Unsaturated Aliphatic Aldehydes Research Articles

Sanguisorba officinalis L. ethanolic extracts and essential oil - chemical composition, antioxidant potential, antibacterial activity, and ex vivo skin permeation study.

Sanguisorba officinalis L. is classified as a medicinal plant and used in traditional medicine. The root of this plant is mainly used as a medicinal raw material, but the above-ground parts are also a valuable source of health-promoting biologically active compounds. The study aimed to evaluate the antioxidant activity and total polyphenol content (TPC) of extracts prepared in 70% and 40% aqueous ethanol solution (dry extract content 50-500g/L) from the aerial parts of S. officinalis. The essential oil was isolated from the tested raw material, and its composition was determined using GC-MS. Ethanolic extracts and essential oil have been tested for antibacterial activity. The extract in 70% v/v ethanol (dry extract content: 500g/L) was subjected to HPLC analysis for the content of selected phenolic acids and an ex vivo skin permeation study. The ability of these metabolites to permeate and accumulate in the skin was analysed. Extracts prepared at both ethanol concentrations showed similar antioxidant activity and TPC. Depending on the method, concentration of solvent, and dry extract content (50-500g/L), the activity ranged from 1.97 to 84.54g Trolox/L. TPC range of 3.80-37.04gGA/L. Gallic acid (424mg/L) and vanillic acid (270mg/L) had the highest concentrations among the phenolic acids analysed. Vanillic acid (10μg) permeates the skin at the highest concentration. The highest accumulation in the skin was found for 2,5-dihydroxybenzoic acid (53μg/g skin), 2,3-dihydroxybenzoic acid (45μg/g skin), and gallic acid (45μg/g skin). The tested ethanolic extracts exhibited antibacterial activity. Samples with a dry extract concentration of 500g/L showed the largest growth inhibition zones. The most sensitive strains to these extracts were P. aeruginosa (24mm), S. lutea (23mm), and S. pneumoniae (22mm). The smallest inhibition zones were observed for B. subtilis (17mm). The essential oil showed weaker antimicrobial activity (growth inhibition zone 8-10mm). The GC-MS method identified 22 major components of the essential oil, including aliphatic hydrocarbons, unsaturated terpene alcohols, aliphatic aldehydes, unsaturated and saturated fatty acids, sesquiterpene, phytyl ester of linoleic acid, nitrogen compound, phytosterol, terpene ketone, phenylpropanoids, aliphatic alcohol, diterpenoid, aromatic aldehyde, and aliphatic carboxylic acid. The conducted research has shown that ethanolic extracts from Sanguisorbae herba are a valuable source of compounds with antibacterial and antioxidant potential, including phenolic acids. The fact that selected phenolic acids contained in the tested extract have the ability to permeate and accumulate in the skin provides the basis for conducting extended research on the use of extracts from this plant raw material in cosmetic and pharmaceutical preparations applied to the skin.

Allosteric modulation of a human odorant receptor

Odor perception is first determined by how the myriad of environmental volatiles are detected at the periphery of the olfactory system. The combinatorial activation of dedicated odorant receptors generates enough encoding power for the discrimination of tens of thousands of odorants. Recent studies have revealed that odorant receptors undergo widespread inhibitory modulation of their activity when presented with mixtures of odorants, a property likely required to maintain discrimination and ensure sparsity of the code for complex mixtures. Here, we establish the role of human OR5AN1 in the detection of musks and identify distinct odorants capable of enhancing its activity in binary mixtures. Chemical and pharmacological characterization indicate that specific α-β unsaturated aliphatic aldehydes act as positive allosteric modulators. Sensory experiments show decreased odor detection threshold in humans, suggesting that allosteric modulation of odorant receptors is perceptually relevant and likely adds another layer of complexity to how odors are encoded in the peripheral olfactory system.

Synthesis and bioactivity of (13Z,15E)‐octadecadienal: A sex pheromone component from Micromelalopha siversi Staudinger (Lepidoptera: Notodontidae)

BACKGROUND Micromelalopha siversi (Staudinger) (Lepidoptera: Notodontidae) is a defoliator of poplar trees, Populus spp. (Salicaceae). In our previous study, 13,15‐octadecadienal has been conformed as a female‐produced candidate sex pheromone component of M. siversi, but the Z/E stereochemistry of the 1,3‐diene system has not been identified so far.RESULTSFour unsaturated aliphatic aldehydes, Z13,E15‐18:Ald, Z13,Z15‐18:Ald, E13,E15‐18:Ald, and E13,Z15‐18:Ald, were synthesized from the commercially available 12‐bromo‐1‐decanol mainly by alkylation of lithium alkyne, normal Wittig or Wittig–Schlosser olefination, and hydroboration‐protonolysis. According to gas chromatography (GC) analysis of pheromone gland extracts, Z13,E15‐18:Ald was the main component, and a small amount of Z13,Z15‐18:Ald was also detected, with a ratio of approximately 7:3. However, the results of GC‐electroantennographic detection (GC‐EAD) showed that Z13,E15‐18:Ald was the only compound with electrophysiological activity, whereas Z13,Z15‐18:Ald elicited no activity. In the field, traps baited with only Z13,E15‐18:Ald resulted in much superior results to those with Z13,Z15‐18:Ald as well as the Z13,E15‐18:Ald and Z13,Z15‐18:Ald binary mixture.CONCLUSIONSBased on geometrically selective synthesis and bioactivity tests, the active sex pheromone component of M. siversi has been identified as Z13,E15‐18:Ald, the pheromone component that has not been identified in Lepidoptera before. The synthetic component was attractive to male moths in preliminary field traps, which provides novel technologies to monitor and control this pest.

Additive scheme of solvation enthalpy for linear, cyclic and branched-chain aliphatic compounds at 298.15 K

In this work, an additive scheme for the estimation of solvation enthalpy of saturated and unsaturated aliphatic hydrocarbons, alcohols, ketones, aldehydes and nitriles in n-heptane was developed. The proposed structural fragments for hydrocarbon group contributions and functional groups (OH, >СО and С(О)H) are independent of the nature of neighbouring atoms. In most cases absolute deviations between experimental and estimated solvation enthalpies for saturated and unsaturated aliphatic hydrocarbons, alcohols, ketones, aldehydes, and nitriles in n-heptane do not exceed 1–2kJ·mol−1. The developed additive approach for solvation enthalpy together with solution enthalpies can be used for quick estimation of standard vaporization and sublimation enthalpies of aliphatic compounds (including biomolecules) at 298.15K.

Testing of the composition of e-cigarette liquids - Manufacturer-declared vs. true contents in a selected series of products

Electronic cigarettes are currently in common use. However, in Poland there is no specific legislation governing the sale of these products. At the same time, no information has been made public about the hazards e-cigarettes pose to the users and bystanders - passive smokers. The aim of the study was to determine the qualitative composition of the analyzed liquid, which is an essential element of regulating the distribution of such cigarettes. Under this study the method for determining the composition of e-cigarette liquids was developed. This method employs gas chromatography with mass spectrometry (GC-MS). Levels of nicotine and flavoring components were determined in 50 e-liquid samples. The results were compared with the information provided by the manufacturer on the packaging. The applied method of qualitative determination helped to identify the main ingredients, such as nicotine and propylene glycol (PG). Propylene glycol was found to be present in all liquids, because it was used as the solvent for nicotine and flavors. There was a good agreement between the declared and the determined content of nicotine in the analyzed samples. The agreement was considerably poorer for the remaining e-liquid ingredients, mainly flavors. There was no agreement between the flavor substances specified by the manufacturer and aroma identified in the e-cigarette liquid, which may pose a risk to users of e-cigarettes, particularly those susceptible to allergies. Several unsaturated aliphatic alcohols and aldehydes found to be present in the liquids, unstable at elevated temperatures, may be more harmful to the smoker than the original compounds. Therefore, it is essential to implement in Poland the legal provisions regarding e-cigarettes. Med Pr 2016;67(2):239-253.

Chromatographic determination of low-molecular mass unsaturated aliphatic aldehydes with peroxyoxalate chemiluminescence detection after fluorescence labeling with 4-(N,N-dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole

A highly sensitive, selective and reproducible chromatographic method is described for determination of low-molecular mass unsaturated aliphatic aldehydes in human serum. The method combines fluorescent labeling using 4-(N,N-Dimethylaminosulfonyl)-7-hydrazino-2,1,3-benzoxadiazole with peroxyoxalate chemiluminescence. The derivatives were separated on a reversed-phase column C8 isocratically using a mixture of acetonitrile and 90mM imidazole-HNO3 buffer (pH 6.4, 1:1, % v/v). The calibration ranges were: 20-420nM for methylglyoxal, 16-320nM for acrolein, 15-360nM for crotonaldehyde and 20-320nM for trans-2-hexenal. The detection limits were ranged from 4.4 to 6.5nM (88-130fmol/injection), the recovery results were within the range of 87.4-103.8% and the intra and inter-day precision results were lower than 5.5%. The proposed validated method has been successfully applied to healthy, diabetic and rheumatic arthritis patients' sera with simple pretreatment method. In conclusion, this new method is suitable for routine analysis of large numbers of clinical samples for assessment of the oxidative stress state in patients.

The Chemical Composition of the Essential Oils of Cirsium palustre and C. rivulare and their Antiproliferative Effect

The composition of the essential oils of Cirsium palustre and C. rivulare and their antiproliferative activity against breast adenocarcinoma cells (MCF-7 and MDA-MBA-231) were investigated. The essential oils obtained by hydro-distillation from the roots (yield 0.2 and 0.1% v/w, respectively), leaves and inflorescences (yield below 0.01%), were analyzed by gas chromatography coupled with mass spectrometry (GC-MS). The composition of the essential oils in the respective organs of each plant differed considerably. On the other hand, similarities were observed in the composition of root and leaf oils. In C. palustre and C. rivulare root oil, 50 and 39 constituents were identified, accounting for 95.3% and 92.4% of the total content. The main components were aplotaxene and its derivatives, representing 78.6% and 46.6% of the total content. In leaf oils of both species, 59 and 49 compounds, respectively, were identified, representing 67.4% and 78.3% of the total content. The major constituents were beta-damascenone (4.1% and 13.4%, respectively) and beta-ionone (6.7% and 5.3%, respectively). Short-chain saturated and unsaturated aliphatic alcohols and aldehydes constituted another important group of compounds (17.7% and 9.0%, respectively). The essential oils of the roots have moderate anti-proliferative activity, with IC50 values ranging from 110 to 140 microg/mL. These concentrations were below the level able to inhibit the proliferation of healthy cells.

Identification of volatile components in Chinese Sinkiang fermented camel milk using SAFE, SDE, and HS-SPME-GC/MS

The volatile components of Chinese Sinkiang fermented camel milk were isolated by solvent assisted flavour evaporation (SAFE), simultaneous distillation extraction (SDE, dichloromethane and diethyl ether as solvent, respectively) and headspace solid-phase microextraction (HS-SPME, CAR/PDMS, PDMS/DVB and DVB/CAR/PDMS fibre extraction, respectively) and analysed by GC/MS. A total of 133 volatile components were identified under 6 different conditions, including 30 esters, 20 acids, 18 saturated alcohols, 15 unsaturated aliphatic alcohols, 8 saturated ketones, 9 saturated aldehydes, 8 unsaturated aliphatic aldehydes, 6 furans, 5 sulphur-containing compounds, 5 ethers, 5 lactones, 3 other compounds, and 1 unsaturated aliphatic ketone. Three pretreatment methods were compared, assisted by principal component analysis (PCA). The results indicated that the volatile components obtained using different methods varied greatly both in categories and in content, and therefore, a multi-pretreatment method should be adopted together with GC/MS. A total of 71 aroma-active compounds were detected by gas chromatography-olfactometry (GC–O), among which 66 aroma-active compounds were found by SDE (60, dichloromethane as solvent; 24, diethyl ether as solvent), 26 by SAFE.

Evaluation of the OECD QSAR Application Toolbox and Toxtree for estimating the mutagenicity of chemicals. Part 2. α-β unsaturated aliphatic aldehydes

The OECD QSAR Application Toolbox versions 1.1.01 and 1.1.02 and Toxtree version 1.60, which were developed for facilitating the practical use of (Q)SAR approaches by regulators, include a mechanistic SAR model for predicting the mutagenicity of α-β unsaturated aliphatic aldehydes. The aim of this study was to estimate the interest and limitations of this model. First, the model was re-computed to check its transparency and to verify its statistical validity. Then, the model implemented in the two software tools was tested on 34 chemicals not previously used for its design and for which experimental mutagenic activity data were available in the literature. A critical analysis of the results was performed and the practical interest of the model was discussed.

Evaluation of the OECD QSAR Application Toolbox and Toxtree for estimating the mutagenicity of chemicals. Part 1. Aromatic amines

The Ames Salmonella typhimurium mutagenicity assay is a short-term bacterial reverse mutation test that was designed to detect mutagens. For several decades, it has been used in research laboratories and by regulatory agencies throughout the world for the detection and characterization of potential mutagens among natural products and man-made chemicals. Faced with the ever-growing number of chemicals available on the market, congeneric and non-congeneric (Q)SAR models have been designed from Ames test results obtained on specific S. typhimurium strains such as TA 100 or TA 98. Such models have great potential for a quick and cheap identification and classification of large numbers of potential chemical mutagens. The OECD QSAR Application Toolbox and Toxtree, which were developed for facilitating the practical use of (Q)SAR approaches in regulatory contexts, include two mechanistic SAR models for predicting the mutagenicity of aromatic amines and α-β unsaturated aliphatic aldehydes. The aim of this study was to estimate the interest and limitations of the former model. The model was first re-computed to check its transparency and to verify its statistical validity. Then, it was tested on about 150 chemicals not previously used for the design of the model but belonging to its domain of application. A critical analysis of the results was performed and proposals were made for increasing the model performances.

Lithium hydroxide as base in the Wittig reaction. A simple method for olefin synthesis

A mild and practical procedure for the Wittig olefination, promoted by lithium hydroxide and triphenylbenzyl phosphonium bromide, has been set up for the synthesis of stilbenes and styrenes. The experimental conditions allow aromatic, heteroaromatic, unsaturated and saturated aliphatic aldehydes to give final products in good yields.

Volatile constituents of cooked bullfrog ( Rana catesbeiana) legs

Volatile extracts obtained from pressure-cooked bullfrog legs by simultaneous steam distillation and solvent extraction were analyzed by gas chromatography–mass spectrometry. Although the raw bullfrog legs used in this study contained 0.6% fat only, the extracts were dominated (qualitatively and quantitatively) by lipid oxidation volatiles such as alkanals, alkenals, alkadienals, alkanols and alkenols. Few Maillard volatiles were found, amongst them 2-acetylthiazole, the only sulfur-containing compound found in the extract. This profile of volatiles may be explained by the high proportion of phospholipids and low concentration of sulfur amino acid cystine in raw bullfrog meat, as previously reported by other researchers. Odour activity values (OAV) of volatiles were also estimated and major OAV compounds were: ( E, E)-2,4-decadienal, ( E, Z)-2,4-decadienal, ( E, Z)-2,6-nonadienal, 1-octanol, and ( E)-2-nonenal. Some of these potent unsaturated aliphatic aldehydes have also been associated with chicken flavour. This may contribute to flavour resemblances between bullfrog and chicken meat.

Identification of trace volatile compounds in freshly distilled Calvados and Cognac: Carbonyl and sulphur compounds

Carbonyl and sulphur compounds were investigated in freshly distilled Calvados and Cognac. Forty-eight aldehydes and ketones were identified in both products using specific extraction, with Girard's T reagent supported on silica-gel. The recovery procedure of these compounds in a high ethanolic medium was optimized. Samples contained a majority of saturated aliphatic aldehydes and ketones. The presence of unsaturated aliphatic aldehydes and ketones, such as alkenals, oct-1-en-3-one, 6-methylhept-5-en-2-one and β -damascenone, was also detected. Numerous terpenoic or norisoprenoic carbonyl compounds were characterized and seem to be specific to Cognac. Twenty-seven sulphur compounds were quantified in the same samples; small amounts of thiols were detected. Concentrations of dimethyl disulphide were from 50–500 μg L −1 of pure alcohol (PA), and a high content of dibutyl sulphide (20–100 μg L −1 of PA) was recorded. Concentrations of ethyl propyl sulphide and diethyl sulphide, which were not significant in Calvados, were above 25 μg L −1 of PA in Cognac. 2- and 3-thiophenecarboxaldehyde were also quantified, and concentrations as high as 1000 μg L −1 in some samples, were the most important in Cognac. The ratio of 3- and 2-thiophenecarboxaldehyde was higher than 10 for Calvados, but was less than 0.5 for Cognac. Although weak concentrations of methional were recorded, this may contribute to the overall aroma of these two spirits due to extremely low detection threshold. The total concentration of sulphur compounds in Cognac samples was five to six times that of Calvados samples.

Determination of aliphatic aldehydes by liquid chromatography with pulsed amperometric detection

An electrochemical detection method for short-chain saturated and unsaturated aliphatic aldehydes separated by liquid chromatography in moderately acidic medium is described. A triple-step waveform of the potentials applied to the polycrystalline platinum electrode, is proposed for sensitive detection of aliphatic aldehydes in flowing streams avoiding tedious pre- or post-column derivatization and/or cleanup procedures. The influences of the perchloric acid concentration and dissolved oxygen in the mobile phase, on the amperometric and chromatographic performance were evaluated and considered in terms of sensitivity and selectivity. Under the optimised experimental conditions (i.e., deoxygenated 50mM HClO4) the proposed analytical method allowed detection limits between 0.2 microM for acrolein and 2.5 microM for valeraldehyde. Regression analysis of calibration data indicates that responses for all investigated compounds are linear over about 2 orders of magnitude above the LOD, with correlation coefficients >0.990. The method was successfully applied to the determination of formaldehyde, acetaldehyde, propionaldehyde and acrolein in real matrices such as spiked water and red wines with good mean recoveries (81-97%).

New insights on the structure of algaenan from Botryoccocus braunii race A and its hexane insoluble botryals based on multidimensional NMR spectroscopy and electrospray–mass spectrometry techniques

Through solution state NMR spectroscopy and quadrupole-time-of-flight mass spectrometry (Q-TOF MS) studies of the hexane insoluble botryal extract of the algae Botryococcus braunii race A, coupled with high-resolution magic-angle-spinning (HR-MAS) NMR spectroscopy of the algaenan from this alga, it has been possible to advance the structural understanding of this geochemically important biopolymer. It was found that the hexane insoluble botryals in this study constitute a mixture of low molecular weight unsaturated aliphatic aldehydes and unsaturated hydrocarbons with an average chain length of about 40 carbons. Exact assignments were provided for many of the structural units present and describe the average constitution of the mixture as a whole. Reticulation of the low molecular weight chains via acetal and ester links explains the primary make up of algaenan. In this study, it is concluded that the algaenan results from the reticulation of low molecular weight hexane insoluble botryal species rather than the polyaldehyde as previously observed in studies of algae at alternate stages of their growth cycle.

A PLP–LIF kinetic study of the atmospheric reactivity of a series of C 4–C 7 saturated and unsaturated aliphatic aldehydes with OH

Absolute rate coefficients for the reaction of OH radical with a series of saturated and unsaturated aliphatic aldehydes were measured with the pulsed laser photolysis/laser-induced fluorescence technique at room temperature and as a function of total pressure ( p T=100–400 Torr). No pressure dependence of the rate coefficients was observed. The weighted average values obtained, k OH±2 σ, in units of 10 −11 cm 3 molecule −1 s −1, were 2.88±0.26 for n-butanal, 2.48±0.24 for n-pentanal, 2.60±0.21 for n-hexanal, 2.96±0.23 for n-heptanal, 3.51±0.71 for crotonaldehyde, 2.35±0.32 for trans-2-pentenal, 2.95±0.45 for trans-2-hexenal and 2.45±0.30 for trans-2-heptenal, respectively. The results are compared with previous data when available and with the corresponding coefficients for the reactions with NO 3 and O 3. The dominant tropospheric chemical loss process for these aliphatic aldehydes is the daytime reaction with OH, except in the case of trans-2-heptenal where the estimated lifetime for the reaction with NO 3 radical is smaller than the corresponding value for the OH reaction.

The production of benzene in the low-temperature oxidation of cyclohexane, cyclohexene, and cyclohexa-1,3-diene

The oxidation and auto-ignition of cyclohexane, cyclohexene, and cyclohexa-1,3-diene have been studied by rapid compression between 600 K to 900 K and 0.7 MPa to 1.4 MPa to identify the low-temperature pathways leading to benzene from cyclohexane. Auto-ignition delay times were measured and concentration-time profiles of the C6 intermediate products of oxidation were measured during the auto-ignition delays. Cyclohexane showed two-stage ignition at low temperatures, but single-stage ignition at higher temperatures, and a well-marked negative-temperature coefficient. By contrast there was neither a cool flame, nor a negative-temperature coefficient for cyclohexa-1,3-diene. Cyclohexene behaved in an intermediate way without a cool flame, but with a narrow, not very marked negative-temperature coefficient. The identified C6 products belong to three families: the bicyclic epoxides and cyclic ketones, the unsaturated aliphatic aldehydes, and the conjugated alkenes, which are always the major products. The formation of C6 products from cyclohexane is explained by the classical scheme for low-temperature oxidation, taking into account addition of O2 to cyclohexyl radicals and the various isomerizations of the resulting peroxy radicals. Most of the C6 products from cyclohexene are predicted by the same scheme, beginning with the formation of the allylic cyclohexenyl radical. However, addition of HO2 to the double bond has to be included to predict the formation of 1,2-epoxycyclohexane. For cyclohexa-1,3-diene, the classical scheme is not valid: the C6 oxygenated products are only formed by addition of HO2 to the double bond. For all three hydrocarbons, the pathways to benzene are those leading to conjugated alkenes, and they are always more efficient than those producing oxygenated products, either by adding HO2 to double bonds, or by addition of O2 to the initial cyclic radical.

Formation of Aliphatic and Aromatic α-Hydroxy Ketones by Zygosaccharomyces bisporus

Abstract The wild-type yeast strain Zygosaccharomyces bisporus CBS 702 produced α-hydroxyketones (acyloins) from amino acid precursors after transamination to the corresponding 2-oxo acids. The key enzyme of the subsequent decarboxylation and C − C bond forming reaction, pyruvate decarboxylase (PDC ), was examined for its substrate- and stereo-specificity. A wide variety of saturated and unsaturated aliphatic and aromatic aldehydes was successfully converted to acyloins. 19 of the biotransformation products identified had not been reported as natural substances before. Product yields were strongly affected by substrate structure.

Headspace Gas Analysis of Volatile Compounds of Light and Deep Roasted Sesame Seed Oil.

Volatile compounds in the headspace gas of light and deep roasted sesame seed oil were analyzed by gas chromatography and gas chromatography-mass spectrometry. The present method resulted in good reproducibility (<6.6% as a relative standard deviation) in the determination of individual volatile components. About 64 compounds, including 30 heterocyclic compounds, 7 aliphatic aldehydes, 11 ketones, and 16 miscellaneous compounds, were identified. Peak area percentages of 2-methylpropanal, 2-butenal, 2- and 3-methylbutanal, 2-propanone, 2-butanone, 3-methyl-2-butanone, 2,3-butanedione, 2- and 3-methylfuran, and 2,5-dimethylfuran, all of which could not be detected by steam distillation and column adsorptive concentration (previous method), increased in deep roasted oil. Hexanal decreased from 6.13% to 2.55% in deep roasted oil. Compared with the previous method, pyridine, thiophenes, and sulfides could be detected only by the present method, but unsaturated aliphatic aldehydes could not.

Human liver fatty aldehyde dehydrogenase: microsomal localization, purification, and biochemical characterization

To better understand the genetic disorder Sjögren–Larsson syndrome which is caused by a deficiency of fatty aldehyde dehydrogenase activity, we determined the subcellular localization of the enzyme and investigated its biochemical properties. Using density gradient centrifugation, we found that fatty aldehyde dehydrogenase activity was predominantly localized in the microsomal fraction in human liver. This fatty aldehyde dehydrogenase was solubilized from human liver microsomes and purified by chromatography on columns consisting of omega-aminohexyl-agarose and 5′-AMP-Sepharose 4B. The enzyme had an apparent subunit molecular weight of 54 000, required NAD + as cofactor, had optimal activity at pH 9.8, and was thermolabile at 47°C. Fatty aldehyde dehydrogenase had high activity towards saturated and unsaturated aliphatic aldehydes ranging from 6 to 24 carbons in length, as well as dihydrophytal, a 20-carbon branched chain aldehyde. In contrast, acetaldehyde, propionaldehyde, crotonaldehyde, glutaraldehyde, benzaldehyde, and retinaldehyde were poor substrates. The enzyme was inhibited by disulfiram, iodoacetamide, α, p-dibromoacetophenone, and p-chloromercuribenzoate. These results indicate that microsomal fatty aldehyde dehydrogenase is a distinct human aldehyde dehydrogenase isozyme that acts on a variety of medium- and long-chain aliphatic substrates.