Formation of malonaldehyde from lipid oxidation products

Physicochemical Characterization and Thermodynamic Analysis of Avocado Oil Enhanced with Haematococcus pluvialis Extract

The consumption of fatty acids offers significant health benefits; however, they are prone to degradation by environmental factors. One method to preserve these fatty acids is the addition of synthetic antioxidants. This study focuses on the determination of peroxide and MDA formation rates at temperatures of 25 °C, 45 °C, and 65 °C. The oxidative stability of cold-pressed avocado oil was evaluated using pure astaxanthin, TBHQ, and H. pluvialis extract at concentrations of 100, 500, and 1000 ppm. Kinetic models and thermodynamic analysis were applied to determine the oxidation rate and compare the antioxidant effects of H. pluvialis extract with astaxanthin and TBHQ. The Arrhenius model was used to estimate activation energy (Ea), enthalpy, entropy, and free energy. Avocado oil with 500 ppm of H. pluvialis extract showed antioxidant effects comparable to TBHQ and pure astaxanthin. The activation energy of plain avocado oil was 40.47 kJ mol-1, while with H. pluvialis extract, it was 54.35 kJ mol-1. These findings suggest that H. pluvialis extract offers effective antioxidant properties and could serve as a natural alternative to synthetic antioxidants in food applications, despite the limitations of unprotected astaxanthin.

Epoxides: an underestimated lipid oxidation product

Immense gains in understanding of mechanisms and effects of lipid oxidation have been achieved in the nearly 90 years over which lipid oxidation has been an active research focus. Even so, the substantial questions still being raised about lipid oxidation in this special issue show clearly that missing pieces remain and must be considered for full accounting of this important reaction in any system. In this context, epoxides are spotlighted as a critical overlooked product of lipid autoxidation - underestimated in analysis, underestimated in presence as a functionally active and competitive intermediate and product of lipid oxidation, and underestimated in potential contributions to impact of lipid oxidation on other molecules and cell functions. Logical reasons for ignoring or not finding epoxides are offered in historical development of lipid oxidation knowledge. Reactions generating lipid epoxides in autoxidation are reviewed, limitations in detecting and tracking epoxides are outlined to explain why epoxides may not be detected when they should be present, and justifications for increased research and analysis of epoxides are argued. The main goal is to provide a context for recognizing epoxides as critical products that must be accounted for in determining the state rather than extent of lipid oxidation and in tracking its consequences in oils, foods, personal care products, and tissues. A secondary goal is to stimulate new research using contemporary analyses to fill in the gaps of knowledge about epoxide formation, structure, and reactions in lipid autoxidation.

Investigation of Oxidative Stress Level and Antioxidant Enzyme Activities in Operated and Nonoperated Patients with Spontaneous Intracerebral Hematoma

BACKGROUND

 Complex underlying mechanisms consisting of cytotoxic, excitotoxic, and inflammatory effects of intraparenchymal hemorrhage (ICH) are responsible for the highly detrimental effects on brain tissue. Oxidative stress also plays a significant role in brain damage after ICH; however, it is less important than other factors. In this study, we aimed to evaluate the oxidative stress parameters malondialdehyde (MDA) and antioxidant-reduced glutathione (GSH), superoxide dismutase (SOD), and catalase (CT) activities in operated and nonoperated patients with spontaneous ICH.

METHODS

 One hundred patients with spontaneous ICH and 100 healthy controls were included in this study. Within the indication, 50 of the 100 patients underwent decompressive surgery. MDA, GSH, SOD, and CT activities were measured in the serum obtained from the patients.

RESULTS

 SOD and CT levels were lower in the nonoperated group than in the operated and control groups. GSH was similar in the operated and nonoperated groups, but it was lower in the control group. However, MDA was higher in those who did not undergo surgery than in the other groups.

CONCLUSIONS

 In our study, MDA, an indicator of oxidative stress, was found to be lower, and CT and SOD activities were found to be higher in ICH patients who underwent decompression than in those who did not. This is the first study to present the correlations of MDA, SOD, CT, and GSH in operated and nonoperated patients with spontaneous ICH.

Lipid Peroxidation Produces a Diverse Mixture of Saturated and Unsaturated Aldehydes in Exhaled Breath That Can Serve as Biomarkers of Lung Cancer-A Review

The peroxidation of unsaturated fatty acids is a widely recognized metabolic process that creates a complex mixture of volatile organic compounds including aldehydes. Elevated levels of reactive oxygen species in cancer cells promote random lipid peroxidation, which leads to a variety of aldehydes. In the case of lung cancer, many of these volatile aldehydes are exhaled and are of interest as potential markers of the disease. Relevant studies reporting aldehydes in the exhaled breath of lung cancer patients were collected for this review by searching the PubMed and SciFinderⁿ databases until 25 May 2022. Information on breath test results, including the biomarker collection, preconcentration, and quantification methods, was extracted and tabulated. Overall, 44 studies were included spanning a period of 34 years. The data show that, as a class, aldehydes are significantly elevated in the breath of lung cancer patients at all stages of the disease relative to healthy control subjects. The type of aldehyde detected and/or deemed to be a biomarker is highly dependent on the method of exhaled breath sampling and analysis. Unsaturated aldehydes, detected primarily when derivatized during preconcentration, are underrepresented as biomarkers given that they are also likely products of lipid peroxidation. Pentanal, hexanal, and heptanal were the most reported aldehydes in studies of exhaled breath from lung cancer patients.

Validated HPTLC and antioxidant activities for quality control of catechin in a fermented tea (Camellia sinensis var. assamica)

Miang, a Thai traditional fermented tea (Camellia sinensis var. assamica), is exploited as nutraceutical and cosmeceutical ingredients despite limited standardization studies. Thus, this research aimed to develop a simple and rapid method for miang quality control using catechin and high-performance thin-layer chromatography (HPTLC) validated according to the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) and the Association of Official Analytical Collaboration (AOAC). The developing solvent consisting of toluene: ethyl acetate: acetone: formic acid (6:6:6:1 v/v/v/v) showed acceptable specificity with R f value of 0.54 ± 0.02 and linearity with correlation coefficient of 0.9951. The recovery was 98.84%-103.53%, and the RSD of intra- and inter-day precision was 0.70%-3.00% and 1.93%-4.94%, respectively. Miang ethyl acetate fraction is suggested to be attractive ingredient due to rich catechin (25.78 ± 0.53%), prolonged stability at 40 ◦C, and strong antioxidants determined by the assays of ABTS (IC50 = 3.32 ± 0.74 mg/ml), FRAP (89.05 ± 15.49 mg equivalent of FeSO4/g), and inhibition of lipid peroxidation (IC50 = 4.36 ± 0.67 mg/ml).

Exploring the Potential of Aromatherapy as an Adjuvant Therapy in Cancer and its Complications: A Comprehensive Update

BACKGROUND

Aromatherapy is a traditional practice of employing essential oils for the therapeutic purposes, currently headed under the category of complementary and adjuvant medicine.

OBJECTIVE

The aim of this review article is to summarize the potential health benefits of aromatic essential oil from traditional times till the present. It also proposed some mechanisms which can be utilized as basis for using aromatherapy in cancer and cancer linked complications.

METHODS

To find out the relevant and authentic data, several search engines like Science direct, Pubmed, research gate, etc. were thoroughly checked by inserting key words like aromatherapy, complementary, adjuvant therapy etc. to collect the relevant material in context of article. Also, the chemical components of essential oil were classified based on the presence of functional groups, which are further explored for their cytotoxic potential.

RESULTS

The result depicted the anti-cancer potential of chemical constituents of essential oil against different types of cancer. Moreover, the essential oils show promising anti-inflammatory, anti-microbial, anti-oxidant and anti-mutagenic potential in several studies, which collectively can form the basis for initiation of its anti-cancer utility.

CONCLUSION

Aromatherapy can serve as adjuvant economic therapy in cancer after the standardization of protocol.

LC-MS Quantification of Malondialdehyde-Dansylhydrazine Derivatives in Urine and Serum Samples

We developed a robust analytical method for quantification of malondialdehyde (MDA) in urine and serum samples using dansylhydrazine (DH) as a derivatizing reagent. The derivatization procedure was partially carried out using an autosampler injection program to minimize errors associated with the low-volume addition of reagents and was optimized to yield a stable hydrazone derivative of MDA and its labeled d2-MDA analogue. The target MDA-DH derivatives were separated on an Agilent Zorbax Eclipse Plus Phenyl-Hexyl (3.0 × 100 mm, 3.5 μm) column. The mass-to-charge ratios of the target derivatives [(M+H)+ of 302 and 304 for MDA-DH and d2-MDA-DH, respectively] were analyzed in single ion monitoring mode using a single quadrupole mass spectrometer operated under positive electrospray ionization. The method limits of quantification were 5.63 nM (or 0.405 ng/mL) for urine analysis and 5.68 nM (or 0.409 ng/mL) for serum analysis. The quantification range for urine analysis was 5.63-500 nM (0.405-36.0 ng/mL) while the quantification range for serum analysis was 5.68-341 nM (0.409-24.6 ng/mL). The method showed good relative recoveries (98-103%), good accuracies (92-98%), and acceptable precisions (relative standard deviations 1.8-7.3% for inter-day precision; 1.8-6.1% for intra-day precision) as observed from the repeat analysis of quality control samples prepared at different concentrations. The method was used to measure MDA in individual urine samples (n = 287) and de-identified archived serum samples (n = 22) to assess the overall performance of the method. The results demonstrated that our method is capable of measuring urinary and serum levels of MDA, allowing its future application in epidemiologic investigations.

Molluscicidal activity of Solidago canadensis L. extracts on the snail Pomacea canaliculata Lam

Extracts from the aerial parts of Solidago canadensis L. were evaluated for molluscicidal activity against Pomacea canaliculata Lam. using an immersion bioassay method. The petroleum ether fraction of the ethanolic extract (PEEE) from S. canadensis exhibited strong molluscicidal activity. The PEEE mode of action in the hepatopancreas tissue of P. canaliculata was tested at several concentrations. Biochemical parameters, namely, soluble sugar content, protein, malondialdehyde (MDA), acetylcholinesterase (AChE) activity, alanine aminotransferase (ALT), and aspartate transaminase (AST) were significantly decreased or increased after exposure to PEEE for 48 h (p<0.05). Histological assessment results showed that hepatopancreas tissue structure was destroyed by exposure to PEEE. Gas chromatography-mass spectrometry analysis (GC-MS) was used to identify 15 compounds that could contribute to the molluscicidal efficacy of the PEEE. Molluscicidal assay, biochemical tests and histological assessments suggest that the PEEE from S. canadensis has potential utility as a molluscicide.

Effects of Marine Oils, Digested with Human Fluids, on Cellular Viability and Stress Protein Expression in Human Intestinal Caco-2 Cells

In vitro digestion of marine oils has been reported to promote lipid oxidation, including the formation of reactive aldehydes (e.g., malondialdehyde (MDA) and 4-hydroxy-2-hexenal (HHE)). We aimed to investigate if human in vitro digestion of supplemental levels of oils from algae, cod liver, and krill, in addition to pure MDA and HHE, affect intestinal Caco-2 cell survival and oxidative stress. Cell viability was not significantly affected by the digests of marine oils or by pure MDA and HHE (0-90 μM). Cellular levels of HSP-70, a chaperone involved in the prevention of stress-induced protein unfolding was significantly decreased (14%, 28%, and 14% of control for algae, cod and krill oil, respectively; p ≤ 0.05). The oxidoreductase thioredoxin-1 (Trx-1) involved in reducing oxidative stress was also lower after incubation with the digested oils (26%, 53%, and 22% of control for algae, cod, and krill oil, respectively; p ≤ 0.001). The aldehydes MDA and HHE did not affect HSP-70 or Trx-1 at low levels (8.3 and 1.4 μM, respectively), whilst a mixture of MDA and HHE lowered Trx-1 at high levels (45 μM), indicating less exposure to oxidative stress. We conclude that human digests of the investigated marine oils and their content of MDA and HHE did not cause a stress response in human intestinal Caco-2 cells.

Weaning Induced Hepatic Oxidative Stress, Apoptosis, and Aminotransferases through MAPK Signaling Pathways in Piglets

This study investigated the effects of weaning on the hepatic redox status, apoptosis, function, and the mitogen-activated protein kinase (MAPK) signaling pathways during the first week after weaning in piglets. A total of 12 litters of piglets were weaned at d 21 and divided into the weaning group (WG) and the control group (CG). Six piglets from each group were slaughtered at d 0 (d 20, referred to weaning), d 1, d 4, and d 7 after weaning. Results showed that weaning significantly increased the concentrations of hepatic free radicals H₂O₂ and NO, malondialdehyde (MDA), and 8-hydroxy-2′-deoxyguanosine (8-OHdG), while significantly decreasing the inhibitory hydroxyl ability (IHA) and glutathione peroxidase (GSH-Px), and altered the level of superoxide dismutase (SOD). The apoptosis results showed that weaning increased the concentrations of caspase-3, caspase-8, caspase-9 and the ratio of Bax/Bcl-2. In addition, aspartate aminotransferase transaminase (AST) and alanine aminotransferase (ALT) in liver homogenates increased after weaning. The phosphorylated JNK and ERK1/2 increased, while the activated p38 initially decreased and then increased. Our results suggested that weaning increased the hepatic oxidative stress and aminotransferases and initiated apoptosis, which may be related to the activated MAPK pathways in postweaning piglets.

Chronic exposure to air pollution particles increases the risk of obesity and metabolic syndrome: findings from a natural experiment in Beijing

Epidemiologic evidence suggests that air pollution is a risk factor for childhood obesity. Limited experimental data have shown that early-life exposure to ambient particles either increases susceptibility to diet-induced weight gain in adulthood or increases insulin resistance, adiposity, and inflammation. However, no data have directly supported a link between air pollution and non-diet-induced weight increases. In a rodent model, we found that breathing Beijing's highly polluted air resulted in weight gain and cardiorespiratory and metabolic dysfunction. Compared to those exposed to filtered air, pregnant rats exposed to unfiltered Beijing air were significantly heavier at the end of pregnancy. At 8 wk old, the offspring prenatally and postnatally exposed to unfiltered air were significantly heavier than those exposed to filtered air. In both rat dams and their offspring, after continuous exposure to unfiltered air we observed pronounced histologic evidence for both perivascular and peribronchial inflammation in the lungs, increased tissue and systemic oxidative stress, dyslipidemia, and an enhanced proinflammatory status of epididymal fat. Results suggest that TLR2/4-dependent inflammatory activation and lipid oxidation in the lung can spill over systemically, leading to metabolic dysfunction and weight gain.-Wei, Y., Zhang, J., Li, Z., Gow, A., Chung, K. F., Hu, M., Sun, Z., Zeng, L., Zhu, T., Jia, G., Li, X., Duarte, M., Tang, X. Chronic exposure to air pollution particles increases the risk of obesity and metabolic syndrome: findings from a natural experiment in Beijing.

Ethylene negatively regulates transcript abundance of ROP-GAP rheostat-encoding genes and affects apoplastic reactive oxygen species homeostasis in epicarps of cold stored apple fruits

Apple (Malus×domestica Borkh) fruits are stored for long periods of time at low temperatures (1 °C) leading to the occurrence of physiological disorders. 'Superficial scald' of Granny Smith apples, an economically important ethylene-dependent disorder, was used as a model to study relationships among ethylene action, the regulation of the ROP-GAP rheostat, and maintenance of H2O2 homeostasis in fruits during prolonged cold exposure. The ROP-GAP rheostat is a key module for adaptation to low oxygen in Arabidopsis through Respiratory Burst NADPH Oxidase Homologs (RBOH)-mediated and ROP GTPase-dependent regulation of reactive oxygen species (ROS) homeostasis. Here, it was shown that the transcriptional expression of several components of the apple ROP-GAP machinery, including genes encoding RBOHs, ROPs, and their ancillary proteins ROP-GEFs and ROP-GAPs, is coordinately and negatively regulated by ethylene in conjunction with the progressive impairment of apoplastic H2O2 homeostatic levels. RNA sequencing analyses showed that several components of the known ROP- and ROS-associated transcriptional networks are regulated along with the ROP-GAP rheostat in response to ethylene perception. These findings may extend the role of the ROP-GAP rheostat beyond hypoxic responses and suggest that it may be a functional regulatory node involved in the integration of ethylene and ROS signalling pathways in abiotic stress.

A novel gas chromatographic method for determination of malondialdehyde from oxidized DNA

Malondialdehyde (MA) is known to form from various lipids upon oxidation as one of secondary oxidation products. Determination of MA formed from lipid peroxidation has been used to examine occurrence of oxidative damages associated with many diseases, such as cancer, Alzheimer's, arthritis, inflammation, diabetes, atherosclerosis, and AIDS as well as aging. Analysis of MA is, however, extremely difficult because it is highly reactive and readily polymerized and forming adducts with biological substances such as proteins, phospholipids, and DNA (Shibamoto, J Pharm Biomed Anal 41:12-25, 2002). Gas chromatographic method using stable derivative, 1-methylpyrazole was advanced and has been successfully used to analyze MA in various lipids and lipid-rich foods. This method was also applied to determine MA formed from DNA and related compounds. The amounts found in oxidized 2'-deoxyribonucleotides were 213.8 nmol/16 mmol in 2'-deoxyguanosine, 130.6 nmol/16 mmol in 2'-deoxycytidine, 85.1 nmol/16 mmol in 2'-deoxyadenosine, and 84.5 nmol/16 mmol in thymidine. When the antioxidant activity of flavonoids and anthocyanins against calf thymus DNA oxidized with Fenton's reagent was examined using this newly developed gas chromatographic method, antioxidant activity of flavonoids and anthocyanins ranged from 48.5% (catechin) to 29.9% (apigenin) and from 45.0% (callistephin) to 10.2% (cyaniding), respectively.

Malondialdehyde in exhaled breath condensate and urine as a biomarker of air pollution induced oxidative stress

Underlying mechanisms by which air pollutants adversely affect human health remain poorly understood. Oxidative stress has been considered as a potential mechanism that may promote lipid peroxidation by reactive oxygen species, leading to the formation of malondialdehyde (MDA) that is excreted in biofluids (e.g., urine and exhaled breath condensate (EBC)). A panel study was conducted to examine whether concentrations of MDA in EBC and urine were associated, respectively, with changes in air pollution levels brought by the Beijing Olympic air pollution control measures. EBC and urine samples from 125 healthy adults were collected twice in each of the pre-, during-, and post-Olympic periods. Period-specific means of MDA and changes in MDA levels associated with increases in 24-h average pollutant concentrations were estimated using linear mixed-effects models. From the pre- to the during-Olympic period, when concentrations of most pollutants decreased, EBC MDA and urinary MDA significantly decreased by 24% (P<0.0001) and 28% (P=0.0002), respectively. From the during-Olympic to the post-Olympic period, when concentrations of most pollutants increased, EBC MDA and urinary MDA increased by 28% (P=0.094) and 55% (P=0.046), respectively. Furthermore, the largest increases in EBC MDA associated with one interquartile range (IQR) increases in all pollutants but ozone ranged from 10% (95% CI: 2%, 18%) to 19% (95% CI: 14%, 25%). The largest increases in urinary MDA associated with IQR increases in pollutant concentration ranged from 9% (95%: 0.3%, 19%) to 15% (95% CI: 3%, 28%). These findings support the utility of EBC MDA as a biomarker of oxidative stress in the respiratory tract and urinary MDA as a biomarker of systemic oxidative stress in relation to air pollution exposure in healthy young adults. Both EBC and urine samples can be collected noninvasively in the general population.

Methodology for measuring malonaldehyde as a product of lipid peroxidation in muscle tissues: A review

The purpose of this review is to summarize concerns regarding the formation and quantification of malonaldehyde as a product of lipid peroxidation in muscle tissues. The spectrophotometric thiobarbituric acid (TBA) method is the most frequently used test for malonaldehyde quantification, especially in muscle tissues, as a marker of lipid peroxidation. However, the TBA method has been criticized as lacking specificity and adequate sensitivity towards malonaldehyde. High performance liquid and gas chromatographic methods offer better specificity and sensitivity for malonaldehyde detection. The TBA method, however, may be preferred over the chromatographic method because of its simplicity, especially when a large number of samples need to be analyzed in a short period of time on a daily basis. In addition, the TBA method has been correlated with other objective and subjective methods of measuring lipid peroxidation and its specificity can be improved with the use of a solid phase extraction C(18) cartridge.

Autoxidation of unsaturated lipids in food emulsion

Unsaturated lipids having various physiological roles are of significance in biochemistry, nutrition, medicine, and food. However, the susceptibility of lipids to oxidation is a major cause of quality deterioration in food emulsions. The reaction mechanism and factors that influence oxidation are appreciably different for emulsified lipids and bulk lipids. This article gives a brief overview of the current knowledge on autoxidation of oil-in-water food emulsions, especially those that contain unsaturated lipids, which are important in the food industry. Autoxidation of unsaturated lipids in oil-in-water emulsion is discussed, and so also their oxidation mechanism, the major factors influencing oxidation, determination measures, research status, and the problems encountered in recent years. Some effective strategies for controlling lipid oxidation in food emulsion have been presented in this review.

New hypotheses on the pathways of formation of malondialdehyde and isofurans

Malondialdehyde (MDA) is a mutagenic compound that has been widely used as a biomarker of oxidative stress. However, the nonenzymatic mechanisms of its formation are not well understood. Some lipid oxidation products were previously suggested to be MDA precursors and found to afford MDA heterolytically under acidic conditions. We predict that some of these compounds are not important MDA sources under the autoxidative conditions under which the bulk of MDA should be formed in vivo and that others require further oxidative modifications to generate MDA homolytically. Thus, we outline the likely important pathways of MDA formation in vivo. All these pathways are intense aldehyde producers, generating two other aldehydic products for every MDA molecule formed. Some of the predicted aldehydes are new and may merit further analytical and biological studies. Peracids derived from the aldehydes are proposed to participate in the formation of isofurans (which at high oxygen tensions are excellent markers of oxidative stress) as well as important bioactive epoxides such as leukotoxins. This generates interest in the biological relevance of lipid aldehyde-derived peracids. The suitability of tissue MDA determination methods is discussed based on their likelihood of involving acid-catalyzed artifactual MDA formation.

How to standardize the multiplicity of methods to evaluate natural antioxidants

A great multiplicity of methods has been used to evaluate the activity of natural antioxidants by using different techniques of inducing and catalyzing oxidation and measuring the end point of oxidation for foods and biological systems. Antioxidant in vitro protocols for foods should be based on analyses at relatively low levels of oxidation under mild conditions and on the formation and decomposition of hydroperoxides. For antioxidant in vivo protocols, widely different methods have been used to test the biological protective activity of phenolic compounds. Unfortunately, many of these protocols have been based on questionable methodology to accurately measure oxidative damage and to assess relevant changes in biological targets. Many studies testing the ex vivo activity of phenolic compounds to inhibit human low-density lilpoprotein (LDL) oxidation have been difficult to evaluate because of the structural complexity of LDL particles and because a multitude of markers of oxidative damage have been used. Although studies with animal models of atherosclerosis have demonstrated the antioxidant effect of phenolic compounds in delaying the progress of this disease, human clinical trials of antioxidants have reported inconsistent and mixed results. Complex mixtures of plant polyphenols have been shown to be absorbed to varying degrees as metabolites in the intestine, but little is known about their interactions, bioavailability, and their in vivo antioxidant activity. Several metabolites identified in human plasma after consuming flavonoids need to be tested for possible nonantioxidant activities. More research and better-designed human studies are required to clarify the complex questions of bioavailability of polyphenols and the factors affecting their in vivo activities. Until we know what relevant in vivo activities to measure, any claims on the biological and health protective effects of natural polyphenolic compounds in our diet are premature.

Implications of oxidative stress in high sucrose low magnesium diet fed rats

BACKGROUND

Magnesium deficiency as well as excess sucrose in the diet have been shown to be associated with the generation of reactive oxygen species (ROS).

AIM OF THE STUDY

In the present study we have investigated the combined effect of low magnesium high sucrose diet on the development of oxidative stress in rats.

METHODS

Male Wistar rats were divided into four groups and fed control (C), low magnesium (LM), high sucrose (HS) and low magnesium high sucrose (HSLM) diet for a period of 3 months. Levels of various antioxidants, viz. ascorbic acid, vitamin E, uric acid, glutathione and non-protein thiols were determined along with malondialdehyde levels (lipid peroxidation marker). Anti-oxidant enzyme activities were determined in livers of experimental diet fed animals.

RESULTS

Compared to controls, significantly increased lipid peroxidation was observed in plasma and liver tissue of animals in the three experimental groups, however, the combined HSLM group showed greater lipid peroxidation. Levels of various antioxidants fell significantly in plasma and tissue of LM, HS and HSLM rats. Total thiols as well as liver non-protein thiols followed a similar trend with the greatest drop in anti-oxidant potential seen in the HSLM rats. The activities of the anti-oxidant enzymes viz. SOD, GST and catalase also declined considerably in test animals w.r.t controls, with the HSLM group showing the lowest activities.

CONCLUSION

These findings suggest that a diet low in magnesium and high in sucrose causes oxidative stress in rats, as reflected by increased lipid peroxidation and reduced anti-oxidant potential.

Evaluation of the ability of antioxidants to counteract lipid oxidation: Existing methods, new trends and challenges

Oxidative degradation of lipids, especially that induced by reactive oxygen species (ROS), leads to quality deterioration of foods and cosmetics and could have harmful effects on health. Currently, a very promising way to overcome this is to use vegetable antioxidants for nutritional, therapeutic or food quality preservation purposes. A major challenge is to develop tools to assess the antioxidant capacity and real efficacy of these molecules. Many rapid in vitro tests are now available, but they are often performed in dissimilar conditions and different properties are thus frequently measured. The so-called 'direct' methods, which use oxidizable substrates, seem to be the only ones capable of measuring real antioxidant power. Some oxidizable substrates correspond to molecules or natural extracts exhibiting biological activity, such as lipids, proteins or nucleic acids, while others are model substrates that are not encountered in biological systems or foods. Only lipid oxidation and direct methods using lipid-like substrates will be discussed in this review. The main mechanisms of autoxidation and antioxidation are recapitulated, then the four components of a standard test (oxidizable substrate, medium, oxidation conditions and antioxidant) applied to a single antioxidant or complex mixtures are dealt with successively. The study is focused particularly on model lipids, but also on dietary and biological lipids isolated from their natural environment, including lipoproteins and phospholipidic membranes. Then the advantages and drawbacks of existing methods and new approaches are compared according to the context. Finally, recent trends based on the chemometric strategy are introduced as a highly promising prospect for harmonizing in vitro methods.

Malondialdehyde as biomarker of oxidative damage to lipids caused by smoking

Thiobarbituric acid reactive substances (TBARS) and malondialdehyde (MDA) have been used as biomarkers of lipid oxidation for more than thirty years. The validity of these biomarkers has been rightfully criticized for a lack of specificity and problems with post sampling formation. Numerous assays have been published for their analysis giving rise to reference intervals for healthy non-smoking humans varying more than to orders of magnitude. In spite of these problems, these biomarkers remain among the most commonly reported indices of oxidative damage and the present review focuses on the problems associated with MDA/TBARS analysis, their potential as biomarkers of oxidative stress and the effect of smoking on MDA status.

Induction of oxidative damage by copper-based antineoplastic drugs (Casiopeínas®)

PURPOSE

The aim of the present study is to determine in HeLa cells and in human lymphocytes, by an easy and fast method, the induction of oxidative damage to plasma membrane lipids and nuclear DNA by Casiopeínas, which are recently synthesized coordination complexes that have been considered as a promising chemotherapeutic alternative for the treatment of cancer, since they have shown cytotoxicity and genotoxicity in several cancer cell lines and xenotransplanted tumours. The presence of an oxidized copper atom in their structure strongly suggests that their mode of action seems to be related to reactive oxygen species (ROS) generation after copper atom reduction through the Fenton and Haber-Weiss system.

METHOD

Lipid peroxidation was evaluated as thiobarbituric acid reactive malondialdehyde, cytotoxicity by the fluorescein diacetate/ethidium bromide stain and genotoxicity as DNA fragmentation by the comet assay. Cells were treated with ten different Casiopeínas in a concentration range higher than their IC(50) (10-100 microM), both oxidized and reduced in the presence of ascorbic acid.

RESULTS

In almost all the cases, copper reduction enhanced cytotoxicity but, unlike copper nitrate used as positive control, none of them induced appreciable lipid peroxidation. Three Casiopeínas: Cas Igly, Cas-III-H-a and Cas-III-E-a, showed low, moderate and high rates of genotoxicity, respectively, and this effect was enhanced upon addition of ascorbic acid.

CONCLUSION

These results suggest that ROS generation might be the cause of cytotoxicity, which seems to be related to initial genetic damage rather than to lipid peroxidation. HeLa cells showed to be more sensitive than normal cells.

Oxidative status and serum leptin levels in obese prepubertal children

The prevalence of obesity in children has increased dramatically over the last 20-30 years in developed countries. The aim of this study was to evaluate the oxidative and antioxidant status and any correlation with leptin in obese prepubertal children. A cross-sectional study was made of healthy children from ten elementary schools in the province of Elazig, Eastern Turkey. Blood samples were drawn from children comprising obese and control groups, on a visit to their school in the morning after an overnight fast. The mean body mass index (BMI) was 24.03 +/- 4.09 kg/m(2) in the obese group and was 17.51 +/- 2.33 kg/m(2) in the control group. Mean plasma leptin concentration was significantly higher in the obese children. Homocysteine and malondialdehyde (MDA) levels were also significantly higher in the obese group. In contrast superoxide dismutase (SOD) and glutathione peroxidase activities were significantly decreased in the obese group (p < 0.001). In conclusion, in prepubertal obese children oxidative stress was increased and MDA and homocysteine levels were well correlated with serum leptin level and BMI. In contrast with the increase in oxidative stress, antioxidant activities of SOD and glutathione peroxidase were decreased in obese prepubertal children.

Contribution of mass spectrometry to assess quality of milk-based products

The vast knowledge of milk chemistry has been extensively used by the dairy manufacturing industry to develop and optimize the modern technology required to produce high-quality milk products to which we are accustomed. A thorough understanding of the chemistry of milk and its numerous components is essential for designing processing equipment and conditions needed for the manufacture and distribution of high-quality dairy products. Knowledge and application of milk chemistry is also indispensable for fractionating milk into its principal components for use as functional and nutritional ingredients by the food industry. For all these reasons, powerful analytical methods are required. Because of the complexity of the milk matrix, mass spectrometry, coupled or not to separation techniques, constitutes a key tool in this area. In the present manuscript, we review the contribution and potentialities of mass spectrometry-based techniques to assess quality of milk-based products.

Analytical methods for trace levels of reactive carbonyl compounds formed in lipid peroxidation systems

Analysis of trace levels of reactive carbonyl compounds (RCCs), including formaldehyde, acetaldehyde, acrolein, malonaldehyde, glyoxal, and methyl glyoxal, is extremely difficult because they are highly reactive, water soluble, and volatile. Determination of these RCCs in trace levels is important because they are major products of lipid peroxidation, which is strongly associated with various diseases such as cancer, Alzheimer's disease, aging, and atherosclerosis. This review covers the development and application of various derivatives for RCC analysis. Among the many derivatives which have been prepared, cysteamine derivatives for formaldehyde and acetaldehyde; N-hydrazine derivatives for acrolein, 4-hydroxy-2-nonenal, and malonaldeyde; and o-phenylene diamine derivatives for glyoxal and methyl glyoxal were selected for extended discussion. The application of advanced instruments, including gas chromatograph with nitrogen-phosphorus detector (GC/NPD), mass spectrometer (MS), high performance liquid chromatograph (HPLC), GC/MS, and LC/MS, to the determination of trace RCCs in various oxidized lipid samples, including fatty acids, skin lipids, beef fats, blood plasma, whole blood, and liver homogenates, is also discussed.

A review of recent studies on malondialdehyde as toxic molecule and biological marker of oxidative stress

AIM

Of the many biological targets of oxidative stress, lipids are the most involved class of biomolecules. Lipid oxidation gives rise to a number of secondary products. Malondialdehyde (MDA) is the principal and most studied product of polyunsaturated fatty acid peroxidation. This aldehyde is a highly toxic molecule and should be considered as more than just a marker of lipid peroxidation. Its interaction with DNA and proteins has often been referred to as potentially mutagenic and atherogenic. This review is intended to briefly describe the physiological origin of MDA, to highlight its toxicity, describe and comment on the most recent methods of detection and discuss its occurrence and significance in pathology.

DATA SYNTHESIS

In vivo origin as well as reactivity and consequent toxicity of MDA are reviewed. The most recent and improved procedures for the evaluation of MDA in biological fluids are described and discussed. The evidence of the occurrence of increased MDA levels in pathology is described.

CONCLUSIONS

In the assessment of MDA, the most common methods of detection are insufficiently sensitive and disturbed by interference coming from related species or overestimation derived from stressing analysis conditions. Moreover, no recent nutritional or medical trials report the use of one of the new and more reliable methods, some of which are undoubtedly accessible to virtually all the laboratories provided with a common HPLC or a spectrofluorimeter.

Protective role of vitamin E on the oxidative stress in Hansen's disease (Leprosy) patients

BACKGROUND

A constellation of reactive oxygen species (ROS) capable of damaging cellular constituents generated in excess during the chronic, inflammatory, neurodegenerative disease process of leprosy. The consequences of this leads to enhanced oxidative stress and lower antioxidant status. Enzymatic antioxidants provide first line defense against ROS. We have measured the levels of oxidative stress indices like lipid peroxidation (LPO), protein carbonyls together with enzymatic antioxidants in the blood samples of control and leprosy patients. Nutritional rehabilitation by way of exogenous supplementation of functionally efficient antioxidants like vitamin E reactivates the enzymatic antioxidant system and guards against the insult caused by ROS during the pathogenesis of the disease and antileprosy chemotherapy.

DESIGN

Untreated leprosy patients were selected on the basis of clinical examination and skin smear. All diagnosed untreated leprosy patients received multi drug therapy (MDT) consisting of rifampicin, dapsone and clofazimine as recommended by World Health Organization. A small number of untreated cases were selected for co-supplementation of vitamin E along with MDT. Oxidative stress indices, enzymatic and nonenzymatic antioxidant status were assayed in untreated, MDT treated and those supplemented vitamin E along with MDT.

STATISTICAL METHODS

We have compared the significance in the mean+/-s.d. values of the oxidative stress indices and the levels of antioxidants using one way analysis of variance (ANOVA) between control, untreated, MDT treated and those supplemented vitamin E with MDT and the results were significant at P < 0.05. Statistical analysis of the results suggests that oral administration of vitamin E lowers oxidative stress and augments antioxidant status in affected individuals.

RESULTS

Enhanced oxidative stress as evidenced by increased LPO and protein carbonyl in leprosy cases lowers the antioxidant status. Treatment with MDT has a limited impact on increased oxidative stress and decreased antioxidant status. Coadministration of vitamin E along with MDT decreases oxidative stress and activate the antioxidant status.

DISCUSSION

The excess production of ROS as seen in leprosy cases could lead to degeneration of tissues and derangement of internal organs. The possible reason for the decreased antioxidant status in leprosy cases may be increased production of ROS, deranged liver function, and the free radical producing ability of drugs used in MDT of leprosy. Intervention with antioxidant supplementation like vitamin E prevents oxidative stress mediated through ROS and activates the net antioxidant status during the chronic course of the disease and antileprosy chemotherapy.

The upstream oxylipin profile of Arabidopsis thaliana: a tool to scan for oxidative stresses

Various physiological imbalances lead to reactive oxygen species (ROS) overproduction and/or increases in lipoxygenase (LOX) activities, both events ending in lipid peroxidation of polyunsaturated fatty acids (PUFAs). Besides the quantification of such a process, the development of tools is necessary in order to allow the identification of the primary cause of its development and localization. A biochemical method assessing 9 LOX, 13 LOX and ROS-mediated peroxidation of membrane-bound and free PUFAs has been improved. The assay is based on the analysis of hydroxy fatty acids derived from PUFA hydroperoxides by both the straight and chiral phase high-performance liquid chromatography. Besides the upstream products of peroxidation of the 18:2 and 18:3 PUFAs, products coming from the 16:3 were characterized and their steady-state level quantified. Moreover, the observation that the relative amounts of the ROS-mediated peroxidation isomers of 18:3 were constant in leaves allowed us to circumvent the chiral analyses for the discrimination and quantification of 9 LOX, 13 LOX and ROS-mediated processes in routine experiments. The methodology has been successfully applied to decipher lipid peroxidation in Arabidopsis leaves submitted to biotic and abiotic stresses. We provide evidence of the relative timing of enzymatic and non-enzymatic lipid peroxidation processes. The 13 LOX pathway is activated early whatever the nature of the stress, leading to the peroxidation of chloroplast lipids. Under cadmium stress, the 9 LOX pathway added to the 13 LOX one. ROS-mediated peroxidation was mainly driven by light and always appeared as a late process.

Formation of genotoxic dicarbonyl compounds in dietary oils upon oxidation

Dietary oils--tuna, salmon, cod liver, soybean, olive, and corn oils--were treated with accelerated storage conditions (60 degrees C for 3 and 7 d) and a cooking condition (200 degrees C for 1 h). Genotoxic malonaldehyde (MA), glyoxal, and methylglyoxal formed in the oils were analyzed by GC. Salmon oil produced the greatest amount of MA (1070+/-77.0 ppm of oil) when it was heated at 60 degrees C for 7 d. The highest formation of glyoxal was obtained from salmon oil heated at 60 degrees C for 3 d. More glyoxal was found from salmon and cod liver oils when they were heated for 3 d (12.8+/-1.10 and 7.07+/-0.19 ppm, respectively) than for 7 d (6.70+/-0.08 and 5.94+/-0.38 ppm, respectively), suggesting that glyoxal underwent secondary reactions during a prolonged time. The amount of methyglyoxal formed ranged from 2.03+/-0.13 (cod liver oil) to 2.89+/-0.11 ppm (tuna oil) in the fish oils heated at 60 degrees C for 7 d. Among vegetable oils, only olive oil yielded methylglyoxal (0.61+/-0.03 ppm) under accelerated storage conditions. When oils were treated under cooking conditions, the aldehydes formed were comparable to those formed under accelerated storage conditions. Fish oils produced more MA, glyoxal, and methylglyoxal than did vegetable oils because the fish oils contained higher levels of long-chain PUFA, such as EPA and DHA, than did the vegetable oils. A statistically significant correlation (P < 0.05) between the alpha-tocopherol content and the oxidation parameters was obtained from only MA and fish oils heated at 60 degrees C for 3 d.

Nickel-induced plasma lipid peroxidation and effect of antioxidants in human blood: involvement hydroxyl radical formation and depletion of alpha-tocopherol

To provide evidence for the oxidative effect of nickel (Ni) treatment on blood, lipid peroxidation (LPO) and hydroxyl radical (*OH) generation were examined in human plasma. Nickel chloride induced LPO in plasma of human blood in vitro in a concentration-dependent (0-10 mM) and time-dependent (0-2 h) manner. The *OH production in plasma was quantified by measurement of conversion of salicylic acid (SA) into its hydroxylated products, 2,3- and 2,5-dihydroxybenzoate (DHB). The concentrations of 2,3- and 2,5-DHB in plasma increased in a concentration-dependent manner after Ni treatment for 1 h. Furthermore, a decreasing trend in alpha-tocopherol levels in plasma was observed after Ni treatment. Concurrent incubation with gluthathione (GSH), catechin (CTCH), and mannitol decreased lipid peroxidation and reduced *OH formation induced by Ni, but exacerbation of the decrease of alpha-tocopherol in plasma occurred with catechin.

The effects of humic acid-arsenate complexes on human red blood cells

Humic acid (HA) has been proposed as factor in the cause of Blackfoot disease (BFD) among individuals who live along the southwest coast of Taiwan. In this study, the interaction of the synthetic humic acid, made from catechol, with sodium arsenate (As(V)) was investigated and assessed with respect to damage to human red blood cells. HA is characterized as phenolic and phenolic carboxylic polymer structures containing both -COOH and -OH as their main functional groups. HA and As(V) alone are able to hemolyze 60-100 and 5-20% human red blood cells at concentrations of 50-300 microg/ml and 5-100 mM, respectively, after 6 h. HA is shown to be relatively ineffective in causing ATP depletion of red blood cells. For organometallic complexes composed of HA-As(V) the inhibition effect of EDTA was completely abolished and the use of the triple complex HA-As(V)-EDTA resulted in an enhancement of hemolysis. HA caused lipid peroxidation in a concentration- and time-dependent manner. However, HA-As(V) and As(V) decreased lipid peroxidation. These results indicated that HA initiates oxidative stress on red blood cells and this results in their dysfunction. HA-chelated high-concentration metal complexes inhibited the structures containing the main functional groups involved in decreasing hemolysis, and, thus, HA may be a significant factor in the etiology of BFD.

Comparison of analytical techniques to quantify malondialdehyde in milk powders

Several analytical methods were compared to quantify malondialdehyde (MDA) in milk powders. Modified thiobarbituric acid (TBA) methods, using either visible spectrophotometry (direct absorbance reading or after third derivative transformation of the spectrum) or HPLC, required derivatisation at elevated temperature, which appeared to catalyse artefactual MDA formation and thus overestimate the MDA content. In contrast to the TBA derivatisation method, the measurement of MDA as the dinitrophenylhydrazone derivative by HPLC or as the phenylhydrazone product by GC-MS with a deuterated internal standard resulted in lower estimates in the ranges of 2-17- and 3-30-fold, respectively; apparently due to the milder derivatisation conditions. The estimates of MDA determined by both HPLC-UV and GC-MS techniques result in lower values which are similar in magnitude even though the GC-MS technique is more sensitive.

Mechanisms of action of malondialdehyde and 4-hydroxynonenal on xanthine oxidoreductase

Studies have been made on the possible involvement of malondialdehyde (MDA) and (E)-4-hydroxynon-2-enal (HNE), two terminal compounds of lipid peroxidation, in modifying xanthine oxidoreductase activity through interaction with the oxidase (XO) and/or dehydrogenase (XDH) forms. The effect of the two aldehydes on XO (reversible, XO(rev), and irreversible, XO(irr)) and XDH was studied using xanthine oxidase from milk and xanthine oxidoreductase partially purified from rat liver. The incubation of milk xanthine oxidase with these aldehydes resulted in the inactivation of the enzyme following pseudo-first-order kinetics: enzyme activity was completely abolished by MDA (0.5-4 mM), while residual activity (5% of the starting value) associated with an XO(irr) form was always observed when the enzyme was incubated in the presence of HNE (0.5-4 mM). The addition of glutathione to the incubation mixtures prevented enzyme inactivation by HNE. The study on the xanthine oxidoreductase partially purified from rat liver showed that MDA decreases the total enzyme activity, acting only with the XO forms. On the contrary HNE leaves the same level of total activity but causes the conversion of XDH into an XO(irr) form.

Beta-ethoxyacrolein contamination increases malondialdehyde inhibition of milk xanthine oxidase activity

beta-Ethoxyacrolein (BEA), a side product that forms during the preparation of malondialdehyde (MDA) by acidic hydrolysis of tetraethoxypropane (TEP), has been found to be an inhibitor of milk xanthine oxidase (XO) several times more potent than pure MDA (NaMDA). The incubation of XO with 10 microM BEA abolished 50% of the enzyme activity within 1 min; the inhibited enzyme was totally regenerated by dialysis and filtration through Sephadex. The BEA inhibition mode of the enzyme was mixed-type with the apparent inhibition constants (Ki) of 2.4 x 10(-6) M. An HPLC method for quantitation of BEA in the crude commonly used MDA preparation was set up.

Analysis of membrane phospholipid peroxidation by isocratic high-performance liquid chromatography with ultraviolet detection

A new high-performance liquid chromatography (HPLC) for separation of phospholipid classes with ultraviolet (UV) detection at 210 nm was applied to study of peroxidation of the human erythrocyte membranes induced by soybean lipoxygenase. Phospholipid hydroperoxide production of each phospholipid was monitored at the same time by UV at 234 nm. Each phospholipid class was collected directly from the HPLC of phospholipids and was subjected to fatty acid analysis. All phospholipid classes except sphingomyelin were significantly decreased by lipoxygenase. Production of each phospholipid hydroperoxide was according to the decrease of its corresponding phospholipid class. Polyunsaturated fatty acids of each phospholipid were preferentially decreased with lipoxygenase, and degrees of the changes of the phospholipid classes corresponded to the amount of polyunsaturated fatty acids of each phospholipid. alpha-Tocopherol suppressed the decrease of the membrane phospholipids by peroxidation and suppressed also the production of malondialdehyde. However, production of phospholipid hydroperoxides appeared to be not suppressed by alpha-tocopherol. The present HPLC method proved to be sensitive to peroxidation of phospholipids and could detect the changes of each phospholipid class including phosphatidylserine and phosphatidylinositol at a single chromatographic elution. Production of hydroperoxide of each phospholipid could be detected simultaneously.

Zinc diffusion through lipid bilayers

Zinc diffusion across liposome bilayers was measured for a set of phosphatidylcholines. These lipids were sonicated to form small unilamellar vesicles in the presence of the metallochromic indicator antipyrylazo III. This chelator sequentially forms two complexes with zinc ion. The rate constant for the first complex formation is shown to increase linearly with zinc concentration. The slope of this line, a [Zn2+]-independent, second-order rate constant, varies with changes in phosphatidylcholine properties. The rate constant is little affected by changes in fluidity as estimated from the reduced temperature [Tr = (Texperimental-Tc)/Tc]. In contrast, the rate constant is directly dependent on lipid oxidation as measured by either a thiobarbituric acid test or a spectrophotometric determination of conjugate dienes. We estimate that zinc diffusion stimulated by lipid oxidation can approach rates observed in hepatocyte zinc transport.

Lipid oxidation on foods

This review discusses the basic chemical reactions that affect food flavor quality. Although there are many reactions that can lead to the deterioration of quality in foods, this review focuses on lipid oxidation and how it adversely affects flavor principals. It also presents technological advances for studying the basic mechanism of lipid oxidation, for measuring its intensity, and for retaining food quality. The food commodities that provide the subject matter for this review include vegetable oils, legumes, cereal grains, eggs, beef, lamb, poultry, seafoods, and catfish. The methodologies for assessing food quality form a multidisciplinary approach that includes primarily instrumental analysis by direct gas chromatography, chemical analysis by the TBA test, and sensory analysis by quantitative descriptive determinations. The author hopes that the information presented in this review is applicable to food commodities not discussed.

Breath pentane and plasma lipid peroxides in ischemic heart disease

This study examined the relationship between breath pentane and plasma lipid peroxide levels sampled simultaneously in patients with stable angina (n = 17), unstable angina (n = 23), and controls (n = 10). Plasma lipid peroxides were measured in venous blood as the adduct formed between thiobarbituric acid and malondialdehyde (MDA) using high performance liquid chromatography. Pentane was measured in end-expiratory air using gas chromatography. MDA concentrations in stable (1.81 +/- 0.84 mumol/l) and unstable (1.5 +/- 1.23 mumol/l) angina were not different. However, both groups had significantly (p < 0.005) elevated MDA levels compared to controls (0.41 +/- 0.26 mumol/l). Breath pentane was 0.20 +/- 0.12 nmol/l in controls and not different from stable angina (0.26 +/- 0.20 nmol/l) or unstable angina (0.15 +/- 0.07 nmol/l). When the data from all three groups were combined, there was no correlation between pentane and MDA (rho = -0.09, p = 0.54). In five of the unstable angina patients treated with balloon angioplasty, MDA in pulmonary arterial blood rose by 69 +/- 15% (p < 0.01), and breath pentane rose by 73 +/- 20% (p < 0.01) immediately after balloon deflation. One minute after balloon deflation MDA and pentane had returned to preinflation levels. The results suggest that basal levels of pentane are less useful than MDA as an index of lipid peroxidation in patients with coronary artery disease. However, breath pentane appears to be a sensitive index of reperfusion-induced lipid peroxidation.

Peroxidation of egg yolk phosphatidylcholine liposomes by hypochlorous acid

The powerful neutrophil-derived oxidant hypochlorous acid HOCl/OCl- is assumed to contribute to tissue injury in a number of pathological states accompanied by massive accumulation of neutrophils. The production of malondialdehyde to indicate lipid peroxidation was studied in egg yolk phosphatidylcholine liposomes upon treatment with NaOCl as a source for hypochlorous acid. Its accumulation was inhibited by alpha-tocopherol and butylated hydroxytoluene. Singlet oxygen, hydroxyl radicals or superoxide anion radicals derived from direct reactions of hypochlorous acid seem not to be involved in initiation of lipid peroxidation because the malondialdehyde accumulation was unaffected by hydrogen peroxide, catalase, superoxide dismutase, ferrous sulphate or ferric chloride. Double bonds of fatty acid residues seem to be the primary target for NaOCl. Their number is continuously diminished in liposomes (2 mg lipids/ml) after incubation with increasing amounts of NaOCl at 37 degrees C for 40 min as detected by two independent methods (iodine bromide reduction and 1H-NMR spectroscopy). A 1:1 molar ratio between the loss of double bonds and NaOCl added was found only at low NaOCl concentrations. Then double bonds are decreased with a lower efficiency. A continuous increase of lipid peroxidation products was only observed up to 0.5-0.7 mmol/l NaOCl. The yield of lipid hydroperoxides kept constant at higher NaOCl concentrations. However, diene conjugates and malondialdehyde exhibit a maximum at 0.7-1 mmol/l or 0.5 mmol/l NaOCl, respectively, while the concentration of these products decreases at higher doses of NaOCl. The decrease of malondialdehyde was more pronounced than for diene conjugates. These results were discussed from the background that at minimum two (diene conjugates) or three (malondialdehyde) double bonds in a fatty acid residue are necessary for formation of lipid peroxidation products.