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PubMed1986

Metabolism of the pyrrolizidine alkaloid metabolite trans-4-hydroxy-2-hexenal by mouse liver aldehyde dehydrogenases.

The metabolism of trans-4-hydroxy-2-hexenal (t-4HH) was compared with that of propionaldehyde (PAL) and trans-2-hexenal (t-2H). Kinetic experiments with hepatic cytosol as a source for aldehyde dehydrogenase(s) (ALDH) (E.C. 1.2.1.3) resulted in linear Lineweaver-Burk plots for both t-4HH and t-2H, while PAL produced biphasic plots. Values of 43 and 3 microM were obtained for the apparent Km values for t-4HH and t-2H, respectively, with the two apparent Kms for PAL being 5 microM and 0.8 mM. DEAE-cellulose chromatography of cytosol isolated two peaks capable of oxidizing PAL, but only one peak was able to metabolize t-4HH. Unlike cytosol, mitochondria produced biphasic Lineweaver-Burk plots for t-4HH with two estimated Kms of 52 microM and 0.2 mM. The majority of activity for the oxidation of t-4HH, like PAL, was localized in the cytosolic fraction. This study indicates that ALDH(s) may play an important role in the detoxification of the pyrrolizidine alkaloid metabolite t-4HH, as well as other 4-hydroxyalkenals that arise from membrane lipid peroxidation.

Aldehyde Dehydrogenase↗

PubMed2006

Detection of 4-oxo-2-hexenal, a novel mutagenic product of lipid peroxidation, in human diet and cooking vapor.

Since the diet plays an important role in the development of human cancer, it is important to identify mutagens in foods. We have detected a novel mutagenic product, 4-oxo-2-hexenal (4-OHE), in a model lipid peroxidation reaction mixture [H. Kasai, M. Maekawa, K. Kawai, K. Hachisuka, Y. Takahashi, H. Nakamura, R. Sawa, S. Matsui, T. Matsuda, 4-Oxo-2-hexenal, a mutagen formed by omega-3 fat peroxidation, causes DNA adduct formation in mouse organs, Ind. Health 43 (2005) 699-701]. In the present study, the contents of 4-OHE in various food samples were determined by a GC/MS method. Commercial perilla oil (derived from the seed of Perilla frutescens var. frutescens), which is rich in linolenic acid triglyceride (TG), the edible part of broiled fish, and various fried foods contained 4-OHE in the range of 1-70 microg/g. Furthermore, from the ethyl acetate trap (extracts) of the smoke released during the broiling of fish, 4-OHE was also detected by GC/MS. These results provide a warning to humans, who may be exposed to this mutagen. The 4-OHE may be produced from omega-3 polyunsaturated fats, such as alpha-linolenic acid-, docosahexaenoic acid (DHA)- and eicosapentaenoic acid (EPA)-TG, which are more easily oxidized than omega-6 fats, such as linoleic acid-TG.

Aldehydes↗

PubMed2001

Products of the OH radical-initiated reaction of 3-hexene-2,5-dione.

3-Hexene-2,5-dione [CH3C(O)CH=CHC(O)CH3] and other unsaturated 1,4-dicarbonyls are formed from the atmospheric photooxidations of aromatic hydrocarbons. We have investigated the products of the gas-phase reaction of OH radicals with 3-hexene-2,5-dione in the presence of NO at room temperature and atmospheric pressure of air using in situ atmospheric pressure ionization tandem mass spectrometry. Products of molecular weight 102 and 191 were identified and from consideration of the potential reactions these are attributed to CH3C(O)CH(OH)CHO and CH3C(O)CH(OH)CH(ONO2)C(O)CH3, respectively. After initial addition of the OH radical, the CH3C(O)CH(OH)(*C)HC(O)CH3 radical adds O2 to form the peroxy radical which reacts with NO to yield the molecular weight 191 hydroxynitrate CH3C(O)CH(OH)CH(ONO2)C(O)CH3 or the hydroxyalkoxy radical CH3C(O)CH(OH)CH(*O)C(O)CH3 plus NO2. Our observation of a molecular weight 102 species indicates that the CH3C(O)CH(OH)CH(*O)C(O)CH3 radical dominantly decomposes to CH3C(O)CH(OH)CHO plus CH3(*C)O, rather than decomposing to CH3C(O)CHO plus CH3C(O)(*C)HOH, isomerizing, or reacting with O2. Thermochemical calculations and an empirical estimation method for calculating alkoxy radical reaction rates are consistent with our experimental observations.

Air Pollutants↗

PubMed2003

OH radical-initiated reaction of 3-hexene-2,5-dione: formation of methylglyoxal.

3-Hexene-2,5-dione [CH3C(O)CH=CHC(O)CH3] and other unsaturated 1,4-dicarbonyls are formed from the atmospheric photooxidations of aromatic hydrocarbons. We have reinvestigated the formation of methylglyoxal from the gas-phase reaction of OH radicals with 3-hexene-2,5-dione in the presence of NO at room temperature and atmospheric pressure of air using in situ Fourier transform infrared spectroscopy. No evidence for the formation of methylglyoxal was obtained, with the IR spectra showing that methylglyoxal is, at most, a minor reaction product with a molar formation yield of <10% (and more likely <1%). This confirms our earlier study (Tuazon et al. Environ. Sci. Technol. 1985, 19, 265) and suggests that the CH3C(O)CH(OH)CHO and CH3C(O)CH(OH)CH(ONO2)C(O)CH3 observed by Bethel et al. (Environ. Sci. Technol. 2001, 35, 4477) are the major first-generation reaction products.

Air Pollutants↗

PubMed2003

Hydroformylation of 1-hexene in supercritical carbon dioxide: characterization, activity, and regioselectivity studies.

The hydroformylation of alkenes is a major commercial process used for the production of oxygenated organic compounds. When the hydroformylation reaction is performed using a homogeneous catalyst, an organic or aqueous solvent is employed, and a significant effort must be expended to recover the catalyst so it can be recycled. Development of a selective heterogeneous catalyst would allow simplification of the process design in an integrated system that minimizes waste generation. Recent studies have shown that supercritical carbon dioxide (scCO2) as a reaction solvent offers optimal environmental performance and presents advantages for ease of product separation. In particular, we have considered the conversion of 1-hexene to heptanal using rhodium- and platinum-phosphine catalysts tethered to supports insoluble in scCO2 to demonstrate the advantages and to understand the limitations of a solid-catalyzed process. One of the historical limitations of supported catalysts is the inability to control product regioselectivity. To address this concern, we have developed tethered catalysts with phosphinated silica and controlled pore size MCM-41 and MCM-20 supports that provide improved regioselectivity and conversion relative to their nonporous equivalents. Platinum catalysts supported on MCM-type supports were the most regioselective whereas the analogous rhodium catalysts were the most active for hydroformylation of 1-hexene in scCO2.

Alkenes↗

PubMed2004

Catalytic isomerization of 1,5-enynes to bicyclo[3.1.0]hexenes.

The cycloisomerization of 1,5-enynes catalyzed by cationic triphenylphosphinegold(I) complexes produces bicyclo[3.1.0]hexenes. Substitution at all positions of the 1,5-enyne is tolerated, leading to a wide range of bicyclo[3.1.0]hexane structures, including those containing quaternary carbons. Substrates containing a 1,2-disubstituted olefin undergo stereospecific cycloisomerization (cis-olefin produces cis-cyclopropane, and trans-olefin gives trans-cyclopropane). Additionally, enantioenriched bicyclo[3.1.0]hexenes can be obtained from the gold(I)-catalyzed cycloisomerization of enantioenriched 1,5-enynes with excellent chirality transfer. The preparation of tricyclic systems is accomplished through a gold(I)-catalyzed tandem cycloisomerization-ring enlargement reaction.

Journal Article↗

PubMed2006

Gold(I) catalyzed isomerization of 5-en-2-yn-1-yl acetates: an efficient access to acetoxy bicyclo[3.1.0]hexenes and 2-cycloalken-1-ones.

The gold(I) catalyzed rearrangement of 5-en-2-yn-1-yl acetates into functionalized acetoxy bicyclo[3.1.0]hexenes is described. The mild reaction conditions employed allow the efficient and rapid synthesis of a variety of such bicyclic compounds via a sequence of two gold(I)-catalyzed isomerization steps. Acetoxy bicyclo[3.1.0]hexenes products can be further transformed to 2-cycloalkenones by simple methanolysis.

Journal Article↗

PubMed2003

Analysis of a model reaction system containing cysteine and (E)-2-methyl-2-butenal, (E)-2-hexenal, or mesityl oxide.

Cysteine conjugates, resulting from the addition of cysteine to alpha,beta-unsaturated carbonyl compounds, are important precursors of odorant sulfur compounds in food flavors. The aim of this work was to better understand this chemistry in the light of the unexpected double addition of cysteine to two unsaturated aldehydes. These reactions were studied as a function of pH. When (E)-2-methyl-2-butenal (tiglic aldehyde, 4) was treated with cysteine in water at pH 8, the major product formed was the new compound (4R)-2-(2-[[(2R)-2-amino-2-carboxyethyl]thio]methylpropyl)-1,3-thiazolidine-4-carboxylic acid (6). Under acidic conditions (pH 1), we also observed a double addition, but the second cysteine was linked by a vinylic sulfide bond to form the previously unreported major product, (2R,2'R,E)-S,S'-(2,3-dimethyl-1-propene-1,3-diyl)bis-cysteine (7). When (E)-2-hexenal (12) was treated with cysteine under acidic conditions, the major product was the novel (4R,2' 'R)-2-[2'-(2' '-amino-2' '-carboxyethylthio)pentyl]-1,3-thiazolidine-4-carboxylic acid (13), and the formation of an vinylic sulfide compound analogous to 7 was not observed. Reduction of the acidic crude reaction mixture with NaBH(4) afforded 13 and the cysteine derivative (R)-S-[1-(2-hydroxyethyl)butyl]cysteine (14) in 14% yield. Treating (E)-2-hexenal with cysteine at pH 8 followed by NaBH(4) reduction yielded the new product (3R)-7-propylhexahydro-1,4-thiazepine-3-carboxylic acid (15). Addition of cysteine to mesityl oxide (16), at pH 8, followed by reduction with NaBH(4) furnished (R)-S-(3-hydroxy-1,1-dimethylbutyl)cysteine (3) and the new compound (3R)-hexahydro-5,7,7-trimethyl-1,4-thiazepine-3-carboxylic acid (18).

Aldehydes↗

PubMed2000

Effects of hexanal, trans-2-hexenal, and storage temperature on shelf life of fresh sliced apples.

In this paper, the effects of hexanal and trans-2-hexenal, which are both natural molecules characterizing apple aroma, on the microbial population and on color retention of fresh sliced apples were evaluated. In particular, a central composite design (CCD) was developed to assess the individual and interactive effects of the chosen volatile molecules and storage temperatures on (i) the growth of the naturally occurring microflora, (ii) the evolution over time of an inoculated spoilage yeast (Pichia subpelliculosa), and (iii) the enzymatic browning reaction in minimally processed apples. The inclusion of hexanal and trans-2-hexenal in the storage atmosphere of apple slices determined a significant extension of shelf life also when P. subpelliculosa was inoculated at levels of 10(3) colony-forming units/g and abusive storage temperatures were used. In fact, the presence of these molecules in the packaging atmospheres considerably prolonged the lag phases of the inoculated yeast and reduced the growth potential of naturally occurring bacteria. Moreover, the addition to the modified atmosphere of low levels of the hexanal increased the color stability of the products up to 16 days.

Aldehydes↗

PubMed2002

Anionic cycloaromatization of 1-aryl-3-hexen-1,5-diynes initiated by methoxide addition: synthesis of phenanthridinones, benzo[c]phenanthridinones, and biaryls.

Treatment of 2-((Z)-6-substituted-3-hexene-1,5-diynyl)benzonitriles with sodium methoxide in refluxing methanol in the presence of a polar aprotic solvent, such as DMSO, HMPA, THF, or 18-crown-6, gave phenanthridinones in 21-77% yields. In these cases, addition of 10% DMSO into the reaction mixture gave the highest yield. On the other hand, methanolysis of 2-(2-(2-alkynylphenyl)ethynyl)benzonitriles under the same reaction conditions gave benzo[c]phenanthridinones in 31-57% yields. Methanolysis of (Z)-1-aryl-3-hexen-1,5-diynes in the presence of 2 equiv of tetrabutylammonium iodide gave biaryls in 14-64% yields. It is found that the reactions with aryl groups bearing electron-withdrawing groups proceeded at greater rates and gave better yields.

Journal Article↗

PubMed2000

Reproduction/developmental toxicity screening test in rats with orally-administered 1-hexene.

This study was conducted to provide screening information concerning the potential systemic, reproductive and developmental toxicity of 1-hexene when administered orally, by gavage, to male and female rats using a modified OECD 421 protocol. 1-Hexene was administered at doses of 100, 500, and 1000 mg/kg/day in corn oil; the control group received the vehicle at an equivalent volume. The males were treated for 28 days prior to mating and until euthanasia (44 days of dosing). The females were treated for 14 days prior to mating and during mating, gestation, and lactation until euthanasia (41-55 total days of dosing). Females were allowed to deliver and rear their offspring until lactation day 4. The parental rats were subject to a gross and microscopic examination. Viability and development of the pups were followed through lactation day 4. There was no mortality, and there were no clinical signs of toxicity or differences in body weights, weight gain, feed consumption or organ weights. Copulation and fertility indices, precoital intervals, gestation lengths and pregnancy rates were comparable among the groups, and no signs of prolonged delivery or unusual nesting behaviors were noted. Pup viability, body weights, external observations and necropsy data were comparable among the groups. Pitted kidneys were observed at necropsy for two parental males in the 500 mg/kg/day group and three males in the 1000 mg/kg/day group. Microscopic changes in the kidneys of some male rats from the 100, 500, and 1000 mg/kg/day groups consisted of dose-related accumulations of hyaline droplets in the epithelial cells of the proximal convoluted tubules of the kidneys. In summary, the only treatment-related effect noted in this study was hydrocarbon nephropathy in male rats, which is not considered relevant for human health. The NOAEL for systemic and reproductive toxicity was 1000 mg/kg/day, excluding the finding of male rat hydrocarbon nephropathy.

Administration, Oral↗

PubMed1985

trans-4-Hydroxy-2-hexenal: a reactive metabolite from the macrocyclic pyrrolizidine alkaloid senecionine.

The toxicity of macrocyclic pyrrolizidine alkaloids in the livers of man and animals has been attributed to the formation of reactive pyrroles from dihydropyrrolizines. Now a novel metabolite, trans-4-hydroxy-2-hexenal, has been isolated from the macrocyclic pyrrolizidine alkaloid senecionine, in an in vitro hepatic microsomal system. Other alkenals such as trans-4-hydroxy-2-nonenal have previously been isolated from microsomal systems when treated with halogenated hydrocarbons or subjected to lipid peroxidation. The in vivo pathology caused by trans-4-hydroxy-2-hexenal appears to be identical to that previously attributed to reactive pyrroles. There are similarities between the toxic effects of this alkenal and those of centrilobular hepatotoxins such as CCl4 and other alkenals formed during lipid peroxidation.

Aldehydes↗

PubMed2005

4-oxo-2-hexenal, a mutagen formed by omega-3 fat peroxidation, causes DNA adduct formation in mouse organs.

To identify mutagens formed in a model reaction of lipid peroxidation, linolenic acid methyl ester and hemin were reacted with dG. As a result, a 4-oxo-2-hexenal-dG adduct (dG*) was identified in the model reaction mixture. The 4-oxo-2-hexenal (4-OHE) showed mutagenic activity in the Salmonella typhimurium strains TA100 and TA104. After 4-OHE was orally administered to mice, dG, 4-OHE-dC- and 4-OHE-5-methyl-dC adducts were detected in esophageal, stomach and intestinal DNA. In the vapor phase released from the methyl linolenate-hemin model system, and in the smoke released during the broiling of fish, 4-OHE was detected by GCMS. The 4-OHE seems to be produced by the auto-oxidation of omega-3 polyunsaturated fatty acids. These results provide a warning to workers dealing with omega-3 fats, who may be exposed to this volatile mutagen.

Air Pollutants, Occupational↗

PubMed2000

A lipid-hydrolysing activity involved in hexenal formation.

Short-chain aldehydes such as (3Z)-hexenal and n-hexanal are formed from lipids through sequential actions of lipid-hydrolysing, lipoxygenase and fatty acid hydroperoxide lyase activities. The aldehydes are formed upon wounding of plant tissues, and are reported to have bactericidal and fungicidal activities. Furthermore, it has been reported that the aldehydes can induce expression of a subset of genes involved in disease resistance and that they are involved in a defence response against insect herbivores. Although several genes encoding lipoxygenases and the lyases have been isolated, and characterized to some extent, only little is known about the enzyme accountable for the lipid-hydrolysing step. In this study, we tried to characterize the lipid-hydrolysing activity involved in the short-chain aldehyde formation in Arabidopsis. When Arabidopsis leaves were homogenized, (3Z)-hexenal was formed rapidly within a few minutes. During this time period, the amount of alpha-linolenic acid and C(16:3) rapidly decreased. Such a rapid increase of the aldehyde was repressed almost completely when the leaves were homogenized under a nitrogen stream, and instead free trienoic acids accumulated. A lipase inhibitor, quinacrine, successfully repressed the hydrolysis. It was revealed that trienoic acids in monogalactosyldiacylglycerol were predominantly hydrolysed during the formation of short-chain aldehydes. Collectively, it is suggested that the lipolytic enzyme involved in the short-chain aldehyde formation is a galactolipid-specific lipase.

Arabidopsis↗

PubMed2003

[Sex factors in effects of aerogenic toxic substances on the duration of hexenal-induced sleep].

Inhalant poisoning with low doses of toxicants during 3 months resulted in slowing the biotransformation of hexenal in male rats, whereas lead acetate and sulphur dioxide were less active. Unlike the male rats, phenol in female ones prolonged hexenal-induced dream. Ammonia did not effect the biotransformation, whereas formaldehyde, lead acetate and sulphur dioxide accelerated it. Sex--linked dimorphism of MOS has been suggested to determine more pronounced hepatotoxicity of the compounds under exploration in male rats.

Administration, Inhalation↗

PubMedDate not supplied

[A comparative evaluation of the changes in the duration of "hexenal sleep" in acute radiation and combined radiation-thermal lesions].

In experiments with Wistar rats it was found that the increase in the length of the "hexenal dream" during the first week after the effect of a mixture of radiation and heat is much more pronounced than that observed after exposure to radiation alone and independent of the severity of a radiation component (gamma radiation, 4, 6 and 7.5 Gy). The peculiarities revealed in the hypnotic effect of hexenal develop against the background of the postirradiation aggravation of hypoalbuminemia and decrease in the liver ATP.

Acute Disease↗

PubMedDate not supplied

[Characteristics of food anaphylactic reactions to proteins and protein preparations in guinea pigs with different duration of hexenal-induced sleep].

The state of guinea pig sensitization was studied in the direct test in vivo by induction of active food anaphylaxis (FA). The animals were orally sensitized with food allergens: chick ovalbumin (OVA), bovine serum albumin, and protein preparations N 1 and N 2 (PP N 1 and N 2). In guinea pigs with null hexenal-induced sleep (NHS) and long hexenal-induced sleep (LHS), 40 min, the duration of HS is reliably reproduced in repeated testing. The intensity of FA reactions in guinea pigs with NHS was less manifested than in the animals with LHS with both food allergens. Significantly higher allergenic properties of PP N 2 were expressed in the animals with LHS. It was shown that varying anaphylactic sensitivity of guinea pigs in the above groups was not related with different permeability of the gastrointestinal tract of these animals for OVA macromolecules. Possibilities of metabolic validation of increasing anaphylactic sensitivity of guinea pigs with LHS have been considered.

Anaphylaxis↗

PubMedDate not supplied

[The dissimilar effects of the single and prolonged administration of melatonin on the hypnogenic action of hexenal in mice in relation to the dose and the time of day].

At the acute administration the pineal hormone melatonin depending on the dose (0.01-10 mg/kg) potentiated the hypnogenic effect of hexenal (hexobarbital sodium) in mice both in the daytime and at night. When low doses of the hormone were chronically administered in the light phase of the day, there was noted a decrease of the duration of barbiturate anesthesia. A similar result was found during its round-the-clock evaluation against the background of 0.1 mg/kg of melatonin (a single dose) in the late daytime hours and on the contrary a sharp enhancement of hexenal action before switching on the light. The relationship between the circadian fluctuations of the hypnogenic effect of barbiturates and the periodical character of the epiphysis activity is suggested.

Animals↗