75899-68-2

Basic information

• Product Name: HNE
• Synonyms: (E)-4-HYDROXYNONENAL;HNE;4-HYDROXY-2-NONENAL;4-HNE;(+/-)-4-HYDROXY-2E-NONENAL;(+/-)-4-HYDROXYNON-2-ENAL;4-HYDROXYNONENAL;4-hydroxy-2-nonena
• CAS NO: 75899-68-2
• Molecular Formula: C₉H₁₆O₂
• Molecular Weight: 156.22
• Mol File: 75899-68-2.mol
• Article Data: 27

Chemical Properties

• Boiling Point: 275.6 °C at 760 mmHg
• Flash Point: 115.2 °C
• Appearance: Colorless oil
• Density: 0.941 g/cm³
• Storage Temp.: -70°C
• PKA: 13.31±0.20(Predicted)
• Water Solubility: Solubile in DMSO, Ethanol, Hexane
• CAS DataBase Reference: HNE(CAS DataBase Reference)
• NIST Chemistry Reference: HNE(75899-68-2)
• EPA Substance Registry System: HNE(75899-68-2)

Safety Data

• Hazardous Substances Data: 75899-68-2(Hazardous Substances Data)

Usage

Description

HNE, also known as 4-hydroxynonenal, is a lipid peroxidation product derived from oxidized ω-6 polyunsaturated fatty acids such as arachidonic acid. It exhibits various biological activities, including cytotoxicity, growth-inhibiting activity, genotoxicity, and chemotactic activity. HNE plays a significant role in cellular processes and has potential applications in various fields due to its unique properties.

Uses

Used in Biochemical Research:
HNE is used as a marker of lipid peroxidation for [application reason] studying the effects of oxidative stress on cellular processes and understanding the mechanisms behind various diseases related to oxidative stress.
Used in Pharmaceutical Industry:
HNE is used as an irreversible inhibitor of Na+/K+-ATPase activity for [application reason] developing drugs that target this enzyme, which plays a crucial role in maintaining cellular ion balance and overall cellular function.

Synthetic route

4-hydroxy-2-trans-nonenal dimethylacetal (109296-10-8) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With sulfuric acid In tetrahydrofuran; water for 1h; Ambient temperature;	97%
With sulfuric acid Yield given;
With hydrogen cation In water Hydrolysis;
With hydrogenchloride In water
With hydrogenchloride In water at 20℃; for 1h; pH=3; Darkness; Inert atmosphere;

C27H29O6(1-)*K(1+) → 1-hydroxy-2-propyl-9,10-anthraquinone-4-carboxylic acid (1086461-21-3) + (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Stage #1: C27H29O6(1-)*K(1+) In water for 2.5h; pH=9; aq. buffer; Irradiation; Stage #2: With hydrogenchloride In water	A n/a B 97%

(±)-anti-4-(2-hydroxyethyl)-5-pentyl-1,3-dioxolan-2-one → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With 1-hydroxy-3H-benz[d][1,2]iodoxole-1,3-dione In ethyl acetate for 3h; Reagent/catalyst; Solvent; Inert atmosphere; Reflux; stereoselective reaction;	94%
With 1-hydroxy-3H-benz[d][1,2]iodoxole-1,3-dione In ethyl acetate for 3h; Inert atmosphere; Reflux; stereoselective reaction;	80%

2-{1-[(E)-2-((S)-2,2-Dimethyl-[1,3]dioxolan-4-yl)-vinyl]-hexyloxy}-tetrahydro-pyran (206050-60-4) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With sodium periodate; acetic acid In water	93%

(E)-4-(tert-butyldimethylsilyloxy)-2-nonenal (130796-43-9) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With hydrogen fluoride In acetonitrile for 1h;	88%

(methoxymethylene)triphenylphosphorane (20763-19-3) + 2,3-epoxyoctanal (42134-50-9) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
In tetrahydrofuran at -78 - 20℃;	83%

3-(tert-butyldimethylsilyl)-2,3-epoxypropyl p-tolyl sulfone + hexanal (66-25-1) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Stage #1: 3-(tert-butyldimethylsilyl)-2,3-epoxypropyl p-tolyl sulfone; hexanal With sodium hexamethyldisilazane In tetrahydrofuran at -80 - -60℃; for 0.333333h; Stage #2: With ethanol; tetrabutyl ammonium fluoride; acetic acid In tetrahydrofuran at -80℃; for 0.166667h;	77%

1-octen-3-ol (3391-86-4) + acrolein (107-02-8) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With Hoveyda-Grubbs catalyst 2nd generation In dichloromethane at 20℃; for 20h;	75%

(E)-4-[(tetrahydro-2H-pyran-2-yl)oxy]-2-nonenal (1256782-46-3) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With toluene-4-sulfonic acid In methanol at 0 - 20℃; for 2h;	70%
With toluene-4-sulfonic acid In methanol
With toluene-4-sulfonic acid

1,1,4-tris(acetyloxy)-2-(E)-nonene → (E)-4-Hydroxy-2-nonenal (75899-68-2) + 4-acetyloxy-2-(E)-nonenal (37423-49-7)

Conditions	Yield
With lipase In phosphate buffer at 37℃; for 0.25h; Product distribution; Further Variations:; reaction time;	A 43% B 57%

1-Bromopentane (110-53-2) + (2E)-4,4-dimethoxybut-2-enal (18778-96-6, 4093-49-6) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Stage #1: 1-Bromopentane With magnesium In diethyl ether Stage #2: (2E)-4,4-dimethoxybut-2-enal In diethyl ether at 0 - 20℃; for 1.5h;	44%

methanol (67-56-1) + 1-(4-hydroxy-2-nonenyloxy)-2-propyl-9,10-anthraquinone (791615-15-1) → (E)-4-Hydroxy-2-nonenal (75899-68-2) + 1-Hydroxy-2-propyl-9,10-anthraquinone (156334-29-1) + 2-(3-hydroxy-oct-1-enyl)-11b-methoxy-4-propyl-11bH-1,3-dioxa-benzo[de]anthracen-7-one (791808-24-7)

Conditions	Yield
for 5h; Irradiation;	A 30% B 32% C 42%

1,1-dimethoxy-non-2t-ene (18287-01-9) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
(i) NBS, AIBN, CCl4, (ii) Ag2O, H2O, acetone, (iii) aq. citric acid; Multistep reaction;

linoleic acid (60-33-3) → pentanal (110-62-3) + (E)-4-Hydroxy-2-nonenal (75899-68-2) + butyraldehyde (123-72-8) + hexanal (66-25-1)

Conditions	Yield
With air at 37℃; for 24h; Product distribution; other unsaturated fatty acids;

(E,E)-2,4-nonadienal (5910-87-2) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With triethylsilane; [5,10,15,20-tetra(2,6-dichlorophenyl)porphyrinato]cobalt(II); oxygen; phosphorous acid trimethyl ester 1.) 2-propanol, CH2Cl2, 28 deg C, 1.5 h, 1 atm, 2.) 2-propanol, CH2Cl2, 2 h, r.t.; Yield given. Multistep reaction;

13-[S-(Z,E)]-9,11-Hydroperoxyoctadecadienoic acid → (E)-4-Hydroxy-2-nonenal (75899-68-2) + (2E)-4-oxo-2-nonenal (103560-62-9) + (E)-4-Hydroperoxy-2-nonenal (7439-43-2)

Conditions	Yield
With ammonium sulfate; potassium phosphate buffer; iron(II) sulfate at 37℃; for 0.5h; pH=7.0; Product distribution; Further Variations:; Reagents; reaction time;

3,4-epoxynonanol (208119-82-8) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With pyridinium chlorochromate In dichloromethane at 20℃;	8.6 mg

(E)-1,1-dimethoxy-2-nonen-4-one (194291-91-3) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With sodium tetrahydroborate

4-hydroxy-trans-non-2-enal diethylacetal (18445-69-7) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
With hydrogenchloride at 20℃; for 1h;

methanol (67-56-1) + 1-(4-hydroxy-2-nonenyloxy)-2-propyl-9,10-anthraquinone (791615-15-1) → (E)-4-Hydroxy-2-nonenal (75899-68-2) + 4-hydroxy-2-trans-nonenal dimethylacetal (109296-10-8) + 1-Hydroxy-2-propyl-9,10-anthraquinone (156334-29-1)

Conditions	Yield
With oxygen In water for 3h; Product distribution; Further Variations:; Reagents; Solvents; Irradiation;

2-(3-hydroxy-oct-1-enyl)-11b-methoxy-4-propyl-11bH-1,3-dioxa-benzo[de]anthracen-7-one (791808-24-7) → (E)-4-Hydroxy-2-nonenal (75899-68-2) + 1-Hydroxy-2-propyl-9,10-anthraquinone (156334-29-1)

Conditions	Yield
In methanol Irradiation;

n-pentylmagnesium bromide (693-25-4) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 4 steps 1: 83 percent / tetrahydrofuran / 0.25 h / 0 °C 2: 64 percent / TBAF / tetrahydrofuran; dimethylformamide / 5 h / 20 °C 3: 42 percent / 5 h / Irradiation 4: methanol / Irradiation View Scheme
Multi-step reaction with 2 steps 1: 84 percent / tetrahydrofuran / 1.5 h / -40 - -15 °C 2: 97 percent / 2.5percent aq. H2SO4 / tetrahydrofuran; H2O / 1 h / Ambient temperature View Scheme

1-bromo-4-hydroxy-(E)-2-nonene (98262-71-6) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 3 steps 1: 64 percent / TBAF / tetrahydrofuran; dimethylformamide / 5 h / 20 °C 2: 42 percent / 5 h / Irradiation 3: methanol / Irradiation View Scheme

1-(4-hydroxy-2-nonenyloxy)-2-propyl-9,10-anthraquinone (791615-15-1) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: 42 percent / 5 h / Irradiation 2: methanol / Irradiation View Scheme

n-pentylmagnesium bromide (693-25-4) + tricyclohexyl germanium-bromide → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: aq. NH4Cl 2: H+ / H2O View Scheme

TETRAHYDROPYRANE (142-68-7) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 7 steps 1: NaI, CaCO3 / tetrahydrofuran 2: 1.) Mg / 1.) Et2O, 1 h, 2.) Et2O, 30 min 3: 97 percent / PPTS / CH2Cl2 / Ambient temperature 4: 99 percent / n-Bu4NF / tetrahydrofuran / Ambient temperature 5: 91 percent / DMAP / CH2Cl2 / 18 h / 0 - 5 °C 6: 80 percent / NaBH4 / dimethylsulfoxide / 2 h / 85 °C 7: 93 percent / NaIO4, AcOH / H2O View Scheme

tert-butyl((5-iodopentyl)oxy)dimethylsilane (85514-45-0) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 6 steps 1: 1.) Mg / 1.) Et2O, 1 h, 2.) Et2O, 30 min 2: 97 percent / PPTS / CH2Cl2 / Ambient temperature 3: 99 percent / n-Bu4NF / tetrahydrofuran / Ambient temperature 4: 91 percent / DMAP / CH2Cl2 / 18 h / 0 - 5 °C 5: 80 percent / NaBH4 / dimethylsulfoxide / 2 h / 85 °C 6: 93 percent / NaIO4, AcOH / H2O View Scheme

(1E)-(3,3-dimethyl-2,4-dioxolanyl)oct-1-en-3-ol → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 2 steps 1: 97 percent / PPTS / CH2Cl2 / Ambient temperature 2: 93 percent / NaIO4, AcOH / H2O View Scheme

(E)-8-((S)-2,2-Dimethyl-[1,3]dioxolan-4-yl)-6-(tetrahydro-pyran-2-yloxy)-oct-7-en-1-ol (206050-56-8) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 3 steps 1: 91 percent / DMAP / CH2Cl2 / 18 h / 0 - 5 °C 2: 80 percent / NaBH4 / dimethylsulfoxide / 2 h / 85 °C 3: 93 percent / NaIO4, AcOH / H2O View Scheme

(1E)-1-[3,3-dimethyl-(2,4-dioxolanyl)-8-(1,1,2,2-tetramethyl)-1-silapropoxy]oct-1-en-3-ol (206050-53-5) → (E)-4-Hydroxy-2-nonenal (75899-68-2)

Conditions	Yield
Multi-step reaction with 5 steps 1: 97 percent / PPTS / CH2Cl2 / Ambient temperature 2: 99 percent / n-Bu4NF / tetrahydrofuran / Ambient temperature 3: 91 percent / DMAP / CH2Cl2 / 18 h / 0 - 5 °C 4: 80 percent / NaBH4 / dimethylsulfoxide / 2 h / 85 °C 5: 93 percent / NaIO4, AcOH / H2O View Scheme

(E)-4-Hydroxy-2-nonenal (75899-68-2) + N-acetylhistamine (673-49-4) → Nα-acetyl-Nτ-(2-hydroxy-5-pentyltetrahydrofuran-4-yl)histamine

Conditions	Yield
With phosphate buffer In acetonitrile at 37℃; for 24h; Addition; cyclization;	86%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + pentafluorophenyl hydrazine (828-73-9) → (1E,2E)-1-[2-(perfluorophenyl)hydrazono]non-2-en-4-ol (1402134-69-3)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid at 20℃; Inert atmosphere;	85%

3,5-bis(trifluoromethyl)phenylhydrazine (886-35-1) + (E)-4-Hydroxy-2-nonenal (75899-68-2) → (1E,2E)-1-{2-[3,5-bis(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol (1402134-67-1)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In ethanol at 20℃; Inert atmosphere;	80%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + 4-(trifluoromethyl)phenylhydrazine (368-90-1) → (1E,2E)-1-{2-[4-(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol (1402134-66-0)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In acetonitrile at 20℃; for 0.25h; Inert atmosphere;	80%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + 2-(trifluoromethyl)phenylhydrazine (365-34-4) → (1E,2E)-1-{2-[2-(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol (1402134-64-8)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In acetonitrile at 20℃; Inert atmosphere;	76%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + N-butylamine (109-73-9) → 3-(butylamino)-1,4-nonanediol + 1,3-bis(butylamino)-4-nonanol

Conditions	Yield
Stage #1: (E)-4-Hydroxy-2-nonenal; N-butylamine With [2,2]bipyridinyl; sodium dihydrogenphosphate; copper(II) sulfate at 20℃; for 144h; pH=7.8; Condensation; Stage #2: With sodium tetrahydroborate Reduction;	A 69% B 6%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + 4-(trifluoromethyl)phenylhydrazine (368-90-1) → 6-pentyl-1-[4-(trifluoromethyl)phenyl]-1,6-dihydropyridazine (1402134-71-7)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In acetonitrile; tert-butyl alcohol at 70℃; for 5h;	64%

(E)-4-Hydroxy-2-nonenal (75899-68-2) + 4-(trifluoromethyl)phenylhydrazine (368-90-1) → 6-pentyl-1-[4-(trifluoromethyl)phenyl]-1,6-dihydropyridazine (1402134-71-7) + 6-pentyl-1-[4-(trifluoromethyl)phenyl]-5-{2-[4-(trifluoromethyl)-phenyl]hydrazinyl}-1,4,5,6-tetrahydropyridazine + C23H26F6N4

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In acetonitrile at 20 - 70℃; for 6h; Inert atmosphere; optical yield given as %de; diastereoselective reaction;	A 64% B n/a C n/a

(E)-4-Hydroxy-2-nonenal (75899-68-2) + 3-(trifluoromethyl)phenylhydrazine (368-78-5) → (1E,2E)-1-{2-[3-(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol (1402134-65-9)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid In ethanol at 20℃; Inert atmosphere;	63%

[2,4-bis(trifluoromethyl)phenyl]hydrazine (1402134-63-7) + (E)-4-Hydroxy-2-nonenal (75899-68-2) → (1E,2E)-1-{2-[2,4-bis(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol (1402134-68-2)

Conditions	Yield
With magnesium sulphate; trifluoroacetic acid at 20℃; Inert atmosphere;	62%

(E)-4-Hydroxy-2-nonenal (75899-68-2) → 2-pentylfuran (3777-69-3)

Conditions	Yield
at 100 - 150℃;	43%

Upstream product

• 18287-01-9 1,1-dimethoxy-non-2t-ene 
• 60-33-3 linoleic acid 
• 20763-19-3 (methoxymethylene)triphenylphosphorane 
• 42134-50-9 2,3-epoxyoctanal 
• 109296-10-8 4-hydroxy-trans-2-nonenal-dimethylacetal 
• 18445-69-7 4-hydroxy-trans-non-2-enal diethylacetal 
• 67-56-1 methanol 
• 791615-15-1 1-(4-hydroxy-2-nonenyloxy)-2-propyl-9,10-anthraquinone 
• 66-25-1 hexanal 
• 3391-86-4 1-octen-3-ol 
• 107-02-8 acrolein 
• 124-19-6 nonan-1-al 
• 1256782-46-3 (E)-4-[(tetrahydro-2H-pyran-2-yl)oxy]-2-nonenal 
• 130796-43-9 (E)-4-(tert-butyldimethylsilyloxy)-2-nonenal 

Downstream Products

• 62962-42-9 N²,3-ethenoguanine 
• 146764-24-1 N-acetyl-S-(tetrahydro-5-hydroxy-2-pentyl-3-furanyl)-L-cysteine 
• 3777-69-3 2-pentylfuran 
• 1402134-68-2 (1E,2E)-1-{2-[2,4-bis(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol 
• 1402134-81-9 (E)-1-[2,4-bis(trifluoromethyl)phenyl]-2-[(E)-4-{2-[2,4-bis(trifluoromethyl)phenyl]hydrazinyl}non-2-enylidene]hydrazine 
• 1402134-71-7 6-pentyl-1-[4-(trifluoromethyl)phenyl]-1,6-dihydropyridazine 
• 1402134-80-8 (E)-1-[(E)-4-Ethoxynon-2-enylidene]-2-[4-(trifluoromethyl)phenyl]- 
• 1402134-67-1 (1E,2E)-1-{2-[3,5-bis(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol 
• 1402134-72-8 1-[3,5-bis(trifluoromethyl)phenyl]-6-pentyl-1,6-dihydropyridazine 
• 1402134-70-6 6-pentyl-1-[3-(trifluoromethyl)phenyl]-1,6-dihydropyridazine 
• 1402134-65-9 (1E,2E)-1-{2-[3-(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol 
• 1402134-64-8 (1E,2E)-1-{2-[2-(trifluoromethyl)phenyl]hydrazono}non-2-en-4-ol 

Relevant articles and documents

Tandem IBX-Promoted Primary Alcohol Oxidation/Opening of Intermediate β,γ-Diolcarbonate Aldehydes to (E)-γ-Hydroxy-α,β-enals

A tandem IBX-promoted oxidation of primary alcohol to aldehyde and opening of intermediate β,γ-diolcarbonate aldehyde to (E)-γ-hydroxy-α,β-enal has been developed. Remarkably, the carbonate opening delivered exclusively (E)-olefin and no over-oxidation of γ-hydroxy was observed. The method developed has been extended to complete the stereoselective total synthesis of both (S)- and (R)-coriolides and d-xylo- and d-arabino-C-20 guggultetrols.

NADP+-dependent dehydrogenase activity of carbonyl reductase on glutathionylhydroxynonanal as a new pathway for hydroxynonenal detoxification

An NADP+-dependent dehydrogenase activity on 3-glutathionyl-4-hydroxynonanal (GSHNE) was purified to electrophoretic homogeneity from a line of human astrocytoma cells (ADF). Proteomic analysis identified this enzymatic activity as associated with carbonyl reductase 1 (EC 1.1.1.184). The enzyme is highly efficient at catalyzing the oxidation of GSHNE (KM 33 μM, kcat 405 min-1), as it is practically inactive toward trans-4-hydroxy-2-nonenal (HNE) and other HNE-adducted thiol-containing amino acid derivatives. Combined mass spectrometry and nuclear magnetic resonance spectroscopy analysis of the reaction products revealed that carbonyl reductase oxidizes the hydroxyl group of GSHNE in its hemiacetal form, with the formation of the corresponding 3-glutathionylnonanoic-δ-lactone. The relevance of this new reaction catalyzed by carbonyl reductase 1 is discussed in terms of HNE detoxification and the recovery of reducing power.

Liquid chromatography/electrospray ionisation mass spectrometric tracking of 4-hydroxy-2(E)-nonenal biotransformations by mouse colon epithelial cells using [1,2-13C2]-4-hydroxy-2(E)-nonenal as stable isotope tracer

4-Hydroxy-2(E)-nonenal (HNE), a product of lipid peroxidation, has been extensively studied in several areas, including metabolism with radio-isotopes and quantification in various matrices with deuterium-labelled HNE as standard. The aim of this work was to evaluate the relevance of 13C-labelled HNE in biotransformation studies to discriminate metabolites from endogens by liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI-MS). 13C-Labelled HNE was synthesised inimproved overall yield (20%), with the incorporation of two labels in the molecule. Immortalisedmouse colon epithelial cells were incubated with 2:3 molar amounts of HNE/13C-HNE in order to gain information on the detection of metabolites in complex media. Our results demonstrated that the stable isotope m/z values determined by mass spectrometry were relevant in distinguishing metabolites from endogens, and that metabolite structures could be deduced. Six conjugate metabolites and 4-hydroxy-2(E)-nonenoic acid were identified, together with an incompletely identified metabolite. Stable-isotope-labelled HNE has already been used for quantification purposes. However, this is the first report on the use of 13C-labelled HNE as a tracer for in vitro metabolism. 13C-Labelled HNE could also be of benefit for in vivo studies. Copyright