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PubMedDate not supplied

Carcinogenic potential of trans-2-hexenal is based on epigenetic effect.

BACKGROUND: Trans-2-hexenal (2-hexenal) is an alpha,beta-unsaturated carbonyl compound protecting plants against harmful substances. Since humans have a permanent intake of 2-hexenal via vegetable products, this genotoxic and mutagenic compound is considered to play a role in human carcinogenicity. MATERIALS AND METHODS: Ha-ras and p53 gene expression changes and tumor development were investigated in mice and rats after 2-hexenal administration. RESULTS: 2-Hexenal exposure did not result in gene expression alterations 24, 48 or 72 hours after administration while 10 out of the 72 mice and rats included in the long-term study developed a malignancy by the end of the 18-month follow-up. CONCLUSION: Our results suggest that, although 2-hexenal showed no effect on the expression of the investigated onco- and suppressor genes, it has a marked carcinogenic potential, which may be explained only by an epigenetic effect of the compound.

Aldehydes↗

PubMed1999

Development of a 32P-postlabeling method for the detection of 1, N2-propanodeoxyguanosine adducts of 2-hexenal in vivo.

2-Hexenal is an alpha,beta-unsaturated carbonyl compound which forms cyclic 1,N2-propano adducts in vitro. The adduct formation in vivo was not reported by others to date. Because this type of adduct is considered promutagenic (2-hexenal is actually mutagenic and genotoxic) and humans are permanently exposed to this compound via vegetarian food, 2-hexenal may play a role in carcinogenicity. To improve the cancer risk assessment, we developed a new 32P-postlabeling technique for this compound and optimized the different steps of the postlabeling procedure. The results of the postlabeling methods are shown. A labeling efficiency of 35%, a recovery of 10% for the synthesized standards, and a detection limit of three 2-hexenal adducts per 10(8) nucleotides was achieved. After gavage of 500 mg/kg of body weight to male Fischer 344 rats, the respective DNA adducts were detected in rat liver DNA. With this study, we demonstrate in vivo adduct formation of 2-hexenal for the first time. Highest adduct levels were found 2 days after gavage, and after 4 days, the level was even higher than after 1 day. No adducts were detected 8 h after gavage. The respective adducts could not be found as a background in tissues of untreated rats or in calf thymus DNA at the limit of detection.

Aldehydes↗

PubMed2004

cis-3-Hexenal production in tobacco is stimulated by 16-carbon monounsaturated fatty acids.

Transgenic tobacco plants O9 and T16 expressing the yeast acyl-CoA Delta9 desaturase and an insect acyl-CoA Delta11 desaturase, respectively, displayed altered profiles of fatty acids compared to wild-type tobacco plants and marked increases in cis-3-hexenal, a major leaf volatile derived from alpha-linolenic acid (18:3). As expected, O9 and T16 plants had increased levels of the major unsaturated fatty acid products formed by the transgenic desaturases they expressed, viz., palmitoleic acid (16:1(Delta9)) and palmitvaccenic acid (16:1(Delta11)), respectively. In addition, levels of 18:3 lipid declined slightly and the pool of free 18:3, which accounts for about 30% of free fatty acids in wild-type plants, disappeared completely in both transgenics. Both O9 and T16 plants were found to have a two-fold increase in 13-lipoxygenase (13-LOX) activity, which catalyzes the first of two steps leading to hexenal production from 18:3. In O9 and T16 plants, the activity of 9-lipoxygenase and hydroperoxide lyase, the latter catalyzing the formation of cis-3-hexenal from alpha-linolenic acid hydroperoxide, was significantly different from that of the wild-type plants. Although 16:1(Delta9) and 16:1(Delta11) had no direct effects on 13-LOX activity in vitro, cis-3-hexenal production increased in tobacco leaves treated with these fatty acids, suggesting that they may act in vivo by stimulating 13-LOX gene expression.

Aldehyde-Lyases↗

PubMed2004

Quantitative 13C NMR analysis of sequence distributions in poly(ethylene-co-1-hexene).

Different 13C NMR methods of determining triad distributions in two poly(ethylene-co-1-hexene) copolymers are examined using high signal-to-noise ratio 13C NMR spectra of the copolymers dissolved in deuterated 1,2,4-trichlorobenzene at 398 K. This examination includes a comparison of three integration techniques. The experimental impact of decoupler sidebands and significantly nonequal 13C NOE values are examined. A least-squares regression analysis technique for solving for triad mole fractions is tested and appears to be more reliable than two published algebraic expressions (and other expressions examined in the work reported here). The resultant triad mole fractions are compared to sequence distribution parameters expected by Bernoullian and first-order Markovian statistical models. On the basis of 13C NMR-determined average reactivity ratios, the copolymer designated sample B (5.3 mol % 1-hexene) appears to be a Bernoullian copolymer resulting from a single-site catalytic system. The copolymer designated sample S (3.6 mol % 1-hexene overall) is better described as a mixture of polyethylene and a Bernoullian copolymer with 6.4 mol % 1-hexene content, and thus appears to result from a multisite catalytic system.

Journal Article↗

PubMed2001

Kinetics of initiation, propagation, and termination for the [rac-(C(2)H(4)(1-indenyl)(2))ZrMe][MeB(C(6)F(5))(3)]-catalyzed polymerization of 1-hexene.

Metallocene-catalyzed polymerization of 1-alkenes offers fine control of critical polymer attributes such as molecular weight, polydispersity, tacticity, and comonomer incorporation. Enormous effort has been expended on the synthesis and discovery of new catalysts and activators, but elementary aspects of the catalytic processes remain unclear. For example, it is unclear how the catalyst is distributed among active and dormant sites and how this distribution influences the order in monomer for the propagation rates, for which widely varying values are reported. Similarly, although empirical relationships between average molecular weights and monomer have been established for many systems, the underlying mechanisms of chain termination are unclear. Another area of intense interest concerns the role of ion-pairing in controlling the activity and termination mechanisms of metallocene-catalyzed polymerizations. Herein we report the application of quenched-flow kinetics, active site counting, polymer microstructure analysis, and molecular weight distribution analysis to the determination of fundamental rate laws for initiation, propagation, and termination for the polymerization of 1-hexene in toluene solution as catalyzed by the contact ion-pair, [rac-(C(2)H(4)(1-indenyl)(2))ZrMe][MeB(C(6)F(5))(3)] (1) over the temperature range of -10 to 50 degrees C. Highly isotactic (>99% mmmm) poly-1-hexene is produced with no apparent enchained regioerrors. Initiation and propagation processes are first order in the concentrations of 1-hexene and 1 but independent of excess borane or the addition of the contact ion-pair [PhNMe(3)][MeB(C(6)F(5))(3)]. Active site counting and the reaction kinetics provide no evidence of catalyst accumulation in dormant or inactive sites. Initiation is slower than propagation by a factor of 70. The principal termination process is the formation of unsaturates of two types: vinylidene end groups that arise from termination after a 1,2 insertion and vinylene end groups that follow 2,1 insertions. The rate law for the former termination process is independent of the 1-hexene concentration, whereas the latter is first order. Analysis of (13)C-labeled polymer provides support for a mechanism of vinylene end group formation that is not chain transfer to monomer. Deterministic modeling of the molecular weight distributions using the fundamental rate laws and kinetic constants demonstrates the robustness of the kinetic analysis. Comparisons of insertion frequencies with estimated limits on the rates of ion-pair symmetrization obtained by NMR suggest that ion-pair separation prior to insertion is not required, but the analysis requires assumptions that cannot be validated.

Alkenes↗

PubMed2003

Application of hexanal, E-2-hexenal, and hexyl acetate to improve the safety of fresh-sliced apples.

The aims of this work were to evaluate the effects of different concentrations of hexanal, (E)-2-hexenal, hexyl acetate, and their mixtures on the fate of pathogenic species such as Escherichia coli, Salmonella enteritidis, and Listeria monocytogenes inoculated in model systems as well as the antimicrobial activity against the target species of the chosen molecules when added to the packaging atmosphere of inoculated fresh-sliced apples. The result obtained in this work pointed out the potential use of compounds such as hexanal, (E)-2-hexenal, and hexyl acetate for both the extension of shelf life and an improvement of hygienic safety of "minimally processed foods". In fact, hexanal, (E)-2-hexenal, and hexyl acetate had a significant inhibitory effect against pathogen microorganisms frequently isolated from raw materials (E. coli, S. enteritidis, and L. monocytogenes) when inoculated in both model and real systems. In this last condition, these compounds, at the levels used (150, 150, and 20 ppm for hexanal, hexyl acetate, and (E)-2-hexenal, respectively), displayed a bactericide effect on L. monocytogenes and they exhibited significant extensions of lag phase of E. coli and S. enteritidis inoculated at levels of 10(4)-10(5) CFU/g.

Acetates↗

PubMed1999

Subchronic inhalation study of 1-hexene in Fischer 344 rats.

The objective of this study was to evaluate the toxicity of 1-hexene following repeated inhalation exposures in male and female Fischer 344 rats. Groups of 40 male and 40 female rats were exposed for 6 hours per day, 5 days per week, over a 13-week period. Treatment groups consisted of air-exposed control (0 ppm) and three test groups of 300, 1000, and 3000 ppm 1-hexene. During the treatment period, the rats were observed daily for clinical signs of toxicity; body weights and neuromuscular coordination [females only] were measured at 7-day intervals. After 7 weeks of exposure and at the end of the treatment period, the rats were subject to macroscopic and microscopic pathology, clinical chemistry, hematology, urinalysis, and sperm counts. No mortalities were observed during the course of the study. No clinical signs of toxicity attributable to 1-hexene exposure were observed. Female rats exposed to 3000 ppm had significantly lower body weights compared to control rats from exposure day 5 persisting throughout the treatment period. Male rats exposed to 3000 ppm had slightly but not statistically significant lower body weights in comparison to controls. Male rats exhibited slightly increased absolute and relative testicular weights, and female rats had slightly decreased absolute [but not relative] liver and kidney weights, at 3000 ppm. There were no gross or microscopic morphological findings attributed to treatment. Exposure to 1-hexene did not affect neuromuscular coordination in females as determined using the Rotarod, nor sperm counts in male rats. Several statistically significant effects in hematology, clinical chemistry, and urinalysis evaluations were observed, but were either of small magnitude or did not correlate with histopathological findings, and thus did not appear to be of biological significance. In summary, the no-adverse-effect-level for this study was determined to be 1000 ppm, based on decreased weight gain in female rats, and on slight organ weight changes in both sexes at 3000 ppm.

Administration, Inhalation↗

PubMed1998

Large-scale preparation of (Z)-3-hexen-1-yl acetate using candida antarctica-immobilized lipase in hexane

A kilogram-scale synthesis of (Z)-3-hexen-1-yl acetate, in hexane, on direct esterification of (Z)-3-hexen-1-ol with acetic acid in the presence of 2% (w/w reactants) of an immobilized lipase from Candida antarctica (Novozym 435) is reported. Conversion yields ranging from 92 to 96% were obtained after optimization of various parameters. In that respect, elimination of the water proved crucial. Using at both the laboratory large scale (preparation of 200-400 g of ester) and the pilot scale (1-5 kg) a "reflux" rotary evaporator equipped with a graduated decantation flask, we were able to trap the water evolved during esterification while at the same time monitor the time course of the reaction. As a consequence of both an efficient water trapping and of a gentle dispersion of the immobilized lipase into the reaction medium, the lifetime of the enzyme was significantly prolonged. At the laboratory large scale (LLS), the yield was still >/=90% after seven consecutive utilizations whereas at the pilot scale (PS), it reached 93% after reusing the enzyme four times. In those conditions, the amount of immobilized enzyme necessary to produce 1 kg of (Z)-3-hexen-1-yl acetate was 18 g (1. 8%) and 60 g (6%) at the LLS and the PS, respectively. Copyright 1998 John Wiley & Sons, Inc.

Journal Article↗

PubMed1997

Genotoxic effects of 2-trans-hexenal in human buccal mucosa cells in vivo.

In 7 non-smoking healthy volunteers, the number of micronuclei (MN) was determined in exfoliated buccal mucosa cells before and after rinsing the mouth with an aqueous 10 ppm solution of 2-trans-hexenal during 3 consecutive days. All individuals showed at least a doubling of the MN frequency during one of the next 4 days. An increase of the mean group MN frequency was observed on the fourth day, becoming significant between the sixth and the seventh day. During the next 2 days, the MN frequency dropped down to nearly the control level. In a second study, 7 other volunteers were examined before and after eating 3-6 bananas per day over a period of 3 days. The bananas contained about 35 ppm of hexenal. Six of the 7 individuals showed at least a doubling of the MN frequency during one of the next 6 days. An increase in the mean MN counts was also observed, but the difference to the control value become non-significant during the test period. The results show for the first time that the flavoring constituent 2-trans-hexenal, which is present in many human foods exerts genotoxic effects on human buccal mucosa cells in vivo.

Adult↗

PubMed2003

Hydroxyaldehyde products from hydroxyl radical reactions of Z-3-hexen-1-ol and 2-methyl-3-buten-2-ol quantified by SPME and API-MS.

Hydroxyaldehyde products of the OH radical-initiated reactions (in the presence of NO) of two volatile vegetative emissions, Z-3-hexen-1-ol and 2-methyl-3-buten-2-ol, were examined to assess the qualitative and quantitative potential of two analysis techniques (1) sampling by Solid-Phase MicroExtraction (SPME) with on-fiber derivatization followed by gas chromatographic analyses and (2) in situ analysis by negative ion mode atmospheric pressure ionization mass spectrometry (API-MS). The compounds were chosen because reaction mechanisms predict hydroxyaldehyde products, and reliable coproduct yield data are available. The API-MS analyses showed product ion peaks attributed to the NO2- adducts of 3-hydroxypropanal and dihydroxynitrates from Z-3-hexen-1-ol, and a formation yield of 3-hydroxypropanal of 44% was derived. Product ion peaks attributed to NO2- adducts of glycolaldehyde [HOCH2CHO], 2-hydroxy-2-methylpropanal [(CH3)2C(OH)CHO], and dihydroxynitrates were observed by API-MS from 2-methyl-3-buten-2-ol, and a formation yield of 2-hydroxy-2-methylpropanal of 16% was obtained. In experiments with SPME sampling, the formation yields of hydroxycarbonyls measured as their oxime derivatives were as follows: from Z-3-hexen-1-ol, propanal, 56 +/- 8%; 3-hydroxypropanal, 101 +/- 24%; and from 2-methyl-3-buten-2-ol, 2-hydroxy-2-methylpropanal, 31 +/- 4%. Both the API-MS and SPME analyses provided product information, and hydroxycarbonyl yields from the SPME data are in reasonable agreement with previously measured formation yields of coproducts.

Chemistry Techniques, Analytical↗

PubMed2006

Biosynthesis of trans-2-hexenal in response to wounding in strawberry fruit.

Wounded strawberry fruit produces a diverse group of volatile compounds including aldehydes, alcohols, and esters derived from the lipoxygenase (LOX) and hydroperoxide lyase (HPL) pathways. Because the wound volatiles may play an important role in plant-fungal interaction, the goal of this study was to develop a greater understanding about the biosynthesis of the major wound volatile, trans-2-hexenal (t-2-H), produced by strawberry fruit upon wounding. To that end, composition and quantity of total and free fatty acids of control and wounded strawberry fruit were analyzed. In addition, activities of the key enzymes, LOX and HPL, and production of C6 aldehydes were determined. Intact strawberry fruit did not produce detectable t-2-H which is derived from alpha-linolenic acid (18:3). However, in response to wounding by bruising, strawberry fruit emitted t-2-H and its precursor cis-3-hexenal (c-3-H). The level of total lipid 18:3 in the fruit increased 2-fold in response to wounding, whereas free 18:3 declined slightly ( approximately 30%). At 10 min following wounding, fruit exhibited a 25% increase in LOX activity, which leads to the production of 13-hydroperoxyoctadecatrienoic acid (13-HPOT) from 18:3. The activity of HPL, which catalyzes formation of cis-3-hexenal from 13-HPOT, increased 2-fold by 10 min after wounding. Thus, during a 15 min period after wounding, free 18:3 substrate availability and the activity of two key enzymes, LOX and HPL, changed in a manner consistent with increased c-3-H and t-2-H biosynthesis.

Aldehyde-Lyases↗

PubMed1997

Modification of horse heart cytochrome c with trans-2-hexenal.

Horse heart cytochrome c reacting with trans-2-hexenal was used as a simple model of the nonspecific interactions of proteins with 2-alkenals. The reaction mixtures containing relatively high concentrations of the protein and aldehyde were characterized using visible spectrophotometry, fluorescence, and circular dichroism measurement, capillary isoelectric focusing, size-exclusion chromatography, polyacrylamide gel electrophoresis, and mass-spectrometric techniques. The mass-spectrometric data indicate that cytochrome c becomes modified with one or two molecules of hexenal as the major reaction product. The modified species with a correspondingly lowered isoelectric point were detected through capillary isoelectric focusing. The results of proteolytic studies indicate nonspecific modifications. Significant quantities of the oligomeric forms of hexenal-modified protein were also observed electrophoretically.

Aldehydes↗

PubMed2001

Effect of trans-2-hexenal on the growth of Aspergillus flavus in relation to its concentration, temperature and water activity.

AIMS: The antifungal activity of trans-2-hexenal on Aspergillus flavus in a model system in relation to its concentration, incubation temperature and aw was assessed. METHODS AND RESULTS: A model describing the antifungal activity of the aldehyde in relation to these variables was obtained. CONCLUSION: According to this model, the inhibition of A. flavus was weakly dependent on the incubation temperature (at least within the range of values considered) and strongly affected by the trans-2-hexenal concentration and aw, which showed a remarkable synergistic effect. SIGNIFICANCE AND IMPACT OF THE STUDY: Trans-2-hexenal proved to be a molecule with remarkable antimicrobial properties, even when added in closed systems at low concentration.

Aldehydes↗

PubMed1967

Trans-2-hexenal: mating stimulant for polyphemus moths.

The volatile compound from oak leaves which stimulates the female polyphemus moth to release her sex pheromone has been isolated and identified as trans-2-hexenal. Although leaves of other food plants contain trans-2-hexenal, they also release masking odors which block the activity of the hexenal.

Aldehydes↗

PubMed1987

[Action of hexenal and ethyl alcohol on hemoglobin and carboanhydrase].

The change of hemoglobin and carbonic anhydrase properties under the action of hexenal and ethyl alcohol has been studied in rabbits and ewes. It has been shown that hexenal causes the decrease of blood ph and p50 of hemoglobin, ethanol causes the increase of blood ph and p50. That contradicts the requirements of the alkaline Bohr effect. Hexenal decreases the activity of carbonic anhydrase.

Animals↗

PubMed2007

Chiral fluorous dialkoxy-diamino zirconium complexes: synthesis and use in stereospecific polymerization of 1-hexene.

New catalysts for the isospecific polymerization of 1-hexene based on cationic zirconium complexes incorporating the tetradentate fluorous dialkoxy-diamino ligands [OC(CF(3))(2)CH(2)N(Me)(CH(2))(2)N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(2)NO)(2-)] and [OC(CF(3))(2)CH(2)N(Me)(1R,2R-C(6)H(10))N(Me)CH(2)C(CF(3))(2)O](2-) [(ON(Cy)NO)(2-)] have been developed. The chiral fluorous diamino-diol [(ON(Cy)NO)H(2), 2] was prepared by ring-opening of the fluorinated oxirane (CF(3))(2)COCH(2) with (R,R)-N,N'-dimethyl-1,2-cyclohexanediamine. Proligand 2 reacts cleanly with [Zr(CH(2)Ph)(4)] and [Ti(OiPr)(4)] precursors to give the corresponding dialkoxy complexes [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3) and [Ti(OiPr)(2)(ON(Cy)NO)] (4), respectively. An X-ray diffraction study revealed that 3 crystallizes as a 1:1 mixture of two diastereomers (Lambda-3 and Delta-3), both of which adopt a distorted octahedral structure with trans-O, cis-N, and cis-CH(2)Ph ligands. The two diastereomers Lambda-3 and Delta-3 adopt a C(2)-symmetric structure in toluene solution, as established by NMR spectroscopy. Cationic complexes [Zr(CH(2)Ph)(ON(2)NO)(THF)(n)](+) (n=0, anion=[B(C(6)F(5))(4)](-), 5; n=1, anion=[PhCH(2)B(C(6)F(5))(3)](-), 6) and [Zr(CH(2)Ph)(ON(Cy)NO)(THF)](+)[PhCH(2)B(C(6)F(5))(3)](-) (7) were generated from the neutral parent precursors [Zr(CH(2)Ph)(2)(ON(2)NO)] (H) and [Zr(CH(2)Ph)(2)(ON(Cy)NO)] (3), and their possible structures were determined on the basis of (1)H, (19)F, and (13)C NMR spectroscopy and DFT methods. The neutral zirconium complexes H and 3 (Lambda-3/Delta-3 mixture), when activated with B(C(6)F(5))(3) or [Ph(3)C](+)[B(C(6)F(5))(4)](-), catalyze the polymerization of 1-hexene with overall activities of up to 4500 kg PH mol Zr(-1) h(-1), to yield isotactic-enriched (up to 74 % mmmm) polymers with low-to-moderate molecular weights (M(w)=4800-47 200) and monodisperse molecular-weight distributions (M(w)/M(n)=1.17-1.79).

Journal Article↗

PubMed1999

Hydrogenation of 1-Hexene and Hexadienes by Ultrafine Pd Particles Supported on the Surface of PrPO(4) Hollow Particles.

Novel fine polymer particles containing ultrafine Pd particles dispersed on the surface of core shell [core, poly(styrene-co-acrylic acid); shell, PrPO(4)]-type microspheres were prepared by the emulsifier-free emulsion polymerization of styrene with acrylic acid followed by the addition of PdCl(2) and a mixture of Pr(NO(3))(3) and NaH(2)PO(2). Pyrolysis of the resulting polymer particles at 900 degrees C provides organic polymer-free hollow particles (diameter, 473-586 nm) composed of Pd metal and PrPO(4). Hydrogenation of 1-hexene, trans-1,3-hexadiene, trans-1,4-hexadiene, and 1,5-hexadiene using the resulting Pd/PrPO(4) particles (reactant/Pd = 500 mol/mol) as catalyst revealed very high activity, especially for hydrogenations of 1-hexene and 1,5-hexadiene as compared with conventional Pd particles/Al(2)O(3) and Pd particles on powdered PrPO(4). Copyright 1999 Academic Press.

Journal Article↗

PubMed1987

Lipid peroxidation and cellular damage caused by the pyrrolizidine alkaloid senecionine, the alkenal trans-4-hydroxy-2-hexenal, and related alkenals.

Lipid peroxidation was examined as a possible mechanism for cell injury by trans-4-OH-2-hexenal, the macrocyclic pyrrolizidine alkaloid senecionine and related alkenals in isolated rat hepatocytes. Each compound elicited a positive dose response for peroxidation of cellular lipids as measured by the formation of thiobarbituric acid-reactive products. The addition of the anti-oxidant N,N'-diphenyl-p-phenylenediamine to the hepatocyte suspensions inhibited the production of thiobarbituric acid-reactants. However, the presence of the anti-oxidant had no protective effects on the cell membrane integrity as evidenced by the leakage of lactate dehydrogenase from the cells into the surrounding media. These results suggest that lipid peroxidation which occurs in the presence of senecionine, trans-4-OH-2-hexenal or related alkenals is not entirely responsible for the cellular damage in isolated rat hepatocytes.

Aldehydes↗