Headspace solid-phase microextraction sampling of endogenous aldehydes in biological fluids using a magnetic metal-organic framework/polyaniline nanocomposite

Nanoporosity, crystal structure, good thermal and mechanical stability, high surface-to-volume ratio, nanoscale cavities, and uniform pore topology have made metal-organic frameworks one of the best class of sorbents for adsorption/separation purposes. In this research, a metal-organic framework/polyaniline magnetite nanocomposite was synthesized and intercalated by polyaniline by electrophoretic deposition on the surface of a thin steel wire, to prepare a solid-phase microextraction fiber. It was coupled with gas chromatography-flame ionization detection and employed for the extraction and determination of aldehydes in biological samples. The magnetic nanocomposite was characterized using scanning electron microscopy, energy dispersive X-ray analysis, and Fourier transform infrared spectroscopy. Under the optimal experimental conditions, the calibration curves were linear in the range of 0.01-1 and 0.1-1 µg/L for hexanal and heptanal, respectively. The limits of detections for hexanal and heptanal were 0.001 and 0.01 µg/L, respectively. Intrafiber repeatability for six replicate analyses of 0.2 µg/L of the analytes was over the range 3.5-7.1%. Interfiber (fiber-to-fiber) reproducibility, calculated by six replicate analyses of the same concentration using three different fibers, and was found to be 10.4-15.7%. The developed procedure was successfully utilized for the analysis of hexanal and heptanal in human plasma and urine samples.

High throughput assay for evaluation of reactive carbonyl scavenging capacity

Many carbonyl species from either lipid peroxidation or glycoxidation are extremely reactive and can disrupt the function of proteins and enzymes. 4-hydroxynonenal and methylglyoxal are the most abundant and toxic lipid-derived reactive carbonyl species. The presence of these toxics leads to carbonyl stress and cause a significant amount of macromolecular damages in several diseases. Much evidence indicates trapping of reactive carbonyl intermediates may be a useful strategy for inhibiting or decreasing carbonyl stress-associated pathologies. There is no rapid and convenient analytical method available for the assessment of direct carbonyl scavenging capacity, and a very limited number of carbonyl scavengers have been identified to date, their therapeutic potential being highlighted only recently. In this context, we have developed a new and rapid sensitive fluorimetric method for the assessment of reactive carbonyl scavengers without involvement glycoxidation systems. Efficacy of various thiol- and non-thiol-carbonyl scavenger pharmacophores was tested both using this screening assay adapted to 96-well microplates and in cultured cells. The scavenging effects on the formation of Advanced Glycation End-product of Bovine Serum Albumin formed with methylglyoxal, 4-hydroxynonenal and glucose-glycated as molecular models were also examined. Low molecular mass thiols with an α-amino-β-mercaptoethane structure showed the highest degree of inhibitory activity toward both α,β-unsaturated aldehydes and dicarbonyls. Cysteine and cysteamine have the best scavenging ability toward methylglyoxal. WR-1065 which is currently approved for clinical use as a protective agent against radiation and renal toxicity was identified as the best inhibitor of 4-hydroxynonenal.

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We describe a rapid method for assessment of reactive carbonyl scavengers.

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We evaluated the carbonyl scavenger activity of various pharmacophores.

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α-amino-β-mercaptoethane structure showed the highest degree of activity.

4-Hydroxy hexenal derived from dietary n-3 polyunsaturated fatty acids induces anti-oxidative enzyme heme oxygenase-1 in multiple organs

It has recently been reported that expression of heme oxygenase-1 (HO-1) plays a protective role against many diseases. Furthermore, n-3 polyunsaturated fatty acids (PUFAs) were shown to induce HO-1 expression in several cells in vitro, and in a few cases also in vivo. However, very few reports have demonstrated that n-3 PUFAs induce HO-1 in vivo. In this study, we examined the effect of fish-oil dietary supplementation on the distribution of fatty acids and their peroxidative metabolites and on the expression of HO-1 in multiple tissues (liver, kidney, heart, lung, spleen, intestine, skeletal muscle, white adipose, brown adipose, brain, aorta, and plasma) of C57BL/6 mice. Mice were divided into 4 groups, and fed a control, safflower-oil, and fish-oil diet for 3 weeks. One group was fed a fish-oil diet for just 1 week. The concentration of fatty acids, 4-hydroxy hexenal (4-HHE), and 4-hydroxy nonenal (4-HNE), and the expression of HO-1 mRNA were measured in the same tissues. We found that the concentration of 4-HHE (a product of n-3 PUFAs peroxidation) and expression of HO-1 mRNA were significantly increased after fish-oil treatment in most tissues. In addition, these increases were paralleled by an increase in the level of docosahexaenoic acid (DHA) but not eicosapentaenoic acid (EPA) in each tissue. These results are consistent with our previous results showing that DHA induces HO-1 expression through 4-HHE in vascular endothelial cells. In conclusion, we hypothesize that the HO-1-mediated protective effect of the fish oil diet may be through production of 4-HHE from DHA but not EPA in various tissues.

RP-HPLC-fluorescence analysis of aliphatic aldehydes: application to aldehyde-generating enzymes HACL1 and SGPL1

Long-chain aldehydes are commonly produced in various processes, such as peroxisomal α-oxidation of long-chain 3-methyl-branched and 2-hydroxy fatty acids and microsomal breakdown of phosphorylated sphingoid bases. The enzymes involved in the aldehyde-generating steps of these processes are 2-hydroxyacyl-CoA lyase (HACL1) and sphingosine-1-phosphate lyase (SGPL1), respectively. In the present work, nonradioactive assays for these enzymes were developed employing the Hantzsch reaction. Tridecanal (C13-al) and heptadecanal (C17-al) were selected as model compounds and cyclohexane-1,3-dione as 1,3-diketone, and the fluorescent derivatives were analyzed by reversed phase (RP)-HPLC. Assay mixture composition, as well as pH and heating, were optimized for C13-al and C17-al. Under optimized conditions, these aldehydes could be quantified in picomolar range and different long-chain aldehyde derivatives were well resolved with a linear gradient elution by RP-HPLC. Aldehydes generated by recombinant enzymes could easily be detected via this method. Moreover, the assay allowed to document activity or deficiency in tissue homogenates and fibroblast lysates without an extraction step. In conclusion, a simple, quick, and cheap assay for the study of HACL1 and SGPL1 activities was developed, without relying on expensive mass spectrometric detectors or radioactive substrates.

Analysis of Derivatized Biogenic Aldehydes by LC Tandem Mass Spectrometry

Lipid peroxidation has been linked to the etiology of several diseases, including Alzheimer's disease (AD). End products of this phenomenon include low molecular weight, water-soluble aldehydes, compounds that covalently modify proteins and nucleic acids, thereby altering function. Aliphatic aldehydes (C3-C10) are generated during lipid peroxidation, along with alpha,beta-unsaturated aldehydes, including acrolein and 4-hydroxynonenal (HNE). The Hantzsch reaction was used to produce heterocyclic aldehyde derivatives that can be conveniently analyzed with mass spectrometry. Liquid chromatographic analyses revealed increasing retention times from derivatized methanal to octanal. HNE derivatives were observed to elute between heptanal and octanal derivatives, while the acrolein derivatives had a retention time similar to the propanal derivative. Smaller aliphatic aldehyde derivatives fragmented in a similar manner to produce a base peak of m/z 273, while the larger derivatives yielded m/z 274 as the base peak. Acrolein and HNE derivatives fragmented in a slightly different manner compared to their aliphatic counterparts. Calibration plots of aliphatic and unsaturated aldehydes were linear (r2 >/= 0.99) in the concentration range explored (approximately 5-1500 pg on column). The LC-MS/MS methodology developed here will be used in subsequent studies to determine aldehyde concentrations for comparing age-matched controls to AD tissues from human subjects.

Oxidative fragmentation of hydroxy octadecadienoates generates biologically active gamma-hydroxyalkenals

Oxidative fragmentation of polyunsaturated fatty acids (PUFAs) in vivo generates cytotoxic aldehydes. Among these, 4-hydroxynon-2-enal and analogous gamma-hydroxyalkenal phosphatidylcholines (PCs) have attracted attention because these oxidatively truncated lipids are biologically active and have been implicated in diseases. A previous study showed that hydroxydienes, generated by allylic oxygenation of linoleic acid, are unreactive toward oxidative fragmentation. We now show that, in the presence of hydroperoxides, hydroxydienes fragment as readily as the corresponding hydroperoxydienes, generating gamma-hydroxyalkenals. In a physiomimetic model study, myeloperoxidase-promoted free radical-induced fragmentation of either hydroperoxy- or hydroxyoctecadienoate esters of 2-lyso-PC in small unilamellar vesicles produced the 9-hydroxy-12-oxododec-10-enoic acid (HODA) ester HODA-PC. Therefore, hydroxydienes, that are generally more abundant in vivo than hydroperoxydienes, are plausible intermediates in the production of oxidatively truncated lipids in vivo where a constant flux of radicals and hydroperoxides is present. Our findings also show that the formation of dioxetane intermediates through peroxyradical cyclization is not required to achieve oxidative fragmentation of PUFAs.

Aldehyde analysis by high performance liquid chromatography/tandem mass spectrometry

This paper describes the development of a high performance liquid chromatography/tandem mass spectrometric (MS/MS) procedure for the specific qualitative and quantitative analysis of lipid aldehydes in biological matrices. A derivatisation method, which results in molecules that exhibit a common product ion on MS/MS, permits informative precursor ion scans, at high sensitivity. This has been applied to the examination of plasma in order to examine the production of aldehydes consequent on in vitro lipid oxidation. Quantitative analysis of target molecules using multiple reaction monitoring has been developed to permit quantitation in the same matrices.

Simultaneous determination of an active metabolite and open-ring metabolites by high performance liquid chromatography and pharmacokinetic studies of a penem antibiotic, FCE22891, in dogs

A sensitive high performance liquid chromatographic method for the simultaneous determination of an active metabolite (FCE22101) and open-ring metabolites (P1, P2) of a penem antibiotic, FCE22891, in dog plasma was developed. Plasma samples were pretreated only by ultrafiltration for the determination of the metabolites. The filtrates were directly analyzed by a reversed-phase high-performance liquid chromatographic system using a two-sided bracketing injection technique. The quantitation limits of FCE22101, P1 and P2 were 0.03, 0.1 and 0.15 microgram ml-1, respectively. Analysis of the spiked plasma samples demonstrated the good accuracy and precision of the method. The proposed method was applied to the pharmacokinetic studies of an active metabolite and open-ring metabolites after oral administration of a penem antibiotic, FCE22891, in dogs. In addition, the plasma levels of unchanged FCE22891 and the possible changes of formaldehyde and acyl-L-carnitine levels in plasma, which will be generated from the ester group of FCE22891, were also investigated.