Measurement by reversed-phase high-performance liquid chromatography of malondialdehyde in normal human urine following derivatisation with 2,4-dinitrophenylhydrazine

Rapid and reliable quantification of urinary malondialdehyde by HILIC-MS/MS: A derivatization-free breakthrough approach

BACKGROUND

The development of fast analytical methods is crucial for the research, discovery, and confirmation of crucial biomarkers. Furthermore, the implementation of fast analytical strategies contributes to efficient and time-effective procedures. In this sense, analysis of malondialdehyde (MDA) has become an important tool for understanding the role of oxidative stress in various diseases and for evaluating the efficacy of therapeutic interventions.

RESULTS

A rapid and robust liquid chromatography tandem mass spectrometry method (HPLC-MS/MS) has been developed to determine endogenous amounts of malondialdehyde (MDA) in human urine without any associated derivatization reaction. MDA was separated in 4 min through a Urea-HILIC column and was analyzed using a triple quadrupole mass spectrometer in negative electrospray ionization mode. With a 50-fold dilution as the only sample pretreatment after alkaline hydrolysis, no matrix effect was present, which allowed for a fast and simple quantification by means of an external standard calibration with a limit of detection of 0.20 ng mL-1. The whole methodology was validated by analyzing unspiked and spiked urine samples from ten healthy individuals and comparing with the results obtained by the standard addition method. MDA was detected in all cases, with natural concentrations varying from 0.11 ± 0.03 to 0.31 ± 0.03 mg g-1 creatinine. Accuracies were found to be satisfactory, ranging from 95 % to 101 %. The proposed method also exhibited good repeatability and reproducibility (RSD<15 %) for four quality control levels.

SIGNIFICANCE

The main significance of this method is the avoidance of a derivatization reaction for the determination of urinary MDA, this constituting a step forward when compared with previous literature. This breakthrough not only streamlines time analysis to less than 5 min per sample but also results in a more robust procedure. Consequently, the method here developed could be applied to subsequent future research involving the determination of MDA as a lipid peroxidation biomarker, where simple, rapid, and reliable methods could represent a significant improvement.

Potential biomarkers and therapeutic targets for obsessive compulsive disorder: Evidences from clinical studies

Obsessive compulsive disorder (OCD) is a prevalent behavioral disorder with a complex etiology. However, the underlying pathogenic molecular pathways and the associated risk factors are largely obscure. This has hindered both the identification of relevant prognostic biomarkers and the development of effective treatment strategies. Because of the diverse range of clinical manifestations, not all patients benefit from therapies currently practiced in the clinical setting. Nevertheless, several lines of evidence indicate that neurotrophic, neurotransmitter, and oxidative signaling are involved in the pathophysiology of OCD. Based upon evidences from clinical (and pre-clinical studies), the present review paper sets out to decipher the utilities of three parameters (i.e. brain-derived neurotrophic factor; BDNF, noradrenalin-synthesizing enzyme dopamine beta-hydroxylase; DBH; and oxidative damage marker malondialdehyde; MDA) as diagnostic peripheral biomarkers as well as bio-targets for therapeutic strategies. While the data indicates promising results, there is necessitation for future studies to further confirm and establish these. Further, based again on the available clinical data, we investigated the possibilities of exploiting the etiological links between disruptions in the sleep-wake cycle and insulin signaling, and OCD for the identification of potential anti-OCD ameliorative agents with the ability to elicit multimodal effects, including attenuation of the alterations in BDNF, noradrenergic and redox pathways. In this respect, agomelatine and metformin may represent particularly interesting candidates; however, further clinical studies are warranted to establish these as singular or complementary medications in OCD subjects.

Oxidative stress biomarker triggered multiplexed tool for auxiliary diagnosis of atherosclerosis

Oxidative stress is integral in the development of atherosclerosis, but knowledge of how oxidative stress affects atherosclerosis remains insufficient. Here, we design a multiplexed diagnostic tool that includes two functions (photoacoustic imaging and urinalysis), for assessing intraplaque and urinary malondialdehyde (MDA), a well-recognized end-product of oxidative stress. Molecular design is conducted to develop the first near-infrared MDA-responsive molecule (MRM). Acid-unlocked ratiometric photoacoustic nanoprobe is designed to report intraplaque MDA, enabling it to reflect plaque burden. Furthermore, MRM is tailored for urinary MDA detection with excellent specificity in a blind study. Moreover, we found a significant difference in urinary MDA between healthy adults and atherosclerotic patients (more than 600 participants). Combining these two functions, such a multiplexed diagnostic tool can dynamically report intraplaque and systemic oxidative stress levels during atherosclerosis progression, pneumonia infection, and drug treatment in atherosclerotic mice, which is promising for the auxiliary diagnosis of atherosclerosis.

Rapid determination of malondialdehyde in serum samples using a porphyrin-functionalized magnetic graphene oxide electrochemical sensor

An electrochemical sensor based on a screen-printed carbon electrode (SPCE) modified with porphyrin-functionalized magnetic graphene oxide (TCPP-MGO) was developed for the sensitive and selective determination of malondialdehyde (MDA), an important biomarker of oxidative damage, in serum samples. The coupling of TCPP with MGO allows the exploitation of the magnetic properties of the material for separation, preconcentration, and manipulation of analyte, which is selectively captured onto the TCPP-MGO surface. The electron-transfer capability in the SPCE was improved through derivatization of MDA with diaminonaphthalene (DAN) (MDA-DAN). TCPP-MGO-SPCEs have been employed to monitor the differential pulse voltammetry (DVP) levels of the whole material, which is related to the amount of the captured analyte. Under optimum conditions, the nanocomposite-based sensing system has proved to be suitable for the monitoring of MDA, presenting a wide linear range (0.01-100 µM) with a correlation coefficient of 0.9996. The practical limit of quantification (P-LOQ) of the analyte was 0.010 µM, and the relative standard deviation (RSD) was 6.87% for 30 µM MDA concentration. Finally, the developed electrochemical sensor has demonstrated to be adequate for bioanalytical applications, presenting an excellent analytical performance for the routine monitoring of MDA in serum samples.

Urinary Malondialdehyde (MDA) Concentrations in the General Population—A Systematic Literature Review and Meta-Analysis

Oxidative stress has been associated with various inflammation-related human diseases. It is defined as an imbalance between the production and elimination of reactive oxygen species (ROS). ROS can oxidize proteins, lipids, and DNA, and some of these oxidized products are excreted in urine, such as malondialdehyde (MDA), which is considered a biomarker for oxidative damage of lipids. To interpret changes of this biomarker as a measure of oxidative species overproduction in humans, a background range for urinary MDA concentration in the general population is needed. We sought to establish urinary MDA concentration ranges for healthy adult populations based on reported values in the available scientific literature. We conducted a systematic review and meta-analysis using the standardized protocol registered in PROSPERO (CRD42020146623). EMBASE, PubMed, Web of Science, and Cochrane library databases were searched from journal inception up to October 2020. We included 35 studies (divided into 47 subgroups for the quantitative analysis). Only studies that measured creatinine-corrected urinary MDA with high-performance liquid chromatography (HPLC) with mass spectrometry (MS), fluorescence detection, or UV photometry were included. The geometric mean (GM) of urinary MDA concentration was 0.10 mg/g creatinine and 95% percentile confidence interval (CI) 0.07–0.12. Age, geographical location but not sex, and smoking status had a significant effect on urinary MDA concentrations. There was a significant increasing trend of urinary MDA concentrations with age. These urinary MDA values should be considered preliminary, as they are based on mostly moderate to some low-quality evidence studies. Although urinary MDA can reliably reflect excessive oxidative stress in a population, the influence of physiological parameters that affect its meaning needs to be addressed as well as harmonizing the chemical analytical methods.

Method Validation and Characterization of the Associated Uncertainty for Malondialdehyde Quantification in Exhaled Breath Condensate

There are several methods for quantifying malondialdehyde (MDA), an oxidative stress biomarker, in exhaled breath condensate (EBC). However, due to the very diluted nature of this biological matrix, a high variability is observed at low concentrations. We aimed to optimize a 2,4-dinitrophenylhydrazine-based method using liquid chromatography coupled to tandem mass spectrometry and characterize the uncertainty associated with this method. We investigated the following parameters for the method validation: calibration linearity, limit of detection (LOD), precision, recovery, and matrix effect. The results were used to identify the main sources of uncertainty and calculating the combined uncertainty. The applicability of this method was evaluated in an ongoing epidemiological study by analyzing 164 EBC samples collected from different professional groups in subway environments. The optimized method was sensitive (LOD: 70 pg/mL), precise (inter-day variation < 19%) and accurate (recovery range: 92–106.5%). The calculated analytical uncertainty was the highest at the LOQ level and reached 23%. Although the analytical uncertainty was high at low MDA concentrations, it was significantly lower than that the observed inter-individual variability. Hence, this method performs sufficiently well and can be recommended for future use in epidemiological researches relying on between-subject differences.

Selenomethionine administration decreases the oxidative stress induced by post mortem ischemia in the heart, liver and kidneys of rats

Selenium is an essential element in human and animal metabolism integrated into the catalytic site of glutathione peroxidase (GPX1), an antioxidant enzyme that protects cells from damage caused by reactive oxygen species (ROS). Oxidative stress refers the imbalance between ROS and antioxidant defense systems. It generates alterations of DNA, proteins and lipid peroxidation. The imbalance occurs particularly during ischemia and lack of postmortem perfusion. This mechanism is of relevance in transplant organs, affecting their survival. The aim of this research is to evaluate the effect of seleno-methionine (SeMet) as a protective agent against postmortem ischemia injury in transplant organs. Wistar rats were orally administered with SeMet. After sacrifice, liver, heart and kidney samples were collected at different postmortem intervals (PMIs). SeMet administration produced a significant increase of Se concentration in the liver (65%, p < 0.001), heart (40%, p < 0.01) and kidneys (45%, p < 0.05). Levels of the oxidative stress marker malondialdehyde (MDA) decreased significantly compared to control in the heart (0.21 ± 0.04 vs. 0.12 ± 0.02 mmol g^-1) and kidneys (0.41 ± 0.02 vs. 0.24 ± 0.03 mmol g^-1) in a PMI of 1-12 h (p < 0.01). After SeMet administration for 21 days, a significant increase in GPX1 activity was observed in the liver (80%, p < 0.001), kidneys (74%, p < 0.01) and heart (35%, p < 0.05). SeMet administration to rats significantly decreased the oxidative stress in the heart, liver and kidneys of rats generated by postmortem ischemia.

Aqueous Extract of Adansonia digitata reversed Cotton Seed Extract-Induced Testicular Damage in Wistar rats

Objective:

Infertility is the inability of sexually active couples without using birth control to get pregnant after one year of uninterrupted sexual intercourse. Cotton Seed Extract (CSE) has been linked to male infertility by causing oxidative damage to the testes due to the action of its active component, Gossypol. Adansonia digitata has been known to have many medically useful properties, including antioxidant effects. This study aimed at evaluating the effects of Adansonia digitata on Cottonseed extract-induced testicular damage.

Methods:

Forty (40) Adult male Wistar rats were divided into 8 groups of five rats per group (n=5). Group 1 served as the control and received 0.5 ml of phosphate buffer orally; Group 2 received 800 mg/kg b.wt A. digitata orally; Group 3 received 300 mg/kg b.wt Vitamin E only orally; Group 4 received 60 mg/kg b.wt CSE intraperitoneally; Group 5 received 20 mg/kg b.wt CSE intraperitoneally; Group 6 received 60 mg/kg b.wt CSE intraperitoneally and 800 mg/kg b.wt A. digitata orally; Group 7 received 20 mg/kg b.wt CSE intraperitoneally and 800 mg/kg b.wt A. digitata orally; Group 8 received 60 mg/kg b.wt CSE intraperitoneally and 300 mg/kg Vit. E orally. It was administered for 21 days. The testes and epididymis were dissected following abdominal incision. The epididymis was used for semen analysis while the testes was processed for histological analysis and biochemical assay. All the data was analyzed by ANOVA, using the SPSS version 17.0 software. A p<0.05 was considered significant.

Results:

CSE administration caused significant (p<0.05) decrease in sperm count, found in the group treated with CSE only. However, the Administration of A. digitata caused significant increase (p<0.05) in sperm count, G6PDH, LDH, GPx and SOD; however, MDA levels were decreased. Histological observations showed a decrease in the number of Spermatogonia and differentiating cells in the testes of rats treated with CSE.

Conclusions:

The results obtained revealed the antioxidant ability of A. digitata in counter-acting the testicular damage caused by CSE administration.

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.

Sensitive determination of malondialdehyde in rat prostate by high performance liquid chromatography with fluorescence detection

An excellent pre-column fluorescent derivatization reagent N-acetylhydrazine acridone for the quantitative determination of malondialdehyde was synthesized. Malondialdehyde was derivatized at 80 °C for 30 min in the presence of trichloroacetic acid. The separation of the derivative was performed on an Agilent ZORBAX SB-C18 column in conjunction with gradient elution. The excitation and emission wavelengths were 370 nm and 420 nm, respectively. The developed method demonstrated good linear relationship in the range of 0.02 pmol to 2.5 pmol (r = 0.9998). The calculated limit of detection and limit of quantification were 2.5 fmol and 8.3 fmol, respectively. The analytical precisions of the method were in the range of 1.36-2.27% (intra-day) and 2.36-3.92% (inter-day) respectively. The method was sensitive, specific and simple. It was successfully implemented to analysis the malondialdehyde in rat prostate.

Effects of reduced exposure to cigarette smoking on changes in biomarkers of potential harm in adult smokers: results of combined analysis of two clinical studies

Purpose: Nonconventional vapor products (NVP), designed to reduce exposure to cigarette smoke toxicants (CSTs), could cause changes in biomarkers of potential harm (BoPH). Although, NVPs reduced CSTs exposure compared to conventional cigarettes (CC), the changes in the BoPH values varied among the studies. Hence, further information on BoPH using NVPs is needed. Material and methods: The data of two similarly designed studies using a kind of NVP, a noncombustion and nonheating inhaler type of smokeless tobacco product (NCIT) used under 31-day confinement, were pooled, and the differences in 15 BoPH between smokers and nonsmokers at baseline and between the 1 mg tar CC (CC1) group and NCIT group at Day 28/29 were analyzed. Results: At baseline, the levels of eight BoPH (red blood cells, white blood cells, 8-epi-prostaglandin F2α, 8-hydroxy-2'-deoxyguanosine, malondialdehyde, 11-dehydrothromboxane B2, total cholesterol and glucose) were significantly different between smokers and nonsmokers. At Day 28/29, the levels of six BoPH were significantly different between NCIT and CC1 (8-epi-prostaglandin F2α, malondialdehyde, 11-dehydrothromboxane B2: CC1 > NCIT, total bilirubin, low-density lipoprotein cholesterol and total cholesterol: CC1 < NCIT). Conclusions: Reduced exposure to CSTs has favorable effects on BoPH associated with oxidative stress, antioxidant capacity and platelet activation/coagulation but not in lipid metabolism.

Lipoxidation in cardiovascular diseases

Lipids can go through lipid peroxidation, an endogenous chain reaction that consists in the oxidative degradation of lipids leading to the generation of a wide variety of highly reactive carbonyl species (RCS), such as short-chain carbonyl derivatives and oxidized truncated phospholipids. RCS exert a wide range of biological effects due to their ability to interact and covalently bind to nucleophilic groups on other macromolecules, such as nucleic acids, phospholipids, and proteins, forming reversible and/or irreversible modifications and generating the so-called advanced lipoxidation end-products (ALEs). Lipoxidation plays a relevant role in the onset of cardiovascular diseases (CVD), mainly in the atherosclerosis-based diseases in which oxidized lipids and their adducts have been extensively characterized and associated with several processes responsible for the onset and development of atherosclerosis, such as endothelial dysfunction and inflammation. Herein we will review the current knowledge on the sources of lipids that undergo oxidation in the context of cardiovascular diseases, both from the bloodstream and tissues, and the methods for detection, characterization, and quantitation of their oxidative products and protein adducts. Moreover, lipoxidation and ALEs have been associated with many oxidative-based diseases, including CVD, not only as potential biomarkers but also as therapeutic targets. Indeed, several therapeutic strategies, acting at different levels of the ALEs cascade, have been proposed, essentially blocking ALEs formation, but also their catabolism or the resulting biological responses they induce. However, a deeper understanding of the mechanisms of formation and targets of ALEs could expand the available therapeutic strategies.

Health benefit of vegetable/fruit juice-based diet: Role of microbiome

The gut microbiota is an important contributor to human health. Vegetable/fruit juices provide polyphenols, oligosaccharides, fiber and nitrate (beet juice), which may induce a prebiotic-like effect. Juice-based diets are becoming popular. However, there is a lack of scientific evidence of their health benefits. It was our hypothesis that changes in the intestinal microbiota induced by a juice-based diet play an important role in their health benefits. Twenty healthy adults consumed only vegetable/fruit juices for 3 days followed by 14 days of customary diet. On day 4 we observed a significant decrease in weight and body mass index (p = 2.0E⁻⁰⁵), which was maintained until day 17 (p = 3.0E⁻⁰⁴). On day 4 the proportion of the phylum Firmicutes and Proteobacteria in stool was significantly decreased and Bacteroidetes and Cyanobacteria was increased compared to baseline and was partially reversed on day 17. On day 4 plasma and urine nitric oxide was increased by 244 ± 89% and 450 ± 360%, respectively, and urinary lipid peroxidation marker malondialdehyde was decreased by 32 ± 21% compared to baseline. General well-being score was increased at the end of the study. In summary a 3-day juice-based diet altered the intestinal microbiota associated with weight loss, increase in the vasodilator NO, and decrease in lipid oxidation.

Development of a Novel, Sensitive, Selective, and Fast Methodology to Determine Malondialdehyde in Leaves of Melon Plants by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Early production of melon plant (Cucumis melo) is carried out using tunnels structures, where extreme temperatures lead to high reactive oxygen species production and, hence, oxidative stress. Malondialdehyde (MDA) is a recognized biomarker of the advanced oxidative status in a biological system. Thus a reliable, sensitive, simple, selective, and rapid separative strategy based on ultra-high-performance liquid chromatography coupled to positive electrospray-tandem mass spectrometry (UPLC-(+)ESI-MS/MS) was developed for the first time to measure MDA, without derivatization, in leaves of melon plants exposed to stress conditions. The detection and quantitation limits were 0.02 μg·L^-1 and 0.08 μg·L^-1, respectively, which was demonstrated to be better than the methodologies currently reported in the literature. The accuracy values were between 96% and 104%. The precision intraday and interday values were 2.7% and 3.8%, respectively. The optimized methodology was applied to monitoring of changes in MDA levels between control and exposed to thermal stress conditions melon leaves samples. Important preliminary conclusions were obtained. Besides, a comparison between MDA levels in melon leaves quantified by the proposed method and the traditional thiobarbituric acid reactive species (TBARS) approach was undertaken. The MDA determination by TBARS could lead to unrealistic conclusions regarding the oxidative stress status in plants.

Elevated urinary excretion of aluminium and iron in multiple sclerosis

Multiple sclerosis (MS) is a chronic, immune-mediated, demyelinating disease of the central nervous system of as yet unknown aetiology. A consensus of opinion has suggested that the disorder is the result of an interplay between environmental factors and susceptibility genes. We have used a battery of analytical techniques to determine if the urinary excretion of i) markers of oxidative damage; ii) iron and iii) the environmental toxin aluminium and its antagonist, silicon, are altered in relapsing remitting (RRMS) and secondary progressive MS (SPMS). Urinary concentrations of oxidative biomarkers, MDA and TBARS, were not found to be useful indicators of inflammatory disease in MS. However, urinary concentrations of another potential marker for inflammation and oxidative stress, iron, were significantly increased in SPMS ( P<0.01) and insignificantly increased in RRMS ( P>0.05). Urinary concentrations of aluminium were also significantly increased in RRMS ( P<0.001) and SPMS ( P<0.05) such that the levels of aluminium excretion in the former were similar to those observed in individuals undergoing metal chelation therapy. The excretion of silicon was lower in MS and significantly so in SPMS ( P<0.05). Increased excretion of iron in urine supported a role for iron dysmetabolism in MS. Levels of urinary aluminium excretion similar to those seen in aluminium intoxication suggested that aluminium may be a hitherto unrecognized environmental factor associated with the aetiology of MS. If aluminium is involved in MS then an increased dietary intake of its natural antagonist, silicon, might be a therapeutic option.

The Co-Induced Effects of Molybdenum and Cadmium on the Trace Elements and the mRNA Expression Levels of CP and MT in Duck Testicles

To investigate the chronic toxicity of molybdenum (Mo) and cadmium (Cd) on the trace elements and the mRNA expression levels of ceruloplasmin (CP) and metallothionein (MT) in duck testicles, 120 healthy 11-day-old male ducks were randomly divided into six groups with 20 ducks in each group. Ducks were treated with the diet containing different dosages of Mo or Cd. The source of Mo and Cd was hexaammonium molybdate ([(NH4)6Mo7O24·4H2O]) and cadmium sulfate (3CdSO4·8H2O), respectively, in this study. After being treated for 60 and 120 days, ten male birds in each group were randomly selected and euthanized and then testicles were aseptically collected for determining the mRNA expression levels of MT and CP, antioxidant indexes, and contents of trace elements in the testicle. In addition, testicle tissues at 120 days were subjected to histopathological analysis with the optical microscope. The results showed that co-exposure to Mo and Cd resulted in an increase in malondialdehyde (MDA) level while decrease in xanthine oxidase (XOD) and catalase (CAT) activities. The mRNA expression level of MT gene was upregulated while CP was decreased in combination groups. Contents of Mo, copper (Cu), iron (Fe), and zinc (Zn) decreased in combined groups while Cd increased in Cd and combined groups at 120 days. Furthermore, severe congestion, low sperm count, and malformation were observed in low dietary of Mo combined with Cd group and high dietary of Mo combined with Cd group. Our results suggested that Mo and Cd might aggravate testicular degeneration synergistically through altering the mRNA expression levels of MT and CP, increasing lipid peroxidation through inhibiting related enzyme activities and disturbing homeostasis of trace elements in testicles. Interaction of Mo and Cd may have a synergistic effect on the testicular toxicity.

A rapid spectrofluorimetric method for the determination of malondialdehyde in human plasma after its derivatization with thiobarbituric acid and vortex assisted liquid–liquid microextraction

A rapid spectrofluorimetric method for the determination of malondialdehyde in human plasma after its derivatization with thiobarbituric acid and vortex assisted liquid–liquid microextraction.

The effect of cryptogein with changed abilities to transfer sterols and altered charge distribution on extracellular alkalinization, ROS and NO generation, lipid peroxidation and LOX gene transcription in Nicotiana tabacum

Cryptogein, a protein from oomycete Phytophthora cryptogea, induces a hypersensitive cell death in Nicotiana tabacum. We prepared a new series of cryptogein mutant proteins with altered abilities to bind sterols and with altered charge distribution in the proteins. The effect of the mutations on the cryptogein ability to induce plant defence mechanisms associated with hypersensitive cell death were examined. Our results with new mutants support the previous findings that the sterol binding does not influence synthesis of ROS, cytosol acidification and development of leaf necrosis as these events seem to be more likely affected by the charge distribution and the overall protein structure. This hypothesis was also applicable on other mechanisms involved in the execution of plant cell death such as the NO generation, the stimulation of lipid peroxidation (determination of malondialdehyde and hydroxy fatty acids levels) and LOX gene transcription. In addition, the ability to bind sterols was found to serve not only for pathogen utilisation in its own metabolism but also to have an important function for the destabilization of plant membrane facilitating the pathogen spread inside the plant tissue as well as intensively contributing to the development of plant cell death. Considering the insertion of charged amino acid residues in the protein structure, the change localized in the protein surface affected its biological activity more effectively than that change inside the protein cavity. Moreover, the insertion of negative charged amino acids influenced mainly the events involved in the early phase of defence reaction, while the positive residues affected especially the necrotic activity of cryptogein.

A rapid, sensitive and solvent-less method for determination of malonaldehyde in meat by stir bar sorptive extraction coupled thermal desorption and gas chromatography/mass spectrometry with in situ derivatization

RATIONALE

The traditional methods for analysis of malonaldehyde (MDA), such as the thiobarbituric acid (TBA) assay, require strong acidity at high temperature for derivatization and lack specificity in analysis. Stir bar sorptive extraction (SBSE) coupled with thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) with in situ derivatization using pentafluorophenylhydrazine (PFPH) under mild conditions is an emerging technique for MDA analysis.

METHODS

MDA in meat was derivatized with PFPH at pH ~4 for 1 h at room temperature, forming a relative stable derivative of MDA-PFPH. The derivative of MDA-PFPH was simultaneously extracted using SBSE. Then, MDA-PFPH was thermally released and quantitatively analyzed by GC/MS in selected ion monitoring (SIM) mode.

RESULTS

The method of SBSE-TD-GC/MS for MDA analysis with in situ derivatization was optimized and validated with good linearity, specificity and limit of detection/quantification (LOD/LOQ). The method was successfully applied for analysis of MDA in raw and cooked meat (pork).

CONCLUSIONS

The SBSE-TD-GC/MS method was suitable to monitor and analyze MDA in meat samples at trace levels. The simple, sensitive and solvent-less method with moderated in situ derivatization can be applied for analysis of MDA in a wide variety of foods and biological samples.

Plasma malondialdehyde levels in children on 12-hour cyclic parenteral nutrition: are there health risks?

In children undergoing total parenteral nutrition (PN), lipids provide a key source of calories preventing or correcting energy deficits and improving outcomes. However, some of these lipids may undergo oxidation leading to the formation of malondialdehyde (MDA), a cytotoxic byproduct found in these patients. This paper aims to describe a sensitive method for detecting MDA and discuss its role in certain diseases commonly found in children on regular PN. To quantify MDA levels in children benefitting from long-term cyclic PN, a reliable and sensitive high-performance liquid chromatographic method based on a 1-step derivatization/extraction procedure analysis with ultraviolet determination at 305 nm wavelength was achieved. In control children without PN, MDA levels were on average 3.30 ± 0.08 µM. However, in children nourished intravenously by fat emulsion for a long time, in which liver problems have been identified, the circulating concentrations of MDA ranged widely at both the start and the end of a session, 3- to 10-fold, respectively, in comparison with the levels measured in controls. This finding indicates that PN administrated long term raises plasma MDA levels, indicating chronic exposure and therefore a possible health risk, particularly liver damage. This preliminary study using a limited number of patients and controls showed that children undergoing long-term PN are strongly exposed to MDA, which must be considered as a potent toxic compound rather than a simple marker of lipid peroxidation.

Mass spectrometry and redox proteomics: applications in disease

Proteomics techniques are continuously being developed to further understanding of biology and disease. Many of the pathways that are relevant to disease mechanisms rely on the identification of post-translational modifications (PTMs) such as phosphorylation, acetylation, and glycosylation. Much attention has also been focused on oxidative PTMs which include protein carbonyls, protein nitration, and the incorporation of fatty acids and advanced glycation products to amino acid side chains, amongst others. The introduction of these PTMs in the cell can occur due to the attack of reactive oxygen and nitrogen species (ROS and RNS, respectively) on proteins. ROS and RNS can be present as a result of normal metabolic processes as well as external factors such as UV radiation, disease, and environmental toxins. The imbalance of ROS and RNS with antioxidant cellular defenses leads to a state of oxidative stress, which has been implicated in many diseases. Redox proteomics techniques have been used to characterize oxidative PTMs that result as a part of normal cell signaling processes as well as oxidative stress conditions. This review highlights many of the redox proteomics techniques which are currently available for several oxidative PTMs and brings to the reader's attention the application of redox proteomics for understanding disease pathogenesis in neurodegenerative disorders and others such as cancer, kidney, and heart diseases.

A fast and validated method for the determination of malondialdehyde in fish liver using high-performance liquid chromatography with a photodiode array detector

Malondialdehyde (MDA) is a biomarker of lipid peroxidation and is present in foods and biological samples such as plasma. A high-performance liquid chromatography (HPLC) method was applied to determine MDA in fish liver samples after derivatization with 2,4-dinitrophenylhydrazine (DNPH) using a ODS2 column (10 cm × 4.6 mm, 3 μm) and a photodiode array detector. The mobile phase consisted of 0.2% acetic acid (v/v) in distilled water and acetonitrile (42:58, v/v). The present method was validated in terms of linearity, lower limit of quantification, lower limit of detection, precision, accuracy, recovery, and stability of MDA according to U.S. Food and Drug Administration (FDA) guidelines. The limit of quantification of MDA was 0.39 μmol/L, which is comparable to other methods. The recovery of the spiked MDA liver samples was in the range of 92.4% to 104.2%. This newly modified HPLC method is specific, sensitive, and accurate and allows the analysis of MDA within 4 min in fish liver but also in other tissues and plasma.

Determination of malondialdehyde in biological fluids by high-performance liquid chromatography using rhodamine B hydrazide as the derivatization reagent

Malondialdehyde (MDA) is a biomarker for lipid peroxidation, and studies of sensitive and selective analytical methods for it are very important for pathological research. The aim of this work was to develop and validate a novel HPLC method for the quantification of MDA in biological fluids using rhodamine B hydrazide (RBH) as the derivatization reagent. After pretreatment and derivatization in acid medium at 50 °C for 40 min, the RBH-derivatized MDA was separated on a Kromasil C18 column at 25 °C and detected by a fluorescence detector at excitation wavelength of 560 nm and emission wavelength of 580 nm. The results showed linearity in the range of 0.8-1500.0 nM with a detection limit of 0.25 nM (S/N = 3). The recovery of MDA from plasma and urine was 91.50 to 99.20%, with a relative standard deviation range of 1.45 to 3.26%. In comparison to other methods reported for the determination of MDA, the proposed method showed superiority in simplicity, more sensitivity, shorter derivatization time, and less interference. The developed method was applied to quantification of MDA in human biological fluids collected from five volunteers with a concentration range of 24.62-245.00 nM.

Short-term changes after a weight reduction intervention in advanced diabetic nephropathy

BACKGROUND AND OBJECTIVES

Obesity precedes and is strongly linked to the development of type 2 diabetic nephropathy in most patients, yet little is known about the effects of weight reduction on this disease. This study aimed to establish proof of concept for the hypothesis that weight reduction ameliorates diabetic nephropathy.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Six obese individuals with advanced diabetic nephropathy (estimated GFR <40 ml/min per 1.73 m(2), urine albumin excretion >30 mg/d) currently taking a renin-aldosterone axis inhibitor underwent a 12-week very low calorie ketogenic weight reduction diet with encouragement of exercise between March and September 2012. Albuminuria and other parameters of kidney health were the main outcome measures.

RESULTS

There was a 12% reduction in weight (median 118.5 versus 104.3 kg, P=0.03). The intervention was associated with a 36% reduction in albuminuria that did not reach statistical significance (2124 versus 1366 mg/24 h, P=0.08) and significant reductions in the filtration markers serum creatinine (3.54 versus 3.13 mg/dl, P<0.05) and cystatin C (2.79 versus 2.46 mg/l, P<0.05). Improvements were also noted for the diabetes markers fasting glucose (166 versus 131 mg/dl, P<0.05), fasting insulin (26.9 versus 10.4 μU/ml, P<0.05), and insulin resistance (9.6 versus 4.2, P=0.03). Physical function, general health, and the number of diabetes medications also showed statistically significant signs of improvement.

CONCLUSIONS

After a short-term intensive weight reduction intervention in patients with advanced diabetic nephropathy, improvements were observed in markers of glomerular filtration, diabetes status, and risk factors for kidney disease progression, as well as other general indicators of health and well-being.

Consumption of Hibiscus sabdariffa L. aqueous extract and its impact on systemic antioxidant potential in healthy subjects

BACKGROUND

To evaluate health benefits attributed to Hibiscus sabdariffa L. a randomized, open-label, two-way crossover study was undertaken to compare the impact of an aqueous H. sabdariffa L. extract (HSE) on the systemic antioxidant potential (AOP; assayed by ferric reducing antioxidant power (FRAP)) with a reference treatment (water) in eight healthy volunteers. The biokinetic variables were the areas under the curve (AUC) of plasma FRAP, ascorbic acid and urate that are above the pre-dose concentration, and the amounts excreted into urine within 24 h (Ae(0-24) ) of antioxidants as assayed by FRAP, ascorbic acid, uric acid, malondialdehyde (biomarker for oxidative stress), and hippuric acid (metabolite and potential biomarker for total polyphenol intake).

RESULTS

HSE caused significantly higher plasma AUC of FRAP, an increase in Ae(0-24) of FRAP, ascorbic acid and hippuric acid, whereas malondialdehyde excretion was reduced. Furthermore, the main hibiscus anthocyanins as well as one glucuronide conjugate could be quantified in the volunteers' urine (0.02% of the administered dose).

CONCLUSION

The aqueous HSE investigated in this study enhanced the systemic AOP and reduced the oxidative stress in humans. Furthermore, the increased urinary hippuric acid excretion after HSE consumption indicates a high biotransformation of the ingested HSE polyphenols, most likely caused by the colonic microbiota.

Urinary biomarkers of oxidative status

Oxidative damage produced by reactive oxygen species (ROS) has been implicated in the etiology and pathology of many health conditions, including a large number of chronic diseases. Urinary biomarkers of oxidative status present a great opportunity to study redox balance in human populations. With urinary biomarkers, specimen collection is non-invasive and the organic/metal content is low, which minimizes the artifactual formation of oxidative damage to molecules in specimens. Also, urinary levels of the biomarkers present intergraded indices of redox balance over a longer period of time compared to blood levels. This review summarizes the criteria for evaluation of biomarkers applicable to epidemiological studies and evaluation of several classes of biomarkers that are formed non-enzymatically: oxidative damage to lipids, proteins, DNA, and allantoin, an oxidative product of uric acid. The review considers formation, metabolism, and exertion of each biomarker, available data on validation in animal and clinical models of oxidative stress, analytical approaches, and their intra- and inter-individual variation. The recommended biomarkers for monitoring oxidative status over time are F₂-isoprostanes and 8-oxodG. For inter-individual comparisons, F₂-isoprostanes are recommended, whereas urinary 8-oxodG levels may be confounded by differences in the DNA repair capacity. Promising urinary biomarkers include allantoin, acrolein-lysine, and dityrosine.

Thermotolerant cyclamen with reduced acrolein and methyl vinyl ketone

Reduced levels of trienoic fatty acids (TAs) in chloroplast membranes induce thermotolerance in several plant species, but the underlying mechanisms remain unclear. TA peroxidation in plant cell membranes generates cytotoxic, TA-derived compounds containing α,β-unsaturated carbonyl groups. The relationship between low TA levels and the amounts of cytotoxic TA-derived compounds was examined using thermotolerant transgenic cyclamen (Cyclamen persicum Mill.) with low TA contents. Changes in the levels of the cytotoxic TA-derived acrolein (ACR), methyl vinyl ketone (MVK), (E)-2-hexenal, 4-hydroxy-2-nonenal, and malondialdehyde were analysed in the leaf tissues of wild-type (WT) and thermotolerant transgenic cyclamen under heat stress. Levels of ACR and MVK in the WT increased in parallel with the occurrence of heat-induced tissue damage, whereas no such changes were observed in the thermotolerant transgenic lines. Furthermore, exogenous ACR and MVK infiltrated into leaves to concentrations similar to those observed in heat-stressed WT leaves caused similar disease symptoms. These results suggest that thermotolerance in transgenic cyclamen depends on reduced production rates of ACR and MVK under heat stress, due to the low level of TAs in these plants.

Recent Advancements in the LC- and GC-Based Analysis of Malondialdehyde (MDA): A Brief Overview

Malondialdehyde (MDA) is an end-product of lipid peroxidation and a side product of thromboxane A₂ synthesis. Moreover, it is not only a frequently measured biomarker of oxidative stress, but its high reactivity and toxicity underline the fact that this molecule is more than “just” a biomarker. Additionally, MDA was proven to be a mutagenic substance. Having said this, it is evident that there is a major interest in the highly selective and sensitive analysis of this molecule in various matrices. In this review, we will provide a brief overview of the most recent developments and techniques for the liquid chromatography (LC) and gas chromatography (GC)-based analysis of MDA in different matrices. While the 2-thiobarbituric acid assay still is the most prominent methodology for determining MDA, several advanced techniques have evolved, including GC–MS(MS), LC–MS(MS) as well as several derivatization-based strategies.

Determination of urinary malondialdehyde by isotope dilution LC-MS/MS with automated solid-phase extraction: a cautionary note on derivatization optimization

A highly sensitive quantitative LC-MS/MS method was developed for measuring urinary malondialdehyde (MDA). With the use of an isotope internal standard and online solid-phase extraction, urine samples can be directly analyzed within 10 min after 2,4-dinitrophenylhydrazine (DNPH) derivatization. The detection limit was estimated as 0.08 pmol. This method was further applied to assess the optimal addition of DNPH for derivatization and to measure urinary MDA in 80 coke oven emission (COE)-exposed and 67 nonexposed workers. Derivatization optimization revealed that to achieve complete derivatization reaction, an excess of DNPH is required (DNPH/MDA molar ratio: 893-8929) for urine samples that is about 100 times higher than that of MDA standard solutions (molar ratio: 10-80). Meanwhile, the mean urinary concentrations of MDA in COE-exposed workers were significantly higher than those in nonexposed workers (0.23±0.17 vs 0.14±0.05 μmol/mmol creatinine, P<0.005). Urinary MDA concentrations were also significantly associated with the COE (P<0.005) and smoking exposure (P<0.05). Taken together, this method is capable of routine high-throughput analysis and accurate quantification of MDA and would be useful for assessing the whole-body burden of oxidative stress. Our findings, however, raise the issue that derivatization optimization should be performed before it is put into routine biological analysis.

Arsenic-induced oxidative stress and its reversibility

This review summarizes the literature describing the molecular mechanisms of arsenic-induced oxidative stress, its relevant biomarkers, and its relation to various diseases, including preventive and therapeutic strategies. Arsenic alters multiple cellular pathways including expression of growth factors, suppression of cell cycle checkpoint proteins, promotion of and resistance to apoptosis, inhibition of DNA repair, alterations in DNA methylation, decreased immunosurveillance, and increased oxidative stress, by disturbing the pro/antioxidant balance. These alterations play prominent roles in disease manifestation, such as carcinogenicity, genotoxicity, diabetes, cardiovascular and nervous systems disorders. The exact molecular and cellular mechanisms involved in arsenic toxicity are rather unrevealed. Arsenic alters cellular glutathione levels either by utilizing this electron donor for the conversion of pentavalent to trivalent arsenicals or directly binding with it or by oxidizing glutathione via arsenic-induced free radical generation. Arsenic forms oxygen-based radicals (OH(•), O(2)(•-)) under physiological conditions by directly binding with critical thiols. As a carcinogen, it acts through epigenetic mechanisms rather than as a classical mutagen. The carcinogenic potential of arsenic may be attributed to activation of redox-sensitive transcription factors and other signaling pathways involving nuclear factor κB, activator protein-1, and p53. Modulation of cellular thiols for protection against reactive oxygen species has been used as a therapeutic strategy against arsenic. N-acetylcysteine, α-lipoic acid, vitamin E, quercetin, and a few herbal extracts show prophylactic activity against the majority of arsenic-mediated injuries in both in vitro and in vivo models. This review also updates the reader on recent advances in chelation therapy and newer therapeutic strategies suggested to treat arsenic-induced oxidative damage.

The simple and sensitive measurement of malondialdehyde in selected specimens of biological origin and some feed by reversed phase high performance liquid chromatography

A method for the determination of malondialdehyde (MDA) concentrations in specimens of animal tissues and feed has been developed using high performance liquid chromatography. The MDA concentration in acidified urine samples was determined after its conversion with 2,4-dinitrophenylhydrazine (DNPH) to a hydrazone (MDA-DNPH). Samples of blood plasma, muscle, liver and feed were prepared by saponification followed by derivatisation with DNPH to MDA-DNPH. The MDA concentration in chicken and hen feed samples was analysed after saponification and derivatisation followed by extractions with hexane. The free MDA in plasma samples was determined after deproteinization followed by derivatisation of MDA with DNPH. The chromatographic separation of MDA-DNPH samples was conducted using Phenomenex C(18)-columns (Synergi 2.5 μm, Hydro-RP, 100 Å, the length of 100mm) with an inner diameter of 2 or 3mm. MDA in processed biological samples was analysed using a linear gradient of acetonitrile in water, and the photodiode detector was set to 307 or 303 nm for detection. The current method that was utilised was based on the high-efficient derivatisation of MDA and was more sensitive compared to previously used methods. The selective and sensitive photodetection of the column effluent was found to be suitable for the routine analysis of MDA in urine, plasma, muscles and liver of animals and some feed samples. Because urine or blood plasma samples can be derivatised in a simple manner, the proposed method can also be suitable for the routine, non-invasive evaluation of oxidative stress in animals and humans.

Mild and selective labeling of malondialdehyde with 2-aminoacridone: assessment of urinary malondialdehyde levels

Malondialdehyde (MDA) has become a well-established biomarker for oxidative stress. The most commonly used way to determine urinary MDA levels is the thiobarbituric acid (TBA) assay, which suffers from several drawbacks. In this manuscript, we describe a novel derivatization strategy for the highly sensitive and selective fluorescence-based determination of MDA in urinary samples. The methodology is based on the mild labeling of MDA with 2-aminoacridone, which can be carried out in aqueous citrate buffer at 40 °C, yielding a highly fluorescent substance. No further sample preparation than mixing with the necessary chemicals is necessary. The formed MDA derivative can conveniently be separated from the label itself and matrix constituents by gradient LC in less than 5 minutes on a cyano-based reversed-phase material. The method was validated with respect to matrix effects, linearity, selectivity and sensitivity (values as low as 1.8 nM for the LOD and 5.8 nM for the LOQ could be achieved). Standard addition quantitation was applied for the determination of MDA in human urine samples. Additionally, the protocol was applied to the measurement of a stability indicating analysis of MDA in urine at different storage conditions.

Effects of spironolactone and losartan on diabetic nephropathy in a type 2 diabetic rat model

BACKGROUND

While there is an evidence that the anti-inflammatory properties of spironolactone can attenuate proteinuria in type 2 diabetes, its effects on vascular endothelial growth factor (VEGF) expression in diabetic nephropathy have not been clearly defined. In this study, we examined the effects of spironolactone, losartan, and a combination of these two drugs on albuminuria, renal VEGF expression, and inflammatory and oxidative stress markers in a type 2 diabetic rat model.

METHODS

Thirty-three Otsuka-Long-Evans-Tokushima-Fatty (OLETF) rats were divided into four groups and treated with different medication regimens from weeks 25 to 50; OLETF diabetic controls (n=5), spironolactone-treated (n=10), losartan-treated (n=9), and combination of spironolactone- and losartan-treated (n=9).

RESULTS

At week 50, the albumin-to-creatinine ratio was significantly decreased in the losartan and combination groups compared to the control OLETF group. No decrease was detected in the spironolactone group. There was a significant reduction in renal VEGF, transforming growth factor (TGF)-β, and type IV collagen mRNA levels in the spironolactone- and combination regimen-treated groups. Twenty-four hour urine monocyte chemotactic protein-1 levels were comparable in all four groups but did show a decreasing trend in the losartan and combination regimen groups. Twenty-four hour urine malondialdehyde levels were significantly decreased in the spironolactone- and combination regimen-treated groups.

CONCLUSION

These results suggest that losartan alone and a combined regimen of spironolactone and losartan could ameliorate albuninuria by reducing renal VEGF expression. Also, simultaneous treatment with spironolactone and losartan may have protective effects against diabetic nephropathy by decreasing TGF-β and type IV collagen expression and by reducing oxidative stress in a type 2 diabetic rat model.

Melatonin improves the survival of cryopreserved callus of Rhodiola crenulata

An important aspect of the function of melatonin seems to be the mediation of stress caused by environmental and chemical factors. In the cryopreservation process, environmental changes including osmotic injury, desiccation, and low temperature can impose a series of stresses on plants. In this study, we evaluated the role of melatonin in stress protection during the process of cryopreservation using callus of an endangered plant species Rhodiola crenulata. The survival rate of the cryopreserved callus significantly increased when the callus was pretreated for 5 days with 0.1 μm melatonin prior to freezing in liquid nitrogen. Analysis of antioxidative activity following the pretreatment of callus with 0.1 μm melatonin showed a significant reduction in malondialdehyde production during various steps of cryopreservation. Enhanced peroxidase and catalase activity was observed in the callus after pretreatment with 0.1 μm melatonin compared to the control. These observations provide new evidence of the antioxidant/anti-stress function of melatonin, and it is the first report of its potential application in the preservation of elite endangered germplasm through the process of cryopreservation.

Cadmium suppresses the proliferation of piglet Sertoli cells and causes their DNA damage, cell apoptosis and aberrant ultrastructure

OBJECTIVE

Very little information is known about the toxic effects of cadmium on somatic cells in mammalian testis. The objective of this study is to explore the toxicity of cadmium on piglet Sertoli cells.

METHODS

Sertoli cells were isolated from piglet testes using a two-step enzyme digestion and followed by differential plating. Piglet Sertoli cells were identified by oil red O staining and Fas ligand (FasL) expression as assayed by immunocytochemistry and expression of transferrin and androgen binding protein by RT-PCR. Sertoli cells were cultured in DMEM/F12 supplemented with 10% fetal calf serum in the absence or presence of various concentrations of cadmium chloride, or treatment with p38 MAPK inhibitor SB202190 and with cadmium chloride exposure. Apoptotic cells in seminiferous tubules of piglets were also performed using TUNEL assay in vivo.

RESULTS

Cadmium chloride inhibited the proliferation of Piglet Sertoli cells as shown by MTT assay, and it increased malondialdehyde (MDA) but reduced superoxide dismutase (SOD) and Glutathione peroxidase (GSH-Px) activity. Inhibitor SB202190 alleviated the proliferation inhibition of cadmium on piglet Sertoli cells. Comet assay revealed that cadmium chloride caused DNA damage of Piglet Sertoli cells and resulted in cell apoptosis as assayed by flow cytometry. The in vivo study confirmed that cadmium induced cell apoptosis in seminiferous tubules of piglets. Transmission electronic microscopy showed abnormal and apoptotic ultrastructure in Piglet Sertoli cells treated with cadmium chloride compared to the control.

CONCLUSION

cadmium has obvious adverse effects on the proliferation of piglet Sertoli cells and causes their DNA damage, cell apoptosis, and aberrant morphology. This study thus offers novel insights into the toxicology of cadmium on male reproduction.

Ibuprofen and lipoic acid diamides as potential codrugs with neuroprotective activity

Current evidences support the hypothesis that non-steroidal anti-inflammatory drugs (NSAIDs) and antioxidant therapy might protect against the development of Alzheimer's disease (AD). In the present work, our attention was focused on ibuprofen (IBU) used in clinical trails to prevent Alzheimer's disease, and (R)-alpha-lipoic acid (LA) considered as a potential neuroprotective agent in AD therapy. In particular, we investigated a series of lipophilic molecular combinations obtained by joining (R)-alpha-lipoic acid and ibuprofen via an amide bond. These new entities might allow targeted delivery of the parent drugs to neurons, where cellular oxidative stress and inflammation seem related to Alzheimer's disease. Our study included the synthesis of conjugates 1-3 and the evaluation of their physicochemical and in-vitro antioxidant properties. The new compounds are extremely stable in aqueous buffer solutions (pH = 1.3 and 7.4), and in rat and human plasma they showed a slow bioconversion to ibuprofen and (R)-alpha-lipoic acid. Codrugs 1-3 displayed in vitro free radical scavenging activity and were hydrolyzed more rapidly in brain tissue than in rat serum indicating that these new entities might allow targeted delivery of the parent drugs to neurons. The immunohistochemical analysis of Abeta (1-40) protein showed that Abeta-injected cerebral cortices treated with ibuprofen or compound 1 showed few plaques within capillary vessels and, in particular, Abeta (1-40) protein was less expressed in codrug-1-treated than in ibuprofen-treated cerebral cortex.