Specific Aldehydes Research Articles

Reduce antibacterial activity against ceftriaxone resist Escherichia coli isolated from urinary tract infections by modification of ceftriaxone

This study focused on clarifying the problem of antibiotic resistance in harmful bacteria and proposed a solution by utilizing the advantages of schiff base synthesis. Seventy-five urine samples were procured from a Baghdad, Iraq medical facility, forming the study's basis. Through a chemical reaction involving ceftriaxone and specific aldehydes, namely 4-hydroxybenzaldehyde and 4-ethoxybenzaldehyde, two novel Schiff base derivatives, labeled as compounds A and B, were synthesized and subsequently characterized using Fourier-transform infrared spectroscopy (FTIR). Intriguingly, conventional aldehyde derivatives and ceftriaxone exhibited limited efficacy in inhibiting Escherichia coli (E. coli) growth, as evidenced by reduced inhibition zones. In contrast, the newly synthesized Schiff base derivatives demonstrated enhanced antimicrobial activity, significantly inhibiting bacterial growth with zones measuring 21 mm for compound A and 18 mm for compound B. These findings underscore the potential of Schiff base synthesis as a promising avenue for developing effective strategies against antibiotic-resistant bacterial strains, highlighting the importance of innovative approaches in combating microbial resistance.

Aldehyde perception induces specific molecular responses in Laminaria digitata and affects algal consumption by a specialist grazer.

In the marine environment, distance signaling based on water-borne cues occurs during interactions between macroalgae and herbivores. In the brown alga Laminaria digitata from North-Atlantic Brittany, oligoalginates elicitation or grazing was shown to induce chemical and transcriptomic regulations, as well as emission of a wide range of volatile aldehydes, but their biological roles as potential defense or warning signals in response to herbivores remain unknown. In this context, bioassays using the limpet Patella pellucida and L. digitata were carried out for determining the effects of algal transient incubation with 4-hydroxyhexenal (4-HHE), 4-hydroxynonenal (4-HNE) and dodecadienal on algal consumption by grazers. Simultaneously, we have developed metabolomic and transcriptomic approaches to study algal molecular responses after treatments of L. digitata with these chemical compounds. The results indicated that, unlike the treatment of the plantlets with 4-HNE or dodecadienal, treatment with 4-HHE decreases algal consumption by herbivores at 100 ng.ml-1 . Moreover, we showed that algal metabolome was significantly modified according to the type of aldehydes, and more specifically the metabolite pathways linked to fatty acid degradation. RNAseq analysis further showed that 4-HHE at 100 ng.ml-1 can activate the regulation of genes related to oxylipin signaling pathways and specific responses, compared to oligoalginates elicitation. As kelp beds constitute complex ecosystems consisting of habitat and food source for marine herbivores, the algal perception of specific aldehydes leading to targeted molecular regulations could have an important biological role on kelps/grazers interactions.

Association of aldehyde exposure with bone mineral density in the national health and nutrition examination survey (NHANES 2013-2014).

The association between aldehyde exposure and bone health in humans remains unclear. This study was to evaluate the association of serum aldehydes with bone mineral density (BMD) and osteopenia/osteoporosis. We analyzed the US National Health and Nutrition Examination Survey cross-sectional data from 2013 to 2014. Weighted multivariate-adjusted linear regression and logistic regression models were used to assess the association between specific aldehydes and osteopenia/osteoporosis. Associations between aldehyde combinations and BMD were also evaluated using the restricted cubic spline (RCS) method. Compared with men in the first tertile, those in the third tertile of propanaldehyde concentration were negatively associated with proximal femur and lumbar spine BMD. Significant inverse associations were observed between benzaldehyde exposure and trochanter BMD in women. Benzaldehyde increased the risk of osteopenia/osteoporosis 2.75-fold [95% confidence interval (CI) = 1.06, 7.11] in the highest tertile in women compared to the lowest tertile concentration. In males, the prevalence of total femur, femur neck, and trochanter osteopenia/osteoporosis was significantly higher in the highest versus the lowest tertile of propanaldehyde exposure, with odds ratios (ORs) of 6.84 (95% CI = 2.33, 20.04), 2.72 (95% CI = 1.18, 6.27), and 3.26 (95% CI = 1.25, 8.56), respectively. RCS regression also showed decreased BMD continuously with increasing serum mixed aldehyde levels. Serum aldehyde concentrations were associated with low BMD and high osteopenia/osteoporosis risk in adults, with propanaldehyde and benzaldehyde being the most critical. Co-exposure to aldehyde combinations was negatively correlated with BMD.

Human Odour Coding in the Yellow Fever Mosquito, Aedes aegypti

Insects use their olfactory systems to obtain chemical information on mating partners, oviposition sites and food. The yellow fever mosquito Aedes aegypti, an important vector of human infectious diseases, shows strong preference for human blood meals. This study investigated the chemical basis of host detection by characterizing the neuronal responses of antennal olfactory sensilla of female Ae. aegypti to 103 compounds from human skin emanations. The effect of blood feeding on the responses of olfactory sensilla to these odorants was examined as well. Sensilla SBTII, GP, and three functional subtypes of SST (SST1, SST2, and SST3) responded to most of the compounds tested. Olfactory receptor neurons (ORNs) ‘A’ and ‘B’ in the trichoid sensilla, either activated or inhibited, were involved in the odour coding process. Compounds from different chemical classes elicited responses with different temporal structures and different response patterns across the olfactory sensilla. Except for their increased responses to several odorants, blood-fed mosquitoes generally evoked reduced responses to specific aldehydes, alcohols, aliphatics/aromatics, ketones, and amines through the SST1, SST2, SBTI, SBTII and GP sensilla. The odorants eliciting diminished responses in female mosquitoes after blood feeding may be important in Ae. aegypti host-seeking activity and thus can be candidates for mosquito attractants in the process of this disease vector management.

Identification of potential indoor air pollutants in schools

Abstract Indoor air quality in school buildings plays an important role in students' wellbeing and performance. The presence and evolution of different compounds are directly affected by indoor activities, classroom materials and equipment, along with outside conditions derived from location and surrounding activities. Despite high CO2 concentration levels in classrooms being regulated in some regions, there is a wide range of pollutant substances that should be considered. This paper analyses a wide spectrum of air pollutants in school buildings to identify their relative impact and relevance. Measured values are compared to the recommended indoor air guideline values (IAGVs) reported in different national regulations and health organisations. This characterisation helps to evaluate the impact of potential indoor and outdoor air pollutant sources in schools; to define appropriate criteria to analyse the exposure to a wide range of air pollutants; and to develop appropriate strategies in order to reduce the exposure to air pollutants and minimise adverse health effects. A set of high priority pollutants, such as CO2, PM2.5, PM10, TVOC and a set of specific aldehydes and volatile organic compounds, were monitored through active and passive measurement in 18 classrooms of 9 Mediterranean schools. These schools were selected according to their construction period, design typology, and students’ ages. The measurements taken during teaching hours show mean CO2 concentration values of 1530 ppm, oscillating in a range from −24% to +31%. The analysis highlights that along with occupancy, the main indoor air pollutant sources in schools are related to settled dust that produces suspension particles during classroom activity, affecting the relative differences in the mean PM concentration value from +36% to +193%. Moreover, aldehydes show high concentration values in infant classrooms, showing relative differences in the mean value from +163% to +313%. Additionally, the study demonstrates that outdoor air pollutant sources in school surroundings, such as high-density traffic areas or industrial activities, play an important role in final indoor air quality performance, affecting PM10, PM2.5, TVOC, benzene and toluene levels. The measurements show good indoor air quality values, below the recommended indoor air quality guidelines, but they also highlight the monitoring interest of some specific compounds for future regulations, such as PM2.5, PM10, TVOC, benzene, toluene or formaldehyde.

Bioanalytical and Mass Spectrometric Methods for Aldehyde Profiling in Biological Fluids.

Human exposure to aldehydes is implicated in multiple diseases including diabetes, cardiovascular diseases, neurodegenerative disorders (i.e., Alzheimer’s and Parkinson’s Diseases), and cancer. Because these compounds are strong electrophiles, they can react with nucleophilic sites in DNA and proteins to form reversible and irreversible modifications. These modifications, if not eliminated or repaired, can lead to alteration in cellular homeostasis, cell death and ultimately contribute to disease pathogenesis. This review provides an overview of the current knowledge of the methods and applications of aldehyde exposure measurements, with a particular focus on bioanalytical and mass spectrometric techniques, including recent advances in mass spectrometry (MS)-based profiling methods for identifying potential biomarkers of aldehyde exposure. We discuss the various derivatization reagents used to capture small polar aldehydes and methods to quantify these compounds in biological matrices. In addition, we present emerging mass spectrometry-based methods, which use high-resolution accurate mass (HR/AM) analysis for characterizing carbonyl compounds and their potential applications in molecular epidemiology studies. With the availability of diverse bioanalytical methods presented here including simple and rapid techniques allowing remote monitoring of aldehydes, real-time imaging of aldehydic load in cells, advances in MS instrumentation, high performance chromatographic separation, and improved bioinformatics tools, the data acquired enable increased sensitivity for identifying specific aldehydes and new biomarkers of aldehyde exposure. Finally, the combination of these techniques with exciting new methods for single cell analysis provides the potential for detection and profiling of aldehydes at a cellular level, opening up the opportunity to minutely dissect their roles and biological consequences in cellular metabolism and diseases pathogenesis.

Synthesis And Characterization of Two Types of Heterogeneous Rings Derived from Sulfamethoxazole and Evaluation Their Bacterial Activity

In this research include preparation three steps of the new derivatives of Sulfamethoxazole drug, the first step involved converting Sulfamethoxazole to Schiff’s bases (1), by reaction Sulfamethoxazole with different specific aldehydes in ethanol, presence in glacial acetic acid. While the second step involved reaction Schiff’s bases (1) with sodium azide in presence of Benzene (dry) to give new tetrazole derivatives (2). Finally, The third reaction requires synthesis of thiazolidine (3) by reaction of Schiff’s bases (1) with 2-mercaptoacetic acid. The prepared compounds were characterized by physical properties, and somewhat of them by IR, 1H-NMR spectroscopy, and study biologic efficacy against two types of bacteria.

Evaluation of lipid peroxidation by the analysis of volatile aldehydes in the headspace of synthetic membranes using Selected Ion Flow Tube Mass Spectrometry, SIFT-MS.

Oxidative stress of cell membranes leads to a number of pathological processes associated with some diseases and is accompanied by the release of volatile aldehydes, which, potentially, can be used as biomarkers. Thus, the aim was to investigate peroxidation of defined synthetic membranes by direct quantitative analysis of volatile aldehydes. The concentration spectra of volatile compounds present in the headspace of synthetic membranes under peroxidation stress and following mechanical stress due to sonication were obtained using solid phase microextraction (SPME) in combination with Gas Chromatography Mass Spectrometry (SPME/GC/MS) and Selected Ion Flow Tube Mass Spectrometry (SIFT-MS). The focus was on the direct, real time quantification of volatile aldehydes. In addition, the total aldehydes in the aqueous membrane suspensions were quantified using the TBARS method. Propanal, butanal, pentanal, hexanal, heptanal and malondialdehyde were detected and quantified in the humid headspace of the media containing the synthetic membranes following peroxidation. The composition and concentration of these saturated aldehydes strongly depend on the unsaturated fatty acids representation in the liposomes. Some protective effect of cholesterol was observed especially for membranes peroxidised by Fenton reagents and after application of a mechanical stress. This study demonstrates that peroxidation of model synthetic membranes in vitro can be tracked in real time using direct quantification by SIFT-MS of several specific aldehydes in the headspace of the membrane suspensions. Cholesterol plays an important role in retaining membrane structure and can indirectly protect membranes from lipid peroxidation.

Aldehydes in Exhaled Breath during E-Cigarette Vaping: Pilot Study Results.

Several studies have shown the presence of aldehydes (i.e., formaldehyde, acrolein) in mainstream emissions of some e-cigarettes. For this reason, concerns have been raised regarding potential toxicity. The purpose of this research was to measure levels of carbonyls in exhaled breath of e-cigarette users during “vaping” sessions and estimate the respiratory tract (RT) uptake of specific aldehydes, including formaldehyde and acetaldehyde. We measured concentrations of 12 carbonyls in e-cigarette aerosols produced directly by e-cigarettes and in the exhaled breath of 12 participants (19 sessions). Carbonyls were sampled on 2,4-dinitrophenylhydrazine (DNPH) cartridges and analyzed with high performance liquid chromatography (HPLC) coupled with a UV/Vis photodiode detector. We found that in most cases, levels of aldehydes and methyl ethyl ketone (MEK) were significantly higher (2–125 times) in exhaled e-cigarette breaths than in pre-exposed breath. Exposure levels for the most abundant individual carbonyls in e-cigarette emissions—formaldehyde, acetaldehyde, acrolein—were between the limit of quantification (LOQ) and 24.4 μg·puff−1. The mean retention of formaldehyde in the respiratory tract was 99.7 ± 0.9% for all participants, while acetaldehyde retention was 91.6 ± 9.9%. Within the limitation of a small number of participants, our results showed that there is an increase in breath carbonyls during e-cigarette use.

Kinetics of Forming Aldehydes in Frying Oils and Their Distribution in French Fries Revealed by LC-MS-Based Chemometrics.

In this study, the kinetics of aldehyde formation in heated frying oils was characterized by 2-hydrazinoquinoline derivatization, liquid chromatography-mass spectrometry (LC-MS) analysis, principal component analysis (PCA), and hierarchical cluster analysis (HCA). The aldehydes contributing to time-dependent separation of heated soybean oil (HSO) in a PCA model were grouped by the HCA into three clusters (A1, A2, and B) on the basis of their kinetics and fatty acid precursors. The increases of 4-hydroxynonenal (4-HNE) and the A2-to-B ratio in HSO were well-correlated with the duration of thermal stress. Chemometric and quantitative analysis of three frying oils (soybean, corn, and canola oils) and French fry extracts further supported the associations between aldehyde profiles and fatty acid precursors and also revealed that the concentrations of pentanal, hexanal, acrolein, and the A2-to-B ratio in French fry extracts were more comparable to their values in the frying oils than other unsaturated aldehydes. All of these results suggest the roles of specific aldehydes or aldehyde clusters as novel markers of the lipid oxidation status for frying oils or fried foods.

Mitochondria as a source and target of lipid peroxidation products in healthy and diseased heart

The heart is a highly oxidative organ in which cardiomyocyte turnover is virtually absent, making it particularly vulnerable to accumulation of lipid peroxidation products (LPP) formed as a result of oxidative damage. Reactive oxygen and nitrogen species are the most common electrophiles formed during lipid peroxidation and lead to the formation of both stable and unstable LPP. Of the LPP formed, highly reactive aldehydes are a well-recognized causative factor in ageing and age-associated diseases, including cardiovascular disease and diabetes. Recent studies have identified that the mitochondria are both a primary source and target of LPP, with specific emphasis on aldehydes in cardiomyocytes and how these affect the electron transport system and Ca(2+) balance. Numerous studies have found that there are functional consequences in the heart following exposure to specific aldehydes (acrolein, trans-2-hexanal, 4-hydroxynonenal and acetaldehyde). Because these LPP are known to form in heart failure, cardiac ischaemia-reperfusion injury and diabetes, they may have an underappreciated role in the pathophysiology of these disease processes. Lipid peroxidation products are involved in the transcriptional regulation of endogenous anti-oxidant systems. Recent evidence demonstrates that transient increases in LPP may be beneficial in cardioprotection by contributing to mitohormesis (i.e. induction of anti-oxidant systems) in cardiomyocytes. Thus, exploitation of the cardioprotective actions of the LPP may represent a novel therapeutic strategy for future treatment of heart disease.

Compositional studies of human RPE lipofuscin: mechanisms of molecular modifications

The accumulation of lipofuscin has previously been implicated in several retinal diseases including Best's macular dystrophy, Stargardt's disease and age-related macular degeneration (AMD). Previously one of the major fluorophores of lipofuscin was identified as a bis-retinoid pyridinium salt called A2E, which is known to photochemically cause damage. In addition to A2E, there are numerous components in RPE lipofuscin that are unidentified. These compounds were determined to be structurally related to A2E by their fragmentation pattern with losses of 106, 190, 174 and/or 150 amu from the parent ion and the formation of fragments of ca 592 amu. The vast majority consists of relatively hydrophobic components corresponding to derivatized A2E with molecular weights in discrete groups of 800-900, 970-1080 and > 1200 m/z regions. In order to determine the mechanism of these modifications, A2E was chemically modified by; (1) the formation of specific esters, (2) reaction with specific aldehydes and (3) spontaneous auto-oxidation. The contribution of ester formation to the naturally occurring components of lipofuscin was discounted since their fragmentation patterns were different to those found in vivo. Alternatively, reactions with specific aldehydes result in nearly identical products as those found in vivo. Artificial aging of RPE lipofuscin gives a complex mixture of structurally related components. This results from the auto- and/or photooxidation of A2E to form aldehydes, which then back react with A2E giving a series of higher molecular weight products. The majority of these modifications result in compounds that are much more hydrophobic than A2E. These higher molecular weight materials have increased values of log P compared to A2E. This increase in hydrophobicity most likely aids in the sequestering of A2E into granules with the concomitant diminution of its reactivity. Therefore, these processes may serve as protective mechanisms for the RPE.

Hydrogenation of a hydroformylated naphtha model (mixture of specific aldehydes) catalysed by Ru/TPPTS complex in aqueous media

Aqueous biphasic hydrogenation of a mixture of 2-methylvaleraldehyde, 2-ethylbutyraldehyde, hexanal, heptaldehyde, 2-phenylpropionaldehyde and hydrocinnamaldehyde, which are all met in a hydroformylated naphtha (the feedstock of gasoline production) in high yield (mol%) according to the literature, was carried out with ruthenium complex containing the water-soluble ligand TPPTS (TPPTS = P[m-C 6H 4SO 3Na] 3, trisodium salt of m-trisulfonated triphenyl phosphine). Ru/TPPTS catalytic system was generated in situ by direct addition of RuCl 3· xH 2O catalyst precursor to TPPTS in aqueous media; and appears to have high activity under mild conditions (80 °C, 20 bar) in the hydrogenation of the above hydroformylated naphtha model to the production of the corresponding alcohols. Thus, the aqueous biphasic hydrogenation of a hydroformylated fuel would upgrade the combustion properties of the ultimate fuel, while at the same time the whole process would be characterised as environmentally friendly. The effect of the reaction pressure, temperature and time, as well as the influence of the organic solvent, the agitation speed, the TPPTS/Ru and aldehydes/Ru molar ratios were investigated.

Effect of Ozone and GAC Process for the Treatment of Micropollutants and DBPs Control in Drinking Water: Pilot Scale Evaluation

To improve the quality of water supplied to the City of Seoul in Korea, a pilot-scale evaluation of how the conventional treatment process could be upgraded was conducted. Three candidate processes were evaluated and compared: a conventional process (consisting of coagulation, sedimentation, and rapid sand filtration) plus GAC (Train A); a conventional process plus ozone and GAC (Train B); and a process consisting of coagulation, sedimentation, intermediate ozone, sand filtration, and GAC (Train C). Treatment efficiency of the unit process and overall treatment trains were evaluated using several parameters such as turbidity, dissolved organic carbon (DOC), UV absorbance at 254 nm (UV254), specific ultraviolet absorbance (SUVA), micropollutants (pesticides, benzenes, and phenols), disinfection by-products (trihalomethanes (THMs), haloacetic acids (HAAs) and aldehydes), and total organic halogen (TOX). Results showed that ozone and/or GAC was effective for removing micropollutants and controlling chlorinated by-products such as THMs and HAAs. However, any synergistic effect of ozonation (adsorption and biodegradation) on GAC was observed due to the low concentration of aldehydes in raw and process water.

Dirhodium(II) Tetrakis[N-benzene-fused Phthaloyl-(S)-piperidinonate] as a Chiral Lewis Acid: Catalytic Enantioselective Aldol Reactions of Acetate-derived Silylketene Acetals and Aldehydes

A first example of chiral dirhodium(II) complex-catalyzed enantioselective Mukaiyama aldol reactions is described. The aldol addition reaction of methyl acetate-derived trimethylsilylketene acetal with specific aldehydes such as benzyloxyacetaldehyde and electron-poor aromatic aldehydes is effectively catalyzed by dirhodium(II) tetrakis[N-benzene-fused phthaloyl-(S)-piperidinonatel (la), providing silylated aldol adducts in up to 94% ee.

Semicarbazide sensitive amine oxidase overexpression has dual consequences: insulin mimicry and diabetes-like complications.

Semicarbazide-sensitive amine oxidases (SSAO) are copper-containing enzymes that oxidatively deaminate primary amines to produce hydrogen peroxide, ammonium, and specific aldehydes. Vascular adhesion protein-1 (VAP-1) is a cell surface and soluble molecule that possesses SSAO activity. VAP-1 protein, SSAO activity, and SSAO reaction products are elevated in the serum of patients with diabetes, congestive heart failure, and specific inflammatory liver diseases. By expressing human VAP-1/SSAO on mouse endothelial cells and subsequently in the serum, and by chronically treating the transgenic mice for 15 months with a high-fat diet and a physiological substrate for SSAO, methylamine, the in vivo roles of SSAO were assessed. The VAP-1 transgene increased the mouse body mass index and subcutaneous abdominal fat pad weights in a manner independent of food consumption. The transgene together with increased SSAO substrate availability enhanced glucose uptake in an SSAO-dependent manner. The increased SSAO activity also led to diabetes-like complications, including advanced glycation end product formation, elevated blood pressure, altered atherosclerosis progression, and nephropathy. These findings suggest that, although manipulation of VAP-1/SSAO has potential to serve as a therapeutic treatment in insulin-resistant conditions, care must be taken to fully understand its impact on obesity and vascular damage.

Cuticular hydrocarbons and novel alkenediol iacetates from wheat stem sawfly (Cephus cinctus): natural oxidation to pheromone components.

The cuticular lipids of the wheat stem sawfly Cephus cinctus (Hymenoptera: Cephidae) were investigated as part of a chemical ecology project with this species. The major cuticular lipids were n-alkenes and n-alkanes. Alkenes were the most abundant and exhibited dramatic sexual dimorphism. (Z)-9-Tricosene accounted for about half of the total hydrocarbon in males but was nearly absent from females. The dominant alkenes in females were (Z)-9-pentacosene and (Z)-9-heptacosene. The alkane profiles were similar in both sexes, with n-tricosane being the most abundant, followed by n-pentacosane and n-heptacosane. In both sexes, there were minor amounts of alkanes and alkenes with other chain lengths and n-alkadienes of 29 and 31 carbons. In males, about one tenth of the surface lipids consisted of (Z)-9-alkene-1, omega-diol diacetates with 22-, 24-, and 26-carbon chains. The same compounds were also detected from females but in much smaller amounts. The structures of these novel diacetates were proven by synthesis. By analogy to methyl oleate, a well-studied food lipid, the alkenes and diacetates were expected to undergo slow oxidation in air to release specific aldehydes and other volatile products, and these were generally detected in volatiles collected from living sawflies. Atmospheric oxidation of the diacetates was also demonstrated in the absence of sawflies. One product from the diacetates, 9-acetyloxynonanal, was shown in other research to be particularly active electrophysiologically and was also attractive in the field. Aldehydes from the alkenes also showed strong electrophysiological activity. The concept of volatile pheromones originating from heavy, unsaturated cuticular lipids is discussed.

Some specific potentiodynamic behaviour of certain aldehydes and monosaccharides: Some simple and some specific aldehydes

Three distinct potentiodynamic features have been scanned on cyclic voltammograms in the presence of simple (formaldehyde, acetaldehyde), and some specific (cinnam aldehyde, croton aldehyde, furfural and benzaldehyde) aldehydes: (a) anodic oxidation of aldehyde group proceeds as a direct heterogeneous reaction with weakly or reversibly adsorbed OH-adatomic group, or in overall, as an electrode kinetics similar to Volmer-Heyrovsky mechanism for hydrogen evolution (R-CHO+2M-OH⇒R-COOH+H 2O+2M+2e), which is practically the same as the Lamy mechanism; (b) as the result, the oxide growth upon Pt, Pd, Au electrode substrates becomes prevailingly or partially prevented and reflects in the proportionally reduced charge capacity for its desorption peak, and (c) the consequence of the latter represents the unusual, but sharply pronounced reverse current jump into anodic range with peaks of repeated aldehyde oxidation during reversal potential scans towards hydrogen evolving limits. Aldehyde reduction, except on Au and Hg, occurs as the heterogeneous catalytic reaction with adsorbed H-adatoms and appears competitive with hydrogen evolution, and while being for about two order of magnitude faster than H-adatom recombination, at lower current densities (about 10 mA cm −2) yields rather high current efficiencies (above 90%). Oxygen evolution proceeds along with aldehyde oxidation and only at rather high positive potentials prevails in both surface oxide formation and thereby reduced rate in carboxylic acid production. At extremely positive anodic potentials on Au electrode, there appears a distinct peak of carboxylic group oxidation with release of CO 2, preceding oxygen evolution, or occurring along with the latter.

Gas-Chromatographic-Mass Spectrometric Assay of Tissue Malondialdehyde, 4-Hydroxynonenal, and Other Aldehydes after Their Reduction to Stable Alcohols

Measurement of specific aldehydes such as malondialdehyde, hexanal, or 4-hydroxynonenal provides a method to evaluate the extent of lipid peroxidation. However, assay of aldehydes is complicated by their high reactivity toward other molecules and their chemical instability. In the proposed method, aldehydes are reduced to stable alcohols. Except for malondialdehyde, this is readily accomplished under neutral conditions at room temperature or at 4°C with either sodium borodeuteride (NaB 2H 4) or sodium horohydride (NaBH 4). Complete reduction of malondialdehyde requires a more powerful reducing agent, borane trimethylamine. After ether extraction and evaporation of the organic phase, the alcohols are converted to t-butyldimethylsilyl ethers and analyzed by selected ion monitoring gas chromatography-mass spectrometry in the positive chemical ionization mode for malondialdehyde and 4-hydroxynonenal and electron impact mode for all other aldehydes. Quantitation is achieved using internal standards of 1,3-[ 2H 8]propanediol for MDA, of 4-[2- 2H]hydroxynonenal for 4-hydroxynonenal, and of the corresponding saturated per-deuterated alcohols for all saturated aldehydes, for example and [ 2H 13]hexanol for hexanal. Saturated per-deuterated alcohols also serve as external standards for their unsaturated aldehydes with same chain length. The detection limit for individual aldehydes is 0.5 nmol in a given sample. In addition to being highly sensitive and selective, the present method allows one to verify the identity of each aldehyde by observing a mass shift when aldehydes are reduced with either NaB 2H 4 or NaBH 4. The usefulness of our method is demonstrated by measuring aldehyde accumulation in autoxidized arachidonic acid solutions and in heart homogenates before and after induction of peroxidation.

Occupational exposures in California wildland fire fighting.

Industrial hygiene measurement of exposures to wildland fire fighters was conducted in northern California during three consecutive fire seasons (1986-1989) in conjunction with three separate health effects studies. Chemicals that were monitored included carbon monoxide, total and respirable particulates, polyaromatic hydrocarbons (PAHs), crystalline silica, aldehydes, and benzene. Measurements were taken at both wildland fires and prescribed (planned) burns. A variety of collection methods were employed--colorimetric detector tubes and a CO monitor were used for direct-reading area measurements; colorimetric diffusion tubes, filter cassettes, sorbent tubes, and passive vapor monitors were used for determining personal time-weighted average exposures. A new screening method (National Institute for Occupational Safety and Health Method 2539) was used to identify the presence of specific aldehydes. Results show that wildland fire fighters may at times be exposed to concentrations of carbon monoxide, total or respirable particulates, or silica at levels near or higher than recommended occupational exposure limits, although group means were generally well below the limits. Time-weighted average formaldehyde levels, measured in a few instances above 0.37 mg/m3 (0.3 ppm), indicate a potential for formaldehyde-induced eye or respiratory irritation under these conditions. Certain characteristics of the work such as high altitude, temperature, and breathing rate; extended work shifts; and additional off-shift exposures suggest that adjustment of 8-hr exposure limits may be necessary to provide adequate protection. In part, because of the rigors of performing industrial hygiene measurements under fire fighting conditions, data are limited and could not be considered representative of the full range of exposures fire fighters may encounter.(ABSTRACT TRUNCATED AT 250 WORDS)