Quantitation of lipid hydroperoxides using enhanced chemiluminescence

To determine lipid hydroperoxides, an analytical procedure was proposed based on enhanced chemiluminescence. The analytical system consisted of a lipid, Fe(II), and coumarin C-525, an enhancer of chemiluminescence. Lipid hydroperoxides were determined with spiked solutions using tert-butyl hydroperoxide as an internal standard. The analytical procedure provided a detection limit as low as 164 nM. Verification was performed by iodometric titration. The assay was used to determine total lipid hydroperoxides in food.     

Chemiliminescence determination of lipid hydroperoxides in biological fluids

To evaluate the oxidative stress under clinical conditions, a procedure is developed for the chemiluminescence determination of the total concentration of lipid hydroperoxides based on their oxidation in the presence of microperoxidase and chemiluminescence activator isoluminol in a borate buffer solution (pH 10.0). The limit of detection for linoleic acid hydroperoxide is 16 nM. The procedure is used to determine lipid hydroperoxides in follicular fluid lipoproteins and in plasma of patients undergoing extracorporeal fertilization.     

A near-infrared fluorescent probe for lipid hydroperoxides in living cells

An NIR (near-infrared) fluorescent probe TCP (tricarbocyanine diphenylphosphine) including a non-conjugated 'pre-tricarbocyanine' was designed and synthesized for visualizing lipid hydroperoxides (ROOH) in living cells. The excitation and emission spectra of tricarbocyanine in the NIR region can effectively avoid background fluorescence interference in biological systems. The probe exhibited a rapid fluorescence response to ROOH and high selectivity for ROOH over other ROS (reactive oxygen species) and some biological compounds, and the limit of detection was 38 pM. In addition, the probe was stable, and less cytotoxic, which indicated that it has potential application in detecting lipid hydroperoxides in living biological systems.     

Colorimetric determination of lipid hydroperoxides in oils and fats with microperoxidase

The use of the peroxidase-like activity of microperoxidase for the calorimetric determination of lipid hydroperoxides in oils and fats has been investigated. The principle of the determination is that 4-aminoantipyrine and N,N-diethylaniline are coupled oxidatively by the hydroperoxides through the action of microperoxidase, yielding a violet colour with maximum absorbance at 554 nm. The response of the microperoxidase system is enhanced by the presence of acetonitrile. The method has been successfully applied to the determination of methyl linoleate hydroperoxide, tert-butyl hydroperoxide and the hydroperoxides in oil and fat samples (soybean oil, linseed oil, olive oil, salad oil, butter and lard). The results agreed closely with those obtained by the iodometric method. The proposed method permitted the determination of the hydroperoxides at 0.5-0.05 mumole levels, with the same sensitivity regardless of sample type tested, with satisfactory reproducibility compared with that obtained by the conventional assay methods.     

Kinetics of oxidation of iron(II) ions with lipid hydroperoxides

One of the pathways for excessive production of free radicals is the decomposition of lipid hydroperoxides catalyzed by iron. A number of hydroperoxides of unsaturated fatty acids (LOOH), some prepared in our laboratory and others extracted from biological materials, were used to determine the rate constants of Fe²⁺ oxidation by measuring the formation rate of Fe³⁺ ions in the presence of simple unidentate ligands, chloride, and thiocyanate as the [FeCl]²⁺ and [FeNCS]²⁺ complexes, in a deoxygenated dichloromethane:methanol (2:1, v/v) mixture. The rates of Fe²⁺ oxidation with prepared LOOHs via the [FeNCS]²⁺ complex were approximately the same-the average second-order reaction rate constant was 1390 ± 340 dm³ mol⁻¹ s⁻¹; the rate constants of LOOHs from different biological materials were in the same range. The rates measured as the [FeNCS]²⁺ complex were somewhat higher than the rates measured as the [FeCl]²⁺ complex, indicating that ligands could interact in the transition state, thus affecting the disruption of the intermediate complex. Since there were no significant differences in the activation thermodynamic parameters for reactions within the reaction series of studied hydroperoxides, it was assumed that the oxidation proceeded by an inner sphere mechanism, considering that the breakdown of the successor inner sphere complex with the homolytic cleavage of peroxide bonds of hydroperoxides forming reactive alkoxyl radicals was the rate-limiting step. Based on this research, an indirect spectrophotometric method for quantitative determination of LOOH was reestimated. The microprocedure proposed for the lipid hydroperoxide assay could be applied to follow the early stages of lipid peroxidation processes in real biological samples.     

Swallow-tailed perylene derivative: a new tool for fluorescent imaging of lipid hydroperoxides

A swallow-tailed perylene derivative including a triphenylphosphine moiety was synthesized and applied to the detection and the live-cell imaging of lipid hydroperoxides. The novel probe, named Spy-LHP, reacted rapidly and quantitatively with lipid hydroperoxides to form the corresponding oxide, Spy-LHPOx, which emits extremely strong fluorescence (Phi approximately 1) in the visible range (lambda(em) = 535 nm, 574 nm). Spy-LHP was highly selective for lipid hydroperoxides, and the addition of other reactive oxygen species (ROS) including hydrogen peroxides, hydroxyl radical, superoxide anion, nitric oxide, peroxynitrite, and alkylperoxyl radical, caused no significant increase in the fluorescence intensity. The probe exhibited good localization to cellular membranes and was successfully applied to the confocal laser scanning microscopy (CLSM) imaging of lipid hydroperoxides in live J774A.1 cells, in which lipid peroxidation was proceeded by the stimulation of 2,2-azobis(2-amidinopropane)dihydrochloride (AAPH). These findings establish Spy-LHP as a promising new tool for investigating the physiology of lipid hydroperoxides.     

Analysis of lipid hydroperoxides and long-chain conjugated keto acids by negative ion electrospray mass spectrometry

Lipid hydroperoxides are important products of enzymatic processes and autooxidation products of polyunsaturated fatty acids. Analysis of such compounds has proved difficult in the past, but negative ion electrospray ionization mass spectrometry was found to be suitable for direct analysis. Abundant [M - H]⁻ ions were observed in full scan mode for hydroperoxyeicosatetraenoic (HPETE), hydroperoxyoctadecenoic acid isomers, and 5,12-diHPETE. Loss of water was observed for all species. Collisional activation and tandem mass spectrometry generated unique and characteristic spectra that shared some common features such as loss of small neutral molecules. More importantly, fragment ions that were indicative of the position of the hydroperoxide were observed. Collision-induced decomposition (CID) of [M - H₂O]⁻ for the HPETE isomers was found to be virtually identical to the CID mass spectra of the [M - H]⁻ anions from corresponding keto-eicosatetraenoic acids, which suggests that the hydroperoxide anions decompose via a dehydration intermediate that resembles the keto acid molecular anion. Cleavage of the double bond allylic to the hydroperoxide formed structurally characteristic ions at m/z 129 from 5-HPETE, m/z 153 from 12-HPETE, and m/z 113 from 15-HPETE. Charge-driven allylic fragmentation led to formation of m/z 203 from 5-HPETE, m/z 179 from 12-HPETE, and m/z 219 from 15-HPETE. Mechanisms consistent with the decomposition of stable isotope analogues are proposed for the formation of these and other characteristic ions. These specific decompositions can be used in multiple reaction monitoring to measure picomolar concentrations of hydroperoxides by direct high performance liquid chromatography tandem mass spectrometry.     

Vitamin C induced decomposition of lipid hydroperoxides: direct evidence of genotoxin-DNA binding detected by QCRS

We report direct evidence for human DNA-binding to precursors of mutagenic lesion-inducing compounds, produced form the vitamin C induced decomposition of lipid hydroperoxides, using a quartz crystal resonant sensor assay.     

Determination of lipid hydroperoxides in low density lipoprotein from human plasma using high performance liquid chromatography with chemiluminescence detection

A high performance liquid chromatographic system with chemiluminescence detection (HPLC-CL) was used for determining phospholipid hydroperoxides in human plasma low density lipoprotein (LDL). This system involved separation of phospholipids from LDL-total lipids with normal phase silica gel HPLC and post-column detection of hydroperoxide-dependent chemiluminescence produced by luminol oxidation during the reaction of hydroperoxide with cytochrome c-haeme. By using HPLC-CL, we could detect phosphatidylcholine hydroperoxide (PCOOH) in human plasma LDL, and the LDL-PCOOH concentration was significantly higher in patients with atherosclerosis and hyperlipidemia than that of healthy volunteers. The LDL-PCOOH level was proportional to the plasma total cholesterol concentration.     

FT-IR study of self-association of some hydroperoxides

Self-association of cumyl, tertiary butyl and 3-phenylmethyl hydroperoxides in solutions of n-decane, carbon tetrachloride and chlorobenzene were studied by IR spectroscopy (3100–3700 cm⁻¹, 293–353 K). The experimental data were interpreted by factor analysis and band contour resolution. The di- and trimerization constants and thermodynamic parameters of self-associates were determined. Intramolecular hydrogen bond of cumyl hydroperoxide was investigated. The conformations of tertiary butyl and cumyl hydroperoxides were studied. The solvent influence on the thermodynamic parameters of hydrogen bond was found.     

Initiating ability of the peroxyacetates of secondary hydroperoxides

The kinetics of ethylbenzene oxidation in the presence of acetic anhydride, the kinetics of acetic anhydride reaction with cyclohexyl hydroperoxide, and the composition of the products of the above reactions were studied in order to evaluate the initiating abilities of 1-phenylethyl and cyclohexyl peroxyacetates generated in situ and to determine the directions of reactions. Anhydride additives significantly accelerated the oxidation of ethylbenzene and the degradation of cyclohexyl hydroperoxide with the predominant formation of corresponding ketones. It was found that the acceleration of ethylbenzene oxidation was due to the homolytic degradation of a peroxy ester, which results in the formation of methyl phenyl carbinol and benzaldehyde (ethylbenzene) or cyclohexanol (cyclohexyl hydroperoxide). The importance of the homolytic degradation of peroxy esters was evaluated using a mixed-initiation method (ethylbenzene) or by measuring the consumption of an inhibitor (cyclohexyl hydroperoxide).Translated from Kinetika i Kataliz, Vol. 45, No. 6, 2004, pp. 808–813.Original Russian Text Copyright © 2004 by Nosacheva, Voronina, Perkel.     

Iron-catalyzed carbonylation-peroxidation of alkenes with aldehydes and hydroperoxides

A three-component reaction of alkenes, aldehydes, and hydroperoxides catalyzed by FeCl(2) to β-peroxy ketones has been achieved. This three-component reaction can be also applied to the synthesis of α-carbonyl epoxides, through either a stepwise base-induced epoxidation of the separated β-peroxy ketone products or a one-pot process by simply adding base to the reaction mixture after the completion of the three-component reaction.